456 Reviews and Notices of Books. 



altogether impracticable — without the aid of more abstruse 

 mathematical processes. 



The present volume is the first of a promised series forming a 

 course on the Philosophy of Chemistry. In this volume the author 

 aims to give a complete development of the theory of weighing 

 and measuring. In the rough these operations are simple enough, 

 and intelligible enough ; but when as in many chemical investi- 

 gations, an error of a hundred thousandth is important, minute 

 sources of error have to be guarded against which demand for 

 their elimination a knowledge of physical laws not always pos- 

 sessed by the tyro. When it is remembered that the chemist 

 must correct his first approximation to the weight or volume ol 

 the substance with which he experiments for errors arising from 

 the buoyancy of the air, its ever varying pressure, its difi'erent de- 

 grees of humidity, from changes of temperature of the mass to be 

 computed, as well as of the vessel that contains it, and from many 

 other more refined and occult influences, it is easy to conceive 

 that an extended acquaintance w^ith the laws of motion, with the 

 nature of matter, with hydrostatics, with pneumatics, with ther- 

 motics and with other branches of Natural Philosophy is neces- 

 sary. 



The author in the development of the subject has adopted a 

 simple natural arrangement. First he gives a chapter of intro- 

 ductory observations in which, by the waj'', he attempts with in- 

 different success to distinguish between chemical and physical 

 changes. The second chapter treats of the general properties of 

 matter and the laws of motion. The third chapter treating of 

 molecular forces, first between homogeneous, and then between 

 heterogeneous molecules, we consider to be the best chapter of 

 the work, giving most valuable information in a clear concise 

 style. The fourth chapter, on heat, contains a large amount of 

 well digested information ; we cannot however avoid expressing 

 our surprise that the author of a work like the present should 

 enumerate but " two theories " of the nature of heat as " current 

 among philosophers " — the material theory and the undula- 

 tory theory — making no reference to the remarkable dynamical 

 theory of heat that has deservedly attracted so much attention in 

 the last few years. If the fifteen or twenty pages devoted to a 

 description of the steam-engine were compressed into two, and 

 the space thus saved devoted to a discussion of the nature of 

 vapours and gases as illustrated by that theory, we think this por- 



