CRUISE OF STEAMER CORWIN IX THE ARCTIC OCEAX. 



141 



size, and alternating ridges and valleys with wide U-shaped cross-sections, and with nearly parallel 

 trends across the island in a general north to south direction, some of them extending from shore 

 to shore, and all showing a true subordination to the grinding, furrowing action of a broad over- 

 sweeping ice-sheet. 



Some of the widest gap-like valleys have been eroded nearly to the level of the sea, indicating 

 that if the ice action had gone on much longer the present single island would have been eroded 

 into a group of small ones; or the entire mass of the island would have been degraded beneath 

 the sea level, obliterating it from the landscape to be in part restored perlfaps by the antagonistic 

 elevating action of the post-Glacial volcanoes now occupying the middle portion. 



VOLCANIC CONES ON SAINT LAWRENCE ISLAND. 



The action of local glaciers has been comparatively light, not enough to greatly obscure or 

 interrupt the overmastering effects of the ice-sheet, though they hive given marked character to 

 the sculpture of some of the higher portions of the islatid not covered by volcanic cones. 



The two Diomede Islands and Fairway Rock are mostly residual masses of granite brought 

 into relief and separated from one another and from the general mass of the continent by the 

 action of ice in removing the missing material, while the islands remain because of their superior 

 power of resistance to the universal degrading force. 



That they are remnants of a once continuous laud now separated by Bering Strait is indicated 

 by the relative conditiou of the sides of the islands and of the continuous shoulders of the conti- 

 nents, Cape East and Cape Prince of Wales, while the general configuration of the islands shows 

 that they have been subjected to glaciatiou of the most comprehensive kind, leaving them as 

 roches moutonnres on a grand scale. 



Traces of local glaciation were discovered ou the largest of the three, but the efforts produced 

 by this cause are of course comparatively slight when the size of the island is taken into consid- 

 eration, while the action of excessive moisture in the form of almost constant fogs and rains 

 throughout the summer months, combined with frost and thaw, has effected a considerable 

 amount of denudation, manifested by groups of crumbling pinnacles occurring here and there on 

 the summit. 



Sledge, King's, and Herald Islands are evidently of similar origiu, bearing the same glacial 

 traces, and varying chiefly in the amount of post-Glacial waste they have suffered, and in the 

 consequent degree of clearness of the testimony they present. 



During our visit to Herald Island an exceptionally favorable opportunity offered as to the 

 time of year, state of the weather, &c, for observation. 



Kellett, who first discovered the island and landed on it under adverse circumstances, describes 

 it as an inaccessible rock. The sides are indeed precipitous in the main, but mountaineers would 

 find many slopes and gullies by which the summit would be easily attained. We landed ou 

 the southwest side, opposite the mouth of a small valley, the bed of a vanished glacier. 

 A short gully which conducts from the water's edge to the mouth of the valley proper is very 

 steep, and at the time of our visit was blocked with compacted snow, in which steps had to be 

 cut, but beyond this uo difficulty was encountered, the ice having graded a fine broad way to 

 the summit. Thence following the highest ground nearly to the northwestern extremity, we 

 obtained views of most of the surface. The highest point was found to be about 1,200 feet above 

 the sea. This point is about 1J miles from the northwest end of the island, ami -U miles from the 

 S. Ex. 204 19* 



