March 28, 1902.] 



SCIENCE. 



503 



trating the relation between equivalent 

 ■weights and certain speciiic properties. The 

 remainder of the book (147 pages) is 'On 

 the relation between the properties of the 

 elements in general and their combining 

 weights; description of the first twenty-five 

 elements and some of their compounds.' 

 These elements are those comprised in the 

 first three horizontal series of Mendeleeff's 

 chart of the periodic system. The properties 

 of the commoner elements of this selection 

 and their compounds are described in consid- 

 erable detail. Here the book proper ends. A 

 second part (106 pages) gives the experi- 

 mental illustrations and instruction in details 

 of laboratory work. The book is illustrated 

 by full-page portraits of many of the chemists 

 and physicists mentioned. 



This is indeed a different treatment from 

 that commonly followed. A course in chem- 

 istry in which copper, mercury, silver and 

 lead are ignored, while beryllium and cobalt 

 find consideration is not co mm on. Yet this 

 does not prove that it is wrong. The author 

 lays chief stress on general laws. The stu- 

 dent's comprehension of a law is based on a 

 roughly quantitative experiment illustrating 

 it which he performs before studying the law. 

 The experiments merit attention; they are 

 well devised and easy to perform. The author 

 illustrates these laws further by the behavior 

 of a number of elements, including important 

 metals, and most of the important acid-form- 

 ing elements. 



It is not the object of a college course in 

 science to form specialists, and, the question 

 may be fairly asked whether the mental dis- 

 cipline and the capacity to pursue the study 

 of chemistry afforded by this method are not 

 of equal value, or (as the author believes) of 

 greater value than can be obtained by the 

 prevailing method. To those who agree with 

 the author this book should be welcome. 



The book has one grave defect, in omitting 

 all mention of electrolytic dissociation. The 

 author anticipates criticism in a passage on 

 page eight of a pamphlet called 'Suggestions 

 to Teachers' which accompanies the book; he 

 says: 'Some perhaps would wish to include 

 osmotic pressure and the electrical phenom- 



ena of conductivity, etc., together with the 

 theory of ionization, but I have judged it 

 impracticable to illustrate these phenomena 

 experimentally without displacing other mat- 

 ter or going beyond the reasonable scope of 

 one year's work.' To this the obvious answer 

 is, that with our present knowledge it would 

 be better to displace other matter, if need be, 

 than to omit anything so fundamental and so 

 easy of illustration as electrol3ftic dissociation, 

 from a book called 'Elementary Principles of 

 Chemistry.' With the hope that this gap may 

 be filled in the next edition, the reviewer com- 

 mends Professor Young's book to the atten- 

 tion of college and advanced high school 

 teachers, who will find it suggestive. 



E. Eenouf. 



Studies in Euolidion. By Charles Ejcersoj? 



Bekcher. jSTew York, Charles Scribner's 



Sons. 1901. 



This is a notable volume. It is one of the 

 series of the Bicentennial Publications of Yale 

 University, and consists mainly of reprints 

 of occasional papers selected from previous 

 publications of the Laboratory of Invertebrate 

 Paleontology, Peabody Museum. The most 

 important are those on the structure and 

 development of trilobites, and the 'Studies in 

 the Development of the Brachiopoda.' 



The aim of the first essay, 'On the Origin 

 and Significance of Spines,' is an attempt, in 

 the terms of ontogeny, phylogeny and chro- 

 nology, to apply the general law of evolution 

 to the spines of plants and animals. The dis- 

 cussion is a very interesting one, and we 

 think Dr. Beecher satisfactorily shows from 

 a gi'eat number of cases discovered by numer- 

 ous observers that spines are a characteristic 

 of the old age, both of the individual and of 

 the type. In old age the organism, during the 

 senescence of the type, 'blossoms out with a 

 galaxy of spines, and with further decadence 

 produces extravagant vagaries of spines, but 

 in extreme senility comes the second child- 

 hood, with its simple growth and the last 

 feeble infantile exhibit of vital power.' 



We are inclined to think that the author is 

 a little too hospitable to Wallace's notion that 

 spines on desert plants may originate from 



