Elizabeth Cary Agassiz, Louis Agassiz: his life and correspondence, third edition

[727] or feet. Any investigation from the upper surface would, therefore, require special apparatus, and much more time than Agassiz and his party could give. Neither was an approach from the side very easy. The glacier arches so much in the centre, and slopes away so steeply, that when one is in the lateral depression between it and the mountain, one faces an almost perpendicular wall of ice, which blocks the vision completely. M. de Pourtales measured one of the crevasses in this wall, and found that it had a depth of some seventy feet. Judging from the remarkable convexity of the glacier, it can hardly be less in the centre than two or three times its thickness on the edges,—something over two hundred feet, therefore. Probably none of these glaciers of the Strait of Magellan are as thick as those of Switzerland, though they are often much broader. The mountains are not so high, the valleys not so deep, as in the Alps; the ice is consequently not packed into such confined troughs. By some of the party an attempt was made to ascertain the rate of movement, signals having been adjusted the day before for its measurement. During the middle of the day, it advanced at the rate of ten inches and a fraction