236 THE JOURNAL OF GEOLOGY. 



Moore's Nunatak. The water escaped from the first lake across 

 a confused mass of debris which had slid from the ice bluff 

 bordering the stream and formed a temporary dam. Below the 

 dam the water soon disappeared beneath deeply crevassed and 

 heavily moraine - covered ice and came to light once more at the 

 mouth of a tunnel about a mile to the southwest. The second 

 lake, at the time of our visit, had almost disappeared, but its 

 former extent was plainly marked by a barren sand flat many 

 acres in extent, and by terraces along its western border. The 

 lake occupied a small embayment in the hills, the outlet of 

 which had been closed by the ice flowing past it. Below the 

 second lake the stream flows along the base of densely wooded 

 knolls and has a steep moraine - covered bluff of ice for its left 

 bank. About a mile below it turns a sharp projection of rocks 

 and cuts deeply into its left bank, which stands as an overhang- 

 ing bluff of dirty ice over lOO feet high. The stream then flows 

 nearly due west for some 3 miles to Crater lake. On its right 

 bank is a terrace about i 50 feet high which skirts the base of 

 the Chaix hills and marks the position of the stream at a former 

 stage. The terrace is about 100 yards broad, and above it are 

 two other terraces on the mountain slope, one at an elevation of 

 50 feet and the other at 75 feet above the broad terrace. The 

 upper terraces were only observed at one locality, and were 

 probably due to deposits formed in a marginal lake at the end of 

 a mountain spur. 



The terraces left by streams flowing between a moraine- 

 covered glacier and a precipitous mountain slope are peculiar 

 and readily distinguishable from other similar topographic 

 features. The channels become filled principally with debris 

 which slides down the bank of ice. This material is angula,r and 

 unassorted, but when it is brought within the reach of flowing 

 waters soon becomes rounded and worn. On the margin of the 

 channel, adjacent to the glacier, there is usually a heavy deposit 

 of unassorted debris which rests partly upon the ice and forms 

 the actual border of the stream. When the glacier is lowered 

 by melting, the steam abandons its former channel and repeats 



