Page:Canadian Alpine Journal I, 2.djvu/155

Rh several stations, shows the positions of these stations and of the rocks from which measurements were made to the ice; also, of the other view-points and the various features of the glacier in its bed. I now wish to acknowledge the assistance given me by Mr. M. P. Bridgland, who has plotted and computed the altitudes of all the points used in outlining the glacier and in drawing the contours here shown.

It may incidentally be mentioned that it is only by the means of the science of photogrammetry that in a single day—not taking into consideration the other work done when locating plates and making measurements, etc.—sufficient data could be obtained by two persons to map the tongue so completely and accurately, without making actual measurements, a process that would entail a considerable expenditure of time and labor. The process, combined with the views taken, enables, in this case, a large amount of additional information to be gathered, such as: thickness of the ice, previous thickness of the ice, slope of ground-floor, etc. It shows how valuable the method is for a survey of this nature.

From it we may gather that the approximate thickness of the ice on the right side is 170 ft., and on the left side 130 ft.; that the height of the cliffs from the ice to the lower edge of the upper growth of timber in illustration No. 1 varies from 300 to 400 ft., a depth of ice that once filled the valley; and that the slope of the portion of the bed beneath the ice tongue is approximately 35 per cent.

The general conclusion that may be drawn from the above is that the glacier receded during the year, July 1906 to July 1907, an average distance of about 20 feet and that the shrinkage of the ice in thickness on the right side has been very considerable. These evident facts appear somewhat peculiar in view of the unusually large amount of snow that fell in that locality during the winter of 1906-07.