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few years have witnessed a remarkable advance in our experimental knowledge of 

 osmotic pressure — an advance chiefly due to Lord Berkeley and Mr. Hartley, on 

 the one hand, and to Messrs. Morse and Frazer, on the other. The work of the 

 latter investigators is of the utmost importance, involving an extension to con- 

 centrated solutions of van 't Hoff 's formula for dilute solutions. In Professor 

 Young's discussion of osmotic pressure, however, no reference is made to Morse 

 and Frazer's work. 



In regard also to the arrangement of the chapters a word of criticism may 

 be permitted. To devise an arrangement which should be universally acceptable 

 is perhaps a vain hope, but it does seem curious that a chapter on "The Dis- 

 sociation of Gases and Vapours " should be placed between one on " The Periodic 

 Law" and one on "The Properties of Liquids." The author may have a good 

 reason for this arrangement, but it would seem more rational to discuss cases of 

 abnormal vapour density in that portion of the book which deals with the molecular 

 weights of gases and vapours. Again, the insertion of a discussion of the kinetic 

 gas theory between chapters on the properties of liquids and the properties of 

 solids is open to criticism. It is no doubt true that this theory is closely connected 

 with van der Waals' equation of state, but it should be discussed primarily in 

 relation to the experimental gaseous laws. The three gaseous laws which must 

 be regarded as fundamental by the physical chemist are (1) Boyle's Law, (2) Gay 

 Lussac's Law, (3) Gay Lussac's Law of Volumes, and the descriptive exposition 

 of these should be followed immediately by a discussion of their theoretical basis 

 in the kinetic gas theory and Avogadro's hypothesis. 



But although there thus appears to be some ground for criticism, Professor 

 Young's volume may be cordially commended to all those who seek to familiarise 

 themselves with the point of view of physical chemistry — a point of view which is 

 both rational and stimulating. 



J. C. Philip. 



Physiography. By Rollin D. Salisbury, Professor of Geology and Head 

 of the Department of Geography in the University of Chicago. London : 

 John Murray. 1907. 



In this country the term physiography is applied by the Board of Education to an 

 assemblage of theoretical and experimental material, gathered from nearly every 

 branch of science, to form a subject for instruction and examination in our 

 * elementary schools. In the United States, on the other hand, it is employed 

 with a more definite meaning and concerns itself with the physical aspects of 

 our planet and their variations in time and space. It is a favourite study in the 

 higher classes in schools, and lower classes in colleges, and the present volume 

 is one of the best that has appeared in recent years to satisfy the demand for a text- 

 book on the subject. Its most striking characteristic is its wealth in illustration. 

 Every stage in the evolution of the land is depicted in clearly reproduced photo- 

 graphs of American scenery ; the diagrams are striking, and in many cases 

 original ; but a still more important feature is the number of maps. These include 

 effective photographs from models, graphic representations of the distribution of 

 physical phenomena, and transcripts and facsimiles of the topographical maps 

 of the United States Geological Survey. These last are closely contoured, 

 and give an excellent idea of the form of the earth's surface. One is glad to 

 be reminded by the author that the originals can be obtained from the Director 

 of the Survey at Washington at the rate of three dollars a hundred, which works 



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