Page:Canadian Alpine Journal I, 1.djvu/233

154 dred feet distant and many feet below. In his monograph, Dr. Sherzer refers to this feature and states that he measured the oldest living tree he could find growing in the path of the avalanche, and it had only 47 rings of growth.

Six plates, eight inches square and a quarter-inch thick, having on the under side a piece of inch and a quarter pipe, one foot long, to act as an anchor, were now set at approximately regular distances across the width of the glacier, at a place where the surface was slightly undulating, and as nearly as possible at right angles to the flow. At each point where a plate was set a hole was bored in the ice with an augur and the anchor dropped into place. A surveyor's transit was next set at each end of the measured base and angular readings taken on poles placed in the centre of the plates, thus fixing their position accurately with regard to the established base line. The ends of the base line, on prominent boulders embedded in the mountain side, were carefully marked with red paint and a suitable inscription. Similar readings taken from the same base points at any future date will at once indicate the changed position of the plates and, provided there has been no local displacement, will give an accurate estimate of the flow of the surface of the glacier at each point where a plate was set.

The plates and method were the same used by Messrs. George and William S. Vaux for the Illecillewaet glacier. It was now found—and has since been learned that the same experience applied to the Illecillewaet glacier—that the kind of plate used was not a good one; for, returning across the ice later on, it was seen that each plate was raised more than an inch above the surface, owing to the melting of the ice where exposed to the sun, which had not taken place to a similar extent at the bottom of the holes. It is presumed this will continue, day by day, until the plate