OSAR STEEAMS AND OSAES IN ALASKA. 357 



sand and gravel is being deposited by this stream in large quantities. This covers 

 the ice over which the stream Hows, and during former stages was deposited in 

 terraces along the lower portion of the channel. These terraces, in part, at least, rest 

 on ice. The rounded and worn condition of the gravel and sand brought out of the 

 tunnel is proof that it has had a long interglacial or subglacial journey. 



On the north side of the open channel of Kame Stream there is a sharp ridge of 

 well-rounded gravel which runs parallel with the present river, and in i>laces can be 

 seen to rest on an icy bed. This was evidently deposited by a stream similar to the 

 present one, but which flowed fully 100 feet higher. This ridge of gravel seems to 

 be of the same general character as the kames of New England and other glaciated 

 regions. * * * The formation of osars seems fully exj)lained by the subglacial 

 drainage of the Malaspina ice-sheet.' 



In two important conditions the Malaspina ice-sheet or Piedmont 

 glacier varies from the ice-sheet of Maine. 1. In Maine the morainal 

 matter was basal, i. e., contained in the lower part of the ice and taken 

 into the ice from below, while the drift of the Malaspina glacier is on its 

 surface (marginal) or scattered through it tO' a great height — the result 

 of avalanches bringing down fragments of rock and depositing them in 

 successive layers on the n^vds of the glaciers. 2. The Mount St. Elias 

 glaciers are bordered by considerable land bare of ice, and a large amount 

 of water warmed above 32° flows onto the g'laciers and helps to form and 

 enlarge the subglacial channels. The amount of heat thus transferred to 

 points beneath the ice is very much greater thau that carried by superficial 

 waters of the ice surface pouring down crevasses. In Maine the hills are 

 so low that in only a few of the most mountainous regions would the con- 

 ditions at all approach those of Alaska. Over most of the State the glacier 

 would be reduced to only 200 or 500 feet in thickness before any of the 

 land would rise above the surface of the ice. In the upper Kennebec 

 Valley there are a few high gravel terraces that may have been formed by 

 streams flowing in the depression that forms at the margin of a glacier next 

 a mountainside, but such gravels are rare. I have nowhere jet found in 

 Maine the delta terraces of such marginal lakes as Professor Russell finds 

 so abundantly in Alaska. The short hillside osars were formed by streams 

 that flowed down steep southern slopes. They often expand into deltas at 

 the bottoms of the hills, but there is no series of terraces marking sixceessive 

 levels of the water, except in the courses of the great osar rivers. These 

 were fed by glacial waters, not by waters of the land bare of ice. 



' Am. Jour. Sci., Sd series, vol. 43, p. 180. 



