GLACIERS OF MOUNT RAINIER 



snow line, loses annually more by melting than it re- 

 ceives by precipitation, and is maintained only by the 

 continued accession of masses from above. The rate 

 at which the ice advances has been determined by 

 Prof. J. N. Le Conte, of the University of California. 

 In 1903 he placed a row of stakes across the glacier, 

 and with the aid of surveying instruments obtained ac- 

 curate measurements of the distances through which 

 they moved from day to day. He found that in sum- 

 mer, when the movement is greatest, it averages 16 

 inches per day. This figure, however, applies only to 

 the central portion of the glacier the main current, 

 so to speak for the margins necessarily move more 

 slowly, being retarded by friction against the channel 

 sides. 



The snout of the Nisqually Glacier, accordingly, is 

 really composed of slowly advancing ice, but so rapid 

 is the melting at this low altitude that it effectually 

 counterbalances the advance, and thus the ice front 

 remains essentially stationary and apparently fixed 

 in place. Actually, it is subject to slight back and 

 forward movements, amounting to a foot or more per 

 day ; for, as one may readily imagine, fluctuations in 

 snowfall and in temperature, above or below the nor- 

 mal, are ever likely to throw the balance one way or 

 another. 



A glacier may also make periodic advances or retreats 

 on a larger scale in obedience to climatic changes ex- 

 tending over many years. Thus all the glaciers on 

 Mount Rainier, as well as many in other parts of the 

 world, are at present, and have been for some time, 

 steadily retreating as the result of milder climate or of 

 a lessening in snow supply. Only so recently as 1885 

 the Nisqually Glacier reached down to the place now 

 occupied by the bridge, and it is safe to say that at 

 that time no engineer would have had the daring to plan 

 the road as it is now laid. In the last 25 years, how- 

 ever, the Nisqually Glacier has retreated fully 1,000 feet, 

 p 209 



