In 1906, three sets of observations were inaugurated: (1) to obtain rate of surface flow; (2) to ascertain retreat or advance; (3) to observe the annual change in the ice formation at the snout.
To Obtain Rate of Surface Flow.
Both ends of the base established in 1906 were now occupied with the transit, and readings taken upon the plates in the positions in which they had been found. Work was completed at the south end, but, while that at the north was still in progress, rain came on, stopping the work and driving the party back to camp.
Next morning, July 17th, work was resumed and the readings completed at the north end of the base. The plates were then set in line afresh and their positions fixed by angular readings from the south end. On the accompanying map the original line of plates is shown and the points at which they were found twelve months later. The table below shows the respective movements as measured from a plot of the several readings taken at the ends of the base.
Table Showing the Motion of Plates Set on the Yoho Glacier, between 15th July, 1906, and 17th July, 1907.
Plate | No. 1 | No. 2 | No. 3 | No. 4 | No. 5 | No. 6 |
Yearly Motion | 29 ft. | 74 ft. | 89 ft. | 124 ft. | 134 ft. | 124 ft. |
Daily Motion | 0.95 in. | 2.43 in. | 2.93 in. | 4.08 in. | 4.41 in. | 4.08 in. |
A glance at the map shows that the greatest movement has taken place in the locality of Plates IV., V. and VI. The reason is that the main body of ice is swung to the right against the cliffs seen in illustration No. 1.