5l8 SHAW: SEDIMJSNTATION 



We sometimes feel that the general arrangement and distribu- 

 tion of deposits on lake and sea floors is fairly well known, yet 

 the only detailed areal survey of any considerable portion of 

 the sea floor — ^that made by Thoulet in the Gulf of Lyons — 

 leads to a map that no physiographer or stratigrapher could 

 have produced in advance. 



Accurate surveys of selected areas of ocean and lake floor are 

 greatly needed; areas not far off shore are of especial interest 

 because of their economic bearing and because here there is 

 greatest variety in process and nature of deposit. Contributions 

 of this sort have already been made by Kindle for certain of the 

 Great Lakes and by Vaughan for waters off the coast of Florida. 

 Inductive work along the same line has been done by many 

 geologists, among the foremost of whom is that eminent geol- 

 ogist of Lehigh and Yale whose loss we are now feeling so keenly. 

 Experimental work has been done by a few, the most noteworthy 

 being perhaps that of Gilbert'' and Engels." 



Not only is there need of increase in the knowledge of sedi- 

 ments but there is need of dissemination of the knowledge here- 

 tofore gained. Some of the discoveries already made are not 

 serving as they might. It has been shown that corals contribute 

 Httle to accumulation of sediments and yet some still speak of 

 coral islands and coral limestone in a way that indicates a mis- 

 conception. We speak of clastic, chemical, and organic depos- 

 its, forgetting that limestones are generally clastic: are com- 

 posed of fragments, now more or less extensively recrystallized, 

 that were transported on the average thousands if not tens of 

 thousands of feet. We interpret a great many sand lenses as 

 fossil beaches, forgetting that shore deposits are as a rule ephe- 

 meral. 



Although the study of sediments has lagged behind other 

 branches of geology, real progress has been made in a number of 

 problems. It is worthy of note that most of this progress has been 

 made by men engaged primarily in other lines of science, by men 



* Gilbert, G. K. The transportation of debris by running water. U. S. Geol. Sur- 

 vey, Prof. Paper 86. 19 14. 



' Engels, H. Fluss-Strecken mil beweglicher Sohle. Zeits. fiir Bauwesen. 1905. 



