Date of the Glacial and the Upper Miocene Period. 371 



" It is impossible," be continues, " to get at rocks over which 

 heavy icebergs now move; but a mass 150 miles wide, perhaps 

 3000 feet thick in some parts, and moving at the rate of a mile 

 an hour or more, appears to be an engine amply sufficient to ac- 

 count for striae on rising rocks/' And in ' American Tramp/ 

 p. 76, he says, " stria must be made in deep water by the large 

 masses which seem to pursue the even tenor of their way in the 

 steady current which flows down the coast." 



Mr. Campbell, from a careful examination of the sea-bottom 

 along the coast, finds that the small icebergs do not produce striae, 

 but the large ones, which move over rocks impossible to be got 

 at, "must" produce them. They "appear" to be amply suffi- 

 cient to do so. If the smaller bergs cannot striate the sea-bot- 

 tom, why must the larger ones do so ? There is no reason why 

 the smaller bergs should not move as swiftly and exert as much 

 pressure on the sea-bottom as the larger ones. And even sup- 

 posing that they did not, one would expect that the light bergs 

 would effect on a smaller scale what the heavy ones would do on 

 a larger. 



I have no doubt that when Mr. Campbell visited Labrador he ex- 

 pected to find the sea-coast under the water-line striated by means 

 of icebergs, and was probably not a little surprised to find that it 

 actually was not. And I have no doubt that were the sea-bottom 

 in the tracks of the large icebergs elevated into view, he would 

 find to his surprise that it was free from striations also. 



So far as observation is concerned, we have no grounds from 

 what Mr. Campbell witnessed to conclude that icebergs striate 

 the sea-bottom. 



The testimony of Dr. Sutherland, who has had opportunities 

 of seeing the effects of icebergs in Arctic regions, leads us to the 

 same conclusion. "Except," he says, "from the evidence 

 afforded by plants and animals at the bottom, we have no means 

 whatever to ascertain the effect produced by icebergs upon the 

 rocks*. In the Malegat and Waigat I have seen whole clusters 

 of these floating islands, drawing from 100 to 250 fathoms, 

 moving to and fro with every return and recession of the tides. 

 I looked very earnestly for grooves and scratches left by icebergs 

 and glaciers in the rocks, but always failed to discover any "t. 



We shall now see whether river-ice actually produces stria- 

 tions or not. If floating ice under any form can striate rocks, 

 one would expect that it ought to be done by river-ice, seeing 

 that such ice is obliged to follow one narrow definite track. 



St. John's River, New Brunswick : — " This river," says Mr. 

 Campbell, " is obstructed by ice during five months of the year. 



* Quart. Journ. Geol. Soc. vol. ix. p. 306. 

 t Journal, vol. i. p. 38. 

 2B 2 



