National Geographic : 1892 Mar 21
The Ice-Front in the Inlet. 700 square miles. Most of the precipitation which falls on this area flows off as water in the subglacial streams; the rest, com pressed into ice, is forced through the narrow gateway 2i miles wide into the inlet, where the glacier terminates in a vertical wall of ice varying from 130 to 210 feet above the water surface, from which large masses are continually separating to become icebergs (see page 48 and plates 1, 2 and 13). As already stated, the depth of the water is in places 720 feet; and as this is not enough to float a mass of ice rising so high above the water as Muir glacier, the ice must reach to the very bottom and must attain a thick ness of 900 feet. The actual length of the ice-front facing the water is 9,200 feet, or 1 miles. On each side the glacier sends forward a wing, which rises in the shape of a wedge over the stratified sands and gravels of the shore.* The upper surfaces of the wings, like the ice-front, are about 200 feet above the water level. This applies only to the parts of the wings overlooking the inlet; the parts nearer the side mountains are 50 to 100 feet lower; and here the ice ends like an ordinary alpine glacier. The wings are fringed by treacherous quicksands, which support large stones and look firm enough; but the tourist who steps upon them carelessly will quickly sink in over his ankles. These quicksands are com posed of fine glacial mud, thoroughly soaked with water from the melting ice. The ice-front has a wonderful coloring. Places from which ice has recently broken off are deep blue, sometimes almost black. This color lightens under exposure to the air and sun, and in a few days becomes pure white. All stages are represented in the ice-front, which therefore shows all shades of blue in striking variety. The blue color of the ice is caused by the absorption of the other constituents of the light passing through it, and is exactly analogous to the hues of colored glasses. When exposed to the sun and rain the ice undergoes a kind of weathering near its surface, which prevents the blue light within from passing out and reflects nearly all of the light which falls on it from out side; so that we then see merely ordinary white light reflected, practically unchanged, from the ice. * Mr Cushing has published (op. cit., pl. iii) a reproduction of a pho tograph showing the glacier riding on the these gravels. 5-NAT. GEOG.MAC., VOL. TV, 1892.
1892 May 15
1892 Feb 19