Notices respecting New Books. 535 



liquefaction and solidification, isomorphism and polymorphism. 

 Section 5 treats of dilute solutions, osmotic pressure, diffusion, and 

 the phenomena connected with the vapour-pressure and the 

 freezing-point of solutions. Section 6 deals with the periodic law 

 of the elements, the molecular theory, and the theory of valency. 

 Part II., which is devoted mainly to a consideration of the 

 energetics of the various chemical processes, embraces the remaining 

 five sections of the book. In section 7 is considered the important 

 subject of thermo-chemistry. This is treated somewhat fully, and 

 a large collection of useful numerical data is given. Section 8 

 deals with chemical equilibrium. Electro-chemistry forms the 

 subject of the next section ; section 10 is devoted to photo- 

 chemistry ; and the concluding section 11 deals with chemical 

 affinity. 



Although the book professes to be only an outline of the subject, 

 it contains an enormous amount of information in a condensed 

 form, and should prove extremely useful as a book of reference to 

 the student of physics as well as of chemistry. A good example 

 of the extremely conscientious and thorough manner in which the 

 author has fulfilled his task is afforded by chapter 3 in the first 

 section of- the book, which deals with the combining weights of the 

 elements. Not only is there a table given of the atomic weights 

 according to the most recent determinations, but there is a full 

 account of the various methods by means of which the atomic 

 weights of the different elements have from time to time been 

 determined, the date of each research and the name of the investi- 

 gator being given. Similar thoroughness of treatment characterizes 

 most sections of the book. 



Among its many noteworthy features may be mentioned the 

 adoption throughout of a system of units based directly on the 

 C.Gr.S. system. Thus, in the section on thermo-chemistry, the 

 joule and kilojoule are adopted as heat units, and the author has 

 gone to the trouble of re-calculating the large mass of data 

 relating to this subject, and expressing them in terms of the 

 kilojoule. It is earnestly to be hoped that in future other writers 

 will follow this lead, and thereby help to remove all unnecessary 

 complexity surrounding this subject. 



The clear way in which the author arrives at many of the funda- 

 mental conceptions of chemistry as a direct result of experimental 

 investigation, and without calling in the aid of particular theories, 

 such as the atomic and molecular theory, is highly to be com- 

 mended, and is well worthy of very close study by all teachers of 

 the subject. 



In a work of such general excellence, it is somewhat of a sur- 

 prise to come upon the slovenly treatment of Ohm's law on p. 377. 

 After giving a definition of resistance, the author writes down 

 the symbolical equation corresponding to the definition, and 

 immediately afterwards states that " this is the celebrated law of 

 Ohm ! " As if a mere definition could constitute a law ! In so 

 doing, however, the author is only following the traditionally 

 inadequate treatment of this subject. Surely it is quite as easy, 



