Encyclopédie – Thermomètre Title: Original Title: Volume and Page: Author: Translator: Subject terms: -1 Thermometer Thermomètre Vol. 16 (1765), pp. 270-273 Jean-Baptiste le Rond d'Alembert David Fleming [david@andeanpast.org] Physics Thermometer is an instrument that is used to know, or more often to measure degrees of heat and of cold. See Heat and Thermoscope. A Dutch countryman, named Drebbel, [1] appears to have had the first idea for this instrument, at the beginning of the 17th century. There are different types of thermometers , of which the means of construction, the defects, the theories, etc. are given below. Former construction of a thermometer, for which the effect depends upon the rarefaction of the air. In a tube B C, Pl. of Pneumatics, fig 3. nº. 2. [2] to which is attached a glass sphere A B, one places an amount of plain water, mixed with aqua regia, [3] to keep the winter from freezing it; one adds to this mixture a tincture of vitriol, [4] dissolved to make it green. In filling the tube, one must take care to leave in the sphere and in the tube, enough air so that it can precisely fill the ball in the depths of winter, while the air is most condensed; and that it cannot drive all the fluid from the tube in the greatest heat of summer, when the air is at its greatest point of rarefaction. To the other end of the tube is attached another glass sphere C D, open on the side of the air at D: [5] to the two sides of the tube one attaches a scale, or a plate E F, upon which one marks the degrees, or a certain number of lines spaced equally one from another. In this state, when the air that surrounds the tube becomes hotter, the air sealed in the sphere and at the top of the tube, in dilating, will drive the fluid in the interior sphere, and consequently make the fluid descend: by contrast, when the air surrounding the tube comes colder, the air sealed in the tube, in condensing, will cause the fluid to rise. See Rarefaction and Condensation. Former construction of a thermometer with quicksilver . It is in the same manner and with the same precautions, that one inserts a small quantity of mercury or quicksilver, which should never exceed the width of a pea, in a tube B C, fig 4 nº. 2. that one bends in several places, so that one may manage it more easily, and so that there is less risk of breaking it; one divides the tube into a certain number of equal parts, which serve as a scale. In this state, the different moves of the mercury towards the sphere A, mark the increases in, or the different degrees of heat. The defects of these two thermometers are that they are liable to receive impressions from two causes: for it is not only an augmentation of the heat, but also an augmentation of the weight of the atmosphere, that will raise the fluid in the first, and the mercury in the second of these thermometers ; and on the other hand it could be the lessening of the weight, as well as the lessening of the heat of the atmosphere, that will bring down the fluid and the mercury in the two thermometers. See Barometer. Encyclopédie – Thermomètre -2 Construction of the common, or Florence thermometer. The academicians of the Cimento, [6] having noted the inconveniences, or defects of the thermometers above, attempted to build another by which they flattered themselves they could measure the degrees of heat and of cold of the air, by the rarefaction and condensation of spirit of wine; as the rarefaction and condensation of this liquor are less than those of the air, and as a consequence the variations in the degrees of heat must be and are much less detectable. Here is the construction of their thermometer. Onto some small pieces of turmeric, which is a sort of root used to cure jaundice, one pours a certain amount of rectified spirit of wine, to give it a red tint; then one filters the spirits of wine several times through grey paper, so that the solid particles of the root are separated from the fluid. With this spirit of wine thus tinted and prepared, one fills a glass sphere A B, fig. 5. nº. 2. and a tube B C, and so that all the spirit of wine does not descend at all into the sphere during the winter, it is correct to put this sphere into a small cup of snow mixed with salt: or if this instrument is made during the summer, one places the sphere into spring water impregnated with saltpeter, so that the spirit of wine being extremely condensed, one can see to what point it will fall during the sharpest cold. If the spirit of wine rises to a great height above the sphere, one must remove a part of it; and so that the tube is not excessively long, it is proper to put the sphere, filled with its spirit of wine, in boiling water, and to mark the furthest point to which the spirit of wine rises. It is at this point that the tube should be hermetically sealed with the flame of a lamp; and one attaches a scale to the two sides of the tube as with other thermometers. Spirit of wine, being subject to considerable rarefaction and condensation, dilates to an extent that exaggerates the heat of the air that surrounds it, and hence it rises in the tube; likewise, as the heat of the air diminishes, the spirit of wine descends in the tube, and one can see on the scale how many degrees it has risen or fallen from one day to another. If one has not taken care to drive from the fluid all the air it contains, something that is extremely difficult, one must leave air in the upper part of the tube. For otherwise if it finds itself without air, the fluid will not fail to separate itself at various places because of the air found in the interstices of its parts. However, if one leaves air in the upper part of the tube, this air produces another inconvenience, for by reason of its weight it should link to that below, and consequently prevent the fluid from rising; or if the fluid rises, it would compress the air, and consequently add to its elasticity. As experience has made it known that a lesser degree of heat more easily reveals itself to the spirit of wine in the sphere, which does not make a greater degree of heat, the rarefactions of the spirit of wine are not proportional to the causes that produce them. It therefore appears that the Florence thermometer, however widely used, gives anything but an exact measurement of heat and cold. To which one can add what Doctor Halley said in the Encyclopédie – Thermomètre -3 Philosophical Transactions, [7] which is, that he has learned from those who have kept the spirit of wine for long periods, that over time this fluid loses part of its expansive quality. In addition the glass is no less dilated by the heat than the fluid, and the cold makes both one and the other condense; consequently when the fluid is hot it does not rise as high as it would rise, if the sphere and the tube were always to have the same capacity. For the same reason the fluid falls less while it is cold, which it would not do if the glass did not condense. One cannot then properly know what the effect of the heat alone is on the fluid. One notices this very forcibly when one has just plunged a thermometer into a fluid that is very cold or boiling hard; for in the first case the fluid begins by rising, because the glass shrinks before the fluid, and when the condensation gets to the fluid it falls again; in the second case, for a contrary reason, the fluid first drops because of the dilation of the glass, and then climbs. Another major defect of this thermometer and others, is that these thermometers cannot be compared one to another. In truth, they do mark the different degrees of heat and of cold, but each one marks these only for itself and in its own fashion. Furthermore they do not at all start from a fixed point for heat or for cold; and this is again a fault common to all thermometers. It is with these instruments like two pendulums, which not having been first set during the hours of sunlight, will in truth mark whether one, or two, or several hours have passed, but will not at all mark the precise hour of the day or of the sun. Hence when the fluid has risen by one degree in two different thermometers, we cannot be assured that each of the two has received the same effect of an equal and additional heat, as it could be that the spirit of wine is not the same in one and the other; and given the proportion to which this spirit is more or less rectified, it will rise more or less in the tube for the same degree of heat. This is still not all, for in regulating the degrees of thermometers, one judges the uniformity of the height of the spirit of wine by the uniformity of the length of the tube, in supposing that the diameter of the tube is the same along its whole length, which happens very rarely; but there are so many irregularities in the interior, that to be filled a certain length of tube sometimes requires twice as much fluid as is needed to fill another tube of the same length and the same diameter; this can come only from the unequal widths of the walls of the tubes and the bumps and cavities that are always found on the interior surfaces, but above all these are almost always thicker at one end than they are at the other. This is why comparisons of thermometers are so faulty and so difficult to make; however what is more curious and more interesting in the use of thermometers, is the result of these comparisons; for it is by this method that one can know the degree of heat or of cold of another season, of another year, of another climate, and what is the degree of heat or of cold that can support men and animals. M. de Réaumur [8] has invented a new thermometer, and he claims that it is free of the defects mentioned above. The main feature of this thermometer is that it serves to compare the different degrees of heat to known measures, like the expansion and condensation of any fluid, such as spirit of wine. Encyclopédie – Thermomètre -4 In order to know the degrees of expansion or of condensation of spirit of wine, one needs only measure the growth or diminution of its volume, in comparison to the volume it has in a certain agreed state. M. de Réaumur takes for this state that of the fluid when it is surrounded by water that is beginning to freeze, or sooner by snow or crushed ice that is beginning to melt. M. de Réaumur begins by graduating the tube by filling it with water and with quicksilver, by means of different small measures that he ensures are very exact; then he empties the tube, and fills it with spirit of wine to about a third of its length above the sphere: then he plunges the sphere into ice, the fluid drops to a certain point at which it remains stationary: and then one adjusts or removes what is necessary of the spirit of wine so that the freezing point is precisely at the point that marks 1000 parts. When the freezing point is thus determined, one removes the little air there is in the tube, and seals it hermetically. Then one writes on one side 0 at the freezing point, and above the numbers 1, 2, 3, 4, etc. that will show the degrees of heat; in the same way below, going towards the sphere, one writes 1, 2, 3, 4, etc. that mark the degrees of cold. On the other side of the tube, opposite, one writes 1000, and as much below as above the numbers 1001, 1002, 1003, etc. that mark the degrees of condensation or of rarefaction of the fluid. It is absolutely necessary to use the same spirit of wine to have thermometers that can be comparable made according to these principles; and as he found some that have differing degrees of expansion, M. de Réaumur chose one in which the volume being 1000 at freezing point, becomes 1080 at the heat of boiling water. See the mém. de l’ac. royale des Sciences, ann. 1730, p. 645. hist. p. 15. item 1731. p. 354. hist. p. 7. In spite of all these precautions, M. Musschenbroek thinks that the thermometer of M. de Réaumur is still subject to several of the defects of the thermometer of Florence, to wit that over time the spirit of wine loses its expansive quality; that the glass dilates as well as the fluid; that in general the thermometers with spirit of wine can be used only to measure low degrees of heat; for from the moment the fluid begins to boil, they cannot mark any further. For rectified spirit of wine boils a little before water does, such that one cannot discover with the aid of this thermometer what is the degree of heat at which water boils, and even less that of greater heat, like that of boiling oil, or boiling soap, of mercury that boils, etc. last of all they cannot mark what the heat of molten metals can be. These are the objections of M. Musschenbroek against this thermometer, which we content ourselves simply with reporting, without any assurances, and without claiming to take from M. de Réaumur any of the utility of its discovery. Several authors have proposed various methods for finding a fixed point or a degree of cold and of heat, with the aim of regulating the other degrees on this degree, and to be able to compare the observations made at the same time, or at different times, and in different places. Some mark the point at which the fluid settles in winter when water begins to freeze, as also in summer when butter placed next to the sphere begins to melt; they divide the space between into two equal parts, of which the mid-point, following their measuring method, corresponds to moderate heat; and they divide each half into ten degrees, also adding four other degrees to each of the two ends. But this method supposes that the same degree of heat and of cold corresponds to the freezing of all sorts of water and to the melting of all sorts of butter; also, that all sorts of Encyclopédie – Thermomètre -5 thermometers experience the same impressions to the same degree of heat, although all these suppositions are contrary to experience. Others propose to place the sphere of the thermometer into a certain quantity of snow and salt, and to mark the point at which the fluid stops; then one lowers the thermometer into a deep cave where the outside air cannot enter; so that the fluid receiving the impressions of a temperate atmosphere, can indicate the degree of temperate heat. Finally one divides the space between into fifteen or more equal parts, which one then continues from there past each end: but this method is subject to the same disadvantages as the preceding. Dr. Halley takes as a fixed degree of heat that point at which spirit of wine begins to boil; but there is room to suspect that this expedient has no more basis than the others, while M. Amontons stopped as he did at the degree of heat corresponding to boiling water to make the scale for his mercury thermometer; but as the different specific gravities of waters mark a difference in their mass and their texture, it is very probable that the heat of all sorts of boiling waters is not the same, with the result that the fixed point remains undetermined. M. Musschenbroek seems to prefer to all other thermometers those made with mercury, which, according to him, has many advantages over spirit of wine, as one can have it pure, it always remains the same whether one has kept it for several years, and it always rarifies equally no matter how old it is. M. Musschenbroek claims that the principal defect of these thermometers is the expansion and contraction of the glass, which no-one knows how to prevent. However, he proposes various expedients to remedy this defect; one can see the details in the chapter on fire in his essay on physics. [9] However, he does not dare to assert that this thermometer yet has all the perfection that one could desire. But he believes it to be superior to all the others. The mercury thermometers most in use today are those of Fahrenheit [10] and of M. de Lisle. [11] These thermometers differ from the Florence thermometer, 1º. in that they use mercury well purged of air, in place of spirit of wine; 2º. in that the glass tube is hair-like and very narrow, and ends not in a sphere, but in a cylindrical bottle, with a capacity proportionate to the diameter of the tube; 3º. in that the divisions are much more exact, above all in the thermometer of M. de Lisle; for these divisions are not at all marked as equal parts along the length of the tube, acknowledging the interior inequalities that can be within it; but one successively adds to the tube a small quantity of mercury that is always the same, and which occupies more or less space of the length of the tube, according to whether the tube is narrower or wider inside; it is by this means that one can come to graduate the thermometers. Those who seek greater detail on this subject, can consult the essay on Physics of Musschenbroek, the miscellenea Berolinensia vol. IV p. 343. and the appendix at the end of the physics lessons of M. Cottes, [12] translated into French, and printed in Paris in 1742 (O). For several years the name thermometer has also been given to a machine made of two metals, which at the same time that it indicates variations in cold and heat, serves to compensate errors resulting from them in pendulum clocks. M. Graham, the distinguished member of the Royal Society of London, was one of the first to attempt to remedy the errors caused in pendulum clocks from the contraction or expansion of Encyclopédie – Thermomètre -6 metals by the different degrees of heat and of cold they experience. [13] See Metal. He sought for this result to replace the pendulum bob with a tube containing mercury, so that when this fluid expands or contracts from heat or cold, it climbs or descends in the tube, and thereby causes the center of oscillation to rise or fall by precisely the same amount it had fallen or risen, through the lengthening of the pendulum rod. The author, apparently, has not derived all the advantages that he might have desired from his invention, for it was not at all used in the pendulum that the academicians took to the north. [14] To get to the same result, M. le Roy used a totally different method, and without doubt preferable. He places perpendicularly to the horizon, on the cock, or in other words the bracket that hold the pendulum, a copper tube T Y ( See Cock [Cock (clock); Cock (watch)]; and our clockmaking plates), [15] 54 inches long, within which passes a steel bar of the same length; its upper end is at the opening of the tube, and at the lower end it is attached to the suspension springs R R, in such a manner that the weight of the pendulum only places a strain on the bracket, after it has acted on the bar and on the tube; by this means the heat, lengthening the brass tube more than the steel bar it contains, causes the pendulum to rise in the slot in the bracket, and shrinks it by as much as it expands, from the excess of the heat, which produces an exact compensation. The effect I have just described, is shown by an index E where the lower end of the bar covers the divisions along the edge. As metals of the same name are not always entirely the same, and experience having shown that different types of yellow copper expand more or less from the heat, according to the proportion of coke or other ingredients included in their makeup: it is relevant to report here the method that M. le Roy put into use to make the length of his tube proportional to that of his rod; one may thereby judge the exactitude that one must apply to its construction. Apart from the index of which we have already spoken, M. le Roy places a second of the same type, at I, at the bottom of the pendulum, as close as possible to its center of oscillation, so that it can be moved by the end of its rod. He then strongly heats the part where this apparatus is located; should he see that the lower index does not move at all, all while the upper runs along all the divisions on its edge, he concludes that the tube has made the pendulum bob rise by as much as it fell because of the expansion; should by contrast he see that it moves, he lengthens or shortens the tube, according to the path shown by the lower index. Sometimes he also puts two tubes one inside the other, and having attached some iron blades to the bottom of the inner one intended to carry the bar to which are fixed the suspension springs, he makes the upper end of the inner tube support the outer tube; by this method, the height of the tube is reduced by half. See Suspension. Many persons, following on from this thermometer, invented in 1738, have imagined others, where they have combined in different manners rods of copper and of steel to produce the same effect, Encyclopédie – Thermomètre -7 but one can say that all the methods that have been brought into use, that of M. le Roi is incontestably the best, as much for its simplicity as for its solidity: for nothing is more proper to support a burden, than the tube; but in order to leave nothing to be desired, I will report on a second which was invented by M. Ellicott, the renowned London clock-maker, [16] it would be useful in the case in which one wished to suspend the pendulum on a knife-edge; and in such a case in which the length of the tube above could lead to some awkwardness, in connection with the arrangement of the places, where the pendulum should be set: according to this new method, at the top of the steel rod of the pendulum, one attaches another of bronze of the same length; it is as one sees held within the width of the steel rod, its extremity supports itself on the ends of the levers E X fitted to the steel rod, and moves around the points I; on the extremities X some levers carry the ends of the screws V V, which hold onto the hollow pendulum bob T T T T inside. Following this description, one can easily understand the effect, for the copper rod I, I, etc. lengthening more than that of steel from the heat, will press at E on the ends of the levers X E, and consequently will make the pendulum bob rise a little, to the middle of the screws V V, whose ends can more or less approach near the center I: one can vary the effect of the rod I, I, I, by lengthening or shortening the arm of lever I X. Translator’s notes 1. Cornelis Jacobszoon Drebbel (1572-1633) of Alkmaar in Holland was a prolific inventor whose interests included optics, chemistry, water management systems, and measurement. He spent part of his life in England in the service of James I and worked on the problems of draining the Norfolk marshes. See Sir Anthony Thomas (1629) The propositions of Sir Anthony Thomas, knight, and Iohn Worsop, Esquire: for making of the bargaine with the country, and Henry Briggs, professor of the mathematicks in the vniuersitie of Oxford, Heldebrand Pruson, citizen and salter of London, and Cornelius Drible, engeneere, with the rest of the undertakers for the drayning of the Levell within the sixe counties of Norfolke, Suffolke, Cambridge, Isle of Elie, Huntington, North-hampton and Lincolne-shire, on the southside of Gleane. London. 2. This volume of plates was not published. 3. “Royal water” is a mixture of nitric acid and hydrochloric acid in the proportions of one part nitric and three parts hydrochloric acid. It is one of the few chemical compounds that will dissolve gold. 4. “Green vitriol” is another name for ferrous sulphate, found in natural mineral form and used as a colorant. 5. That is, the sphere CD is attached to the top of the tube containing the treated water so that the air in the sphere can mix with that in the tube, but the sphere and tube are hermetically sealed from the outside atmosphere. 6. The Accademia del Cimento (Academy of Experiment) in Florence was founded in 1657 and closed in 1667. Encyclopédie – Thermomètre -8 7. Edmund Halley (1693) An Account of Several Experiments Made to Examine the Nature of the Expansion & Contraction of Fluids by Heat & Cold, in Order to Ascertain the Divisions of the Thermometer, & to Make That Instrument, in All Places, without Adjusting by a Standard. By Mr. Edm. Halley, S. R. S. Phil. Trans. January 1, 1693, Vol. 17, Nº 192-206, pages 650-656. 8. René Antoine Ferchault de Réaumur (1683-1757) created a temperature scale based on the freezing and boiling points of water. Réaumur set the freezing point of water at 0° on his scale, and the boiling point of water at 80° on the same scale. 9. Petrus van Musschenbroek (1739) Essai de physique avec Une description de nouvelles sortes de machines pneumatiques et un recueil d’experiences par J.V.M. / traduit du Hollandois par Pierre Massuet. Leyden: Samuel Luchtman. 10. Daniel Gabriel Fahrenheit (1686-1736) developed a thermometer scale that is still in general use. See Arthur von Oettingen (1894) Abhandlungen über thermometrie, von Fahrenheit, Réaumur, Celsius, (1724, 1730-1733, 1742) Hrsg. von A.J. von Oettingen. Mit 17 figuren im text. Leipzig: W. Engelmann. 11. Joseph Nicolas de L’isle (1738) Memoires pour servir a l’histoire & au progrès de l’astronomie, de la geographie & de la physique, recueillis de plusieurs dissertations lües dans les assemblées de l’Academie roiale des sciences de Paris, & de celle de St. Petersbourg, qui n’ont point encore été imprimées; comme aussi de plusieurs pieces nouvelles, observations & reflexions. St. Pétersbourg: Imprimerie de l’Academie des sciences. 12. Roger Cotes (1682-1716), English mathematician and colleague of Isaac Newton. Leçons de physique experimentale / traduites de l'anglais de M. Roger Côtes, 1742. 13. George Graham (1726) A Contrivance to Avoid the Irregularities in a Clock’s Motion, Occasion’d by the Action of Heat & Cold upon the Rod of the Pendulum. By Mr. George Graham, Watch-Maker, F.R.S. Philosophical Transactions of the Royal Society 1726-1727 34, 40-44, published 1 January 1726. 14. A reference to the French geodesic expedition to Lapland in 1736 to determine the shape of the earth. The Lapland mission was led by Academician Pierre Louis Moreau de Maupertuis (1698-1759). See his 1738 publication La figure de la terre, déterminée par les observations de Messieurs de Maupertuis, Clairaut, Camus, Le Monnier ...& de M. l'Abbé Outhier ... accompagnes de M. Celsius ... faites par ordre du roy au cercle polaire, par M. de Maupertuis. Paris: Impremerie royale. 15. For an understanding of the technical aspects of this discussion, see Plate VIII N of the article Horlogerie: “Thermomêtre et Cadrature d’une Pendule d’Equation de Julien de Roy”. 16. John Ellicott (1706-1772) experimented with methods to make pendulum clocks more accurate. See Ellicott (1753) A description of two methods, by which the irregularities in the motion of a clock, arising from the influence of heat & cold upon the rod of the pendulum, may be prevented. By John Ellicot, F.R.S. Read at the Royal Society, June 4, 1752. London: R. Willock. Encyclopédie – Thermomètre -9 Original Version (ARTFL): Link Availability: This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License. To use this work in a way not covered by the license, please see http://quod.lib.umich.edu/d/did/terms.html. URL: http://hdl.handle.net/2027/spo.did2222.0003.320 Citation (MLA): d'Alembert, Jean-Baptiste le Rond. “Thermometer.” The Encyclopedia of Diderot & d’Alembert Collaborative Translation Project. Translated by David Fleming. Ann Arbor: Michigan Publishing, University of Michigan Library, 2017. Web. <http://hdl.handle.net/2027/spo.did2222.0003.320> (accessed [fill in today’s date in the form April 18, 2009 and remove square brackets]). Trans. of “Thermomètre,” Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, vol. 16. Paris, 1765. Citation (Chicago): d'Alembert, Jean-Baptiste le Rond. “Thermometer.” The Encyclopedia of Diderot & d’Alembert Collaborative Translation Project. Translated by David Fleming. Ann Arbor: Michigan Publishing, University of Michigan Library, 2017. http://hdl.handle.net/2027/spo.did2222.0003.320 (accessed [fill in today’s date in the form April 18, 2009 and remove square brackets]). Originally published s “Thermomètre,” Encyclopédie ou Dictionnaire raisonné des sciences, des arts et des métiers, 16:270–273 (Paris, 1765).