moist surfaces, when placed in contact, freeze together to a rigid mass; this is called Regelation.

"When the attachments of pressed ice are broken, the continuity of the mass is restored by the regelation of the new contiguous surfaces. Regelation also enables two tributary glaciers to weld themselves to form a continuous trunk; thus, also, the crevasses are mended, and the dislocations of the glacier consequent on descending cascades are repaired. This healing of ruptures extends to the smallest particles of the mass, and it enables us to account for the continued compactness of the ice during the descent of the glacier.

"The quality of viscosity is practically absent in glacier-ice. Where pressure comes into play, the phenomena are suggestive of viscosity, but where tension comes into play, the analogy with a viscous body breaks down. When subjected to strain, the glacier does not yield by stretching, but by breaking; this is the origin of the crevasses."

In explanation of the curious phenomena, known respectively as dirt bands and blue veins, Professor Tyndall has the following:

"The dirt bands have their origin in the ice cascades. The glacier in passing the brow is transversely fractured; ridges are formed with hollows between them; these transverse hollows are the principal receptacles of the fine débris scattered over the glacier; and after the ridges have been melted away, the dirt remains in successive stripes upon the glacier.

"The ice of many glaciers is laminated, and when weathered, may be cloven into thin plates, In the sound ice the lamination manifests itself in blue stripes, drawn through the general whitish mass of the glacier; these blue veins representing portions of ice from which the air-bubbles have been more completely expelled. This is the veined structure of ice. It is divided into marginal, transverse, and longitudinal structure, which may be regarded as complementary to marginal, longitudinal, and transverse crevasses. The latter are produced by tension, the former by pressure, which acts in two different ways: firstly, the pressure acts upon the ice as it has acted upon rocks, which exhibit the lamination technically called cleavage; secondly, it produces partial liquefaction of the ice. The liquid spaces thus formed help the escape of the air from the glacier; and the water produced 'being re-frozen when the pressure is relieved, helps to form the blue veins."

These views are sufficiently diverse from those previously propounded by Professor Forbes to account for the controversy which has arisen between these eminent men; yet in the opinion of some of the ablest judges Tyndall has not overthrown Forbes' theory, neither has he confirmed it; but he has enlarged and completed it. "Forbes established the law of glacier motion; Tyndall showed how the glacier is enabled to obey that law. Whether they agree to do so or not, they must share between them the honour of

It is not our place to follow the track of controversy, or even that more enticing, but not less perilous track which aims at the ascent of Mont Blanc, Monte Rosa, or any other grand elevation of the Alps. But we may, perhaps, be permitted to give a sketch of a more familiar ascent, which is within the reach of any ordinary traveller, supposing him to possess health and spirits for the task.

Many tourists, in common with the writer, have experienced the highest delight in the ascent of the Mer de Glace, one of the five principal glaciers of Mont Blanc. In approaching this glacier, we travel on mules from Chamouny, and pass through a magnificent forest of pines and larches, situated on the steep slope of the Montanvert. The road winds up this in a series of zigzags; a great height is soon attained, and a glorious view is often seen as in a picture, with the noble forest trees for a framing. The road is bad, and the turns are frequent, but there is really no danger if the surefooted mule be allowed to take its own course. The road is, in fact, ploughed up and nearly destroyed by the descending avalanches of winter, and only a few loose stones, thrown hastily down, Ishow that there is a road. The trees also bear fearful evidence of the power of falling masses of snow. Many of the monarchs of the forest lie * Edinburgh Review, January, 1861.

prostrate; others have been snapped asunder, as if they were reeds, their blackened stumps remaining to tell of the conflict.

On reaching the summit of the Montanvert, the traveller first begins truly to appreciate the wild grandeur of the glacier-here called the Mer de Glace, although properly a river, not a sea of ice. From a height of about 240 feet, we look down upon the icy stream, and see it, for about two leagues, following the windings of the valley, pent in between walls of rock, surmounted by a thousand pinnacles, which often rise beyond the clouds, the loftiest of which, the Aiguille Verte, is more than 13,000 feet above the level of the sea, and about 7,000 feet above the grassy platform from which we now behold it.

Wishing to see more of this magnificent glacier, we set out with a guide to pay a visit to le Jardin, a place situated in the centre of a snowy basin, above the snow line, where, from its peculiar situation, some scanty herbage and a few Alpine flowers grow during the short-lived summer. distance from Montanvert, in a direct line, is about nine miles; but the surface to be crossed is so broken up, and requires so zigzag a course, as to render the distance much greater.

The

On leaving Montanvert we proceeded along a footpath in the west bank of the Mer de Glace, which is here extremely steep, and consists of a slaty gneiss. It is covered with grass, and the Alpine rhododendron; and here and there the

spruce fir is seen. Large blocks of granite are scattered about wherever a ledge is found sufficient to maintain them, and they extend quite up to the dwelling of Montanvert. The face of the rock soon becomes smooth, and continues so down to the ice, the motion of which serves to wear away and polish the rock. The passage is here somewhat difficult, but is effected by means of rude steps cut in the slaty rock. There are two passes of this description, called the premier et second ponts, or the "first and second bridges." Here the glacier is greatly heaved and contorted; the icy hillocks, or waves, are of enormous size, and rise to a great height.

The second pont being passed, the path descends to the moraine, or immense collection of stones which fringe the edge of the glacier. These stones are torn from the rocks on both sides by the expansive force of ice. The rain and melting

snow which fills the crevices with water is frozen during winter, and in freezing the icy wedges expand, and rend off masses of stone often measuring fifty feet along one of their sides. The first thaw melts the ice which binds the blocks to the parent rock, and they come rolling down upon the glacier throughout the whole of the summer. This constitutes one of the chief dangers of glacier travelling. As the glacier creeps on, some of these stones also move with it until they are brought to the extremity of the glacier, when they are shot over its edge, and form what is called the terminal