ANCIENT ICEBERG WORK 145 



were almost necessarily led to the supposition that those 

 scorings of the rocks and carriage of detrital materials had 

 been brought about by berg action. Explorers who liad 

 cruised in high latitudes had noted that the floating ice con- 

 tained quantities of glacial waste, and also that the masses 

 were often driven by the wind against the bottoms of the 

 shallow seas. It was, moreover, well known that in the pro- 

 cess of geographical change regions which have recently been 

 sea bottom have been converted into dry land. Thus a 

 natural explanation of the facts appeared to be attained. 

 Further inquiry has shown, however, that the greater part of 

 the ice work in glaciated districts is not due to iceberg action, 

 but to the movement of vast united masses of ice such as now 

 covers the central portion of Greenland. Here and there, 

 however, along the shores, and even at heights of some hun- 

 dred feet above the sea level, we find indications that during 

 the waning stages of the ice epoch the land was lower than at 

 present, that it was cruised over by bergs which now and then 

 grounded and often dropped the waste embedded in their 

 masses, and released during the process of melting, upon the 

 surface of the earth. Thus the original theory adduced to 

 explain drift phenomena has, by the evidence, been pushed 

 into a very subordinate position. 



In a number of ancient geological formations we find 

 evidence through the presence of stray blocks or heaps of 

 detrital matter embedded in finer materials, serving to show 

 that the seas in sucli periods were cruised over by icebergs. 

 These indices are of great value for the reason that the land 

 record made by a glacial period is quickh- destro)-ed by decay, 

 so that the work done by icebergs, the record of which is 

 quickly buried in the submarine strata, may be all that is 



