THE GREAT ICE AGE 353 



channel from the great bank of Newfoundland to Cape Cod, 

 we cannot avoid the conclusion that the Arctic current and 

 its ice have great power both of excavation and deposition. 

 On the one hand, deep hollows are cut out where the current 

 flows over the bottom, and on the other, great banks are heaped 

 up where the ice thaws and the force of the current is abated. 

 I have been much struck with the worn and abraded appear- 

 ance of stones and dead shells taken up from the banks off the 

 American coast, and am convinced that an erosive power com- 

 parable to that of a river carrying sand over its bed, and mate- 

 rially aided by the grinding action of ice, is constantly in action 

 under the waters of the Arctic current. 1 The unequal pres- 

 sure resulting from this deposition and abrasion is not improb- 

 ably connected with the slight earthquakes experienced in 

 Eastern America, and also with the slow depression of the 

 coast ; and if we go back to that earliest of all geological 

 periods when the Laurentian rocks of Sir Wm. Logan, consti- 

 tuting the Labrador coast and the Laurentide Hills, were alone 

 above water, we may even attribute in no small degree to the 

 Arctic current of that old time the heaping up of those thou- 

 sands of feet of deposits which now constitute the great range 

 of the Alleghany and Aalachian mountains, and form the 

 breast bone of the American continent. In those ancient 

 times also large stones were floated southward, and enter into 

 the composition of very old conglomerates. 



1 At the time when this was written I had only studied stones brought 

 up accidentally by fishermen and others from the banks of Newfoundland 

 and elsewhere. At a later date Murray of the Challenger has given 

 more ample material, He states that the bottom in the Labrador current, 

 100 miles from land, was found to be blue mud with 60 per cent, of sand 

 and stones ; and mentions a block of syenite weighing 490 Ibs. taken up 

 in 1,340 fathoms, and stones and pebbles of quartzite, limestone, dolomite, 

 mica schist and serpentine, one of which was glaciated. This is the 

 modern boulder clay produced by Greenland glaciers and the field ice of 

 Baffin's Bay and the Labrador coast. 



