First, we may notice the effect of rains in washing away the disintegrated particles to lower levels or into river-courses whereby fresh portions of rock become exposed to the decomposing forces. Rains also act powerfully in altering the form of cliff-lines and steep declivities, especially where these consist more or less of friable earthy matter. After a long continuance of wet weather, I have seen the abrupt sides of a river-channel that were formed of a stiff blue clay completely cut up by rents of various dimensions, whereby large masses had subsided many feet, while others had rolled down altogether and lay in the bed of the stream where they were undergoing a rapid abrasion. The cause of this alteration was obvious. The rains pouring down from the sloping grounds on either side of the river had excavated deep channels on the abrupt face of the cliffs, while a considerable quantity of water finding its way through the soil, had permeated through joints and crevices in the clay some feet from the edge of the bank. By the combined operation of these causes, masses of clay several yards in extent lost their cohesion and either settled down a few feet, or found their way to the bottom. Such landslips are of frequent occurrence where large masses of rock of a hard compact nature rest upon loose shales and clays more or less inclined. Whole hills have been known to be hurled in this way into the valleys below. But these results become perhaps still more marked where to the ordinary operations of water there are added those of intense frost. The effects of a severe winter (such, for instance, as a Canadian one), in loosening the particles of rocks and facilitating the breaking-up of large masses, must be ranked among the most powerful agencies of nature. In such a season, the percolating water with which nearly every surface-rock is charged becomes frozen, and in the act of congelation expands. The result of this dilatation is to exert great pressure on the particles of the rock, and thereby loosen their cohesion. When thaw comes the frozen liquid contracts again, but the loosened particles have no such elastic power, and so, having lost hold of each other, crumble down. If the season be a changeable one, frost and thaw quickly alternating, the amount of waste produced becomes very great. Not only is the outer surface of the stone decomposed, but the water filtering through the joints of the rock freezes there, and thus on the arrival of milder weather vast masses become detached from the cliffs, and roll down, to be worn by the grinding action either of waves or of rivers, as the case may be. Spring at last sets in with its warmth and its showers; the snow rapidly melts away; the whole country streams with water; every valley and hollow has its red turbid rivulet, that bears a burden of muddy sediment into the nearest river; and thus the loosened portions of the rocks get washed away down to sea, leaving a