250 PROCEEDINGS OF THE ACADEMY OF [1883. 



immense ice-fields of Alaska themselves that we have to look for 

 the singularly moderate climnte of southeastern Alaska, rather 

 than to the mere action of heated water alone. They furnish the 

 heavy power which draws the warm current to it? shores. With 

 the disappearance of these huge glaciers, or the diversion of the 

 immense volume of cold water to another channel, the cold of tliis 

 ■portion of Alaska would probably be as intense as that experienced 

 along its northern coast. The distinction was one of vast import- 

 ance, and he ventured an opinion that much of the disappointment 

 often experienced in Arctic navigation arose from overlooking 

 it, and in regarding the warm current as the active agent in circu- 

 lation. 



In examining the Davidson, tlie Muir, and other glaciers, it also 

 occurred to him that there were active agencies at work, over- 

 looked by those who had made specialties of glacial study. 

 Beneath the Muir glacier, which was said by various authorities 

 to be about four hundred miles long, a large volume of water was 

 flowing in a rapid torrent — this volume, on a carefully considered 

 guess, being about one hundred feet wide with an average depth 

 of four feet. According to information from a white man who had 

 long lived with the Indians of this section, this subglacial river 

 was flowing in about the same volume, summer and winter. The 

 mouth of this glacier hung over into the sea, and formed icebergs 

 in three dillerent modes. Sometimes tlie edge of the glacier would, 

 in its tliinner sections, float over and be lifted off" .by the rise and 

 fall of the tide; at other times huge masses would break off by 

 their own weight; and at other times the upper edges, which, by 

 the action of running surfice water, would be worn into all sorts 

 of rough forms, would topple over, rubbing their faces against the 

 more solid ice, and making a sound which reverberated through 

 the ranges of hills like peals of artillery, and which could be 

 heard many miles away. There were thousands- of smallei* ice- 

 bergs floating down Glacier Bay, the most of these evidently 

 formed by the latter mode. It was not safe for the vessel on 

 which he made the visit to approach nearer than a quarter of a 

 mile to the i'ace of this glacier, where it anchored for a day in 

 oriier to make tlie examination ; but it was near enough, especially 

 with the aid of the ship's boats and good field-glasses, to muke 

 excellent observations. So far as could be ascertained through 

 occasional deep fissures, no water came out from under the face of 

 the glacier to the ocean. Tiie mass of ice was apparently l^'ing 

 flat on a bed of rock, the ice occupying a width of something less 

 than two miles, and estimated to be about 300 feet thick on an 

 average of its whole width. This would, of course, obstruct the 

 run of water directly to the ocean, and thus we had the lateral 

 flow which diverged from the glacier's bed about four miles from 

 its mouth. The Davidson glacier, in Pyramid Harbor, had retreated 

 from the ocean, and by comparing facts observed in tracing a 

 portion of its bed with what was seen in connection with this 



