140 



CRUISE OF STEAMER CORWIN IN THE ARCTIC OCEAN. 



mountain range, extending along the North Pacific coast, into its present condition as a chain of 

 islands. 



OVERSWEPT GLACIAL VALLEYS AND RIDGES ON SAINT LAWIiENCE ISLAND. 



The Pribylov Group, Saint Paul, Saint George, ^Walrus, and Otter Islands appear in general 

 views from the sea as mere storm-beaten remnants of a once continuous laud, wasted into bluffs 

 around their shores by the action of the waves, and all their upper surfaces planed down by a 

 heavy oversweeping ice-sheet, and slightly roughened here and there with low ridges and hillocks 

 that alternate with shallow valleys. None of their features, as far as I could discover without 

 opportunity for close observation, showed any trace of local glaciation or of volcanic actiou sub- 

 sequent to the period of universal glaciation. 



Saint Lawrence Island, the largest in Bering Sea, is situated at a distance of about 120 miles 

 off the mouths of the Yukon and 40 miles from the nearest point on the coast of Siberia. It is 

 about 100 miles long from east to west, 15 miles in average width, and is chiefly composed of 

 various kinds of granite, shite, and lava. 



The highest portion along the middle is diversified with groups of volcanic cones, some of 

 which are of considerable size and clearly post-Glacial in age, presenting well-defined craters and 

 regular slopes down to the base, though I saw no evidence of their having poured forth streams 

 of molten lava over the adjacent rocks since the close of the Glacial period; for, with the exception 



BED OF LOCAL GLACIER, SAINT LAWRENCE ISLAND. 



of the ground occupied by the cones, all the surface is marked with glacial inscriptions of the most 

 telling kind — moraines, erratic bowlders, roohes moutonnees, in great abundance and variety as to 



