534 Notices of Books. [Odlober, 



■ * 



expression to which it relates should be squared. These minor 

 errors greatly deteriorate a work that would otherwise be of the 

 highest utility, not only to the student, but in every office where 

 drawing has to be done. 



Switches and Crossings. Formulae for ascertaining the Angles of 

 Crossings, the Lengths of Switches, and the Distances of 

 the Points of the Crossings and Heels of the Switches from 

 the Springing of the Curve. By William Donaldson, M.A., 

 A.I.C.E., Author of a Treatise on Oblique Arches. London: 

 E. and F. N. Spon. 1871. 



If plate layers, or even the foremen, for whom Mr. Donaldson 

 professes to write, have to study works of this character, one 

 can hardly wonder that something should go wrong somewhere. 

 From beginning to end the book is a mass of inexplicable formulas 

 — inexplicable because ordinary mathematical expressions are 

 made subservient to other renderings. Having his symbols to 

 construe!:, surely Mr. Donaldson could have devised something 

 better than the employment of the ordinary signs of the powers 

 and the series. Formulae for practical application should be so 

 written that a mathematician of tolerable acquirements can read 

 them at sight ; but here one is perplexed by the subversion of 

 conventional symbols, and has continually to turn to the first 

 chapter for explanation. But, this notwithstanding, every credit 

 must be given for the patient labour entailed by so much cal- 

 culation. The idea is good, and all cases of junctions are dis- 

 cussed ; but is all this labyrinth of signs and letters necessary ? 

 If so, there can never be a dearth of mathematicians as long as 

 a platelayer is to be found. 



Elementary Treatise on Natural Philosophy . By A. Privat 

 Deschanel, formerly Professor of Physics in the Lycee 

 Louis-le-Grand ; Translated and Edited, with extensive 

 additions, by J. D. Everett, M.A., D.C.L., Professor of 

 Natural Philosophy in the Queen's College, Belfast. In 

 four parts: Part II. London: Blackie and Son. 1871." 

 Medium 8vo. 



This is the second volume of Professor Everett's translation of 

 M. Deschanel's " Traite Elementaire de Physique," and is ex- 

 clusively devoted to the consideration of Heat. Of the admirable 

 character of the work we have already had occasion to speak 

 when noticing Part I. ; and this character is fully maintained. The 

 subject is considered under the heads of Thermometry, Ex- 

 pansion of Solids, Liquids, and Gases, Fusion and Solidification, 

 Evaporation and Condensation, Ebullition, &c. A very clearly 



