136 



SCIENCE 



[N. S. Vol. XL. No. 1021 



in English manuals; but it is in the presenta- 

 tion of the facts as a basis for the interpreta- 

 tion of the past that it shows a different point 

 of view. 



The author has made large use of physio- 

 graphic data. In fact, many chapters could be 

 used without change in a work on physiog- 

 raphy. This the reviewer regards as an ele- 

 ment of great strength in the book. Physiog- 

 raphy, a younger member of the family of 

 geological sciences, rests upon a stratigraphic 

 and structural foundation. The present can 

 not be understood without a knowledge of the 

 past. On the other hand, the past can not be 

 interpreted without an understanding of the 

 present, but stratigraphers and students of 

 historical geology have not learned as yet to 

 make full use of physiographic principles. It 

 is the purpose of an investigation which should 

 determine the classification of the field of 

 science rather than the facts which are used. 

 Defined by this standard, physiography is that 

 division of geology whose purpose is to explain 

 the present; the purpose of stratigraphy and 

 historical geology is to explain the past. But 

 as both involve an understanding of past and 

 present, no man can work to advantage in 

 either field without a knowledge of both. For 

 these reasons Grabau rightly regards the work 

 of W. M. Davis as of great importance for 

 the principles of stratigraphy. 



The aim and scope of a volume are best 

 shown by a statement of the conditions which 

 developed its need and led to its production. 

 Quotations from the author's preface will best 

 give this view. 



This book is written for the student and for the 

 professional geologist. It aims to bring together 

 those facts and principles which lie at the founda- 

 tion of all our attempts to interpret the history of 

 the earth from the records left in the rocks. Many 

 of these facts have been the common heritage of 

 the rising generation of geologists, but many more 

 have been buried in the literature of the science, 

 especially the works of foreign investigators, and 

 so have generally escaped the attention of the stu- 

 dent, though familiar to the specialist. Hereto- 

 fore there has been no satisfactory comprehensive 

 treatise on lithogenesis in the English language, 

 and we have had to rely upon books in the foreign 



tongue for such summaries. It is the hope of the 

 author that the present work may, in a measure, 

 supply this need. 



The book was begun more than fifteen years ago, 

 and the material here incorporated has been col- 

 lected and sifted during this interval. . . . 



The "Einleitung in die Geologie als historisch© 

 Wissenschaf t " had appeared only a few years 

 before, and its influence in shaping geologie 

 thought, especially among the younger men, was 

 just beginning to be felt. The "Lithogenesis der 

 Gegenwart" presented such a wealth of facts con- 

 cerning the origin of sedimentary rocks, that at- 

 tention began to be diverted from the problems 

 of the igneous rocks which had heretofore almost 

 exclusively occupied petrographers, and "Sedi- 

 ment-Petrographie, " or the petrography of the 

 sedimentary rocks, attracted more and more of the 

 younger geologists, especially in Germany and 

 Prance. . . . 



It was at this period, too, that the attention of 

 geologists and especially stratigraphers was first 

 seriously directed toward the desert regions of the 

 world and the phenomena of extensive subaerial 

 deposition. Here, again, Walther led the way in 

 that classic, "Die Denudation in der Wiiste," fol- 

 lowed in 1900 by his epoch-making book, "Das 

 Gesetz der Wiistenbildung, " which, in its revised 

 edition, appeared in 1912. It is, of course, true 

 that important studies of the desert regions were 

 made earlier, notably those of von Zittel on the 

 Libyan desert (1883), but the significance of the 

 desert deposits in terms of stratigraphy was first 

 fully appreciated within the last decade. That 

 the importance of the desert as a geological factor 

 has become widely recognized is shown by the nu- 

 merous recent studies, especially those on the 

 Kalahari by Passarge, and those on the Asiatic 

 deserts, by Sven Hedin, Pumpelly, Huntington 

 and others. 



It is during this decade that the sciences of 

 glyptogenesis and geomorphology have come into 

 being, notably through the labors of Davis in 

 America, and of Suess and Penck in Europe. 

 Suess's "Antlitz der Erde" began to appear, it is 

 true, in 1883, but it is only in recent years that this 

 work has been readily accessible to most American 

 students, through the medium of the English 

 translation by Sollas and Sollas (1904-1909). 

 Penck 's "Morphologie der Erdoberfiache" ap- 

 peared in 1894, but did not become well known in 

 this country until much later. It was, however, 

 Davis's publications in this country, chiefly during 

 the early nineties of the last century, which gave 



