that the motion of the glacier may present unexpected differences in different parts of its course, we have good authority to believe. The motion of the well-known glacier called the Mer de Glace, or Sea of Ice, was stated by Shirwell to be 300 feet per annum; Rendu made it 365 feet, Saussure 375 feet, Bakewell 540, and De la Beche 600 feet, while Ebel had placed it at only fourteen feet. These strange discrepancies are not, however, to be despised; for Professor Tyndall declares that every one of them may be perfectly true, and quotes the words of Rendu, Bishop of Aunecy, who is the author of one of the most remarkable essays on glaciers which have ever been published. "It is easy," says Rendu, "to comprehend that it is impossible to obtain a general measure-that there ought to be one for each particular glacier. The nature of the slope, the number of changes to which it is subjected, the depth of the ice, the width of the couloir [ie. channel or passage], the form of its sides, and a thousand other circumstances, must produce variations in the velocity of the glacier, and these circumstances cannot be everywhere absolutely the same. Much more, it

is not easy to obtain this velocity for a single glacier, and for this reason. In those portions where the inclination is steep, the layer of ice is thin, and its velocity is great. In those where the slope is almost nothing, the "glacier swells and accumulates; the mass in motion being double, triple, &c., the motion is only the half, the third,

&c. But this is not all. Between the Mer de Glace and a river there is a resemblance so complete that it is impossible to find in the latter a circumstance which does not exist in the former. In currents of water the motion is not uniform, neither throughout their width, nor throughout their depth; the friction of the bottom, that of the sides, the action of obstacles, cause the motion to vary."

The analogy between a glacier and a river must not, however, lead those who have never seen a glacier to imagine that the surface is smooth, or only slightly rippled, like the surface of running water, or that the glacier discharges itself into the sea in a similar manner. Where glaciers terminate on the sea-coast, as in the Arctic Regions, they are gradually protruded until large portions break off, and fall with a tremendous crash into the ocean, where they begin a new existence as icebergs. Where glaciers terminate on dry land, they form a sort of promontory of ice, rising with a broken and steep ascent to a considerable elevation. Having gained this elevation, and turning the back on the icy mass, the traveller finds that the promontory on which he is standing is surrounded by forests, green fields, and smiling orchards. Flocks are feeding, perhaps, in the meadows, attended by a shepherd playing on his flute. Reapers may be busy gathering in crops of barley, or peasants may be collecting orchard fruits. A neat village, perhaps, stands on the

banks of the river of whitish-green waters which issues forth from beneath the ice. But, when the traveller pursues his way over the glacier ice, he finds that the masses which lie behind this projecting promontory are much broken, traversed by

GLACIER OF ZERMATT.-Middle Portion.

deep chasms, and surmounted by numerous isolated pieces of ice, which exhibit the most fantastic shapes. Farther on the glacier may resemble a

gently sloping icy-stream, from half-a-mile to three miles wide, with a surface more or less undulating and rippled ; broken up, however, by chasms which, at their upper opening, differ in width from a few inches to many feet. These chasms sometimes extend nearly across the whole width of the glacier; and the colour of the ice, as you look down into them, is generally tinged with an exquisite blue colour passing into green. These chasms render travelling on the glacier a slow and difficult work. The fatigue is also increased by the melting snow and ice which, in summer, make the surface wet and slushy. Innumerable rills are flowing on all sides, and, when these unite and pour down the chasms, a loud throbbing noise is sometimes heard, like the clack of a mill, and hence called by the guides le moulin, or the water-mill. It is remarkable that, whatever be the state or progress of the glacier, these moulins are found in almost exactly the same position, and opposite the same fixed objects. Immediately after sunset a change comes over the scene. vapours, elastic and invisible in the sunlight, condense, creep along the rocks, and descend like a veil of gauze. A mournful bluish livid light takes the place of the golden lustre of day, the rills cease or lessen, frost re-asserts its power, and the wet surface of the glacier becomes hard and glassy. Along the sides of the glacier are icy walls, sometimes sixty feet high and more, on which masses of bare rock of all sizes are lodged. Similar

The

masses are frequently found in the middle of a glacier. These accumulations of rock are called moraines: those at the side are called lateral moraines; that in the middle forms the medial moraine. There are also sometimes large pieces of rock supported by blocks or columns of ice: these are called glacier tables. One of these, described by Forbes, consisted of a flat block of granite, 23 feet by 17 feet, and about 3 feet thick. In June, 1842, it was easy to step on this block from the surface of the glacier; but, as the season advanced, the glacier sank all round it, and left the block elevated on a beautiful pedestal of veined ice, which had been preserved from melting by the shelter from sun and rain which the block afforded. "Each time I visited it," says Forbes, "it was more difficult of ascent, and at last, on the 6th of August, the pillar of ice was 13 feet high, and the broad stone so delicately placed on the summit of it, (which measured but a few feet in any direction,) that it was almost impossible to guess on what it would ultimately fall." This beautiful object, the icy pedestal of which was of a lamellar structure, parallel to the length of the glacier, fell and was destroyed in the month of August; but the block soon began to rise again on another pedestal of ice. Glacier-tables can only be formed by thick blocks of stone. Thin slabs, when of a dark colour, sink instead of rising: the heat is absorbed so quickly that it melts the ice beneath, and the slab disappears. A leaf wafted upon the glacier, a dead