Joseph Barrell. 269 



is to be expected that the size of the delta and the 

 character of its deposits will depend not only on the 

 original relation of the other physiographic elements of 

 the continent, but on the progress of the cycle of ero- 

 sion on the one hand and of the cycle of deposition on 

 the other." 



In 1913-1914 followed the application of the criteria 

 of the previous paper to an ancient or fossil delta in 

 the study entitled ''The Upper Devonian Delta of the 

 Appalachian Geosyncline. " This is one of Barrell's 

 best pieces of work, and a very philosophic one, for it 

 brings out the relations of the Appalachian delta, both 

 to the interior sea and to the extensive eastern land 

 Appalachia and the Atlantic Ocean beyond. This exten- 

 sive delta system began to form in the Middle Devonian 

 and ceased in early Mississippian time. Its sedimen- 

 tary volume Barrell computes at about 16,500 cubic 

 miles for the Middle Devonian and 63,000 cubic miles for 

 Upper Devonian time. "This is an impressive measure 

 of the volume of the adjacent land which was eroded in 

 Upper Devonian times. But it is a minimum measure, 

 since that part of the rocks which was taken into solu- 

 tion was carried farther away, and of the mechanical 

 sediments it represents only that part which was carried 

 westward into the trap of the geosyncline." 



This great amount of Upper Devonian sediments im- 

 plies a much greater Appalachia than is usually assumed. 

 In elevation it must have exceeded the present Sierra 

 Nevadas, Barrell states that this old land "was not 

 confined to the limits of the present continental shelf. 

 . . , The foundations of Appalachia are buried some 

 thousands of feet beneath it, extend beyond it, and 

 doubtless slope gradually for an unknown distance 

 toward and beneath the basin of the Atlantic," where 

 is now deep ocean. "In Upper Devonian times the 

 mountains which rose above these foundations stood on 

 the eastern side of the Appalachian system." Accord- 

 ingly, great parts of eastern Appalachia have been frag- 

 mented and sunk into the depths of the Atlantic during 

 Mesozoic time. 



As early as 1905, Barrell began to ask himself, "What 

 were the geographic and climatic conditions which con- 

 trolled the nature of the Old Red Sandstone deposits?" 

 In 1907 he wrote out his views but withheld them from 



