1132 Notices respecting JSew Books. 



state are noteworthy facts which are well brought out by ex- 

 periment. 



Sir G-eorge Beilby's best known work is, perhaps, that on the 

 nature of polish, in which he showed that the effect of polishing is 

 to flow a thin layer of hard amorphous material over the otherwise 

 crystalline surface of the solid. His beautiful coloured photo- 

 graphs showing how a film of the amorphous modification, thin 

 enough to be transparent, can be actually made to flow over empty 

 pits in the surface of copper by the process of polishing are 

 reproduced. The depth of the disturbance produced by polishing, 

 the increased hardness of the surface, and the transmission of the 

 directive action of the crystals through a layer of non-crystalline 

 material were all investigated, and the whole question of polish 

 was put in order. Two other sections of the book deal with the 

 flow of rocks and ice, and the phosphorescence of crystals respec- 

 tively. The latter shows, a certain disregard of work which had 

 been previously carried out by Lenard and others. 



The book is beautifully printed and produced, and adorned with 

 over a hundred reproductions of microphotographs printed as 

 thirty-four plates at the end of the book. It is very moderately 

 priced as books go nowadays, and we congratulate Sir George 

 Beilby on having brought together his work in so attractive a 

 form. 



The Physical Properties of Colloidal Solutions. By E. F. Buiitow. 

 Pp. viii-j- 221. Second Edition. Longmans. Price 12s. 6d. 



The second edition of Professor Burton's book contains some 

 twenty pages more than the first, which appeared in 1916. The 

 chapter on Coagulation of Colloids has been rewritten and greatly 

 extended : it now contains a table showing the relative coagulating 

 power of different ions. Changes and additions have been made 

 in other parts of the book, one of the most interesting being the 

 discussion of limitations of Perrin's distribution law, which is 

 known not to hold for large depths ; in such cases there is a 

 limiting concentration. By taking into account the charge on the 

 colloidal particles a correction term is introduced. Perrin's 

 original formula was applicable, however, to such conditions as he 

 employed, and his numerical results are not questioned. The 

 book is warmly recommended. 



Series Spectra. By Norman E. Campbell. Pp. viii -f 110. 

 Cambridge University Press. Price 10s. 6d. net. 



The second edition of Dr. Campbell's well-known ' Modern 

 Electrical Theory,' which appeared early in 1913, is now necessarily 

 largely out of date — the theories described are now no longer, in 

 many cases, modern. The author has decided not to issue a fresh 



