1881.J ^-'^ IPrice. 



and naturally inferred that it was the cause of the deposit here of these 

 transported rocks. 



In 1878 Professor Cook published his "Report on the Geology of the 

 State of New Jersey," and placed the glacial drift northward, on a line 

 from a point of the Raritan river (lat. 40° 30'), thence N. W. to Den- 

 ville (near the 41°), thence westward and south-westward to Belvidere on 

 the Delaware (lat. 40° 50'). 



In 1881 Professor Henry Carvill Lewis, also of the Second Geological 

 Survey of Pennsylvania, has traced the southern line of the glacial drift 

 through this State for a distance of about 400 miles. He informs me, in 

 advance of publication, that this line, which is marked by a terminal 

 moraine, starts at a point opposite Belvidere, and passes in a north-west 

 direction over the Kittatinny and Pocono mountains, and across the 

 Lehigh and Susquehanna rivers into Lycoming county, where it ascends 

 the Alleghany Mountains, and continues thence in a nearly straight line 

 into Cattaraugus County, IST-. Y. (lat. 42° 15'). It there curves south- 

 westward and, re-entering Pennsylvania in Warren County, passes south- 

 west through Venango, Butler and Lawrence Counties, until in Beaver 

 County (lat. 40° 50') it crosses the Ohio State Line. 



In his "Essay on the Antiquity and Origin of the Trenton Gravels," 

 Mr. Lewis states his belief as to " the Terminal Moraine " ■which he had 

 explored, which "winds over hills and across valleys in such a manner 

 that by no other known agency than a great glacier could it have been 

 produced," p. 17. This is the product, he says, of the last glacial epoch. 

 There is some evidence that in an earlier period a glacier advanced south 

 of that limit. To the north "the great glacier has left undoubted traces, 

 in the universal covering of unstratified boulder clay or till, in the 

 smoothed and grooved rocks, the transported boulders, &c." "There are 

 many facts which indicate that the ice, even close to its lower terminus, 

 had a thickness of over 1000 feet, which increased northward," pp. 

 18, 19. 



Mr. Lewis also speaks of a post-glacial flood, "at a time when the river 

 [Delaware] was larger than at present," as a " conclusion warranted by 

 many facts, and as a cause of the deposit of the Trenton gravels, " p. 19, &c. ; 

 and " that the boulders upon its surface were dropped from ice-cakes is, 

 however, probable," p. 23. 



Did, then, these transported rocks come here by glacial action ? If so, at 

 a first or second glacial epoch? By a great glacier or by floated ice? 

 Were they lifted upon the hills by ice dr water ? Or was the earth sunk 

 when they were brought, and the rocks afterwards lifted by the rising 

 of the earth's surface ? Professor Lewis gives to these transported rocks 

 a transporting cause common to the Philadelphia red graveland our brick 

 clay, at "an epoch of submergence as indicated by the elevation of their 

 deposit;" and that "it is probable that this clay may be assigned to a 

 period when the land stood 150 feet or more below its present level, and 



