550 STEVENSON— THE FORMATION OF COAL BEDS. [Nov. i, 



region is a vast lake with floating grass and weeds, only a few 

 islands remain here and there, on which wild animals find refuge. 



Near Bahia Blanca, just beyond the limits of the Pampean 

 deposits, Darwin'"'^ found pebbles of quartz on the coast which must 

 have travelled 45 miles. The Tertiary beds of Patagonia are capped 

 by a conglomerate, extending northward from the Strait of Magellan 

 about 800 miles with an average width of 200 miles and an average 

 thickness of 50 feet. Its porphyry pebbles came from the Cor- 

 dillera. The rock was derived from masses falling on old coast lines 

 and on river banks. The country is terraced, which leads Darwin 

 to see in the phenomena the influence of wave action on the rising 

 coast. He describes graphically the clashing of fragments as they 

 are driven along by torrents in flood. 



Conclusions. 



That a sea or an ocean is needed for accumulation of thick sedi- 

 mentary deposits has been long a prevalent opinion among geologists. 

 It is a survival of the period when observation within narrow areas 

 provided a warp of fact to be filled in with a woof of fancy, when 

 cataclysms were thought the rule of nature and modern conditions 

 were believed to be exceptional in the earth's history. It so pervades 

 geological literature that one, in disputing the doctrine, is very apt 

 to employ conventional phrases which concede it. When the study 

 of actual conditions had been prosecuted systematically, when phe- 

 nomena in great and widely separated areas had been ascertained 

 and compared, it became evident that the accepted doctrine was at 

 least defective. During the last quarter century, intimate study of 

 Quaternary deposits in Europe and America, as well as detailed 

 investigations in physical geography — due largely to the initiative 

 by W. M. Davis in America and A. Penck in Europe — has developed 

 anew the conception that, great as has been the work of ocean forces, 

 that of land forces has been vastly greater. As Ramsay saw for 

 Siberia and Medlicott for India, the activities of rivers in conveying 

 and distributing deposits far from the sea have brought about almost 



"' C. Darwin, " Journal of Researches," New York, 1846. Vol. I., pp. 96, 

 137, 138, 219. 



