42 H. F. Reld — Studies of Miiir Glacier. 



interpretation of Vancouver's description seems perfectly in ac- 

 cord with what our observations would lead us to conclude. 



The retreat is probably not regular but faster some years than 

 others, and even varies considerably at different j^arts of the same 

 season. For two or three weeks in Augaist, 1890, there was 

 scarcely an}^ fall of ice ; in the two weeks following the fall was 

 so rapid that a great bay fully a quarter of a mile deep was made 

 in the eastern part of the ice-front, which was before this only 

 slightly concave. Plate 13, from a photograph taken on Sep- 

 tember 7, 1890, shows this indentation. I have collected on the 

 map (plate 15) the positions of the ice-front at several periods ; 

 this shows the retreat at a glance much better than it can be de- 

 scribed in words. The changes in the shape of the front will 

 also be evident. 



The present rate of recession of the ice-front in Muir inlet, a 

 mile in seven years, will probably be exceeded in the near future ; 

 for it has reached a point where the conditions change. The de- 

 posits which support the wings are almost at the water level at the 

 ice-front, and slope down at an angle of 6° or 7° ; a little further 

 back they will be below the water level and the ice-front will be 

 broader, resulting in an increased amount of loss by breakage 

 and hence a more rapid retreat. Ten or 15 years will probably 

 see Dirt glacier on the east and the western tributary on the 

 west entirely se23arate from the main ice stream. 



Dying glacier is rapidly disappearing ; in 15 or 20 years I 

 think its bed will be empty. The maps I have made will enable 

 us to determine with considerable accuracy the amount of these 

 changes in the future. I should, however, say that although the 

 northern end of Main lake is in its right place, the southern 

 end is only approximately determined. The ends of Dying 

 glacier are also only approximate.* 



* Note added November, 1891. From j>hotographs and descriptions sent 

 me by Miss E. R. Scidmore I find that there have been some changes in 

 the ice-front in the past year. The northwestern corner seems to liave 

 advanced slightly ; the northeastern corner has receded 50 or 100 yards, 

 and the rest of the front, which is nearly a straight line, has retreated 

 some 300 yards since July 26, 1890. It is not, however, quite so far back 

 as the extreme end of the bay formed .,ast before we left in 1890. The 

 stream which issued from the ice at the nortlieastern corner now comes 

 out from under the M'ing and rushes across the beach, which it thus sepa- 

 rates from the ice-front. The large glacial stream on the east Avill undoubt- 

 edly follow the channel of this stream before long and fulfill Professor 

 Wright's prophecy (Ice Age in North America, p. 54). 



