The Motion of the Nisqually Glacier. 113 



in the weather. The weather had been cold and stormy 

 previous to July 17th. On that day it cleared off, and 

 a reconnaissance of the glacier was made. The holes 

 were bored on the i8th, and between that date and the 

 20th, when the first measurement was made, the weather 

 continued fine though cool. Professor A. G. McAdie, 

 of the U. S. Weather Bureau, noted a mean temperature 

 of 55° F. on the glacier during the day of the i8th, and 

 the following day was a trifle warmer. The 20th and 

 2 1 St were warm, clear days, with the temperature on 

 the glacier averaging 70° to 75° F. at noon, and with 

 a strong wind blowing from the north. From the 22d 

 to the 26th, the days were cool and clear (about 60° F.), 

 while from the 26th to the 28th the weather was stormy, 

 with rain much of the time. 



In order to ascertain whether or not the upper por- 

 tions of the glacier moved at a more rapid rate, a sight 

 was taken on July 22d on a large boulder in the middle 

 of the glacier, and about a half-mile above the base-line. 

 It was sighted again on the 28th, at the same time of 

 day, and was found to have moved about nine feet. 

 This gives a mean daily motion of about eighteen inches 

 during the period, but the method is not susceptible of 

 much accuracy. 



A rough minimum measure of the amount of surface 

 melting can be obtained from the changes in the depth 

 of the holes. The depth of each was measured when 

 first bored, and whenever deepened. The lateral melting 

 was small, and it is probable also that the melting at the 

 bottom was also small. As there was no freezing at any 

 time during the observations, the surface melting could 

 not have been less than the changes in the depth of the 

 holes. These measurements were so irregular as to show 

 no general law, except a distinct increase on the two hot 

 days above mentioned. The mean rate of surface melt- 

 ing and evaporation thus obtained by twenty-eight meas- 

 urements on all parts of the line was 4^ inches per day, 

 which is probably not far from the true value. 



