glaciers of the canadian rockies and selkirks. i03 



6. Ice Structure. 



The n^vd-covered portion of the ice acquires a very perfect stratification as 

 the result of wind distributed dust and periodic melting over the surface. This 

 structure is beautifully shown in the crevasse walls and the faces of the niunerous 

 faults in the ice. In the photograph of the Detroit Publishing Co., reproduced 

 in plate xli, the successive layers, with the minor stratification seams, are clearly 

 shown. The con-espondence of the strata upon opposite sides of the crevasse 

 shows that there had been no faulting. From his heel to the crown of his hat 

 this guide pictured is about six feet in length and, by comparison, we ascertain 

 that the strata shown range from three to twelve feet in thickness. The picture 

 was taken during the summer of 1902, and in looking at the uppermost stratum 

 it is forced upon one's belief that this represents the compacted snow that accum- 

 ulated over this spot during the season of 1901-2. Part of this snow was pre- 

 cipitated directly, part of it may have been drifted by wind action. It may have 

 lost some by wind action, as well, during the season of accumulation. It has 

 been compacted by melting, pressure, and occasional rain into a fine granular 

 ice. If we are right in supposing that this stratum represents the accumulation 

 during the season of 190 1-2, minus the loss by the combined agencies, then the 

 stratum upon which it rests must have accumulated during the season of 1 900-1. 

 Passing down the side of the crevasse we may thus assign dates to the successive 

 strata, finding that they reach back to the season of 1895-6. It is especially 

 interesting to note that the deposits supposed to have been laid down between 

 the summer of 1898 and that of 1902 average considerably thicker than those 

 between the summers of 1895 and 1898, since this dividing date falls very near 

 the supposed date of the beginning of the phase of increased precipitation in this 

 region. It is further to be noted that the stratum marked 1898-9 is the thickest 

 of the series. It is very unfortunate that our precipitation data are not fuller 

 for the locality. In order to serve the present purpose in establishing a rela- 

 tionship between the amount of precipitation and the thickness of the strata in 

 the neve, a combination should be made of the last three months of the year with 

 the first nine of the following year. This would unite practically all of the snow- 

 fall and the rain and melting water of the following summer, as it is combined 

 in the stratum itself. In a paper upon the Canadian Pacific Railway, from 

 Laggan to Revelstoke,' Mr. William Vaux gives the average snowfall for Glacier 

 House from 1895 to 1898 as 3 1 feet, based upon records kept by the station agent, 

 this being but 83 per cent, of the normal. From October, 1898, to May, 1899, in- 

 clusive, the snowfall alone amounted to 43 feet 8i inches, being 17 per cent, above 

 the normal. The records are lacking up to 1902 , for which year the Meteorological 

 Service reports 13.88 inches of rain and 347 inches of snow, or a total equivalent 

 of 40?, feet in snow, or 14 per cent, below the normal. By refen-ing to plate xli 

 it will be seen that the stratum assigned to the year 189 8- 1899 is the heaviest of 

 the series while that for 1901-1902 is light. From 1895 to 1898 the strata are 



' Proceedings of the Engineers' Club of Philadelphia, vol. -xvii, 1900, p. 73. 



