534 



CENOZOIC TIME. 



the British Channel north, and abound on the coast of Norway. They 

 are remarkably displayed on the coasts of Greenland, Labrador, Nova 

 Scotia, and Maine. On the northwest coast of America, from the 

 Straits of De Fuca north, they are as wonderful as along Norway. On 

 the coast of South America, they occur in Drift latitudes, from 41° S. 

 Drift latitudes are therefore nearly identical with fiord latitudes. 



III. Origin of the Phenomena of the Glacial Period. 



The Drift period is usually called the Glacial period, under the 

 idea that ice, in the form of either icebergs or glaciers, was concerned 

 in the transportation of the bowlders, pebbles, and earth. Ice may 

 float masses of many thousand tons' weight, when in the condition of 

 an iceberg ; and so glaciers, as in the Alps, may bear along equally 

 great masses of rock or earth. But simple running or moving water 

 is incapable of such work. There are, then, two theories, the Iceberg 

 and the Glacier. The former supposes large parts of the continents 

 under the sea ; the latter places the same regions above the sea, and 

 perhaps at a higher elevation than now. They thus diverge at the 

 outset. 



1. Iceberg Theory. — (1.) The Iceberg theory supposes New Eng- 

 land to have been submerged 5,000 feet or more below its present 

 level. It requires, in fact, that the submerged area should have ex- 

 tended wherever the Drift occurs : and therefore this must have 

 reached to the Ohio on the south, and beyond, according to some ad- 

 vocates of it, along the Mississippi valley to the Gulf of Mexico ; and 

 far to the north, over the British possessions, to a limit yet undeter- 

 mined. But, in opposition to this hypothesis, there are, south of the 

 latitude of Hudson's Bay, no shell-bearing sea-beaches, as evidence of 

 such a submergence, beyond a height, at the most, of 500 feet. 



It appeals, also, to the facts that — 



(2. ) The icebergs of the Atlantic are floated southward from the Arctic regions, and 

 descend along the coast of Labrador and Newfoundland, and over the Newfoundland 

 Banks, and, as they melt, cover the coast with bowlders and strew the sea-bottom with 

 stones and earth. 



(3.) The Labrador current (p. 40) has the direction of the Drift stories and scratches. 



(4.) The material deposited by melting bergs would contain few, if any, sea relics. 



(5) Stones in the foot of a grounded berg would scratch the surface beneath. 



(6.) The courses of the scratches in the St. Lawrence valley, not far from the river;, 

 and the Drift transportation were up stream, as if from the flow of the Labrador current, 

 carrying ice, while the continent was submerged. 



In the Iceberg theor}', there are the following difficulties: — 



(1.) There are no marine deposits or fossils of the era over the interior of the conti- 

 nent. The shore of the sea of the Drift period has not been traced by either beaches or 

 shells. The greatest height of shore shell-beds in or near the United States is 470 feet; 

 and this occurs on the St. Lawrence (p. 550); nothing of the kind occurs over the Ohio 

 region, north or south of the river. 



