THE VARIATIONS OF GLACIERS 261 



1 901. (Langille.) The glaciers on the south side of Mount Hood 

 also show evidence of retreat during the same interval. (Mont- 

 gomery.) 



There are two or three glaciers on Mount Jefferson, but we have 

 no evidence as to their variations. The peaks of the Three Sisters 

 surround a large amphitheater five miles wide, which opens toward 

 the east and formerly held a large glacier, but this has shrunk so 

 much that it has now broken up into four small glaciers. There 

 are three others on the outer slopes of the mountain. The moraines 

 of the glaciers in the amphitheater stand up 30 or 40 feet above 

 their surface. They are still fresh and free of vegetation, showing 

 that this diminution of the ice has taken place in comparatively 

 recent years. The reduction in thickness of the ice seems to be 

 more marked than the reduction in length. Ice still remains under 

 the moraines, which is a further indication of the short time since 

 they were formed. The double crests which some, of these moraines 

 present are ascribed to the melting of the ice under them. One 

 of these glaciers showed in its Bergschrund projecting layers of 

 ice separated by layers of dirt similar, on a small scale, to the 

 projecting layers of ice found at the end of Greenland glaciers.' 

 In the present instance, however, these projections are not ascribed 

 to shear, but to differential melting; for where the snow is shaded 

 from the sun the projections do not exist. (Russell.) 



Comparison of photographs of Lyell Glacier in California taken 

 in 1883 by I. C. Russell and in 1903 by G. K. Gilbert show only 

 very slight recession, whereas the McClure Glacier, close by, has 

 suffered a marked retreat during the same interval. (Gilbert.) This 

 difference may be due in part to the shapes of the two glaciers, Lyell 

 being much broader than it is long, whereas the McClure presents 

 a definite tongue. 



Professor LeConte has found a new glacier just below the east- 

 ern precipice of Mount Jordan, in northern California, and thinks 

 that there are other small glaciers along the eastern slope of the 

 Sierras in this neighborhood. There has been less snow in the Sierras 



'I. C. Russell, "Glacier Cornices," Journal of Geolosy, Vol. XI (1903), 

 PP- 783-85- 



