450 Probable influence of y 



icebergs at the time of their separation from the glacier or 

 land, especially the level bergs, which are not liable to be 

 overturned, the materials attached would never become ex- 

 posed, while they would soon be loosened by the action of 

 the water. Another consideration is to be observed. It 

 cannot be questioned that the foreign materials are more 

 abundant upon the icebergs near their source. Around the 

 smaller stones and sand the ice is melted, so that they would 

 be easily detached. Around the larger blocks, from the state- 

 ments of Captain Pendleton, and the observations of Agassiz, 

 the ice is melted, so that the large blocks project upon the ice ; 

 they might thus be easily detached by contact with other ice- 

 bergs, the overturning of the iceberg, or the washing of waves 

 produced by the fall or overturn of neighboring masses of ice. 

 I am so fully aware of the danger which exists of forming 

 altogether too broad conclusions as to past phenomena, from 

 the limited examination of actual causes, that I hesitate to 

 present any more general inferences from the facts now ex- 

 hibited than such as have been already hinted at. But, as 

 there seems to exist a ri^ht to demand of evcrv collector or 

 observer of facts the conclusions which he has been led to 

 form from their examination, I will briefly present the infer- 

 ences which may be drawn from the facts which I have ex- 

 hibited as to the mechanical and transporting agency of ice 

 in the ancient seas. 



1. The steadiness in the movement of the icebergs of our 

 present seas, in the direction and under the influence of the 

 great under currents, and the southerly course of these under 

 currents in our northern hemispheres, from causes which must 

 have prevailed, as well in the ancient as in our present seas, 

 favor the theory that icebergs, with gravers of rock in their 

 lower portions, or pressing the sand and gravel, by their im- 

 mense weii^ht, along the surface of the rocks, in the bottoms 

 of the ancient oceans, might have scored and grated along 

 the rocks, grinding off their salient points, and leaving the 

 surfaces smootlied and striated in the fixed southerly direction 

 in which now they occur. 



