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Process Control: Modeling,
Design, and Simulation

B. Wayne Bequette

Pearson
Contents
Preface
About the Author
Chapter 1: Introduction
Chapter 2: Fundamental Models
Chapter 3: Dynamic Behavior
Chapter 4: Dynamic Behavior: Complex Systems
Chapter 5: Empirical and Discrete-Time Models
Chapter 6: Introduction to Feedback Control
Chapter 7: Model-Based Control
Chapter 8: PID Controller Tuning
Chapter 9: Frequency-Response Analysis
Chapter 10: Cascade and Feedforward Control
Chapter 11: PID Enhancements
Chapter 12: Ratio, Selective, and Split-Range Control
Chapter 13: Control-Loop Interaction
Chapter 14: Multivariable Control
Chapter 15: Plantwide Control
Chapter 16: Model Predictive Control
Chapter 17: Summary

Module 1: Introduction to MATLAB

Module 2: Introduction to SIMULINK
Module 3: Ordinary Differential Equations
Module 4: MATLAB LTI Models
Module 5: Isothermal Chemical Reactor
Module 6: First-Order + Time-Delay Processes
Module 7: Biochemical Reactors
Module 8: CSTR
Module 9: Steam Drum Level
Module 10: Surge Vessel Level Control
Module 11: Batch Reactor
Module 12: Biomedical Systems
Module 13: Distillation Control
Module 14: Case Study Problems
Module 15: Plug Flow Reactor
Module 16: Digital Control
Table of Contents
Preface
About the Author
Chapter 1. Introduction
1.1 Introduction
1.2 Instrumentation
1.3 Process Models and Dynamic Behavior
1.4 Redundancy and Operability
1.5 Industrial IoT and Smart Manufacturing
1.6 Control Textbooks
1.7 A Look Ahead
1.8 Summary
References
Chapter 2. Fundamental Models
2.1 Background
2.2 Balance Equations
2.3 Material Balances
2.4 Constitutive Relationships
2.5 Material and Energy Balances
2.6 Form of Dynamic Models
2.7 Linear Models and Deviation Variables
2.8 Summary
Chapter 3. Dynamic Behavior
3.1 Background
3.2 Linear State-Space Models
3.3 Laplace Transforms
3.4 Transfer Functions
3.5 First-Order Behavior
3.6 Integrating Behavior Purely Integrating Systems
3.7 Second-Order Behavior
3.8 Summary
References

Chapter 4. Dynamic Behavior: Complex Systems

4.1 Introduction
4.2 Poles and Zeros
4.3 Lead-Lag Behavior
4.4 Processes with Deadtime
4.5 Padé Approximation for Deadtime
4.6 Converting State-Space Models to Transfer Functions
4.7 Converting Transfer Functions to State-Space Models
4.8 Matlab and Simulink
4.9 Summary

Chapter 5. Empirical and Discrete-Time Models

5.1 Introduction
5.2 First-Order + Deadtime
5.3 Integrator + Deadtime
5.4 Other Continuous Models
 5.5 Discrete-Time Autoregressive Models
5.6 Parameter Estimation
5.7 Discrete Step and Impulse Response Models
5.8 Converting Continuous Models to Discrete
5.9 Digital Filtering
5.10 Summary
References

Chapter 6. Introduction to Feedback Control

Chapter 7. Model-Based Control

7.1 Introduction
7.2 Direct Synthesis
7.3 Internal Model Control
7.4 IMC-Based PID
7.5 IMC-Based PID Design for Processes with a Time Delay
7.6 IMC-Based PID Controller Design for Unstable
Processes
7.7 Summary
References

Chapter 8. PID Controller Tuning

8.1 Introduction
8.2 Closed-Loop Oscillation-Based Tuning
8.3 Tuning Rules for First-Order + Deadtime Processes
8.4 Digital Control
8.5 Stability of Digital Control Systems
8.6 Performance of Digital Control Systems
 8.7 Summary
References

Chapter 9. Frequency-Response Analysis

9.1 Motivation
9.2 Bode and Nyquist Plots
9.3 Effect of Process Parameters on Bode and Nyquist
Plots
9.4 Closed-Loop Stability
9.5 Bode and Nyquist Stability
9.6 Robustness
9.7 Matlab Control Toolbox: Bode and Nyquist Functions
9.8 Summary
Chapter 10. Cascade and Feedforward Control
10.1 Background
10.2 Introduction to Cascade Control
10.3 Cascade-Control Analysis
10.4 Cascade-Control Design
10.5 Feedforward Control
10.6 Feedforward Controller Design
10.7 Summary of Feedforward Control
10.8 Combined Feedforward and Cascade
10.9 Summary
Chapter 11. PID Enhancements

Chapter 12. Ratio, Selective, and Split-Range Control

12.1 Motivation
 12.2 Ratio Control
12.3 Selective and Override Control
12.4 Split-Range Control
12.5 Simulink Functions
12.6 Summary

Chapter 13. Control-Loop Interaction

13.1 Introduction
13.2 Motivation
13.3 The General Pairing Problem
13.4 The Relative Gain Array
13.5 Properties and Application of the RGA Sum of Rows
and Columns
13.6 Return to the Motivating Example
13.7 RGA and Sensitivity
13.8 Using the RGA to Determine Variable Pairings
13.9 Matlab RGA Function File
13.10 Summary
References
Appendix 13.1: Derivation of the Relative Gain for an n-
Input–n-Output System
Chapter 14. Multivariable Control
Chapter 15. Plantwide Control

Chapter 16. Model Predictive Control

Chapter 17. Summary

Module 1. Introduction to MATLAB

Module 2. Introduction to SIMULINK
Module 3. Ordinary Differential Equations

Module 4. MATLAB LTI Models

Module 5. Isothermal Chemical Reactor

Module 6. First-Order + Time-Delay Processes

Module 7. Biochemical Reactors

Module 8. CSTR
Module 9. Steam Drum Level
Module 10. Surge Vessel Level Control

Module 11. Batch Reactor

Module 12. Biomedical Systems

Module 13. Distillation Control

Module 14. Case Study Problems

Module 15. Plug Flow Reactor

Module 16. Digital Control
Preface
This content is currently in development.
About the Author
This content is currently in development.
Chapter 1. Introduction
The goal of this chapter is to provide a motivation for and an
introduction to process control and instrumentation. After studying this
chapter, the reader, given a process, should be able to
• Determine possible control objectives, input variables (manipulated
and disturbance) and output variables (measured and
unmeasured), and constraints (hard or soft), as well as classify the
process as continuous, batch, or semicontinuous.
• Assess the importance of process control from safety,
environmental, and economic points of view.
• Sketch a process instrumentation and control diagram.
• Draw a simplified control block diagram.
• Understand the basic ideas of feedback and feedforward control.
• Understand basic sensors (measurement devices) and actuators
(manipulated inputs).
• Begin to develop intuition about characteristic timescales of
dynamic behavior.
• Describe simple control loops associated with physiological systems.
The major sections of this chapter are as follows:
1.1 Introduction
1.2 Instrumentation
1.3 Process Models and Dynamic Behavior
1.4 Redundancy and Operability
1.5 Industrial IoT and Smart Manufacturing
1.6 Control Textbooks and Journals
1.7 A Look Ahead
 1.8 Summary

1.1 Introduction
Process engineers are often responsible for the operation of chemical
processes. As these processes become larger in scale and/or more
complex, the role of process automation becomes increasingly
important. The primary objective of this textbook is to teach process
engineers how to design and tune controllers for the automated
operation of chemical processes.
A conceptual process block diagram for a chemical process is shown in
Figure 1–1. Notice that inputs are classified as either manipulated or
disturbance, and the outputs are classified as measured or unmeasured
in Figure 1–1a. To automate the operation of a process, it is important
to use measurements of process outputs or disturbance inputs to make
decisions about the proper values of manipulated inputs. This is the
purpose of the controller shown in Figure 1–1b; the measurement and
control signals are shown as dashed lines. These initial concepts
probably seem very vague or abstract at this point. Do not worry,
because we present a number of examples in this chapter to clarify
these ideas.
The development of a control strategy consists of formulating or
identifying the following:
1. Control objective(s)
2. Input variables
3. Output variables
4. Constraints
5. Operating characteristics
6. Safety, environmental, and economic considerations
7. Control structure
We discuss in more detail the steps in formulating a control problem:
1. The first step of developing a control strategy is to formulate the
control objective(s). A chemical-process operating unit often
consists of several unit operations. The control of an operating unit
is generally reduced to considering the control of each unit
operation separately. Even so, each unit operation may have
multiple, sometimes conflicting objectives, so the development of
control objectives is not a trivial problem.

Figure 1–1 Conceptual process input/output block diagram

2. Input variables can be classified as manipulated or disturbance

variables. A manipulated input is one that can be adjusted by the
control system (or process operator). A disturbance input is a
variable that affects the process outputs but that cannot be
adjusted by the control system. Inputs may change continuously or
at discrete intervals of time.
3. Output variables can be classified as measured or unmeasured
variables. Measurements may be made continuously or at discrete
intervals of time.
4. All processes have certain operating constraints, which are
classified as hard or soft. An example of a hard constraint is a
minimum or maximum flow rate—a valve operates between the
extremes of fully closed or fully open. An example of a soft
constraint is a product composition—it may be desirable to specify
a composition between certain values to sell a product, but it is
possible to violate this specification without posing a safety or
environmental hazard.
5. Operating characteristics are usually classified as continuous,
batch, or semi-continuous (semibatch). Continuous processes
operate for long periods of time under relatively constant operating
conditions before being shut down for cleaning, catalyst
regeneration, and so forth. For example, some processes in the oil-
refining industry operate for 18 months between shutdowns. Batch
processes are dynamic in nature—that is, they generally operate
for a short period of time, and the operating conditions may vary
quite a bit during that time. Example batch processes include beer
or wine fermentation, as well as many specialty chemical
processes. For a batch reactor, an initial charge is made to the
reactor, and conditions (temperature, pressure) are varied to
produce a desired product at the end of the batch time. A typical
semibatch process may have an initial charge to the reactor, but
feed components may be added to the reactor during the course of
the batch run.
Another important consideration is the dominant timescale of a
process. For continuous processes, this is very often related to the
residence time of the vessel. For example, a vessel with a liquid
volume of 100 liters and a flow rate of 10 liters/minute would have
a residence time of 10 minutes; that is, on the average, an element
of fluid is retained in the vessel for 10 minutes.
6. Safety, environmental, and economic considerations are all very
important. In a sense, economics is the ultimate driving force—an
 unsafe or environmentally hazardous process will ultimately cost
more to operate because of fines paid, insurance costs, and so
forth. In many industries (petroleum refining, for example), it is
important to minimize energy costs while producing products that
meet certain specifications. Better process automation and control
allows processes to operate closer to optimum conditions and to
produce products where variability specifications are satisfied.
The concept of failsafe is always important in the selection of
instrumentation. For example, a control valve needs an energy
source to move the valve stem and change the flow; most often,
this is a pneumatic signal (usually 3–15 psig). If the signal is lost,
then the valve stem will go to the 3-psig limit. If the valve is air-to-
open, then the loss of instrument air will cause the valve to close;
this is known as a fail-closed valve. If, on the other hand, a valve is
air-to-close, when instrument air is lost, the valve will go to its fully
open state; this is known as a fail-open valve. These concepts are
illustrated in Figure 1–2.
7. The two standard control types are feedforward and feedback. A
feedforward controller measures the disturbance variable and
sends this value to a controller, which adjusts the manipulated
variable. A feedback control system measures the output variable,
compares that value to the desired output value, and uses this
information to adjust the manipulated variable. For the first part of
this book, we emphasize feedback control of single-input
(manipulated) and single-output (measured) systems. Determining
the feedback control structure for these systems consists of
deciding which manipulated variable will be adjusted to control
which measured variable. The desired value of the measured
process output is called the setpoint.
 Figure 1–2 Fail-closed and fail-open valves. The fail-closed valve
(left) has instrument air entering below the actuator, whereas the
fail-open valve (right) has instrument air engineering above the
actuator. In each case, the loss of instrument air will cause the
valve to move in the direction forced by the spring attached to the
actuator. Source: GlobalSpec, s.v. How can we change the action of
a control valve? Response by tonykuphaldt, September 2011,
http://cr4.globalspec.com/thread/75751/How-Can-We-Change-the-
Action-of-a-Control-Valve.

A particularly important concept used in control system design is

process gain. The process gain is the sensitivity of a process output to a
change in the process input. If an increase in a process input leads to
an increase in the process output, it is known as a positive gain.
Conversely, if an increase in the process input leads to a decrease in the
process output, it is known as a negative gain. The magnitude of the
process gain is also important. For example, a change in power (input)
of 0.5 kW to a laboratory-scale heater may lead to a fluid temperature
(output) change of 10°C; this change is a process gain (change in
output/change in input) of 20°C/kW. The same input power change of
0.5 kW to a larger-scale heater may yield an output change of only
0.5°C, corresponding to a process gain of 1°C/kW.
Once the control structure is determined, it is important to decide on
the control algorithm. The control algorithm uses measured output
variable values (along with desired output values) to change the
manipulated input variable. A control algorithm has a number of control
parameters, which must be tuned (adjusted) to have acceptable
performance. Often, the tuning is done on a simulation model before
implementing the control strategy on the actual process. Also, many
advanced strategies use model-based control, that is, controllers with a
built-in model of the process.
This approach is best illustrated by way of example. Because many
important concepts, such as control instrumentation diagrams and
control block diagrams, are introduced in the next examples, it is
important that you study them thoroughly.

Example 1.1: Surge Tank

Surge tanks are often used as intermediate storage for fluid streams
being transferred between process units. Consider the process flow
diagram shown in Figure 1–3, where a fluid stream from process 1 is
fed to the surge tank; the effluent from the surge tank is sent to
process 2.
There are obvious constraints on the height in this tank. If the tank
overflows, it may create safety and environmental hazards, which may
also have economic significance. Let us analyze this system using a
step-by-step procedure.
1. Control objective: The control objective is to maintain the height
within certain bounds. If it is too high, it will overflow, and if it is
too low, problems with the flow to process 2 may occur. Usually, a
specific desired height will be selected. This desired height is
known as the setpoint.
2. Input variables: The input variables are the flow from process 1
and the flow to process 2. Notice that an outlet flow rate is
considered an input to this system. The question is, which input is
manipulated and which is a disturbance? That depends. We discuss
this problem further in a moment.
3. Output variables: The most important output variable is the liquid
level. We assume that it is measured.

Figure 1–3 Tank level problem

4. Constraints: A number of constraints exist in this problem. There is

a maximum liquid level; if it is exceeded, the tank will overflow.
There are minimum and maximum flow rates through the inlet and
outlet valves.
5. Operating characteristics: We assume that this is a continuous
process, that is, that there is a continuous flow in and out of the
tank. It would be a semicontinuous process if, for example, there
was an inlet flow with no outlet flow (if the tank was simply being
filled).
6. Safety, environmental, and economic considerations: These
aspects depend somewhat on the fluid characteristics. If it is a
hazardous chemical, then there is a tremendous incentive from
safety and environmental considerations to not allow the tank to
 overflow. Indeed, this is also an economic consideration, because
injuries to employees or environmental cleanup costs money. Even
if the substance is water, it has likely been treated by an upstream
process unit, so losing water owing to overflow will incur an
economic penalty.
Safety considerations play an important role in the specification of
control valves (fail-open or fail-closed). For this particular problem,
the control-valve specification will depend on which input is
manipulated. This is discussed in detail shortly.
7. Control structure: There are numerous possibilities for control of
this system. We discuss first the feedback strategies, then the
feedforward strategies.

Feedback Control
The measured variable for a feedback control strategy is the tank
height. Which input variable is manipulated depends on what is
happening in process 1 and process 2. Let us consider two different
scenarios. In scenario 1, process 2 regulates the flow rate F2, leaving F1
to be manipulated by a controller. In scenario 2, process 1 regulates the
flow rate F1, leaving F2 to be manipulated by a controller. Here we
further discuss scenario 2; scenario 1 is used as a student exercise
(exercise 5).
Scenario 2 Process 1 regulates flow rate F1. This could happen, for
example, if process 1 is producing a chemical compound that must be
processed by process 2. Perhaps process 1 is set to produce F1 at a
certain rate. F1 is then considered “wild” (a disturbance) by the tank
process. In this case, we would adjust F2 to maintain the tank height.
Notice that the control valve should be specified as fail-open or air-to-
close so that the tank will not overflow on loss of instrument air or
other valve failure.
The control and instrumentation diagram for a feedback control
strategy for this scenario is shown in Figure 1–4a. Notice that the level
transmitter (LT) sends the measured height of liquid in the tank (hm) to
the level controller (LC). The LC compares the measured level with the
desired level (hsp, the height setpoint) and sends a pressure signal (Pv)
to the valve. This valve op pressure moves the valve stem up and
down, changing the flow rate through the valve (F2). If the controller is
designed properly, the flow rate changes to bring the tank height close
to the desired setpoint. In this process and instrumentation diagram,
we use dashed lines to indicate signals between different pieces of
instrumentation.

Figure 1–4 Instrumentation and control block diagrams for the

tank level feedback control problem. The outlet flow rate (F2) is
manipulated, the inlet flow rate (F1) is a disturbance, and the tank
height (h) is measured and controlled.

A simplified block diagram representing this system is shown in Figure

1–4b. Each signal and device (or process) is shown on the block
diagram. We use a slightly different form for block diagrams when we
use transfer function notation for control system analysis in Chapter 5,
“Empirical and Discrete-Time Models.” Note that each block represents a
dynamic element. We expect that the valve and LT dynamics will be
much faster than the process dynamics. We also see clearly from the
block diagram why this is known as a feedback control “loop.” The
controller “decides” on the valve position, which affects the outlet flow
rate (the manipulated input), which affects the level; the inlet flow rate
(the disturbance input) also affects the level. The level is measured,
and that value is fed back to the controller (which compares the
measured level with the desired level [setpoint]).

Feedforward Control
The previous feedback control strategy was based on measuring the
output (tank height) and manipulating an input (the outlet flow rate).
In this case, the manipulated variable is changed after a disturbance
affects the output. The advantage of a feedforward control strategy is
that a disturbance variable is measured and a manipulated variable is
changed before the output is affected. Consider the preceding case
where the inlet flow rate can be changed by the upstream process unit
and is therefore considered a disturbance variable. If we can measure
the inlet flow rate, we can manipulate the outlet flow rate to maintain a
constant tank height. This feedforward control strategy is shown in
Figure 1–5a, where FM is the flow measurement device and FFC is the
feedforward controller. The corresponding control block diagram is
shown in Figure 1–5b. F1 is a disturbance input that directly affects the
tank height; the value of F1 is measured by the FM device, and the
information is used by an FFC to change the manipulated input, F2.
 Figure 1–5 Instrumentation and control block diagrams for the
tank level feedforward control problem. The inlet flow rate is
measured and outlet flow rate is manipulated.

The main disadvantage to this approach is sensitivity to uncertainty. If

the inlet flow rate is not perfectly measured or if the outlet flow rate
cannot be manipulated perfectly, then the tank height will not be
perfectly controlled. With any small disturbance or uncertainty, the tank
will eventually overflow or run dry. In practice, FFC is combined with
feedback control to account for uncertainty. A feedforward/feedback
strategy is shown in Figure 1–6a, and the corresponding block diagram
is shown in Figure 1–6b. Here, the feedforward portion allows
immediate corrective action to be taken before the disturbance (inlet
flow rate) actually affects the output measurement (tank height). The
feedback controller adjusts the outlet flow rate to maintain the desired
tank height, even with errors in the inlet flow-rate measurement.
 Figure 1–6 Feedforward/feedback control of tank level. The inlet
flow rate is the measured disturbance, tank height is the measured
output, and outlet flow rate is the manipulated input.

Discussion of Level Controller Tuning and the

Dominant Timescale
Notice that we have not discussed the actual control algorithms; the
details of control algorithms and tuning are delayed until Chapter 5.
Conceptually, would you prefer to tune level controllers for fast or slow
responses?
When tanks are used as surge vessels, it is usually desirable to tune the
controllers for a slow return to the setpoint. This is particularly true for
scenario 2, where the inlet flow rate is considered a disturbance
variable. The outlet flow rate is manipulated but affects another
process. To avoid upsetting the downstream process, we would like to
change the outlet flow rate slowly yet fast enough that the tank does
not overflow or go dry.
Related to the controller tuning issue is the importance of the dominant
timescale of the process. Consider the case where the maximum tank
volume is 200 gallons and the steady-state operating volume is 100
gallons. If the steady-state flow rate is 100 gallons/minute, the
residence time would be 1 minute. Assume the inlet flow rate is a
disturbance and outlet flow rate is manipulated. If the feed flow rate
increased to 150 gallons/minute and the outlet flow rate did not
change, the tank would overflow in 2 minutes. On the other hand, if the
same vessel had a steady-state flow rate of 10 gallons/minute and the
inlet flow suddenly increased to 15 gallons/minute (with no change in
the outlet flow), it would take 20 minutes for the tank to overflow.
Clearly, controller tuning and concern about controller failure are
different for these two cases.
The first example was fairly easy compared with most control-system
synthesis problems in industry. Even for this simple example, we found
that many issues must be considered and a number of decisions
(specification of a fail-open or fail-closed valve, etc.) must be made.
Often, there are many (and usually conflicting) objectives, many
possible manipulated variables, and numerous possible measured
variables.
It is helpful to think of common, everyday activities in the context of
control to familiarize yourself with the types of control problems that
can arise in practice. Examples include taking a shower (which is
analyzed in the supplemental material) and driving a car. It is suggested
that you work through such examples provided in problem 1 in the
Student Exercises section of this chapter.
Examples of control loops abound in nature, and particularly in
physiological systems. The human body regulates many variables
through homeostasis; examples include temperature, blood pressure,
and blood glucose—which is the topic of the next example.
Example 1.2: Glucose Regulation by the
Pancreas
The primary energy source for the human body is glucose, so it is
important that the human body be able to regulate the blood glucose
concentration. The basic mechanisms for blood glucose regulation are
shown in Figure 1–7. If the blood glucose is high, due to a recently
consumed meal, for example, then the beta cells of the pancreas are
activated to produce insulin. The insulin then stimulates the uptake of
glucose from the blood into the cells for maintenance and growth and
the conversion of glucose into glycogen in the liver, thus lowering the
blood glucose. If the blood glucose is low, the alpha cells of the
pancreas promote the conversion of glycogen back into glucose in the
liver, thus raising the blood glucose.
Here we analyze this glucose regulatory system in the context of a
control problem:
1. Control objective: The control objective is to maintain the desired
glucose level, or setpoint.
2. Input variables: One manipulated input variable is the production
of insulin by the beta cells; another manipulated input is the
production of glucagon by the alpha cells. A number of disturbance
inputs affect blood glucose, including meals (that tend to raise
glucose) and exercise; aerobic exercise decreases glucose, whereas
vigorous anaerobic exercise can briefly increase the glucose level.
3. Output variables: The key output variable is blood glucose
concentration.
4. Constraints: There are possibly a number of constraints in this
problem. The insulin and glucagon values cannot go below zero,
and there are maximum rates on their values (as well as their rates
of change); these are likely hard constraints that may be time-
dependent. Soft constraints include lower and upper bounds on the
blood glucose concentration, as discussed further in the safety
analysis.
Figure 1–7 Blood glucose regulation by the pancreas. Source:
Craig Freudenrich, “How Diabetes Works,”
http://science.howstuffworks.com/life/human-
biology/diabetes1.htm.

5. Operating characteristics: This is a continuous process, with

discrete events such as meals and exercise.
6. Safety, environmental, and economic considerations: Too low of a
blood glucose level (known as hypoglycemia) has short-term
effects, including possible dizziness, while high blood glucose for an
extended period of time has long-term health consequences,
including retinal diseases.
 7. Control structure: In play are numerous control actions because
many hormones have a role in blood glucose regulation. The
diagram primarily describes feedback control because insulin and
glucagon rates are changed once there is a glucose change; as a
side note, this two-input strategy is similar to split-range control,
which is covered in Chapter 12, “Ratio, Selective, and Split-Range
Control.” Not discussed in the diagram are feedforward strategies—
for example, the salivation that occurs when eating is anticipated
may actually prime the beta cells for insulin production before the
blood glucose actually changes.
The glucose regulatory system is disrupted if an individual has diabetes,
of which there are two primary forms: type 1 and type 2. Roughly 5%
to 10% of people with diabetes have type 1, which was formerly known
as juvenile diabetes. In type 1 diabetes, most of the beta cells of the
pancreas cease to produce insulin. Thus, an individual with type 1
diabetes must take insulin subcutaneously—either with multiple daily
injections of insulin or with a continuous insulin infusion pump. As
shown in examples in this textbook, an automated insulin delivery
system (closed-loop artificial pancreas) consists of a glucose sensor,
insulin infusion pump, and control algorithm (usually on a wearable
microprocessor, such as a smartphone) to automatically adjust insulin
delivery rates based on the glucose signal (see Figure 1–8). In an
individual with type 2 diabetes, the pancreas still produces insulin, but
either the amount is insufficient or the individual is insulin resistant
(does not respond effectively to insulin). Usual interventions include
oral medications and changes in diet and exercise, although an
increasing number of people with type 2 diabetes use insulin and check
their blood glucose.
This chapter covered the important first step of control system
development, identifying seven basic steps in analyzing a process
control problem. We used simple examples with which you are familiar.
As you learn about more chemical, biological, and environmental
processes, you should get in the habit of thinking about them from a
process systems point of view, just as you have with these simple
systems.
 Figure 1–8 An automated insulin delivery system. The glucose
sensor sends a signal to the smartphone, which calculates the next
insulin delivery rate and sends a signal to the insulin pump, leading
to changes in the blood glucose concentration. In addition, the
smart watch provides feedforward information about exercise to
the smart phone.
(Photo: Carlo Prearo/Shutterstock; smart phone monitor:
Andrey_Popov/Shutterstock; smart watch: WakoPako/Shutterstock; wifi icon:
iconmonstr/Shutterstock)

1.2 Instrumentation
The example level-control problem had three critical pieces of
instrumentation: a sensor (measurement device), actuator
(manipulated input device), and controller. The sensor measured the
tank level, the actuator changed the flow rate, and the controller
determined, on the basis of the sensor signal, how much to vary the
actuator.
There are many common sensors used for chemical processes. These
include temperature, level, pressure, flow, composition, and pH. The
most common manipulated input is the valve actuator signal (usually
pneumatic).
Each device in a control loop must supply or receive a signal from
another device. When these signals are continuous, such as electrical
current or voltage, we use the term analog. If the signals are
communicated at discrete intervals of time, we use the term digital.

Analog
Analog or continuous signals provide the foundation for control theory
and design and analysis. A common measurement device might supply
either a 4- to 20-mA or 0- to 5-V signal as a function of time. Pneumatic
analog controllers (developed primarily in the 1930s, but used in some
plants today) use instrument air, as well as a bellows-and-springs
arrangement, to “calculate” a controller output based on an input from
a measurement device (typically supplied as a 3- to 15-psig pneumatic
signal). The controller output of 3 to 15 psig is sent to an actuator,
typically a control valve where the pneumatic signal moves the valve
stem. For large valves, the 3- to 15-psig signal might be amplified to
supply enough pressure to move the valve stem.
Electronic analog controllers typically receive a 4- to 20-mA or 0- to 5-V
signal from a measurement device and use an electronic circuit to
determine the controller output, which is usually a 4- to 20-mA or 0- to
5-V signal. Again, the controller output is often sent to a control valve
that may require a 3- to 15-psig signal for valve stem actuation. In this
case, the 4- to 20-mA current signal is converted to the 3- to 15-psig
signal using an I/P (current-to-pneumatic) converter.
Digital
Most devices and controllers are now based on digital communication
technology. A sensor may send a digital signal to a controller, which
then does a discrete computation and sends a digital output to the
actuator. Very often, the actuator is a valve, so there is usually a D/I
(digital-to-electronic analog) converter involved. If the valve stem is
moved by a pneumatic rather than electronic actuator, then an I/P
converter may also be used.
Digital control-system design techniques explicitly account for the
discrete (rather than continuous) nature of the control computations. If
small sample times are used, the tuning and performance of the digital
controllers is nearly equal to that of analog controllers, as shown in
Chapter 7, “Model-Based Control.”

Wireless
The cost to run wiring between sensors, controllers, and actuators can
be substantial. For noncritical applications, particularly for monitoring
and infrequent actions, it can be desirable to use wireless systems. This
has been done in household systems for years, with remote operation
of garage doors and, more recently, lighting systems. A biomedical
application that is studied several times in this text is automated insulin
delivery for people with type 1 diabetes. Bluetooth is used to send
signals from a glucose sensor to smart-phone or other control device
and to an insulin pump. Similar methods are likely to be used on select
chemical processes in the future.

Techniques Used in This Textbook

Most of the techniques used in this book are based on analog
(continuous) control. Although many of the control computations
performed on industrial processes are digital, the discrete sample time
is usually small enough that virtually identical performance to analog
control is obtained. Our understanding of chemical processes is based
on ordinary differential equations, so it makes sense to continue to
think of control in a continuous fashion. We find that controller tuning is
much more intuitive in a continuous, rather than discrete, framework.
In Chapter 17, “Summary,” we spend some time discussing techniques
that are specific to digital control systems, namely model predictive
control (MPC).

1.3 Process Models and Dynamic

Behavior
Thus far we have mentioned the term model a number of times, and
you probably have a vague notion of what we mean. The following
definition of a model is from the McGraw-Hill Dictionary of Scientific and
Technical Terms:
A mathematical or physical system, obeying
certain specified conditions, whose behavior is
used to understand a physical, biological, or
social system to which it is analogous in some
way.
In this textbook, model is taken to mean mathematical model. More
specifically, we develop process models. A working definition of process
model is
A set of equations (including the necessary input
data to solve the equations) that allows us to
predict the behavior of a chemical process.
Models play a very important role in control-system design. Models can
be used to simulate expected process behavior with a proposed control
system. Also, models are often embedded in the controller itself; in
effect, the controller can use a process model to anticipate the effect of
a control action. We can see from Example 1.1 that we at least need to
know whether an increase in the flow rate will increase or decrease the
tank level. For example, an increase in the inlet flow rate increases the
tank level (positive gain), whereas an increase in the outlet flow rate
decreases the tank level (negative gain). In order to design a controller,
then, we need to know whether an increase in the manipulated input
increases or decreases the process output variable; that is, we need to
know whether the process gain is positive or negative.
An example of a process model is shown next. A number of other
examples are developed in Chapter 2, “Fundamental Models.”

Example 1.3: Liquid Surge Vessel Model

In the development of a dynamic model, simplifying assumptions are
often made. Also, the model requirements are a function of the end-use
of the model. In this case, we are ultimately interested in designing a
controller and in simulating control-system behavior. Because we have
not covered control algorithms in depth, our objective here is to
develop a model that relates the inputs (manipulated and disturbance)
to measured outputs that we wish to regulate.
For this process, we first assume that the density is constant. The
model we develop should allow us to determine how the volume of
liquid in the vessel varies as a function of the inlet and outlet flow rates.
We list the state variables, parameters, and the input and output
variables. We must also specify the required information to solve this
problem (see Figure 1–2). The system is the liquid in the tank, and the
liquid surface is the top boundary of the system. The following notation
is used in the modeling equations:
F1 = inlet volumetric flow rate (volume/time)
F2 = outlet volumetric flow rate
V = volume of liquid in vessel
h = height of liquid in vessel
ρ = liquid density (mass/volume)
A = cross-sectional area of vessel
Here we write the balance equations based on an instantaneous rate of
change,
where the total mass of fluid in the vessel is Vρ, the rate of change is
dVρ/dt, and the density of the outlet stream is equal to the density of
the vessel contents:

Notice the implicit assumption that the density of fluid in the vessel
does not depend on position (the perfect mixing assumption). This
assumption allows an ordinary differential equation (ODE) formulation.
We refer to any system that can be modeled by ODEs as lumped
parameter systems. Also notice that the outlet stream density was
assumed to be equal to the density of fluid in the tank. Assuming that
the density of the inlet stream and fluid in the vessel are equal, this
equation is then reduced to1
1
It might be tempting to begin to directly write a “volume balance”
expression, which looks similar to Equation (1.3). We wish to make it
clear that there is no such thing as a volume balance, and Equation
(1.3) is only correct because of the constant density assumption. It is a
good idea to always write a mass balance expression, such as Equation
(1.2), before making assumptions about the fluid density, which may
lead to Equation (1.3).

In Equation (1.3), we refer to V as a state variable and to F1 and F2 as

input variables (even though F2 is an outlet stream flow rate). If density
remained in the equation, we would refer to it as a parameter.
To solve this problem, we must specify the inputs F1(t) and F2(t) and
the initial condition V(0). Direct integration of Equation (1.3) yields

If, for example, the initial volume is 500 liters, the inlet flow rate is 5
liters/second and the outlet flow rate is 4.5 liters/second, we find
 V(t) = 500 + 0.5 · t
Example 1.3 provides an introduction to the notion of states, inputs,
and parameters. Consider now the notion of an output. We may
consider fluid volume to be a desired output that we wish to control, for
example. In that case, volume would not only be a state, it would also
be considered an output. On the other hand, we may be concerned
about fluid height rather than volume. Volume and height are related
through the constant cross- sectional area, A:

Then we have the following modeling equations:

where V is a state, F1 and F2 are inputs, h is an output, and A is a

parameter. We could also rewrite the state variable equation to find

or

where fluid height is now the state variable. It should also be noted
that inputs can be classified as either manipulated inputs (that we may
regulate with a control valve, for example) or disturbance inputs. If we
wanted to measure fluid height and manipulate the flow rate of stream
1, for example, then F1 would be a manipulated input, while F2 would
be a disturbance input.
We have found that a single process can have different modeling
equations and variables, depending on assumptions and the objectives
used when developing the model.
The liquid level process is an example of an integrating process. If the
process is initially at steady state, the inlet and outlet flow rates are
equal (see Equation 1.3 or 1.7). If the inlet flow rate is suddenly
increased while the outlet flow rate remains constant, the liquid level
(volume) will increase until the vessel overflows. Similarly, if the outlet
flow rate is increased while the inlet flow rate remains constant, the
tank level will decrease until the vessel is empty.
In this book, we first develop process models based on fundamental or
first- principles analysis, that is, models that are based on known
physical-chemical relationships, such as material and energy balances,
as well as reaction kinetics, transport phenomena, and thermodynamic
relationships. We then develop empirical models. An empirical model is
usually developed on the basis of applying input changes to a process
and observing the response of measured outputs. Model parameters
are adjusted so that the model outputs match the observed process
outputs. This technique is particularly useful for developing models that
can be used for controller design.

1.4 Redundancy and Operability

While the focus of this book is on modeling and control system design,
it should be understood that processes need to be designed to ensure
safe operation even when components fail. For processes that operate
continuously for long periods of time, it is important to have redundant
pumps placed in parallel. Then, if one pump fails, the other can be
immediately switched on. On the other hand, due to high capital costs,
it is less common to have redundant compressors except in the case of
instrument air systems. Usually, when a process compressor fails, the
process must be shut down while the compressor is being repaired or
replaced.
In Example 1.1 and in most of the examples given in this textbook, we
use a simplified representation for the main components in a control
loop. A classic piping and instrumentation diagram (P&ID) would also
include pipe sizes and additional equipment for redundancy and safety.
Figure 1–9 is a characteristic process and instrumentation diagram
(P&ID without piping specifications) that shows redundant pumps,
check valves to assure flow through pumps occurs in one direction, a
pressure relief valve, and a bypass line around the control valve. When
the control valve fails, the adjacent block valves can be closed; the
control valve can then be removed and replaced. During the interim,
the bypass valve can be adjusted manually to maintain the desired flow
rate. Generally, these control valve “stations” are placed at ground level
for easy access, even if the pipeline is in a pipe rack far above the
ground. Pictures of redundant pumps and control valve with bypass are
shown in Figure 1–10.

1.5 Industrial IoT and Smart

Manufacturing
The terms Industry 4.0 and smart manufacturing are frequently used to
describe efforts in the manufacturing industries to make better use of
data and mathematical models to make manufacturing operations more
efficient. As the Internet has had a tremendous impact on our ability to
access data and communicate for personal applications, industry is
benefiting from a similar industrial internet of things (IIoT).
Manufacturers can now keep better track of the status of raw materials
being delivered to their facilities as well as products being shipped to
warehouses or directly to consumers. Industry 4.0 and smart
manufacturing techniques seek to make it easier to use data to improve
manufacturing performance. For example, a chemical process engineer
might wish to download data from a plant historian (database of plant
data), use the data to develop a model, and perform an optimization to
determine better operating conditions. In the past, this process required
a significant effort because each part of the system used different data
formats, and the software packages did not “talk” to each other. A goal
of smart manufacturing is to have a transparent framework to better
integrate each of these components.
Figure 1–9 Process and instrumentation diagram for surge drum
level control. There is a pressure relief valve on the drum,
redundant pumps, check valves on the discharge of each pump,
bypass around the control valve, and high (LAH) and low level
(LAL) alarms as part of the controller interface (LIC, level indicating
controller).
 Figure 1–10 Redundant pumps and control valve bypass

1.6 Control Textbooks

There are a large number of undergraduate control textbooks that focus
on control-system design and theory. The following books include an
introduction to process modeling and dynamics, in addition to control-
system design.
Chau, P.C. (2002). Process Control: A First Course with MATLAB. New
York: Cambridge University Press.
Coughanowr, D.R., and S.E. LeBlanc. (2009). Process Systems Analysis
and Control, 3rd ed. New York: McGraw-Hill.
Luyben, M.L., and W.L. Luyben. (1997). Essentials of Process Control.
New York: McGraw-Hill.
Luyben, W.L. (1990). Process Modeling Simulation and Control for
Chemical Engineers, 2nd ed. New York: McGraw-Hill.
Marlin, T.E. (2000). Process Control: Designing Processes and Control
Systems for Dynamic Performance, 2nd ed. New York: McGraw-Hill.
Available at http://www.pc-education.mcmaster.ca/Book_Links.htm.
Ogunnaike, B.A., and W.H. Ray. (1994). Process Dynamics, Modeling
and Control. New York: Oxford University Press.
Riggs, J.B., and M.N. Karim. (2016). Chemical and Bio-Process Control,
4th ed. Lubbock, TX: Ferret Publishing.
Seames, W.S. (2017). Designing Controls for the Process Industries.
Boca Raton, FL: CRC Press.
Seborg, D.E., T.F. Edgar, D.A. Mellichamp, and F.J. Doyle III. (2016).
Process Dynamics and Control, 4th ed., New York: Wiley.
Smith, C.A., and A.B. Corripio. (2005). Principles and Practice of
Automatic Process Control, 3rd ed. New York: Wiley.
Stephanopoulos, G. (1984). Chemical Process Control. Englewood Cliffs,
NJ: Prentice Hall.
Svrcek, W.Y., D.P. Mahoney, and B.R. Young. (2014). A Real-Time
Approach to Process Control, 3rd ed. Chichester, UK: Wiley.
 The following books are generally more applied, with specific
control applications detailed.
Levine, W.S. (ed.). (2010). The Control Handbook, 3rd ed., Boca Raton,
FL: CRC Press.
Liptak, B.G., and K. Venczel (eds.).(2005). Instrument Engineers
Handbook, Vol. 2: Process Control Volume, 4th ed. Boca Raton, FL:
CRC Press.
Luyben, W.L. (2006). Chemical Reactor Design and Control. New York:
Wiley.
Luyben, W.L. (2013). Distillation Design and Control Using Aspen
Simulation, 2nd ed. New York: Wiley.
Luyben, W.L., B.D. Tyreus, and M.L. Luyben. (1999). Plantwide Process
Control. New York: McGraw-Hill.
Schork, F.J., P.B. Deshpande, and K.W. Leffew. (1993). Control of
Polymerization Reactors. New York: Marcel Dekker.
Shinskey, F.G. (1977). Distillation Control. New York: McGraw-Hill.
Shinskey, F.G. (1996). Process Control Systems: Application, Design and
Tuning, 4th ed. New York: McGraw-Hill.
Shunta, J.P. (1995). Achieving World Class Manufacturing Through
Process Control. Upper Saddle River, NJ: Prentice Hall.

1.7 A Look Ahead

Chapter 2 develops fundamental models based on material and energy
balances, while Chapters 3 and 4 cover dynamic analysis. Chapter 5
shows how to develop empirical models from plant tests. Chapter 6 is
an introduction to feedback control and provides the first look at
quantitative control-system design procedures.
The best way to understand process control is to work many problems.
In particular, it is important to use simulation for complex problems. A
numerical package that is particularly useful for control-system analysis
and simulation is MATLAB; the SIMULINK block-diagram simulator is
particularly useful. If you are not familiar with MATLAB/SIMULINK, we
recommend that you work through the MATLAB and SIMULINK tutorials
(Modules 1 and 2). Simply reading the tutorials will not give you much
insight into the use of MATLAB; you must sit at a computer, work through
the examples, and try new ideas that you have.

1.8 Summary
You should now be able to formulate a control problem in terms of the
following:
• Control objective
• Inputs (manipulated or disturbance)
• Outputs (measured
• or unmeasured)
• Constraints (hard or soft)
• Operating characteristics (continuous, batch, semibatch)
• Safety, environmental, and economic issues
• Control structure (feedback, feedforward)
You should also be able to sketch control and instrumentation diagrams
and control block diagrams. In addition, you should be able to
recommend whether a control valve should be fail-open or fail-closed.
The following terms were introduced in this chapter:
• Actuator
• Air-to-close
• Air-to-open
• Algorithm
• Control block diagram
• Control valve
• Controller
• Digital
Another random document with
no related content on Scribd:
the rabble, as he runs by the monarch’s side, has wit enough to think
—‘There goes my royal self!’ From the most absolute despot to the
lowest slave there is but one step (no, not one) in point of real merit.
As far as truth or reason is concerned, they might change situations
to-morrow—nay, they constantly do so without the smallest loss or
benefit to mankind! Tyranny, in a word, is a farce got up for the
entertainment of poor human nature; and it might pass very well, if
it did not so often turn into a tragedy.
We once heard a celebrated and elegant historian and a hearty
Whig declare, he liked a king like George III. better than such a one as
Buonaparte; because, in the former case, there was nothing to
overawe the imagination but birth and situation; whereas he could
not so easily brook the double superiority of the other, mental as well
as adventitious. So does the spirit of independence and the levelling
pride of intellect join in with the servile rage of the vulgar! This is the
advantage which an hereditary has over an elective monarchy: for
there is no end of the dispute about precedence while merit is
supposed to determine it, each man laying claim to this in his own
person; so that there is no other way to set aside all controversy and
heart-burnings, but by precluding moral and intellectual
qualifications altogether, and referring the choice to accident, and
giving the preference to a nonentity. ‘A good king,’ says Swift, ‘should
be, in all other respects, a mere cypher.’
It has been remarked, as a peculiarity in modern criticism, that the
courtly and loyal make a point of crying up Mr. Young, as an actor,
and equally running down Mr. Kean; and it has been conjectured in
consequence that Mr. Kean was a radical. Truly, he is not a radical
politician; but what is as bad, he is a radical actor. He savours too
much of the reality. He is not a mock-tragedian, an automaton player
—he is something besides his paraphernalia. He has ‘that within
which passes shew.’ There is not a particle of affinity between him
and the patrons of the court-writers. Mr. Young, on the contrary, is
the very thing—all assumption and strut and measured pomp, full of
self-importance, void of truth and nature, the mask of the characters
he takes, a pasteboard figure, a stiff piece of wax-work. He fills the
throne of tragedy, not like an upstart or usurper, but as a matter of
course, decked out in his plumes of feathers, and robes of state, stuck
into a posture, and repeating certain words by rote. Mr. Kean has a
heart in his bosom, beating with human passion (a thing for the great
‘to fear, not to delight in!’) he is a living man, and not an artificial
one. How should those, who look to the surface, and never probe
deeper, endure him? He is the antithesis of a court-actor. It is the
object there to suppress and varnish over the feelings, not to give way
to them. His overt manner must shock them, and be thought a
breach of all decorum. They are in dread of his fiery humours, of
coming near his Voltaic Battery—they chuse rather to be roused
gently from their self-complacent apathy by the application of
Metallic Tractors. They dare not trust their delicate nerves within the
estuary of the passions, but would slumber out their torpid existence
in a calm, a Dead Sea—the air of which extinguishes life and motion!
Would it not be hard upon a little girl, who is busy in dressing up a
favourite doll, to pull it in pieces before her face in order to shew her
the bits of wood, the wool, and rags it is composed of? So it would be
hard upon that great baby, the world, to take any of its idols to
pieces, and shew that they are nothing but painted wood. Neither of
them would thank you, but would consider the offer as an insult. The
little girl knows as well as you do that her doll is a cheat; but she shut
her eyes to it, for she finds her account in keeping up the deception.
Her doll is her pretty little self. In its glazed eyes, its cherry cheeks,
its flaxen locks, its finery and its baby-house, she has a fairy vision of
her own future charms, her future triumphs, a thousand hearts led
captive, and an establishment for life. Harmless illusion! that can
create something out of nothing, can make that which is good for
nothing in itself so fine in appearance, and clothe a shapeless piece of
deal-board with the attributes of a divinity! But the great world has
been doing little else but playing at make-believe all its lifetime. For
several thousand years its chief rage was to paint larger pieces of
wood and smear them with gore and call them Gods and offer
victims to them—slaughtered hecatombs, the fat of goats and oxen,
or human sacrifices—shewing in this its love of shew, of cruelty, and
imposture; and woe to him who should ‘peep through the blanket of
the dark to cry, Hold, hold.’—Great is Diana of the Ephesians, was
the answer in all ages. It was in vain to represent to them, ‘Your Gods
have eyes but they see not, ears but they hear not, neither do they
understand’—the more stupid, brutish, helpless, and contemptible
they were, the more furious, bigotted, and implacable were their
votaries in their behalf.[43] The more absurd the fiction, the louder
was the noise made to hide it—the more mischievous its tendency,
the more did it excite all the phrenzy of the passions. Superstition
nursed, with peculiar zeal, her ricketty, deformed, and preposterous
offspring. She passed by the nobler races of animals even, to pay
divine honours to the odious and unclean—she took toads and
serpents, cats, rats, dogs, crocodiles, goats and monkeys, and hugged
them to her bosom, and dandled them into deities, and set up altars
to them, and drenched the earth with tears and blood in their
defence; and those who did not believe in them were cursed, and
were forbidden the use of bread, of fire, and water, and to worship
them was piety, and their images were held sacred, and their race
became Gods in perpetuity and by divine right. To touch them, was
sacrilege: to kill them, death, even in your own defence. If they stung
you, you must die: if they infested the land with their numbers and
their pollutions, there was no remedy. The nuisance was intolerable,
impassive, immortal. Fear, religious horror, disgust, hatred,
heightened the flame of bigotry and intolerance. There was nothing
so odious or contemptible but it found a sanctuary in the more
odious and contemptible perversity of human nature. The barbarous
Gods of antiquity reigned in contempt of their worshippers!
This game was carried on through all the first ages of the world,
and is still kept up in many parts of it; and it is impossible to
describe the wars, massacres, horrors, miseries and crimes, to which
it gave colour, sanctity, and sway. The idea of a God, beneficent and
just, the invisible maker of all things, was abhorrent to their gross,
material notions. No, they must have Gods of their own making, that
they could see and handle, that they knew to be nothing in
themselves but senseless images, and these they daubed over with
the gaudy emblems of their own pride and passions, and these they
lauded to the skies, and grew fierce, obscene, frantic before them, as
the representatives of their sordid ignorance and barbaric vices.
Truth, Good, were idle names to them, without a meaning. They
must have a lie, a palpable, pernicious lie, to pamper their crude,
unhallowed conceptions with, and to exercise the untameable
fierceness of their wills. The Jews were the only people of antiquity
who were withheld from running headlong into this abomination; yet
so strong was the propensity in them (from inherent frailty as well as
neighbouring example) that it could only be curbed and kept back by
the hands of Omnipotence.[44] At length, reason prevailed over
imagination so far, that these brute idols and their altars were
overturned; it was thought too much to set up stocks and stones,
Golden Calves and Brazen Serpents, as bonâ-fide Gods and
Goddesses, which men were to fall down and worship at their peril—
and Pope long after summed up the merits of the whole mythologic
tribe in a handsome distich—
‘Gods partial, changeful, passionate, unjust,
Whose attributes were rage, revenge, or lust.’

It was thought a bold stride to divert the course of our imaginations,

the overflowings of our enthusiasm, our love of the mighty and the
marvellous, from the dead to the living subject, and there we stick.
We have got living idols, instead of dead ones; and we fancy that they
are real, and put faith in them accordingly. Oh, Reason! when will
thy long minority expire? It is not now the fashion to make Gods of
wood and stone and brass, but we make kings of common men, and
are proud of our own handy-work. We take a child from his birth,
and we agree, when he grows up to be a man, to heap the highest
honours of the state upon him, and to pay the most devoted homage
to his will. Is there any thing in the person, ‘any mark, any
likelihood,’ to warrant this sovereign awe and dread? No: he may be
little better than an ideot, little short of a madman, and yet he is no
less qualified for king.[45] If he can contrive to pass the College of
Physicians, the Herald’s College dub him divine. Can we make any
given individual taller or stronger or wiser than other men, or
different in any respect from what nature intended him to be? No;
but we can make a king of him. We cannot add a cubit to the stature,
or instil a virtue into the minds of monarchs—but we can put a
sceptre into their hands, a crown upon their heads, we can set them
on an eminence, we can surround them with circumstance, we can
aggrandise them with power, we can pamper their appetites, we can
pander to their wills. We can do every thing to exalt them in external
rank and station—nothing to lift them one step higher in the scale of
moral or intellectual excellence. Education does not give capacity or
temper; and the education of kings is not especially directed to useful
knowledge or liberal sentiment. What then is the state of the case?
The highest respect of the community and of every individual in it is
paid and is due of right there, where perhaps not an idea can take
root, or a single virtue be engrafted. Is not this to erect a standard of
esteem directly opposite to that of mind and morals? The lawful
monarch may be the best or the worst man in his dominions, he may
be the wisest or the weakest, the wittiest or the stupidest: still he is
equally entitled to our homage as king, for it is the place and power
we bow to, and not the man. He may be a sublimation of all the vices
and diseases of the human heart; yet we are not to say so, we dare
not even think so. ‘Fear God, and honour the King,’ is equally a
maxim at all times and seasons. The personal character of the king
has nothing to do with the question. Thus the extrinsic is set up over
the intrinsic by authority: wealth and interest lend their countenance
to gilded vice and infamy on principle, and outward shew and
advantages become the symbols and the standard of respect in
despite of useful qualities or well-directed efforts through all ranks
and gradations of society. ‘From the crown of the head to the sole of
the foot there is no soundness left.’ The whole style of moral
thinking, feeling, acting, is in a false tone—is hollow, spurious,
meretricious. Virtue, says Montesquieu, is the principle of republics;
honour, of a monarchy. But it is ‘honour dishonourable, sin-bred’—it
is the honour of trucking a principle for a place, of exchanging our
honest convictions for a ribbon or a garter. The business of life is a
scramble for unmerited precedence. Is not the highest respect
entailed, the highest station filled without any possible proofs or
pretensions to public spirit or public principle? Shall not the next
places to it be secured by the sacrifice of them? It is the order of the
day, the understood etiquette of courts and kingdoms. For the
servants of the crown to presume on merit, when the crown itself is
held as an heir-loom by prescription, is a kind of lèse majesté, an
indirect attainder of the title to the succession. Are not all eyes
turned to the sun of court-favour? Who would not then reflect its
smile by the performance of any acts which can avail in the eye of the
great, and by the surrender of any virtue, which attracts neither
notice nor applause? The stream of corruption begins at the
fountainhead of court influence. The sympathy of mankind is that on
which all strong feeling and opinion floats; and this sets in full in
every absolute monarchy to the side of tinsel shew and iron-handed
power, in contempt and defiance of right and wrong. The right and
the wrong are of little consequence, compared to the in and the out.
The distinction between Whig and Tory is merely nominal: neither
have their country one bit at heart. Phaw! we had forgot—Our British
monarchy is a mixed, and the only perfect form of government; and
therefore what is here said cannot properly apply to it. But Might
before Right is the motto blazoned on the front of unimpaired and
undivided Sovereignty!—
A court is the centre of fashion; and no less so, for being the sink of
luxury and vice—
——‘Of outward shew
Elaborate, of inward less exact.’

The goods of fortune, the baits of power, the indulgences of vanity,

may be accumulated without end, and the taste for them increases as
it is gratified: the love of virtue, the pursuit of truth, grow stale and
dull in the dissipation of a court. Virtue is thought crabbed and
morose, knowledge pedantic, while every sense is pampered, and
every folly tolerated. Every thing tends naturally to personal
aggrandisement and unrestrained self-will. It is easier for monarchs
as well as other men ‘to tread the primrose path of dalliance’ than ‘to
scale the steep and thorny road to heaven.’ The vices, when they have
leave from power and authority, go greater lengths than the virtues;
example justifies almost every excess, and ‘nice customs curtsey to
great kings.’ What chance is there that monarchs should not yield to
the temptations of gallantry there, where youth and beauty are as
wax? What female heart can indeed withstand the attractions of a
throne—the smile that melts all hearts, the air that awes rebellion,
the frown that kings dread, the hand that scatters fairy wealth, that
bestows titles, places, honour, power, the breast on which the star
glitters, the head circled with a diadem, whose dress dazzles with its
richness and its taste, who has nations at his command, senates at
his controul, ‘in form and motion so express and admirable, in action
how like an angel, in apprehension how like a God; the beauty of the
world, the paragon of animals!’ The power of resistance is so much
the less, where fashion extends impunity to the frail offender, and
screens the loss of character.
‘Vice is undone, if she forgets her birth,
And stoops from angels to the dregs of earth;
But ’tis the fall degrades her to a whore:
Let greatness own her, and she’s mean no more.
Her birth, her beauty, crowds and courts confess,
 Chaste matrons praise her, and grave bishops bless.
In golden chains the willing world she draws,
And hers the Gospel is, and hers the laws.’[46]

The air of a court is not assuredly that which is most favourable to

the practice of self-denial and strict morality. We increase the
temptations of wealth, of power, and pleasure a thousand-fold, while
we can give no additional force to the antagonist principles of reason,
disinterested integrity and goodness of heart. Is it to be wondered at
that courts and palaces have produced so many monsters of avarice,
cruelty, and lust? The adept in voluptuousness is not likely to be a
proportionable proficient in humanity. To feed on plate or be clothed
in purple, is not to feel for the hungry and the naked. He who has the
greatest power put into his hands, will only become more impatient
of any restraint in the use of it. To have the welfare and the lives of
millions placed at our disposal, is a sort of warrant, a challenge to
squander them without mercy. An arbitrary monarch set over the
heads of his fellows does not identify himself with them, or learn to
comprehend their rights or sympathise with their interests, but looks
down upon them as of a different species from himself, as insects
crawling on the face of the earth, that he may trample on at his
pleasure, or if he spares them, it is an act of royal grace—he is
besotted with power, blinded with prerogative, an alien to his nature,
a traitor to his trust, and instead of being the organ of public feeling
and public opinion, is an excrescence and an anomaly in the state, a
bloated mass of morbid humours and proud flesh! A constitutional
king, on the other hand, is a servant of the public, a representative of
the people’s wants and wishes, dispensing justice and mercy
according to law. Such a monarch is the King of England! Such was
his late, and such is his present Majesty George the IVth!—
Let us take the Spirit of Monarchy in its highest state of exaltation,
in the moment of its proudest triumph—a Coronation-day. We now
see it in our mind’s eye; the preparation of weeks—the expectation of
months—the seats, the privileged places, are occupied in the
obscurity of night, and in silence—the day dawns slowly, big with the
hope of Cæsar and of Rome—the golden censers are set in order, the
tables groan with splendour and with luxury—within the inner space
the rows of peeresses are set, and revealed to the eye decked out in
ostrich feathers and pearls, like beds of lilies sparkling with a
thousand dew-drops—the marshals and the heralds are in motion—
the full organ, majestic, peals forth the Coronation Anthem—every
thing is ready—and all at once the Majesty of kingdoms bursts upon
the astonished sight—his person is swelled out with all the
gorgeousness of dress, and swathed in bales of silk and golden
tissues—the bow with which he greets the assembled multitude, and
the representatives of foreign kings, is the climax of conscious
dignity, bending gracefully on its own bosom, and instantly thrown
back into the sightless air, as if asking no recognition in return—the
oath of mutual fealty between him and his people is taken—the
fairest flowers of female beauty precede the Sovereign, scattering
roses; the sons of princes page his heels, holding up the robes of
crimson and ermine—he staggers and reels under the weight of royal
pomp, and of a nation’s eyes; and thus the pageant is launched into
the open day, dazzling the sun, whose beams seem beaten back by
the sun of royalty—there were the warrior, the statesman, and the
mitred head—there was Prince Leopold, like a panther in its dark
glossy pride, and Castlereagh, clad in triumphant smiles and snowy
satin, unstained with his own blood—the loud trumpet brays, the
cannon roars, the spires are mad with music, the stones in the street
are startled at the presence of a king:—the crowd press on, the
metropolis heaves like a sea in restless motion, the air is thick with
loyalty’s quick pants in its monarch’s arms—all eyes drink up the
sight, all tongues reverberate the sound—
‘A present deity they shout around,
A present deity the vaulted roofs rebound!’

What does it all amount to? A shew—a theatrical spectacle! What

does it prove? That a king is crowned, that a king is dead! What is the
moral to be drawn from it, that is likely to sink into the heart of a
nation? That greatness consists in finery, and that supreme merit is
the dower of birth and fortune! It is a form, a ceremony to which
each successor to the throne is entitled in his turn as a matter of
right. Does it depend on the inheritance of virtue, on the acquisition
of knowledge in the new monarch, whether he shall be thus exalted
in the eyes of the people? No;—to say so is not only an offence in
manners, but a violation of the laws. The king reigns in contempt of
any such pragmatical distinctions. They are set aside, proscribed,
treasonable, as it relates to the august person of the monarch; what is
likely to become of them in the minds of the people? A Coronation
overlays and drowns all such considerations for a generation to
come, and so far it serves its purpose well. It debauches the
understandings of the people, and makes them the slaves of sense
and show. It laughs to scorn and tramples upon every other claim to
distinction or respect. Is the chief person in the pageant a tyrant? It
does not lessen, but aggrandise him to the imagination. Is he the
king of a free people? We make up in love and loyalty what we want
in fear. Is he young? He borrows understanding and experience from
the learning and tried wisdom of councils and parliaments. Is he old?
He leans upon the youth and beauty that attend his triumph. Is he
weak? Armies support him with their myriads. Is he diseased? What
is health to a staff of physicians? Does he die? The truth is out, and
he is then—nothing!
There is a cant among court-sycophants of calling all those who are
opposed to them, ‘the rabble,’ ‘fellows,’ ‘miscreants,’ &c. This shews
the grossness of their ideas of all true merit, and the false standard of
rank and power by which they measure every thing; like footmen,
who suppose their masters must be gentlemen, and that the rest of
the world are low people. Whatever is opposed to power, they think
despicable; whatever suffers oppression, they think deserves it. They
are ever ready to side with the strong, to insult and trample on the
weak. This is with us a pitiful fashion of thinking. They are not of the
mind of Pope, who was so full of the opposite conviction, that he has
even written a bad couplet to express it:—
‘Worth makes the man, and want of it the fellow:
The rest is all but leather and prunella.’

Those lines in Cowper also must sound very puerile or old-

fashioned to courtly ears:—
‘The only amaranthine flower on earth
Is virtue; the only lasting treasure, truth.’

To this sentiment, however, we subscribe our hearts and hands.

There is nothing truly liberal but that which postpones its own claims
to those of propriety—or great, but that which looks out of itself to
others. All power is but an unabated nuisance, a barbarous
assumption, an aggravated injustice, that is not directed to the
common good: all grandeur that has not something corresponding to
it in personal merit and heroic acts, is a deliberate burlesque, and an
insult on common sense and human nature. That which is true, the
understanding ratifies: that which is good, the heart owns: all other
claims are spurious, vitiated, mischevious, false—fit only for those
who are sunk below contempt, or raised above opinion. We hold in
scorn all right-lined pretensions but those of rectitude. If there is
offence in this, we are ready to abide by it. If there is shame, we take
it to ourselves: and we hope and hold that the time will come, when
all other idols but those which represent pure truth and real good,
will be looked upon with the same feelings of pity and wonder that
we now look back to the images of Thor and Woden!
Really, that men born to a throne (limited or unlimited) should
employ the brief span of their existence here in doing all the mischief
in their power, in levying cruel wars and undermining the liberties of
the world, to prove to themselves and others that their pride and
passions are of more consequence than the welfare of mankind at
large, would seem a little astonishing, but that the fact is so. It is not
our business to preach lectures to monarchs, but if we were at all
disposed to attempt the ungracious task, we should do it in the words
of an author who often addressed the ear of monarchs.
‘A man may read a sermon,’ says Jeremy Taylor, ‘the best and most
passionate that ever man preached, if he shall but enter into the
sepulchres of kings. In the same Escurial where the Spanish princes
live in greatness and power, and decree war or peace, they have
wisely placed a cemetery where their ashes and their glory shall sleep
till time shall be no more: and where our kings have been crowned,
their ancestors lie interred, and they must walk over their grandsire’s
head to take his crown. There is an acre sown with royal seed, the
copy of the greatest change from rich to naked, from ceiled roofs to
arched coffins, from living like Gods to die like men. There is enough
to cool the flames of lust, to abate the height of pride, to appease the
itch of covetous desires, to sully and dash out the dissembling
colours of a lustful, artificial, and imaginary beauty. There the
warlike and the peaceful, the fortunate and the miserable, the
beloved and the despised princes mingle their dust, and pay down
their symbol of mortality, and tell all the world, that when we die our
ashes shall be equal to kings, and our accounts shall be easier, and
our pains for our crimes shall be less. To my apprehension, it is a sad
record which is left by Athenæus concerning Ninus, the great
Assyrian monarch, whose life and death is summed up in these
words: “Ninus, the Assyrian, had an ocean of gold, and other riches
more than the sand in the Caspian sea; he never saw the stars, and
perhaps he never desired it; he never stirred up the holy fire among
the Magi; nor touched his God with the sacred rod, according to the
laws; he never offered sacrifice, nor worshipped the Deity, nor
administered justice, nor spake to the people, nor numbered them;
but he was most valiant to eat and drink, and having mingled his
wines, he threw the rest upon the stones. This man is dead: behold
his sepulchre, and now hear where Ninus is. Sometime I was Ninus,
and drew the breath of a living man, but now am nothing but clay. I
have nothing but what I did eat, and what I served to myself in lust
is all my portion: the wealth with which I was blest, my enemies
meeting together shall carry away, as the mad Thyades carry a
raw goat. I am gone to Hell; and when I went thither, I carried
neither gold nor horse, nor a silver chariot. I that wore a mitre, am
now a little heap of dust!”‘—Taylor’s Holy Living and Dying.
 ON THE SCOTCH CHARACTER

(A Fragment.)
The Liberal.]
[1822.

The Scotch nation are a body-corporate. They hang together like a

swarm of bees. I do not know how it may be among themselves, but
with us they are all united as one man. They are not straggling
individuals, but embodied, formidable abstractions—determined
personifications of the land they come from. A Scotchman gets on in
the world, because he is not one, but many. He moves in himself a
host, drawn up in battle-array, and armed at all points against all
impugners. He is a double existence—he stands for himself and his
country. Every Scotchman is bond and surety for every other
Scotchman—he thinks nothing Scotch foreign to him. If you see a
Scotchman in the street, you may be almost sure it is another
Scotchman he is arm in arm with; and what is more, you may be sure
they are talking of Scotchmen. Begin at the Arctic Circle, and they
take Scotland in their way back. Plant the foot of the compasses in
the meridian, and they turn it by degrees to ‘Edina’s darling seat’—
true as the needle to the Pole. If you happen to say it is a high wind,
they say there are high winds in Edinburgh. Should you mention
Hampstead or Highgate, they smile at this as a local prejudice, and
remind you of the Calton Hill. The conversation wanders and is
impertinent, unless it hangs by this loop. It ‘runs the great mile, and
is still at home.’ You would think there was no other place in the
world but Scotland, but that they strive to convince you at every turn
of its superiority to all other places. Nothing goes down but Scotch
Magazines and Reviews, Scotch airs, Scotch bravery, Scotch
hospitality, Scotch novels, and Scotch logic. Some one the other day
at a literary dinner in Scotland apologised for alluding to the name of
Shakespear so often, because he was not a Scotchman. What a
blessing that the Duke of Wellington was not a Scotchman, or we
should never have heard the last of him! Even Sir Walter Scott, I
understand, talks of the Scotch novels in all companies; and by
waving the title of the author, is at liberty to repeat the subject ad
infinitum.
Lismahago in Smollett is a striking and laughable picture of this
national propensity. He maintained with good discretion and
method that oat-cakes were better than wheaten bread, and that the
air of the old town of Edinburgh was sweet and salubrious. He was a
favourable specimen of the class—acute though pertinacious,
pleasant but wrong.[47] In general, his countrymen only plod on with
the national character fastened behind them, looking round with
wary eye and warning voice to those who would pick out a single
article of their precious charge; and are as drawling and troublesome
as if they were hired by the hour to disclaim and exemplify all the
vices of which they stand accused. Is this repulsive egotism peculiar
to them merely in their travelling capacity, when they have to make
their way amongst strangers, and are jealous of the honour of the
parent-country, on which they have ungraciously turned their backs?
So Lord Erskine, after an absence of fifty years, made an appropriate
eulogy on the place of his birth, and having traced the feeling of
patriotism in himself to its source in that habitual attachment which
all wandering tribes have to their places of fixed residence, turned
his horses’ heads towards England—and farewell sentiment!
The Irish and others, who come and stay among us, however full
they may be of the same prejudice, keep it in a great measure to
themselves, and do not vent it in all companies and on all occasions,
proper or improper. The natives of the sister-kingdom in particular
rather cut their country like a poor relation, are shy of being seen in
one another’s company, and try to soften down the brogue into a
natural gentility of expression. A Scotchman, on the contrary, is
never easy but when his favourite subject is started, treats it with
unqualified breadth of accent, and seems assured that every one else
must be as fond of talking of Scotland and Scotchmen as he is.
 Is it a relic of the ancient system of clanship? And are the Scotch
pitted against all the rest of the world, on the same principle that
they formerly herded and banded together under some chosen
leader, and harried the neighbouring district? This seems to be the
most likely solution. A feeling of antipathy and partisanship, of
offensive and defensive warfare, may be considered as necessary to
the mind of a Scotchman. He is nothing in himself but as he is
opposed to or in league with others. He must be for or against
somebody. He must have a cause to fight for; a point to carry in
argument. He is not an unit but an aggregate; he is not a link, but a
chain. He belongs to the regiment. I should hardly call a Scotchman
conceited, though there is often something that borders strongly on
the appearance of it. He has (speaking in the lump) no personal or
individual pretensions. He is not proud of himself, but of being a
Scotchman. He has no existence or excellence except what he derives
from some external accident, or shares with some body of men. He is
a Brunonian, a Cameronian, a Jacobite, a Covenanter; he is of some
party, he espouses some creed, he is great in some controversy, he
was bred in some University, has attended a certain course of
lectures, understands Gaelic, and upon occasion wears the Highland
dress. An Englishman is satisfied with the character of his country,
and proceeds to set up for himself; an Irishman despairs of that of
his, and leaves it to shift for itself; a Scotchman pretends to
respectability as such, and owes it to his country to make you hate
the very name by his ceaseless importunity and intolerance in its
behalf. An Irishman is mostly vain of his person, an Englishman of
his understanding, a Frenchman of his politeness—a Scotchman
thanks God for the place of his birth. The face of a Scotchman is to
him accordingly the face of a friend. It is enough for him to let you
know that he speaks the dialect that Wilkie speaks, that he has sat in
company with the Author of Waverley. He does not endeavour to put
forward his own notions so much as to inform you of the school in
politics, in morals, in physic, in which he is an adept; nor does he
attempt to overpower you by wit, by reason, by eloquence, but to tire
you out by dint of verbal logic; and in common-places it must be
confessed that he is invincible. There he is teres et rotundus. He
fortifies himself in these, circumvallation within circumvallation, till
his strong-hold is impregnable by art and nature. I never knew a
Scotchman give up an argument but once. It was a very learned man,
the Editor of an Encyclopedia,—not my friend, Mr. Macvey Napier.
On some one’s proposing the question why Greek should not be
printed in the Roman type, this gentleman answered, that in that
case it would be impossible to distinguish the two languages. Every
one stared, and it was asked how at this rate we distinguished French
from English? It was the forlorn hope. Any one else would have
laughed, and confessed the blunder. But the Editor was a grave man
—made an obstinate defence (the best his situation allowed of) and
yielded in the forms and with the honours of war.
A Scotchman is generally a dealer in staple-propositions, and not
in rarities and curiosities of the understanding. He does not like an
idea the worse for its coming to him from a reputable, well-
authenticated source, as I conceive he might feel more respect for a
son of Burns than for Burns himself, on the same hereditary or
genealogical principle. He swears (of course) by the Edinburgh
Review, and thinks Blackwood not easily put down. He takes the
word of a Professor in the University-chair in a point of philosophy
as he formerly took the Laird’s word in a matter of life and death;
and has the names of the Says, the Benthams, the Mills, the
Malthuses, in his mouth, instead of the Montroses, the Gordons, and
the Macullamores. He follows in a train; he enlists under some
standard; he comes under some collateral description. He is of the
tribe of Issachar, and not of Judah. He stickles for no higher
distinction than that of his clan, or vicinage.[48] In a word, the Scotch
are the creatures of inveterate habit. They pin their faith on example
and authority. All their ideas are cast in a previous mould, and
rivetted to those of others. It is not a single blow, but a repetition of
blows, that leaves an impression on them. They are strong only in the
strength of prejudice and numbers. The genius of their greatest living
writer is the genius of national tradition. He has ‘damnable iteration
in him’; but hardly one grain of sheer invention. His mind is turned
instinctively backward on the past—he cannot project it forward to
the future. He has not the faculty of imagining any thing, either in
individual or general truth, different from what has been handed
down to him for such. Give him costume, dialect, manners, popular
superstitions, grotesque characters, supernatural events, and local
scenery, and he is a prodigy, a man-monster among writers—take
these actually embodied and endless materials from him, and he is a
common man, with as little original power of mind as he has
(unfortunately) independence or boldness of spirit!
The Scotch, with all their mechanical, wholesale attachment to
names and parties, are venal in politics,[49] and cowardly in
friendship. They crouch to power; and would be more disposed to fall
upon and crush, than come forward to the support of, a sinking
individual. They are not like La Fleur in the Sentimental Journey,
who advanced three steps forward to his master when the Gens-d’
Armes arrested him: they are like the Maitre d’ Hotel, who retired
three paces backwards on the same occasion. They will support a
generic denomination, where they have numbers to support them
again: they make a great gulp, and swallow down a feudal lord with
all the retinue he can muster—the more, the merrier—but of a single
unprotected straggler they are shy, jealous, scrupulous in the
extreme as to character, inquisitive as to connections, curious in all
the particulars of birth, parentage and education. Setting his
prejudices of country, religion, or party aside, you have no hold of a
Scotchman but by his self-interest. If it is for his credit or advantage
to stand by you, he will do it: otherwise, it will go very much against
both his stomach and his conscience to do so, and you must e’en shift
for yourself. You may trust something to the generosity and
magnanimity of an Englishman or an Irishman; they act from an
impulse of the blood or from a sense of justice: A Scotchman (the
exceptions are splendid indeed) uniformly calculates the
consequences to himself. He is naturally faithful to a leader, as I said
before, that is, to a powerful head; but his fidelity amounts to little
more than servility. He is a bigot to the shadow of power and
authority, a slave to prejudice and custom, and a coward in every
thing else. He has not a particle of mental courage. Cæsar’s wife was
not to be suspected; and it is the same with a Scotchman’s friend. If a
word is said against your moral character, they shun you like a
plague-spot. They are not only afraid of a charge being proved
against you, but they dare not disprove it, lest by clearing you of it
they should be supposed a party to what had no existence or
foundation. They thus imbibe a bad opinion of you from hearsay, and
conceal the good they know of you both from themselves and the
world. If your political orthodoxy is called in question, they take the
alarm as much as if they were apprehensive of being involved in a
charge of high treason. One would think that the whole country
laboured, as they did Sixty Years Since, under an imputation of
disaffection, and were exposed to the utmost vigilance of the police,
so that each person had too little character for loyalty himself to run
any additional risk by his neighbour’s bad name. This is not the case
at present: but they carry their precautions and circumspection in
this respect to such an idle and stupid excess, as can only be
accounted for from local circumstances and history—that is to say,
from the effects of that long system of suspicion, persecution and
surveillance, to which they were exposed during a century of
ridiculous (at least of unsuccessful) wars and rebellions, in favour of
the House of Stuart. They suffered much for King James and the
Good Cause; but since that time their self-love must be excused to
look at home. On my once complaining to a Scotchman of what I
thought a dereliction of his client’s cause by the counsel for the
defendant in a prosecution for libel, I received for answer—That ‘Mr.
—— had defended the accused as far as he could, consistently with
his character,’—though the only character the Learned Gentleman
could boast, had been acquired by his skill, if not his courage, in
resisting prosecutions of this kind.
The delicate sensibility (not to say soreness) of the Scotch in
matters of moral reputation, may in like manner be accounted for
(indirectly) from their domiciliary system of church-government, of
Kirk-assemblies, and Ruling Elders: and in the unprincipled
assurance with which aspersions of this sort are thrown out, and the
panic-terror which they strike into the timid or hypocritical, one may
see the remaining effects of Penance-Sheets and Cutty-Stools! Poor
Burns! he called up the ghost of Dr. Hornbook, but did not lay the
spirit of cant and lying in the Cunning North!
Something however, it must be confessed, has been done; a change
has been effected. Extremes meet; and the Saint has been (in some
instances) merged in the Sinner. The essential character of the
Scotch is determined self-will, the driving at a purpose; so that
whatever they undertake, they make thorough-stitch work, and carry
as far as it will go. This is the case in the pretensions some of their
writers have lately set up to a contempt for Cutty-Stools, and to all
the freedom of wit and humour. They have been so long under
interdict that they break out with double violence, and stop at
nothing. Of all blackguards (I use the term for want of any other) a
Scotch blackguard is for this reason the worst. First, the character
sits ill upon him for want of use, and is sure to be most outrageously
caricatured. He is only just broke loose from the shackles of
regularity and restraint, and is forced to play strange antics to be
convinced that they are not still clinging to his heels. Secondly,
formality, hypocrisy, and a deference to opinion, are the ‘sins that
most easily beset him.’ When therefore he has once made up his
mind to disregard appearances, he becomes totally reckless of
character, and ‘at one bound high overleaps all bound’ of decency
and common sense. Again, there is perhaps a natural hardness and
want of nervous sensibility about the Scotch, which renders them
(rules and the consideration of consequences apart) not very nice or
scrupulous in their proceedings. If they are not withheld by
conscience or prudence, they have no mauvaise honte, no
involuntary qualms or tremors, to qualify their effrontery and
disregard of principle. Their impudence is extreme, their malice is
cold-blooded, covert, crawling, deliberate, without the frailty or
excuse of passion. They club their vices and their venality together,
and by the help of both together are invincible. The choice spirits
who have lately figured in a much-talked-of publication, with ‘old
Sylvanus at their head,’—
‘Leaning on cypress stadle stout,’—

in their ‘pious orgies’ resemble a troop of Yahoos, or a herd of

Satyrs—
‘And with their horned feet they beat the ground!’—

that is to say, the floor of Mr. Blackwood’s shop! There is one other
publication, a match for this in flagrant impudence and dauntless
dulness, which is the John Bull. The Editor is supposed, for the
honour of Scotland, to be an Irishman. What the Beacon might have
proved, there is no saying; but it would have been curious to have
seen some articles of Sir Walter’s undoubted hand proceeding from
this quarter, as it has been always contended that Blackwood’s
Edinburgh Magazine was too low and scurrilous a publication for
him to have any share in it. The adventure of the Beacon has perhaps
discovered to Sir Walter’s admirers and the friends of humanity in
general, that
 ‘Entire affection scorneth nicer hands!’

Old Dr. Burney, about the middle of the last century, called one
morning on Thomson, the Author of The Seasons, at a late hour, and
on expressing his surprise at the poet’s not having risen sooner,
received for answer,—‘I had no motive, young man!’ A Scotchman
acts always from a motive, and on due consideration; and if he does
not act right or with a view to honest ends, is more dangerous than
any one else. Others may plead the vices of their blood in extenuation
of their errors; but a Scotchman is a machine, and should be
constructed on sound moral, and philosophical principles, or should
be put a stop to altogether.
 MY FIRST ACQUAINTANCE WITH POETS

The Liberal.]
[1823.

My father was a Dissenting Minister at W——m in Shropshire; and

in the year 1798 (the figures that compose that date are to me like the
‘dreaded name of Demogorgon’) Mr. Coleridge came to Shrewsbury,
to succeed Mr. Rowe in the spiritual charge of a Unitarian
Congregation there. He did not come till late on the Saturday
afternoon before he was to preach; and Mr. Rowe, who himself went
down to the coach in a state of anxiety and expectation, to look for
the arrival of his successor, could find no one at all answering the
description but a round-faced man in a short black coat (like a
shooting jacket) which hardly seemed to have been made for him,
but who seemed to be talking at a great rate to his fellow-passengers.
Mr. Rowe had scarce returned to give an account of his
disappointment, when the round-faced man in black entered, and
dissipated all doubts on the subject, by beginning to talk. He did not
cease while he staid; nor has he since, that I know of. He held the
good town of Shrewsbury in delightful suspense for three weeks that
he remained there, ‘fluttering the proud Salopians like an eagle in a
dove-cote; ‘and the Welch mountains that skirt the horizon with their
tempestuous confusion, agree to have heard no such mystic sounds
since the days of
‘High-born Hoel’s harp or soft Llewellyn’s lay!’

As we passed along between W——m and Shrewsbury, and I eyed

their blue tops seen through the wintry branches, or the red rustling
leaves of the sturdy oak-trees by the road-side, a sound was in my