Page:Popular Science Monthly Volume 76.djvu/299

Rh the best-known glaciers in Switzerland, and the length of the upper parts of the three longest tongues is entirely unknown and the longest may exceed forty miles. No one of the tributaries as yet bears a name.

The main glacier flows southward from the unexplored central part of the St. Elias Range past Mount Hubbard (Fig. 2), a beautiful 16,400-foot peak named, like the glacier, for Gardiner G. Hubbard, former president of the National Geographic Society of Washington. North of Mount Seattle the Hubbard Glacier has a width of three and one half miles and receives a tributary nearly two miles wide which rises twelve miles back on the slopes of Mt. Hubbard.

Another great tributary from the east, as wide as the main glacier, has its confluence just to the southward. These three ice tongues form the main upper glacier. It is near this confluence that civilized man has made his farthermost traverse upon the Hubbard Glacier. Several intrepid prospectors advanced this far up an adjacent glacier highway and over a snow divide to the Upper Hubbard Glacier during the gold rushes of 1898 and 1899.

Below this confluence, the Hubbard Glacier is crevassed and entirely impassable, and moves down its valley imperceptibly, like the hour hand of a watch, in its irresistible progress to the sea. It descends southwestward over a broad step near the steeply-cascading glacier, shown on the map and in the photographs (Figs. 3 and 4), where it is joined by its longest tributary, the northwest arm. This tributary, two miles wide and at least twelve and one half and probably over twenty miles in length, rises on the slopes of Mt. Vancouver and joins the main glacier at right angles. The combined glacier, with a width of over four miles, advances into Disenchantment Bay in a sinuous cliff four and one half to five miles long and 250 to 300 feet high, one of the most magnificent in the world. Upon this lower glacier surface the Aletsch Glacier, the Rhone Glacier and the Mer de Glace of Switzerland might be placed without covering over two thirds of the lower Hubbard ice tongue.

The surface of the Hubbard Glacier is traversed by several prominent medial moraines. One of these comes from the northwest tributary and sweeps in a broad curve to the ice front. Another comes from near the west side of the main glacier. The east side of the Hubbard ice cliff is dark and debris-laden (Fig. 5) because this side of the glacier is covered with lateral moraine. The basal layers are filled with dirt and stones (Fig. 6) which perform the work of ice erosion. To the eastward this nearly stagnant border almost joins the entirely