topples over. Even then, it should remain stationary on the surface, unless struck by a rolling boulder or undermined by a rivulet.
Work was next carried to the moraines in front of the ice-tongue, on the east side of the river. They are of a somewhat nondescript character and represent rather incipient lateral moraines, formed by the ice-nose during its protracted retreat, than perfectly formed terminal moraines. The valley floor is here traversed by rock ribs, grooved and polished by the ice, stretching down it longitudinally. On one of these moraines two, deeply imbedded, boulders were marked with red paint and the distance measured to the nearest ice for future reference. Photographs, also, were taken from the boulders for annual comparison of the changes occurring in the ice front through melting and disintegration.
Mr. George Vaux pointed out the marks placed by Miss Vaux in 1901, which were still quite legible. At that date a line was drawn in red paint down one of the rock ribs referred to, as nearly as possible at right angles to the flow of the most advanced ice. It was now found that the most advanced ice had retreated about seventy-six feet, yielding an annual average retreat of fifteen feet. This, however, would not necessarily represent the retreat for any one year, for the ice may have been stationary or even have advanced a little during the period.
In his notes of the Yoho glacier, Dr. Sherzer writes: "In August, 1901, independent marks were established by Miss Vaux and H. W. DuBois, from the former of which it was found that the ice here has retreated 111 feet in three years, or at an average rate of 37 feet a year. This measurement was made to the glacier itself and not to the detached block which has been the nose. Measured to the block, the distance was 92.1 feet, giving an average of nearly 31 feet a year, with a
