The earthquake is propagated to enormous distances from the region in which the shock originates, the rate at which the motion travels varying not merely with the violence of the originating impulse, but also with the nature of the formations through which it passes. Rocks of solid and homogeneous texture, as granite, favor the transmission of the shock; while formations of loose texture, such as sand, most retard its speed. The well-known Lisbon earthquake of 1755, by which sixty thousand persons are said to have perished within the brief space of six minutes, was felt in the British Islands, as well as upon the coast of Barbary, and even among the islands of the West Indies, on the opposite side of the Atlantic. MOUNTAINS --A. KEITH JOHNSTON The number and altitude of the mountains of the globe are so great that they form almost everywhere prominent objects, and operate to a large extent in modifying the climatic conditions of every country in the world. Yet the amount of solid material so raised above the ordinary level of the land is not so much as might be expected. Remembering that elevated plateaus of great extent occur in several regions, and that the general surface of the earth is considerably higher than the sea-level, it has been estimated that were the whole dry land reduced to a uniform level, it would form a plain having an elevation of 1,800 feet above the sea. And were these solid materials scattered over the whole surface of the globe, so as to fill up the bed of the ocean, the resulting level would be considerably below the present surface of the sea, inasmuch as the main height of the dry land most probably does not exceed one-fifteenth of the mean depth of the bed of the ocean. Mountains, and especially mountain-chains, subserve important uses in the economy of nature, especially in connection with the water system of the world. They are at once the great collectors and distributers of water. In the passage of moisture-charged winds across them the moisture is precipitated as rain or snow. When mountain ranges intersect the course of constant winds by thus abstracting the moisture, they produce a moist country on the windward side, and a comparatively dry and arid one on the leeward. This is exemplified in the Andes, the precipitous western surface of which has a different aspect from the sloping eastern plains; and so also the greater supply of moisture on the southern sides of the Himalayas brings the snow-line 5,000 feet lower than on the northern side.