The Forms of Water in Clouds and Rivers, Ice and Glaciers

by John Tyndall

136. Walk with me now alongside the moraine from the Jardin down towards the ice-fall. For a time our work is easy, such fissures as appear offering no impediment to our march. But the crevasses become gradually wider and wilder, following each other at length so rapidly as to leave merely walls of ice between them. Here perfect steadiness of foot is necessary a slip would be death. We look towards the fall, and observe the confusion of walls and blocks and chasms below us increasing. At length prudence and reason cry "Halt!" We may swerve to the right or to the left, and making our way along crests of ice, with chasms on both hands, reach either the right lateral moraine or the left lateral moraine of the glacier.

[§ 18.] First Questions regarding Glacier Motion. Drifting of Bodies buried in a Crevasse.

137. But what are these lateral moraines? As you and I go from day to day along the glaciers, their origin is gradually made plain. We see at intervals the stones and rubbish descending from the mountain sides and arrested by the ice. All along the fringe of the glacier the stones and rubbish fall, and it soon becomes evident that we have here the source of the lateral moraines.

138. But how are the medial moraines to be accounted for? How does the débris range itself upon the glacier in stripes some hundreds of yards from its edge, leaving the space between them and the edge clear of rubbish? Some have supposed the stones to have rolled over the glacier from the sides, but the supposition will not bear examination. Call to mind now our reasoning regarding the excess of snow which falls above the snow-line, and our subsequent question, How is the snow disposed of. Can it be that the entire mass is moving slowly downwards? If so, the lateral moraines would be carried along by the ice on which they rest, and when two branch glaciers unite they would lay their adjacent lateral moraines together to form a medial moraine upon the trunk glacier.

139. There is, in fact, no way that we can see of disposing of the excess of snow above the snow-line; there is no way of making good the constant waste of the ice below the snow-line; there is no way of accounting for the medial moraines of the glacier, but by supposing that from the highest snow-fields of the Col du Géant, the Léchaud, and the Talèfre, to the extreme end of the Glacier des Bois, the whole mass of frozen matter is moving downwards.

140. If you were older, it would give me pleasure to take you up Mont Blanc. Starting from Chamouni, we should first pass through woods and pastures, then up the steep hill-face with the Glacier des Bossons to our right, to a rock known as the Pierre Pointue; thence to a higher rock called the Pierre l'Échelle, because here a ladder is usually placed to assist in crossing the chasms of the glacier. At the Pierre l'Échelle we should strike the ice, and passing under the Aiguille du Midi, which towers to the left, and which sometimes sweeps a portion of the track with stone avalanches, we should cross the Glacier des Bossons; amid heaped-up mounds and broken towers of ice; up steep slopes; over chasms so deep that their bottoms are hid in darkness.

141. We reach the rocks of the Grands Mulets, which form a kind of barren islet in the icy sea; thence to the higher snow-fields, crossing the Petit Plateau, which we should find cumbered by blocks of ice. Looking to the right, we should see whence they came, for rising here with threatening aspect high above us are the broken ice-crags[B] of the Dôme du Goûté. The guides wish to pass this place in silence, and it is just as well to humour them, however much you may doubt the competence of the human voice to bring the ice-crags down. From the Petit Plateau a steep snow-slope would carry us to the Grand Plateau, and at day-dawn I know nothing in the whole Alps more grand and solemn than this place.

[B] Named séracs from their resemblance in shape and colour to an inferior kind of curdy cheese called by this name at Chamouni.

142. One object of our ascent would be now attained; for here at the head of the Grand Plateau, and at the foot of the final slope of Mont Blanc, I should show you a great crevasse, into which three guides were poured by an avalanche in the year 1820.