542 CENOZOIC TIME — MAMMALIAN AGE. 



that it extended beyond this limit the facts give no evidence. It 

 therefore reached to the Ohio on the south, if not bej^ond, and 

 far to the north over the British possessions, to a limit north which 

 is yet undetermined. 



It appeals, further, to the facts that — 



(2.) The icebergs of the Atlantic are floated southward from the 

 Arctic, and come freighted with a vast amount of stones and earth ; 

 and that many of them at the present day descend along the coast 

 of Labrador and Newfoundland and over the Newfoundland 

 Banks, and, as they melt, cover the coast with blocks that are as 

 large as any of the Drift epoch, and also strew the sea-bottom with 

 both stones and earth. 



(3.) The great Labrador current (p. 41) has the general direc- 

 tion of the drift stones and scratches, or from the northward, and 

 must have always had this course. 



(4.) The material deposited by melting bergs would be unstrati- 

 fied, and contain few if any sea-relics. 



(5.) Stones in the foot or under surface of a grounded berg 

 would scratch the surface over which it might move. 



(6.) Accumulations of sand and pebbles having a resemblance 

 to beach-deposits occur at different heights in Massachusetts from 

 800 and under to 2600 feet, — the last in the White Mountains and 

 elsewhere (Hitchcock). 



In the Iceberg theory there are the following difficulties : — 



(1.) If any zone or part of the continent were under the sea, 

 we should somewhere look for that sure evidence, marine fossils. 

 But none have been found. One-half of the Pliocene species of 

 sea-shells still live ; and therefore the waters were not destitute of 

 life. The Tertiary and Cretaceous coasts are well marked by these 

 means on the Atlantic and Gulf borders. The shore of the sea of the 

 Drift period has not been traced by either beaches or shells. The 

 highest point of shore shell-beds known is 500 feet, and this occurs 

 on the St. Lawrence (p. 549) : nothing of the kind occurs over the 

 Ohio region north or south of the river. 



(2.) The icebergs of the Atlantic bring their burdens from the 

 Arctic, having gathered them while glaciers about the Arctic 

 mountains, — for all icebergs are fragments from the lower ends of 

 glaciers broken off and floated away by the sea; and they are 

 therefore not exactly parallel in their operations with the means 

 of transport over New England, where the stones and earth were 

 carried usually less than fifty miles. Consequently, if icebergs were 

 the means of transport in New England, those icebergs must have 

 commenced as glaciers about New England mountains, — an idea 



