82 Tbaxsactioxs of the American Institute. 



animals wliich have li\'ed upon the sea bottom. We are not only 

 able to trace these formations by their contained characteristic 

 fossils, but we know which have been formed nearest the shore ; for 

 there are certain animals living near the shore-line, and others which 

 live only in the deeper sea. Tracing these deposits, as we go westward 

 the materials become liner and finer until at last the}' die out almost 

 entirely. But along the line where we now have the Apalachian 

 chain of mountains, stretching from the north-east down to the 

 extreme southern limit of the country, \;e find coarse materials 

 accumulated in large quantities. The same formations of which these 

 mountains are composed extend westward, but the sediments are there 

 finely comminuted mud ; so that tlie geological formation which in 

 the east is sandstone often becomes a soft calcareous mud in the west. 

 This is in consequence of the law I mentioned just now, that near 

 the coast we have sand and coarse materials, but no clay or mud 

 except in quiet places. Wherever' the sea has full force of action we 

 have sandstone, or coarse deposits ; but toward the center of the 

 ocean, finer muds are carried. We have then, in the neighbor- 

 hood of the original land from which the sediments were derived, 

 the coarser materials, and finer materials as we proceed westward and 

 south-westward. We have here, along this belt of greatest accumu- 

 lation, the successive formations one above the otlier, until they 

 reach a thickness of 20,000, 30,000, or even 40,000 feet. After the 

 deposition of this older sandstone, we have a long period where the 

 limestone prevailed, when calcareous deposits covered the bottom of 

 the quiet ocean, and corals and shells in great numbers lived in the sea. 

 This condition, however, prevailed more completely in the central 

 portion of this ocean area, while there was little accumulation of 

 that kind in the eastern part. In this area, which now constitutes 

 the eastern middle portion of tlie continent, we find in New England, ' 

 New Brunswick and Nova Scotia, comparatively little limestone, 

 while it is the prevailing rock over large areas in the west. This line 

 from the north-east to the south-west has been, from the beginning 

 of this geologic period, the line of littoral currents and the accumu- 

 lation of the coarser sediments. 



There may have been some source of these materials which we do 

 not know ; but we know from the laws which govern the breaking 

 down of rocks, and distribution of sediments, that most of them have 

 been derived from a direction to the eastward of this portion of the 

 continent. [New York and New England.] We say most emphati- 



