The Geology of H Ingham. 21 



and became imbedded in the substance of the glacier below, they 

 must necessarily have exerted an immense gouging force as they 

 were borne on ; and consequently we see everywhere upon the 

 rock-surfaces of New England deep traces of their passage, always 

 showing the direction of the great glacial movement. These 

 generally are found to be not far from south, 40° east, in this 

 region. Many thousands of years have elapsed since these were 

 traced, but still they are distinctly visible. 



The Glacial Period of intense cold, of the wearing away by the 

 ice of the rocks over which it passed, of the excavation of valleys 

 by its action, at length came to an end, and was followed by the 

 Champlain Period. This period was of marked contrast with the 

 preceding. It was one of great depression of the whole surface 

 of the North in both hemispheres, and this was probably the cause, 

 partly at least, of the great increase in the temperature which led 

 to the melting away of the ice sheet that had for an immense 

 period covered the earth. Land that now stands at considerable 

 height was below the level of the sea, as shown by forms of 

 marine life found at various elevations in northern New England, 

 where it is evident they lived and died when submerged in the 

 waters. Contrary to views that have been hitherto presented, 

 this depression did not affect the surface to any considerable 

 degree south of Maine, New Hampshire, and Vermont. The 

 occurrence of shells and other marine remains in elevated posi- 

 tions above the sea, often cited as proofs of depression, at Point 

 Shirley near Boston, and at Sancati Head, Nantucket, has been 

 satisfactorily demonstrated to have been the result of the scoop- 

 ing up from the bottom of the adjacent waters by the ice-sheet 

 the material forming the Till Hills, in which such remains have 

 been found. In these hills the shells do not occur, as in Maine 

 and elsewhere north, in beds, showing the places they occupied in 

 life, but scattered indiscriminately throughout the mass of ma- 

 terial, and generally in a fragmentary condition. 



The degree of subsidence north, as shown by the heights at 

 which remains of marine life have been found, increased with the 

 latitude. On the coast of Maine the highest stated is 217 feet 

 above the sea ; at Lake Champlain near 400 feet ; on the St. 

 Lawrence near Montreal, 500 feet ; about the Bay of Fundy, near 

 400 feet ; on the Labrador coast, from 400 to 500 feet ; and at 

 places in the Arctic regions, 1,000 feet. These figures are taken 

 from Dana. 



As the glacier melted, great floods poured over and from it, 

 and the stones, sand, and gravel in it were distributed over the 

 land. It was a period of deposition of earthy matter from the ice, 

 and of subsequent redistribution of portions of it by the waters. 

 The direct deposits as now found are not stratified, or but very 

 partially so, and are known as diluvium, while those which fol- 

 lowed, the result of the action of the waters in redistributing the 

 material, are known as alluvium. It was in this period that 



