REVIEWS 705 



tions for recording observations. In this volume also much originality is shown 

 in the substances chosen for experimentation and the methods to be employed. 

 In spite of this we are afraid, however, that in most cases a great amount of the 

 success of experimental work of young students is beyond the powers of the most 

 carefully compiled book directions and lies in the hands of the teacher. 



In this edition of the textbook two new chapters have been added, one on 

 the Laws of Chemical Combination and the Experimental Determination of 

 Equivalent and Atomic Weights, and the other on the Periodic Classification of 

 the Elements. In the practical book corresponding exercises on the determination 

 of Equivalent and Molecular Weights have been included which are absent in 

 the previous American editions. 



C. S. G. 



An Introduction to the Physics and Chemistry of Colloids. By Emil 

 Hatschek. [Pp. ix + 105, with 17 illustrations. Second edition.] 

 (London : J. & A. Churchill, 1916. Price 3s. net.) 



This little volume belongs to that very excellent series of " Text-Books of Chemical 

 Research and Engineering " edited by W. P. Dreaper, and without doubt it has 

 proved itself one of the best introductory volumes extant on this difficult and to 

 little known subject. 



Starting from the original observations of Graham, the unfolding of the several 

 properties which are associated with the colloidal state is historically traced, and 

 before the third chapter has been reached the reader has become acquainted with 

 the order of the size of colloidal particles and the pioneer work of Bechhold, 

 Zsigmondy and Siententopf, and Lord Rayleigh in this sphere. 



Next comes the disperse phase conception and its viscosity variations conse- 

 quent on its solid or liquid state, and this leads on to a description and explanation 

 of the Brownian movement and the possession of electric charges by colloidal 

 particles. Emulsoids, suspensoids, protective colloids and their "gold values," 

 emulsions, the phenomenon of interfacial tension, the Hofmeister series of 

 albumens and semi-colloids are then surveyed. Several chapters are devoted 

 to gels and the various properties which are associated with them, whilst Chaps. 

 VIII. and IX. are concerned with the complex phenomena of colloidal adsorption. 

 The final chapter contains a general survey of the whole subject, and discusses 

 critically the theories advanced in explanation. The great applicability of colloidal 

 science to many of the problems of industrial work is pointed out, and the need 

 for further research is emphasised. 



This edition is supplemented with an Appendix on experimental technique, 

 which, in view of the unfamiliar nature of much of the practical work associated 

 with colloidal investigations, will be found to be very helpful. 



C. S. G. 



ZOOLOGY 



The Migrations of Fish. By A. Meek, M.Sc. [Pp. xviii + 427, with 12 plates 

 and 128 illustrations.] (London : Edwin Arnold, 1916. Price16j.net.) 



The problem of the supply of food fish is one of the greatest importance in this 

 country, surrounded as it is by the sea, and moreover it is beyond doubt that in 

 many parts of the coast the fishing which might employ many thousands of 

 persons has been declining for years past. At the present time the question of 

 food supply is an urgent one, and with the advent of peace there is little doubt 

 that the means of employing the millions that will return to this country will also 

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