PREFACE ix 



It is during this same decade that the Sciences of Glyptogenesis 

 and Geomorphology have come into being, notably tlirough the 

 labors of Davis in America, and of Sness and Penck in Europe. 

 Suess's Antlita 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 trans- 

 lation by Sollas and Sollas (1904-1909). Penck's Morphologic der 

 Erdoherflaclie appeared in 1894, but did not become well known 

 in this country until much later. It was, however, Davis's publica- 

 tions in this country, chiefly during the early nineties of the last 

 century, which gave the great impetus to the study of land forms, 

 and especially of the influence of erosion on their production. The 

 concept of the peneplain, of the cycle of erosion, of the sequential 

 development of rivers and erosion forms on the coastal plain and 

 on folded strata, and others chiefly due to him, have become of 

 incalculable value to the stratigrapher. The more recent develop- 

 ment of the idea of desert planation by Passarge and Davis, has 

 opened further promising fields to the stratigrapher, who seeks to 

 interpret the record in the strata by the aid of modern results 

 achieved by universal processes. 



The science of earth deformations, or Orogenesis, also received 

 renewed impetus during the last decade, in the work of Bailey 

 Willis in this country {Mechanics of Appalachian Structure, 1893), 

 and the researches of the European geologists on the deformations 

 of the Alps and other great mountain chains. True, this field had 

 been opened up in a masterful way by Heim, when in 1878 he 

 published his Mechanismus der Gebirgsbildiiiig, and by Suess in his 

 earlier studies, but such work was of the nature of pioneer investi- 

 gations. In the Face of the Earth, too, emphasis is laid on de- 

 formation as the principal agent in the production of the diversi- 

 fied surface features of the earth. 



In the field of Correlative Stratigraphy the past decade has like- 

 wise seen striking advances. The publication of the Lethaea falls 

 into this period, and so does Marr's comprehensive little volume. 

 The Principles of Stratigraphical Geology, not to mention the elab- 

 orate recent texts of Haug. Kayser, and others, or the numerous 

 publications of Government surveys, and of individual contributors. 

 That questions of correlation have reached an / acute stage in 

 American Geology is manifested by such recent publications as the 

 Outlines of Geological History and Ulrich's Revision of the Paleo- 

 zoic Systems, and the numerous papers accompanying or called 

 forth by these. Finally. Palaeogeography, as a science, is of very 

 recent development, most of the works of importance having ap- 



