Mat 13, 1921] 



SCIENCE 



459 



any importance only one page is shewn in 

 facsimile in tie present edition. The rest of 

 the text is reproduced on the left hand pages 

 while the translation appears on the following 

 pages. The last six pages are devoted to 

 algebra, chiefly relating to quadratic equa- 

 tions, and, in closing, the author states that 

 he "wished to set down the things which are 

 necessary and familiar in this kingdom." The 

 formula near the bottom of page 37 is not 

 clearly stated. Professor Smith's name is a 

 sufficient guarantee that the work is in an 

 atti'active form. 



G. A. Miller 

 University of Illinois 



Introduction a I'etude petrographique des 

 roches sedimentaires. Par M. Lucien 

 Cayeux. Memoires pour servir a I'explica- 

 tion de la carte geologique detaillee de la 

 France. Paris: Imprimerie Nationale 1916. 

 Quarto, 1 vol. text, pp. viii + 524, 80 

 figures; 1 vol. LVI plates. 

 It is a curious fact that although Sorby, 

 the father of modern petrography, was espe- 

 cially interested in sedimentary rocks, those 

 who followed him, with the exception of a 

 small but persistent succession of workers in 

 his own country, almost abandoned them in 

 favor of the igneous rocks. The author of 

 the book under review has elsewhere sug- 

 gested that this was perhaps due to the lure 

 of greater mystery in the igneous rocks and 

 to the lack of knowledge, before the Chal- 

 lenger expedition, about the sediments of to- 

 day. The reviewer has always been inclined 

 to attribute the preference for the study of 

 igneous rocks to their greater and more ob- 

 vious diversity, which made it easier to find 

 something new in them and gave them a 

 greater esthetic attractiveness. Whatever the 

 cause the present work will be the most 

 powerful influence that has yet been brought 

 to bear in changing that tendency. Indeed, 

 in French-speaking countries Cayeux's in- 

 fluence is already very manifest. If the 

 beauty of the sedimentary rocks has been 

 considered inferior the enthusiasm of the 

 author will surely correct that impression. 



The work marks an epoch in its field and 

 IS written with a breadth of view worthy of 

 the fundamental importance of the sedimen- 

 tary rocks in the interpretation of the history 

 of the earth. The author not only stands 

 alone in the extent and thoroughness of his 

 monographic investigations in this field, but 

 as the successor of Elie de Beaumont, Fouquo 

 and Michel-Levy at the College de France 

 he is, so far as the reviewer knows, the only 

 person occupying a chair devoted entirely to 

 the teaching of the petrology of sedimentary 

 rocks. On his inauguration the name of the 

 chair he occupies was changed from " Chair 

 of the ISTatural History of Inorganic Bodies," 

 to " Chair of Geology," but it might well 

 have retained its old name, for as he says in 

 his inaugural address, " The science of the 

 sedimentary rocks is and will remain for us 

 a natural history of the ancient and modem 

 sediments." Tt is the treatment from this 

 point of view and the enthusiasm and wide 

 personal experience which the author brings 

 to it that gives to a book which one might 

 expect to find dry and technical a freshness, 

 interest, and charm that make it fascinating 

 reading. Furthermore, the book is so full of 

 original observations drawn from the writer's 

 many years of study that no student of sedi- 

 mentary rocks, be he petrographer or merely 

 stratigrapher, can afford to leave it unread. 



The work is divided into two parts. The 

 first deals with methods of analysis of sedi- 

 mentary rocks, the second with the diagnostic 

 characters of the constituents, which fall into 

 two gi'oups — the minerals and the remains of 

 organisms. 



The first part is refreshingly free from 

 pedantry or love of technique as an end in 

 itself, though the artist's pleasure in some 

 refined and delicate method often finds 

 expression. Methods of handling rocks of 

 diiferent types according to their induration 

 or susceptibility to attack by acid are dis- 

 cussed, but the possible complexity of the 

 procedure appropriate to any individual rock 

 and the need of adapting the methods used 

 to the particular rock and to the object of 

 the investigation are pointed out. Quantita- 



