574 



NA TURE 



[April 19, 1894 



it may not be quite accurate, but it gives in most cases a 

 very fair approximation. The method (page 104) of 

 cleaning the bulb and stem of mercurial thermometers, 

 with boiling nitric acid before filling, has not yet, so far 

 as we know, been generally adopted. 



Chapter iv. deals with Calorimetry. The general notion 

 of a quantity of heat introduced in the first chapter is 

 here used without further discussion of what is essentially 

 implied in it. This leaves it on a not altogether satisfac- 

 tory basis. The notion as first brought in is somewhat 

 metaphysical : 



" in order to account for the sensation experienced in 

 presence of a hot body, an active agent is postulated 

 and the name given to this agent is heat." (p. 21.) 



This is hardly the ground, or the kind of ground, on 

 which the idea of heat as a measurable quantity rests. 

 We need to recognise that objects which can give rise to 

 the sensation of heat can also produce various measur- 

 able effects — can melt ice, for instance ; that the power 

 to produce these effects is communicable from one body 

 to another ; that, unless there is expenditure of some 

 form of energy, such power when possessed by one 

 body is exhausted in proportion as it is transferred to 

 others ; and so on. 



It is much to be desired that writers on physics would 

 make a point of following, whenever possible, the precise 

 and carefully considered terminology adopted by Prof. 

 Everett in " The C.G.S. System of Units." They would 

 not then speak of thermal capacity and specific heat as 

 though they meant the same thing. 



A useful part of this chapter is a good description, with 

 figures, of Joly's condensation-method of calorimetry. 



Chapter v., extending to more than 170 pages, is 

 devoted to "Change of State." It contains valuable 

 discussions of the properties of bodies at and near the 

 " critical point " and the equations by which Van der 

 Waals and Clausius have attempted to express generally 

 the properties of fluids in relation to pressure, volume, 

 and temperature. 



This chapter contains much valuable matter that has 

 not previously been made so fully accessible to English 

 students. We are, however, rather surprised not to find 

 any reference to the experiments of Rudorff, Guthrie, 

 Raoult and others on the effect of substances in solution 

 on the freezing points and vapour-pressures of liquids, nor 

 to Van t'Hoff's theoretical discussion of such results. 

 Another even more important omission is any mention 

 of the liquefaction by Cailletet and Pictet of what every- 

 body used to call, and Mr. Preston still calls, the per- 

 manent gases. As a natural consequence there is no 

 reference to the determination of the boiling points and 

 critical points of several of these gases by Wroblewski 

 and Olzewski. 



Chapter vi. is on "Radiation." The most novel 

 matters included in it are descriptions and figures of 

 Prof. Langley's bolometer and Prof. Boys's radio- 

 micrometer. 



In chapter vii., on " Conduction," we must point out a 

 very good description and discussion of Angstrom's 

 method (alternate heating and cooling) of determining 

 the conductivity of metals. 



Chapter viii., on "Thermodynamics," we are inclined 



NO. 1277, VOL. 49] 



to think the most valuable in the book, in the sense that 

 it contains a specially large amount of important matter 

 that has never before been readily accessible to English 

 students. The section on the dynamical equivalent of 

 heat includes the recent results of Miculescu and of 

 Mr. E. H. Griffiths, as well as a full description of 

 Rowland's experiments, which ought years ago to have 

 attracted more attention in this country than they seem 

 to have done. In the theoretical part of this chapter the 

 author has, in the main, followed Clausius's method of 

 presentation, but he has included admirable expositions 

 of Massieu's Characteristic Function, of Duhem's 

 Thermodynamic Potential, of the allied work of 

 Gibbs, and of the last author's geometrical treatment 

 of thermodynamic questions. 



Notwithstanding omissions, some of which we have 

 mentioned, every chapter affords evidence of care in 

 looking up authorities and collecting material. But the 

 value of the book as a work of reference might be a 

 good deal increased by more numerous and more ex- 

 tended tables of numerical results. For some reason 

 French books are quoted very largely, and not only for 

 the work of Frenchmen ; even Tredgold is referred to in 

 a French translation. 



If, in the course of the above notice, criticism seems to 

 be more prominent than commendation, we should do 

 injustice to ourselves, as well as to the author, if we did 

 not say distinctly that, in our opinion, he has produced a 

 very valuable and useful book which we earnestly 

 recommend to all serious students of the subject. When 

 an author obviously aims at a high standard, he invites 

 a critic to adopt a similar standard. And in a short 

 notice such as this, fault-finding necessarily occupies a 

 disproportionate space as compared with praise : if we 

 find fault, it is only fair to particularise, whereas praise 

 applicable to hundreds of pages can be put into a very 

 few words. 



We ought to add that printing, paper, and wood-cuts 

 are all excellent, and for a book of so many pages there 

 are very few misprints. The index has one rather 

 irritating characteristic, which, however, is by no means 

 peculiar to this work. If we wish to know what has been 

 done on a given subject by a particular author, we very 

 likely find his name followed by references to ten or a 

 dozen different pages, but without anything to show on 

 which, if on any of them, we shall find the matter we 

 want. 



It may perhaps save some reader trouble if we 

 point out that, on p. 202 (in " Cor. 2 "), X, ju, v are printed 

 instead of a, /3, -y, and on p. 588, the column headed 

 "C.G.S. System" should be headed Kilogramme- 

 metres. G. C.\REY Foster. 



AN EDUCATIONAL ATLAS. 

 Philip's Systematic Atlas, Physical and Political ^ 

 specially designed for the use of Higher Schools and 

 Private Stiidents. By E. G. Ravenstein. (London : 

 George Philip and Co., 1894.) 



THE chief claim of this atlas to consideration, as 

 indicated in the title, is the careful design and 

 plan of construction ; the order and selection of the 



