NA TORE 



573 



THURSDAY, APRIL 19, 1894. 



THE THE OR V OF HE A T. 

 The Theory of Heat. By Thomas Preston, M.A. Pp. 

 xvi. and 719. (London : Macmillan and Co., 1S94.) 



F'ROM the point of view of scope and comprehen- 

 siveness this work forms the most important trea- 

 tise on heat that has yet been published in this country. 

 It does not teem with new ideas or new modes of pre- 

 sentation, lilce the book bearing the same title that Max- 

 well contributed to a series of text-books announced as 

 primarily intended for the instruction of artisans ; nor 

 does it appeal to the general reader in the same way as 

 the remarkable book in which Tyndall undertook to 

 present to him the " rudiments of a new philosophy " 

 a generation ago. Each in its own way, both the 

 books we have referred to far surpass the one now 

 before us in originality and individuality. These 

 qualities, indeed, are not specially characteristic of the 

 present work. A systematic and comparatively com- 

 plete presentation of the present state of the science 

 of heat, both in respect of experimental methods and 

 theoretical developments, has been what the author 

 has striven to furnish, and in this he has attained 

 a degree of success which makes his book one of great 

 value, and amounts to a kind of originality. In French 

 and German we find works dealing with the whole round 

 of Physics (^..i,'., Jamin and Bouty, WuUner), in which 

 the section devoted to Heat is planned on as comprehen- 

 sive a scale and carried out in as much detail as the 

 work before us, but hitherto no similar treatises have 

 existed in English. Mr. Preston's book thus supplies, 

 for the branch of which he treats, a distinct want in our 

 scientific literature, and it may be confidently expected to 

 contribute a good deal towards raising the culture and 

 widening the scientific horizon of English students. 



Mr. Preston deals with his subject in eight chapters, 

 each of which is divided into sections, and these again 

 into articles. The articles are numbered consecutively 

 throughout for facility of reference. 



Chapter i. is entitled " Preliminary Sketch," and is 

 partly historical and partly expository. It contains some 

 valuable and suggestive matter, specially perhaps in the 

 section relating to energy ; but on the whole it does not 

 strike us as equally successful with the parts in which 

 the author gets to closer quarters with his subject. He 

 sets out with a luxuriance of language which happily 

 makes room after a page or two to something more 

 common-place and business-like : — 



" With its return in springtime the bud breaks into 

 blossom, and new life animates \sic\ the vegetable king- 

 dom. By its agency the incubation of the &gg progresses, 

 a living thing is brought into the world, and heat is still 

 necessary to its support. Finally, to the power which 

 man has acquired over it is due that supernatural 

 strength which has made him superior to all other 

 animals, and master of land and sea." 



But this is only while we are getting under way : once 

 fairly started, there is practically nothing more to fear. 



Opinions may fairly dilTer as to the value of an his- 

 torical sketch so very much in outline as that contained 

 NO. 1277, VOL. 49] 



in the author's first dozen pages. Our own opinion is 

 that the value is little or nothing. It is impossible in a 

 two-line phrase to indicate the points of view and general 

 intellectual surroundings that gave birth to the scientific 

 doctrines of former times. This part of the book accord- 

 ingly seems defective in historical perspective and 

 " relativity " of view. One statement, not referring to 

 the far past, seems to call for modification or 

 explanation : — 



" The systematic study of heat, as a distinct branch of 

 experimental science, commenced little more than half a 

 century ago.'' 



Such a period can hardly be made to include Black, 

 Lavoisier, Laplace, Rumford, Leslie, Gay-Lussac, Dulong 

 and many others whom the rest of the book shows that 

 our author cannot have intended to overlook or under- 

 value. 



Chapter ii. deals with " Thermometry," and contains 

 a good and full description of many of the methods that 

 have been devised for the measurement of temperatures. 

 The general nature of the problem of thermometry is 

 dealt with to some extent in chapter i., but with some 

 want of distinctness, and we do not find anywhere a 

 clear statement that what is. commonly called measuring 

 a temperature is in reality the comparison oi sltl interval 

 of temperature with a conventionally adopted standard 

 interval. The only problem is to find a satisfactory 

 experimental method of making the comparison. As 

 to this, there is again a want of definiteness. At page 

 17 we are told about the mercury thermometer that " we 

 have now a perfectly definite standard of reference for all 

 other temperatures"; but on page 115 we are told that, in 

 consequence of differences in the glass, two mercury ther- 

 mometers "generally differ, sometimes considerably, in 

 their indications," and should therefore be " corrected by 

 direct comparison with the standard air thermometer.^' 

 Apparently, if it were practicable to construct mercurial 

 thermometers to read accurately alike, no appeal to the 

 air thermometer would be wanted. It is not till page 

 120 that we learn that — 



" The ultimate standard for thermometry is, for reasons 

 which will appear later, afforded by the use of a per- 

 manent gas, such as hydrogen or nitrogen." 



Of course the reference here is to Lord Kelvin's ther- 

 modynamic correction of the gas thermometer, but the 

 secret is not fully revealed till we get to the last section 

 of the last chapter of the book. We may admit that, 

 with the arrangement of matter which the author has 

 adopted, the full discussion of this point could not well 

 come earlier than he has placed it ; but surely it would be 

 possible, without going beyond quite elementary con- 

 siderations, to show why a gas thermometer affords a 

 more trustworthy comparison of intervals of temperature 

 than a mercurial thermometer. 



The care bestowed on the more purely descriptive 

 parts of this chapter induce us to mention that the author 

 does not seem to have come across M. Guiilaume's recent 

 work in the same field, or to be acquainted with the high- 

 rano-e mercurial thermometers now made in Germany, or 

 the instruments made in this country by Messrs. Baly 

 and Chorley with sodium-potassium alloy. Kopp's cor- 

 rection for the exposed part of the stem is also omitted : 



B B 



