496 PROCEEDINGS OF COLUMBUS MEETING. 



border of the Saint Elias mountains and just west of the 141st meridian. Several 

 glaciers were found flowing northward, but the ice drainage in that direction is 

 small compared with that southward from the same mountains, and the lower limit 

 <>f the neve fields is over 4,000 feet higher on the northern than on the southern 

 side of the range. The northern limit of glaciation in the White river basin is 

 only about forty miles north of the present termination of existing glaciers, and 

 the greater part of the basin appears never to have been covered by an ice sheet. 



The substance of this paper will be found in the National Geographic 

 Magazine, volume iv, 1892, pages 117-152, with plates 18-20, under the 

 title "An Expedition through the Yukon District." 



The next communication was entitled : 



GEOLOGY OF THE PRIBILOF [SLANDS. 

 BY JOSEPH STANLEY-BROWN. 



On the chart of Bering sea and the Arctic ocean issued by the Hydrographic 

 Bureau for 1889 are compiled the soundings made in those waters up to that date. 

 It requires hut a glance at this chart to make plain the fact that Bering sea is in 

 large part an extremely shallow body of water. An elevation of 300 or 400 feet 

 would convert most of the present sea bottom into a vast verdure-covered tundra, 

 whose gently undulating surface would be dotted with lakes and intersected by 

 sluggish winding streams. Upon such a land surface the four tiny islets to which 

 this brief sketch refers would appear as conspicuous elevations. 



In the waters of this shallow sea in very recent geologic time were created the 

 Pribilof or Seal islands.* Their formation was a simple process, and it- successive 

 steps are recorded with unusual legibility. 



In offering the results of a study f of this little geologic unit, the facts upon which 

 conclusions are based will he given only when clearness demands their presentation. 



The islands owe their origin to vulcanism. The geologic agents still busily en- 

 gaged in modifying them are the surf that heats ceaselessly upon their shores; the 

 ire which surrounds them in winter ; the drifting sands; and the luxuriant wild 

 grasses and other herbage. Precipitation, though generous, is rarely violent, and 

 erosion plays an insignificant role. 



Saint Paid island, the Largest member of the group, is 12 miles long and from li 

 to S miles wide. Its surface is diversified by at least a dozen cones and vents of 

 unusual symmetry, surrounding in irregular fashion a true crater some 600 feet in 

 height, called Bogoslof. The shores are lowlying, and sea-cliffs of conspicuous 

 height are infrequent. 



After the initial establishment of an outlet for the molton material, free from the 

 intrusion of the sea, there were four well marked episodes in the career of the 

 island. From this central point, that probably finally became the present Bogeslof, 

 there welled out great masses of lava which made their way outward in all direc- 



* The Pribilof islands are in latitude J7° north, longitude 170° west from Greenwich, and an- about 

 201) milt's northwest of (Jnimak pass, one of the natural waterways of tin- Aleutian chain through 

 which vessels find their way into Bering sea. 



f i (pportunity for this st,udy was had in the summer of 1891. while the writer was acting t i-i n t >. •- 

 rarily as an agent of the Treasury 1 > spartment for the investigation of the condition of seal life on 

 the islands, 



