THE LEDA CLAY. 35 1 



fathoms be thus raised, the Gulf of St. Lawrence would 

 be represented by a river delta, one hiouth in the Straits 

 of Belle Isle, the other flowing out between Cape Bre- 

 ton and Cape Ray. All the submarine plateaux, such 

 as the Grand Bank of Newfoundland, and the banks'ly- 

 ing off the coast of Nova Scotia, Maine, and Cape Cod, 

 would be elevated above the sea, and probably form 

 broad plains. Thus the effects on the distribution of 

 life would essentially differ from those of the region 

 north of 50° N. Such a rise and enlarged area of land 

 would, as has been stated by physicists, produce an ex- 

 tension southward of an extreme arctic temperature. 

 While the climate would be greatly lowered, we still 

 have added the proximity of the Gulf Stream, as evi- 

 denced by the temperate rather than arctic fauna of the 

 glacial beds of New York and Nantucket, and the more 

 tropical assemblage of South Carolina. Such a blending 

 of hot and cold currents of air and water must have pro- 

 duced even more fogs and a much greater rainfall than 

 now, to feed the enormous glaciers which moved into the 

 sea from off the principal water-sheds. 



II. Leda Clay. — There was a gradual change of level 

 in the sea. At the close of the glacial period the snow 

 line gradually receded from the coast, and the glaciers 

 retreated to the mountains. During the slow and gen- 

 tle submergence of the land ushering in this epoch, the 

 crude moraine matter was sorted into beds of regularly 

 stratified clays one hundred to three hundred feet in 

 thickness. The lowest beds consequently are the most 

 ancient, as is also evidenced by the greater prevalence of 

 arctic forms. During this time the sea was filled with 

 floating ice, as at present on the Labrador coast, and the 



