GENEEAL REMARKS. 143 



represent an approximate terrace-level, having relation to a former de- 

 pression of the land of about the amount stated. 



In Plover bay, on August 16, large masses of snow occupied many of 

 the hollows, sometimes quite down to the edge of the sea. Portions of 

 these accumulations undoubtedly last throughout the summer. No 

 glaciated rock surfaces were actually observed, but this negative evidence 

 is here of small value, as it depends upon observations made in a very 

 short time and over a very small area. Mr Muir speaks of having found 

 glaciated rock surfaces in Plover bay, and pictures it as havinpj been at 

 one time filled by a glacier thirty miles in length and from 2,000 to 3,000 

 feet in thickness.* 



General Remarks. 



Bering sea is a dependency of the north Pacific, marked off from it 

 by a bordering chain of islands like those which outline Okhotsk 

 sea and the sea of Japan. It differs from these two seas by reason of 

 its connection to the north with the Arctic ocean, and in the fact that 

 Avhile the whole eastern part of its extent is comparatively shallow, the 

 profounder depths of the north Pacific (in continuation of the Tuscarora 

 deep) are continued into its western part. The Aleutian islands, regarded 

 as a line of demarkation between the main ocean and Bering sea, are 

 analogous to the Kurile islands with Kamchatka, and to the islands of 

 Japan. As to the Commander islands, though these appear to lie in the 

 continuation of the arc formed by the Aleutians, they are separated by 

 a wide and, so far as known, very deep stretch of ocean from the last of 

 these islands, and it is wholly probable that they may represent an 

 altogether independent local elevation analogous to that to which Saint 

 Matthew and its adjacent islands are due. 



The western part of Bering sea has as yet been very imperfectly ex- 

 plored with the deep-sea lead, but the following general facts may be 

 gathered from the existing charts : The entire chain of the Aleutian 

 islands is bordered at no great distance to the south by abyssal depths 

 of the Pacific. The whole western portion of the chain likewise slopes 

 rapidly down on the northern side into very deep water, exceeding 1,000 

 fathoms as far to the eastward as Unimak island ; but from the vicinity 

 of Unimak pass (longitude 165° west) the depths to the north of the isl- 

 ands are consistently less than 100 fathoms. Beginning near the Unimak ^ 

 pass, the edge of the hundred-fathom bank runs northwestward, passing 

 to the west of the Pribilofs and Saint Matthew island and meeting the 

 Asiatic coast in the vicinity of cape Navarin, in about north latitude 60°. 

 Thus all parts of Bering sea to the north and east of this line, together 



* Report of the Cruise of the Corwin, 1881, p. 143. 



