378 REPORT OF NATIONAL MUSEUM, 1904. 



daga salt and plaster rocks, and the Manlius water lime. The third 

 included the Pentamerus lime, the Oriskany sand, Schoharie grits, and 

 Helderberg limestone. The fourth included the Marcellus and Ham- 

 ilton shales, the Tulley lime, Genesee slate, and the Ithaca and Che- 

 mung slates and grits. 



He regarded the transition rocks of Essex and St. Lawrence counties 

 as equivalent to the graywacke series of European authorities. The 

 so-called primitive limestone — the peculiar, coarsely crystalline, ser- 

 pentinous limestone occurring in Essex County — he conceived might 

 be an eruptive rock in which the carbonic acid had been retained by 

 the pressure of superincumbent masses, the experiment of Sir flames 

 Hall, as he believed, bearing him out in this. The occurrence of 

 plumbago he also regarded as favoring the igneous origin of the lime- 

 stone, since plumbago is itself so often produced in furnaces. 



He believed the agent of drift transportation to be water and ice. 

 The bowlders he thought to be the work of icebergs, but he did not 

 regard the st nations and polishing as due to them, since the bottom 

 of the ocean is not bare rock but covered by debris; and. moreover, 

 icebergs would not move in straight lines (a point which some more 

 recent writers have quite overlooked.) The bergs might act as agents 

 of transportation, he argued, but not of erosion. According to his 

 ideas, the drift-covered region was, during the drift period, depressed, 



the country low and connected at the north with :i wide and extensive region, giving 

 rise to Large rivers, which flowed in succession over different parts of the region 

 lying between Champlain and the St. Lawrence. These rivers were wide, shallow, 

 and swift in some parts of their courses, and frequently found new channels. They 

 communicated with the Atlantic on the south through the Champlain, Hudson, and 

 Mohawk valleys. They bore along ice loaded with sand, pebbles, etc., which 

 scratched and grooved the surface of rocks over which they flowed, and were the 

 agents, also, of perforating the rocks in the form of potholes. 



Emmons was, at this time, a catastrophist, going so far as to assert 

 that the deep canyons in the Potsdam sandstone, like the An Sable 

 chasm, were "opened by some convulsion of nature."" 



It was while connected with the New York State survey that 

 Emmonsconceived the idea that a series of obscure rocks, forming a belt 

 some fifteen miles wide along the western border of Berkshire County, 

 and lying along both sides of theTaconic Mountains, were distinct from 

 any of the so-called primary rocks, and lay below those of the New York 

 system.' He therefore proposed, on stratigraphic grounds, to raise 

 these rocks to the dignity of a system by themselves, which should be 

 called the Taconic system. Inasmuch as the controversy which arose 

 over this new system raged vigorously for nearly half a century, the 

 subject is considered worthy of a special chapter. (See p. 059.) 



Vanuxem's report on the third district, a volume of 306 pages, con- 

 sisted of little more than an uninteresting account of the geographic 



