312 



Sierra Club Bulletin. 



65 feet. Eighteen hundred and eighty-one shows the 

 least snowfall (154 inches, or nearly 13 feet), but 1877, 

 with 178 inches, and 1874, with 200 inches, are nearly 

 as low. Of late years, 1898 has been the driest. 



Unfortunately the amount of summer snow does not 

 depend entirely on the winter snowfall, but primarily 

 upon the amount remaining on the ground at the end of 

 spring, or after the heavy storms have ceased. The fol- 

 lowing eleven plats show record of snow on the ground 

 at Summit Station from 1897-98 to the present year, with 

 the exception of 1900-01. All records previous to these 

 were in the office of the Chief Engineer of the Southern 

 Pacific Railroad, and were destroyed by the San Fran- 

 cisco fire. It will be noticed that each of these consist 

 of an extremely irregular curve up to March, the high 

 "peaks" representing, of course, storms. After the month 

 of March, however, there is a fairly smooth curve of 

 melting, for the reason that no violent storms occur after 

 that date. By averaging up the curves of ten years, we 

 get the curve shown on the last plat, which gives the 

 mean depth of snow on the ground at Summit Station 

 during that period. This curve is quite regular through- 

 out, rising gradually to a maximum of 129 inches on 

 March 26th. The portion in which we are the most 

 interested is the descending portion A D, or curve of 

 mean rate of melting. If we average the depth of snow 

 by simply taking the sum of such snow as is on the 

 ground at a given date and dividing by ten, filling in 

 with zeros such years as may have bare ground at the 

 date in question, we get the curve A B C D. This curve 

 will evidently extend as far as the latest date at which 

 we find snow in the record, viz., July 14th (1907). This 

 does not give the correct rate of melting, however, beyond 

 the date where the first curve touches zero, viz., April 

 23 (1898). In order to get the curve showing the true 

 rate of melting we must find the average date at which 

 snow is of a certain depth. For example, we find that 



