E. M. Kindle — Diatomaceous Dust. 175 



Art. XIX.— Diatomaceous Dust on the Bering Sea Ice 

 Floes* ; by E. M. Kindle. 



In ordinary seasons the winter's accumulation of ice in 

 Bering Sea disappears to a sufficient extent by the end of the 

 first week in June to offer no serious obstacle to navigation. 

 The ice conditions during the spring and early summer of 1908 

 in Bering Sea were very unusual, however, and all of the 

 steamers sailing for Nome in Jane were imprisoned for brief 

 periods in the Bering Sea ice packs. Most of the vessels 

 occupied from 8 to 10 days in working through the 300 

 miles of ice floes which lay between the Seward Peninsula and 

 the open water in the southern part of Bering Sea. The 

 steamer Umatilla, on which the writer was a passenger, first 

 encountered the ice pack off the southwest coast of Tn univak 

 Island, June 11, in scattering cakes. Daring the succeeding 

 eight days, which the vessel spent among the ice floes, the 

 opportunities were favorable for observing the character of the 

 materials appearing upon the surface of the ice and for collect- 

 ing samples of the dirt on the floes. 



At the time of the writer's observations the long-continued 

 attrition of the ice cakes comprising the floes had broken them 

 into pieces generally not exceeding 200 feet in diameter. A 

 few cakes much larger than this still remained, however, and 

 one was observed with a length of not less than 350 yards. 



A very large percentage of the ice cakes were more or less 

 discolored by dirt or dust. Probably 80 per cent of the ice 

 bore small amounts of tine dust or dirt in sufficient quantity to 

 give it a slight gray or blackish color in spots. No pebbles or 

 rocks of any kind were observed on the floes. The very fine 

 texture of the dirt together with its dissemination through the 

 snow on the ice suggest that most of it reached the surface 

 of the ice through transportation by the wind. This fine 

 material was observed to show a strong tendency to segregate 

 itself into little pellets as the melting of the snow and ice con- 

 taining the dirt proceeds. These ranged in size from bird shot 

 up to the size of peas. They were nearly or quite spherical and 

 in the case of the larger ones sufficiently firm and compact to 

 i)robably reach the bottom without dissolution on the complete 

 melting of the ice in shallow water like that of the northern 

 half of Bering Sea. 



The color of the dust seen on the ice was generally gray, 

 dark brownish or black. A sample of the black dust which 

 was examined by Mr. A. Knopf at the writer's request is 

 stated by Mr. Knopf to be unquestionably of volcanic origin. 

 It may represent a fall of volcanic dust which occurred Novem- 

 * Published by permission of the Director of the U. S. Geol. Survey. 



