Switzerland is a little country without any seacoast, mountainous, with steep, lofty peaks, and narrow valleys. The climate is cool and moist, and snow falls the year round on the mountain slopes. A snow-cap covers the lower peaks and ridges. Above the level of nine thousand feet the bare peaks rise into a dry atmosphere; but below this altitude, and above the six thousand-foot mark, lies the belt of greatest snowfall. Peaks between six and nine thousand feet high are buried under the Alpine snow-field, which adds thickness with each storm, and is drained away to feed the rushing mountain streams in the lower valleys.

The snow that falls on the steep, smooth slope clings at first; but as the thickness and the weight of these snow banks increase, their hold on the slope weakens. They may slip off, at any moment. The village at the foot of the slope is in danger of being buried under a snow-slide, which people call an avalanche. "Challanche" is another name for it. The hunter on the snow-clad mountains dares not shout for fear that his voice, reËchoing among the silent mountains, may start an avalanche on its deadly plunge into the valley.

On the surface of the snow-field, light snow-flakes rest. Under them the snow is packed closer. Deeper down, the snow is granular, like pellets of ice; and still under this is ice, made of snow under pressure. The weight of the accumulated snow presses the underlying ice out into the valleys. These streams are the glaciers—rivers of ice.

The glaciers of the Alps vary in length from five to fifteen miles, from one to three miles in width, and from two hundred to six hundred feet in thickness. They flow at the rate of from one to three feet a day, going faster on the steeper slopes.

It is hard to believe that any substance as solid and brittle as ice can flow. Its movement is like that of stiff molasses, or wax, or pitch. The tremendous pressure of the snow-field pushes the mass of ice out into the valleys, and its own weight, combined with the constant pressure from behind, keeps it moving.

The glacier's progress is hindered by the uneven walls and bed of the valley, and by any decrease in the slope of the bed. When a flat, broad area is reached, a lake of ice may be formed. These are not frequent in the Alps. The water near the banks and at the bottom of a river does not flow as swiftly as in the middle and at the surface of the stream. The flow of ice in a glacier is just so. Friction with the banks and bottom retards the ice while the middle parts go forward, melting under the strain, and freezing again. There is a constant readjusting of particles, which does not affect the solidity of the mass.

The ice moulds itself over any unevenness in its bed if it cannot remove the obstruction. The drop which would cause a small waterfall in a river, makes a bend in the thick body of the ice river. Great cracks, called crevasses, are made at the surface, along the line of the bend. The width of the V-shaped openings depends upon the depth of the glacier and the sharpness of the bend that causes the breaks.

Rocky ridges in the bed of the ice-stream may cause crevasses that run lengthwise of the glacier. Snow may fill these chasms or bridge them over. The hunter or the tourist who ventures on the glacier is in constant danger, unless he sees solid ice under him. Men rope themselves together in climbing over perilous places, so that if one slips into a crevasse his mates can save him.

A glacier tears away and carries away quantities of rock and earth that form the walls of its bed. As the valley narrows, tremendous pressure crowds the ice against the sides, tearing trees out by the roots and causing rock masses to fall on the top of the glacier, or to be dragged along frozen solidly into its sides. The weight of the ice bears on the bed of the glacier, and its progress crowds irresistibly against all loose rock material. The glacier's tools are the rocks it carries frozen into its icy walls and bottom. These rocks rub against the walls, grinding off dÉbris which is pushed or carried along. No matter how heavy the boulders are that fall in the way of the ice river, the ice carries them along. It cannot drop them as a river of water would do. Slowly they travel, and finally stop where the nose of the glacier melts and leaves all dÉbris that the mountain stream, fed by the melting of the ice, cannot carry away.

The bedrock under a glacier is scraped and ground and scored by the glacier's tools—the rock fragments frozen into the bottom of the ice. These rocks are worn away by constant grinding, just as a steel knife becomes thin and narrow by use. Scratches and scorings and polished surfaces are found in all rocks that pass one another in close contact. Its worn-out tools the glacier drops at the point where its ice melts. This great, unsorted mass of rock meal and coarser dÉbris the stream is gradually scattering down the valley.

The name "moraine" has been given to the earth rubbish a glacier collects and finally dumps. The top moraine is at the surface of the ice. The lateral moraines, one at each side, are the dÉbris gathered from the sides of the valley. The ground moraine is what dÉbris the ice pushes and drags along on the bottom. The terminal moraine is the dumping-ground of this mass of material, where the ice river melts.

Glaciers, like other rivers, often have tributary streams. A median moraine, seen as a dark streak running lengthwise on the surface of a glacier, means that two branch glaciers have united to form this one. Go back far enough and you will reach the place where the two streams come together. The two lateral moraines that join form the middle line of dÉbris, the median moraine. Three ice-streams joined produce two top moraines. They locate the lateral moraines of the middle glacier.

The surface of a glacier is often a mass of broken and rough ice, forming a series of pits and pinnacles that make crossing impossible. The sun melts the surface, forming pools and percolating streams of water, that honeycomb the mass. Underneath, the ice is tunnelled, and a rushing stream flows out under the end of the glacier. It is not clear, but black with mud, called boulder clay, or till, made of ground rock, and mixed with fragments of all shapes and sizes. This is the meal from the glacier's mill, dumped where the water can sift it.

"Balanced rocks" are boulders, one upon another, that once lay on a glacier, and were left in this strange, unstable position when the supporting ice walls melted away from them. In Bronx Park in New York the "rocking stone" always attracts attention. The glacier that lodged it there, also rounded the granite dome in Central Park and scattered the rock-strewn boulder clay on Long Island. Doubtless in an earlier day the edges of this glacier were thrust out into the Atlantic, not far from the Great South Bay, and icebergs broke off and floated away.

Glaciers are small to-day compared with what they were long ago, in Europe and in America. The climate became warmer, and the ice-cap retreated. Old moraines show that the ice rivers of the Alps once came much farther down the valleys than they do now. Smooth, deeply scored domes of rock, the one in Central Park and the bald head of Mount Tom, are just like those that lie in Alpine valleys from which the glaciers have long ago retreated. There are old moraines far up the sides of valleys, showing that once the glaciers were far deeper than now. No other power could have brought rocks from strata higher up the mountains, and lodged them thus.

Nearer home, Mt. Shasta and Mt. Rainier still have glaciers that have dwindled in size, until they bear little comparison to the gigantic ice-streams that once filled the smooth beds their puny successors flow into. Remnants of glaciers lie in the hollows of the Sierras. We must go north to find the snow-fields of Alaska and glaciers worthy to be compared with those ancient ice rivers whose work is plainly to be seen, though they are gone.