great basin. The western or Rocky mountain region is the great source of the precious metals, the deposits of which, as has been observed, may be described in a general way as arranged in parallel zones coinciding with the mountain belts. Along the Pacific Coast range are deposits of quicksilver, tin, and chrome, while the belt of the Sierra Nevada and the Cascades carries a range of copper mines near its base, and a line of gold-bearing veins and gold alluvium on its western flank. Along the E. slope of the Sierra lies a zone of silver mines stretching into Mexico, and including the great Comstock lode of Nevada, while silver ores abound in the subordinate ranges between the Sierra and the Wahsatch. The silver-lead ores of New Mexico, Utah, and western Montana, and the still more eastern gold deposits of New Mexico, Colorado, Wyoming, and Montana, follow the same general distribution. (For particulars of the mineral deposits of the United States, see Anthracite, Borax, Coal, Copper Mines, Gypsum, Iron Ore, Marble, Petroleum, Salt, and the articles on the different metals and states.)—The republic abounds in natural curiosities and other objects of interest. Immense numbers of persons annually resort to the mineral springs, the most prominent of which are mentioned in the article Mineral Springs. The White mountains and other portions of the Appalachian chain are noted for their striking or picturesque scenery; while the great mountain ranges of the Pacific slope present innumerable scenes of unsurpassed beauty and sublimity, among which are the “parks” and lofty peaks of Colorado, the Yellowstone national park in Wyoming, and the Yosemite valley in California. The prairies and arid plains are noteworthy features. Besides the great cataract of Niagara and the Yosemite falls, the falls of the Missouri in Montana, St. Anthony's falls of the Mississippi in Minnesota, and the falls of the Snake river in Idaho may be instanced. The most remarkable caves are the Mammoth cave in Kentucky; Madison's cave and Weyer's cave, Virginia; Nicojack cave, Georgia; and Fountain cave, near St. Paul, Minnesota. Not the least interesting among the picturesque features of the country are the remarkable channels cut by some of the rivers through ranges of hills or rocky ridges. Such are the passage of the Hudson through the Highlands of New York; the Delaware Water Gap; the passage of the Potomac through the Blue Ridge at Harper's Ferry; the “gates of the Rocky mountains” on the upper course of the Missouri in Montana; the deep cañons of the Colorado of the West; and the “cascades” where the Columbia river breaks through the Cascade range on the boundary between Washington territory and Oregon. The natural bridge of Virginia, the pictured rocks on the shore of Lake Superior in Michigan, the mammoth trees of California, the geysers, and the popular seaside resorts, as well as nearly all the scenes above mentioned, are described in other articles.—The climate of the United States is as varied as might be expected in a country stretching through 25 degrees of latitude, and rising from low swampy shores to vast elevated and arid table lands and prodigious mountain ranges. Except in the extreme south and on the Pacific coast, it is characterized by fickleness and by great difference in temperature between summer and winter. Transitions from heat to cold and from cold to heat, to the extent of 30° in a few hours, are common at all seasons, and the alternations from rain to drought are nearly as remarkable. The summer is marked by intense heat, the thermometer rising sometimes several degrees above 100° F. In the north this extreme is seldom continued for more than a few days at a time, and in the southern states the heat, though long continued, is seldom so great. In winter the thermometer often falls below zero in the north, and it has been known, particularly in Minnesota and Dakota, to reach the freezing point of mercury (−40°). The Atlantic states have in general a temperature about 10° more severe than countries of the same latitude in western Europe, while California has a climate as mild as that of Italy. The northeastern states are subject to chill winds from the Atlantic (and at points along the coast to fogs), especially in the spring months; and the ice fields of British North America are the cradle of cold blasts which, having no mountain barrier to overcome, sweep over the northern states upon every considerable rise in the temperature further south. The great lakes mitigate to some extent the temperature of the country surrounding them, and other local features, such as the elevated plains and lofty ranges of the Rocky mountain system, affect the climate of particular parts of the country. The average annual temperature varies from 76° in S. Florida to 36° in N. E. Minnesota. The isothermal lines are irregular, but between the Pacific and the upper Mississippi they have a general tendency toward the north. On the Pacific coast the annual temperature of 52° in lat. 48° corresponds to a like temperature on the Atlantic coast in lat. 41.° Rain is abundant over the greater part of the republic, and pretty equally distributed throughout the year. In the north Atlantic states the fall is more regular than in the coast states S. of Washington, being in the latter more plentiful than in the former, and more frequent in summer than in winter. On the Pacific coast the rains are periodical, occurring chiefly in winter and spring, and S. of lat. 40° in autumn also. In the northern states snow frequently falls to a considerable depth, and in the most northerly portions it does not melt until spring. It is comparatively rare S. of the Potomac and on the Pacific coast, and when it does occur in these districts it lasts but a short time. The average annual precipitation of rain and melted snow on the Atlantic coast and on the gulf as far W. as the Sabine
