530 Notices of Books. [Ocftober 



but because they were too scattered for immediate reference. 

 Great good has been done by their collection, for they are, to use 

 a German expression, " science-making" in their nature. 



We will note in the order of the papers as nearly as possible 

 the chief points of Sir William Thomson's work. The first 

 paper deals with the exceedingly difficult problem of the uniform 

 motion of heat in homogeneous solid bodies and its connection 

 with the mathematical theory of electricity. Before this paper 

 there were prominently current two questions — one resulting 

 from Fourier's investigation, by which it appeared that the 

 conduction of heat is proportional to the rate of variation of 

 temperature at point to point of the conductor ; the other re- 

 lated to the distribution of electricity on conductors, and in- 

 cluded the assumption that the electrical particles exerted 

 mutual forces varying as the square of the distance. One 

 implies a flow, the other instantaneous action. Yet these 

 questions, so contrary in the experimental methods of investi- 

 gation, were proved by Thomson to be mathematically one. 

 Substitute in Fourier's formulas electrical surface for heat surface, 

 electric potential for temperature, and at once they are fitted to 

 the use of the electrician. 



And very much more than this collation of scientific principle, 

 the highest of generalisation do we owe to the present occupier 

 of the Professorial Chair at Glasgow. To SirW T illiam Thomson 

 are due the embodiment of Faraday's idea of continuous action 

 in mathematical formulae, the method of electrical images, and 

 of electrical inversion. The practical applications of his mathe- 

 matical theories are too well known to need detailing here, and 

 the list is too long, for it includes researches into atmospheric 

 electricity, the construction of electrometers, of galvanometers, 

 telegraphic instruments, and experimental researches into all 

 branches of electricity. 



In Professor Thomson's book we really find the germ of much 

 important work of our second author; ior in one of Thomson's 

 earliest papers — that on the attractions of conducting and non- 

 conducting electrified bodies, published in 1843 — we find the 

 speculation commenced that Professor Maxwell has since made 

 famous, the complete mathematical rendering of Faraday's 

 physical lines of force. Then passing on to the consideration of 

 vortex motion, we have Professor Maxwell again in the same 

 field. But these developments are essentially original works, 

 for so narrow and yet so liberal must be the reasoning that every 

 step is an opus magnus. Here the resemblance between the two 

 books ceases. Professor Maxwell's book, while it affords in- 

 struction to the student, really includes the most important of 

 the higher theories of electrical science, the first issue being the 

 treatment of Faraday's lines of force. How he has attempted 

 this we must let our author speak for himself, The general 

 complexion, he says, of the treatise differs considerably from 



