120 NEW YORK STATE MUSEUM 



Huntington, Barrell and Leith and by his own widening experience; 

 he is " now inclined to consider the Keweenawan as more largely 

 a land surface formation" than he did in earlier writings; 1 and 

 Van Hise (see Leith, 1920, p. 101) believed that the " Precambrian 

 rocks and history, from earliest known vestiges, indicate the same 

 behavior and conditions of development as in later times " and 

 " that Hutton's conception of uniformitarianism applies to the 

 Precambrian." Indeed, from Lyell to Van Hise a long line of investi- 

 gators both here and in Europe have claimed that all Precambrian 

 gneisses are metamorphosed sediments and dynamometamorphically 

 changed eruptive rocks ; and that these immense masses of sediments 

 can indicate only epicontinental and continental marginal deposits. 

 If we add to this that the extensive graphite beds that appear as 

 early as the Archeozoic Grenville beds, under the principle of 

 uniformitarianism, indicate extensive swamp or at least shallow 

 water conditions with algal growth, and that likewise the quartzite 

 and marble beds with which they are associated are considered as 

 epicontinental deposits, 2 it seems safe to assert that the existence 

 of the Precambrian continental mass of North America, suggested 

 by the uniform Precambrian fold lines, is well supported by the 

 character of the sediments that have formed its component rocks. 



Eurasia suffered such a wide transgression of its eastern portion in 

 Cambrian time that- it does not appear, on maps of the early Cam- 

 brian as the vast continent we see it today. And yet the great 

 unconformity which everywhere marks the contact of Precambrian 

 and Cambrian beds in eastern Asia leaves no doubt of the former 

 existence of a great continental mass in eastern Asia, and the later 

 Paleozoic history with its alternating emergences and submergences 

 of this area sustains the continental character of eastern Eurasia 

 to the present time, although the great Mediterranean sea, the 

 " Tethys " of Suess, passed across the continent from east- west from 

 Devonian to Triassic time, separating the northern Angara land 

 from the southern Gondwanaland. 



In Europe we have in the Proterozoic age the great formation 

 of the Torridon sandstone of Scotland, which even contains 



1 Camsell (1916, p. 478) also found in the Athabasca sandstone of Keweenawan 

 age, at the northeast end of Tazin lake in the Northwest Territories a conglom- 

 erate deposit which he considers as of terrestric origin, and Coleman (191 5, 

 op. cit.) states that deposition during Keweenawan time was chiefly on the land 

 in a warm dry climate. 



2 Daly (1909, p. 157) e. g. states that the Huronian sea was largely an 

 epicontinental sea, an inference that can with equal force be applied to the 

 preceding invasions, and Schuchert (1918, p. 64) states that of the 14 miles of 

 coarse Proterozoic sediments in south-central Canada, probably more than 

 three-fourths were deposited in fresh water. 



