94 GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 



mean of the two. This would bring it to about 1898 or 9, when it was especially 

 noted b_y the Messrs. Vaux. The gradual reduction in the rate of retreat observed 

 during the past three seasons would indicate that this impulse is making itself 

 felt about the nose and that either a halt, or an advance, is about to be in- 

 augurated. If we are coiTect in the inference that the n6vd line was marked by 

 a trough, or low stage in the height of the ice, about 1887 or 8 and that a return 

 to this condition has been reached about 1905 or 6 with a crest, or high-stage 

 condition of the ice between, an interesting relation is at once established with 

 Bruckner's climatic cycle (page 16). The time between the appearance of these 

 troughs for the passage of one-half of the wave is 18 years, and we may venture 

 to predict that the present relative depression will be followed by the passage 

 of another crest requiring about the same number of years. The nose has been 

 in retreat from 1888 to 1906, some 18 years, and we should expect another period 

 of halt or advance to soon set in. Such a condition was to be anticipated from 

 the marked reduction in the rate of retreat from 1902 to 1905, but the very 

 remarkable recession of 84 feet determined by the Messrs. Vaux for the year 

 [905-1906, leaves the matter in doubt. 



The relation of the glacial movements to the precipitation cycles becomes 

 a matter of much interest and here, as above, with our meager data, we can only 

 point out possibilities, which will either stand or fall, when the next half -century's 

 obser.vations have been collected. From our available meteorological records 

 there was a deficiency of precipitation over the mountains from 1885 to 1896; 

 how much before 1885 this condition existed we have no means of knowing. 

 Since 1897 there seems to have been an excess over the normal amount, but it 

 was at this time that the crest of the wave made its appearance at the n^ve line. 

 Then instead of continuing to increase, as we might expect, it gave way to a 

 trough. The inference is, and it is only an inference, that this wave represents 

 the gush of ice from the collecting basin due to the excess deposited during the 

 phase of the cycle which antedated 1885, and probably to be correlated with the 

 excess in the Rockies, as recorded so strikingly in the evidence of higher lake levels, 

 described by Dawson (page 17). The approaching trough shown about the neve line 

 in 1905 must then be ascribed to diminished precipitation received over the collect- 

 ing region from 1 885 to 1 896, being then 9 years delayed from the close of the phase 

 which gave rise to it. The crest of the wave from the basin was delayed some 

 17 to 18 years from the close of the preceding phase. In a paper read before 

 the International Geographic Congress, at its Washington meeting {Proceedings, 

 1904, p. 487), Doctor Reid gave a discussion of "reservoir lag," in which he demon- 

 strates mathematically that the thickening of ice in the collecting basin does not 

 keep pace with the variation in precipitation, but lags behind it. In the case of 

 large glaciers this lag amounts to about one-fourth of the period of the variation, 

 and the ice in the basin should attain its maximum thickness, only about the time 

 that the annual supply has settled back to the normal amount and is ready 

 to diminish. After the maximum ice thickness has been attained toward the 

 center, time is still required for the imjDulse to reach its maximum at the crest of 



