WORK OF EARLY AND MORE RECENT INVESTIGATORS 737 



the nature and origin of modern sediments A\^hich had previously appeared 

 in geological and oceanographic literature^ and to which Walther added 

 extensivel}' from his store of observations in all parts of the world. 



Although tliis \\ork tended to focus attention on the several types of 

 modern sediments and on the conditions under which they were forming, 

 and thus placed a distinct milestone along the path originally blazed by 

 Lyell, M'alther's name will probably always be most fully identified with 

 the study of modern terrestrial sediments, for here he made most exten- 

 sive contributions. Tliougli many pioneers preceded him, their work was 

 mainly that of gathering the blocks which were incorporated by Walther 

 in the foundation of the structure on which Ave are building today. At- 

 tention of the geological AvorJd was directed to this previously little- 

 known field by the appearance in 1891. of Walther's epoch-making studies 

 on "Die Denudation in der Wiiste und ihre geologische Bedeutung," and 

 was firmly riveted Avhen, at the opening of the ncAv century, appeared the 

 first edition of "Das Gesetz der Wiistenbildung.^' Henceforth the name 

 of Johannes Walther was closely linked with the subject of desert studies 

 in the minds of geologists, so much so that his continental brothers of the 

 hammer came facetiously to refer to him as "den Wtisten Walther," a 

 designation susceptible of two quite distinct interpretations. 



While thus giving to Walther the credit of inaugurating, though not 

 originating, a new line of investigation, we must not neglect to mention 

 others Avho contributed to the development of this new field. Probably 

 foremost among them should be noted the Russian geologist Sokolow, 

 Avliose Avork on the structure of sand-dunes Avas made available by the 

 appearance of the German translation in 1894; nor must we neglect the 

 contributions of the physiographers who so frequently have pointed the 

 way Avhich the student of lithogenesis should folloAv. Penck's "Morphol- 

 ogic der Erdoberflache," which appeared in 1894, can not be ignored by 

 the students of sediments any more than can Passarge's ponderous AA^ork 

 on the Kalahari, Avhich appeared ten years later (1904). The importance 

 of Suess's work is too we]] understood by the student of lithogenesis to re- 

 quire further comment. In our own country, the writings and teachings 

 of W. M. Davis have formed perhaps the most valuable training for the 

 rising school of American lithogejiesists,.and probably most of the Amer- 

 ican workers in this field, and not a fcAv foreign ones as well, acknowledge 

 their faith in the soundness of his principles. 



While speaking of the Avorks on modern continental sediments which 

 appeared in the closing decade of the last century, we must not forget the 

 studies of Johan A. I'dcU^n on the mechanical composition of wind de- 



