28 H. F. Reid— Studies of Muir Glacier. 



IVibutnnes. 



Beginning at the right, we find three tributaries coming in 

 from the southeast. The Dirt glacier (see plate 3) sweeps around 

 in a great curve from behind mount Wright ; its lower part is 

 completely covered with debris for fully a mile and a half from 

 its mouth ; above this the glacier is particularly clean. The 

 White glacier (see plate 4), which joins the Muir just beyond 

 mount Case, is remarkably beautiful. Arising in a circle of 

 snowy mountains it flows down a deep narrow valley at an angle 

 of about 10°, its perfectly white surface marked by the wonder- 

 fully symmetrical parallel curves of three or four dark moraines. 

 It is about four miles long and half a mile wide. A little further 

 is the southeastern tributary (see plate 5), fed by a number of 

 smaller glaciers. This glacier is not hemmed in by mountains 

 but crosses a divide east of a,3, over which the ice flows into 

 some valley on the other side. This divide has an altitude of 

 2,000 or 2,500 feet. About ten miles southeast of our camp a 

 large glacial stream discharges into Glacier bay. It must drain 

 the southern side of the mountains which bound these three 

 tributaries. 



Still further eastward is Main valley, which, though it proba- 

 bly once contained a tributary, is now an outlet of Muir glacier. 

 The ice flows down this valley in a stream three miles wide, 

 apparently with a very slow motion. A few miles down the 

 valley the ice ends in a high wall facing Main lake, into which 

 it occasionally discharges a berg. The stream draining this lake 

 flows through a broad flat valley of sands and gravels toward the 

 southeast, and finally empties into Lynn canal. The three val- 

 leys entering the eastern side of Main valley also have flat gravel- 

 covered floors, through which rush the streams from the snow 

 fields and small glaciers at their heads. Two of these valleys 

 are beyond the present termination of the glacier. Formerly 

 the ice must have extended across their mouths, hemming them 

 in and converting them into lake beds. The upper valley is now 

 in just this condition. The lake which occupies it has been 

 called Berg lake on account of the great number of icebergs in it 

 last summer (1890). Just north of the entrance to Main valley 

 lies Girdled glacier, so called on account of the moraine which 

 completely surrounds it (see plates 6 and 11). It can be seen 

 from the end of Muir glacier, but is so foreshortened that one 



