Page:The Selkirk mountains (1912).djvu/177

Rh movement, rate of flow, and general change of appearance of the Illecillewaet and Asulkan Glaciers.

It is aimed in this statement, illustrated by photographs and a map, to supply information that will enable interested visitors to make intelligent observations carrying them on from where they were last left off, and so to enter their records in the book.

The lllecillewaet Glacier.

The investigations carried on by Messrs and Miss Vaux deal chieily with the two principal movements of glaciers—the rate of How and the advance or retreat of the forefoot. The third study dealing with changes in the general appearance of glaciers is best conducted by means of photographs taken year by year from the same position.

The Messrs and Miss Vaux began observations on the lllecillewaet Glacier on July 16, 1887, and took a number of photographs, now of special interest and value. At that time the forefoot came down to within 20 feet of the alder bushes; and a great mass of ice with steeply sloping sides covered what is now a long stretch of bare moraine. The general conditions then pointed to a recent period of advance.

In 1888, Mr. W. S. Green and the Rev. H. Swanzy included in their topographical survey some observations on this glacier. Holes were bored in the ice and a row of poles set up. Twelve days afterwards, all the poles had fallen, owing to the surface melting at their bases. The bottom of the holes was found in a few cases, the poles set up and observations taken. It was then ascertained that a pole near the moraine had in twelve days moved seven feet, one further out ten feet, and one in the centre twenty feet. From two rows of boulders dropped in front of the snout, it was deduced that the glacier had retreated about sixty feet during that past year, and from the inner row within that present year (1888). Mr. Green concluded his observations by tarring some of the boulders in closest proximity to the ice, so that the future retreat might be observed by other travellers. (W. S. Green's "Among the Selkirk Glaciers.")

In 1890 Mr. Harold W. Topham also made some observations on the same glacier, and at the close of his article in the Alpine "Journal" (May, 1891) makes the following request:—"In conclusion. I will ask any one intending to visit the Selkirks to obtain from me certain data, which will enable him to continue the observations which I commenced for the measurement of several of the glaciers."

In 1894, the Messrs. Vaux renewed their observations and with few omissions have continued them regularly until the present (1911).

In 1899, Mr. W. S. Vaux made an instrumental survey of the Illecillewaet Forefoot and its vicinity, and published a map. The copy here reproduced, which is corrected to July, 1906. will be useful in all future observations. At the time of this survey eight metal plates were placed in line across the glacier at right angles to its flow, where it was about one-third of a mile wide.

A base of 229 feet 6 inches was then measured on the high