GLACIERS OF THE CANADIAN ROCKIES AND SELKIRKS. 53 



ment of one of the lateral points opposite station D as 483 feet for the year 

 and suggests that "the movement of the center is probably, at least, two-fifths 

 greater, corresponding closely with the intervals of the /dirt bands' of the 

 glacier." Although the size of the intervals in this series differs plainly to the 

 eye, still Forbes states that the difference for any one interval is probably not 

 a tenth of the mean. From the same point of view as that used by Forbes in 

 1842, Tyndall counted upon the Mer-de-Glace, 17 years later, exactly the same 

 number of bands and remarked: 'The entire series of bands which I observed 

 with the exception of one or two, must have been the successors of those 

 observed by Professor Forbes; and my finding the same number after an interval 

 of so many years proves that the bands must be due to some regularly recurrent 

 cause." In Chapter xxxn of his Glaciers of the Alps, Tyndall has described his 

 "white ice-seams," the "bandes lactees" of the French and "weissen Blatter" 

 of the Germans. These are due, in part, to the filling of transverse crevasses, 

 left open during the fall, with snow and then its later compression into a white 

 vesicular ice. Since, in general, these crevasses would be those which had been 

 acted upon by the summer sun, they would be the counterpart of the dirt bands 

 under discussion. Seve" found the average interval for these white seams upon 

 the Boium Glacier, in Norway, to be 218 feet and that this represented also the 

 average forward annual movement. 1 So far as the Victoria Glacier is concerned 

 we have not sufficient data at hand to settle the- question of the annual character 

 of the dirt bands. At the line of plates, about a third of a mile below, the 

 maximum annual movement of the ice was found to be 65.85 feet. The average 

 annual interval for the lower half of the series is 76.56 feet, which is about what 

 would be expected in the way of annual ice movement, when compared with the 

 above. We should also expect the movement to increase as we approached 

 the crest of the ice slope. So that the actual and relative spacing of the bands 

 very strongly suggests their annual character. If due to some "regularly 

 recurrent cause," as Tyndall suggests, this cause must recur with the seasons. 

 We are, however, not entirely without evidence that the intervals between 

 the dirt bands indicate approximately the annual movement of the ice. As 

 pointed out upon page 30, the Messrs. Vaux marked the location of a large 

 boulder upon this portion of the glacier July 26, 1899. From range lines, one 

 year later, they determined that the boulder had moved forward 147 feet. In 

 September, 1905, this boulder was found opposite the gth band of the series 

 given upon page 51. In 1899 it should have lain opposite the 3rd band and, 

 if the motion there had been the same as it was in 1904-5, it should have moved 

 in 1899-1900 the distance of 126 feet. The previous year it should have moved 

 174 feet. My field notes say that the second and third bands were indistinct, 

 so that there is strong probability that the three intervals between one and four 

 may not have been properly distributed. The average for the three is 153 feet, 

 which agrees very well with the actual observed motion of the boulder. If the 

 dirt band intervals are an approximate indication of the annual ice movement 



1 Quoted from Helm's Gletscherkunde, p. 140. 



