tarded by friction; the heavier grains remain at rest in the slow bottom current, while the lighter grains are carried away by the quirk top current. Magnetic separators utilize the action of an air current to separate particles of low specific gravity from those of higher specific gravity. For a comprehensive discussion of the methods and machinery used in crushing and separating ores, see Richard, Ore Dressing (New York, 1900); and for an annual record of current progress in this art, see the annual volumes of the Mineral Industry (New York).
OR′EGON (named from the Oregon, now the Columbia River, probably an American Indian name). A western State of the United States, lying on the Pacific Slope, between latitudes 42° and 46° 18′ N., and between longitudes 110° 33′ and 124° 25′ W. It is bounded on the north by the State of Washington, on the east by Idaho, on the south by Nevada and California, and on the west by the Pacific Ocean. Its extreme length from east to west is 396 miles, and from north to south 300 miles. Its area is 96,030 square miles, of which 94,560 square miles, or 60,518,400 acres, are land surface. It ranks seventh in size among the States.
Topography. The salient features of the topography are the two mountain ranges extending parallel with the coast through the western part of the State, and the great inland plateau in the east. The coast is rocky and abrupt, and runs in an almost straight line north and south, with no very prominent inlets or headlands. There are, however, besides the wide mouth of the Columbia River on the north boundary, several small bays or harbors, such as Tillamook, Winchester, and Coos bays, all of which are landlocked, with narrow entrances. Near the southern boundary the coast runs out in an obtuse angle ending in Cape Blanco. The land rises immediately from the coast to the crest of the Coast Range, which is about 20 miles inland, and has a height of 1000 to 4000 feet. It is heavily forested, and though of irregular outline, with many transverse valleys, it is unbroken, save in two or three places, throughout the length of the State. The Cascade Mountains run parallel with the Coast Range about 120 miles from the coast. They are the prolongation of the Sierra Nevada, rise to an average height of over 6000 feet, and are crowned by a line of extinct volcanic cones, several of which are over 9000 feet high, while Mount Hood, the culminating point near the northern boundary, has an altitude of 11,225 feet. Like the Coast Range, the Cascades are heavily forested, and their summits are covered with snow. Between the two ranges extends a broad valley, divided by several spurs and cross ranges, and becoming rough and mountainous in the south, while the northern half forms the rolling prairie valley of the Willamette. The region lying east of the Cascades covers two-thirds of the area of the State, and consists of an elevated plateau. The southern half of this belongs to the Great American Basin, though its floor has an elevation of 5000 feet, rising to 6000 feet in the southeast. Several of the longitudinal Basin Ranges of Nevada extend into this plateau, and large areas are covered with lava flows. The northern half slopes northward toward the valley of the Columbia River. It is more undulating than the southern plateau, and is traversed in the northeast by the Blue Mountains, an irregular chain rising to a height of 7000 feet, and sending out side spurs flanked by deep valleys. Some of the rivers in this region have cut deep cañons, especially the Snake River on the northeastern boundary, whose cañon almost rivals that of the Colorado.
Hydrography. The Columbia River forms, with an interruption at the Falls of the Dalles, a large, navigable waterway for 300 miles along the northern boundary. Its chief tributaries in the State are the Willamette west of the Cascades, and on the eastern plateau the Deschutes, John Day, and Umatilla, whose branches form a considerable network of minor streams. The Snake River, which joins the Columbia in Washington, forms about one-half of the eastern boundary, and its chief tributary, the Owyhee, runs inside the boundary along the remaining half. The streams flowing directly into the ocean are mostly short, but two of them, the Umpqua and the Rogue, rise on the Cascades and break through the Coast Range. On the interior plateau there are a number of streams running into lakes which have no outlet. There are a number of lakes of considerable size in the south-central portion, the largest of which are Goose Lake, which lies partly in California; Klamath Lake, at the base of the Cascades, 30 miles long; and Malheur Lake, on the eastern plateau, 22 miles long.
Climate. In few places is the influence of topography on climate more apparent than in Oregon. The winds from the ocean are deprived of nearly all their moisture by the Coast and Cascade ranges, which also bar out the tempering influence of the sea, so that the portion west of the Cascades has a moist and equable insular climate, while east of the mountains the climate is dry and continental, with great extremes. On the coast winds from the sea temper the summer heat, and tend to reduce the cold of winter, while cold winds from the northeast are barred out by the mountains. Here the mean temperature for January is 42.2°, and for July 62.3°, while great extremes are rare. On the eastern plateau the mean temperature is 29.6° for January and 66.9° for July, while the extremes fall below zero every winter, sometimes nearly 30° below, and rise above 100° every summer, the maximum record being 119°. In regard to rainfall there is a still greater difference between the two regions. In the west the rainfall is abundant, and in some places excessive. West of the Coast Range it averages 89.6 inches, in the Willamette Valley it is 50.8 inches, while in Tillamook County it is nearly 140 inches. On the eastern plateau it is insufficient for the needs of agriculture, being on the average 12.7 inches, and in the south-central portion only 6.5 inches. More than three-fourths of the rainfall of the State occurs in the wet season from October to March. Thunderstorms are rare in Oregon, and never severe, while hurricanes are unknown.
Soil and Vegetation. The soil on the highlands and plateau consists of decomposed lava, and in the valleys it is a rich black alluvial deposit. With the exception of some extensive tracts of sand and of volcanic ashes and pumice in the east, the soil is everywhere of great fertility, and even in the east capable of yielding heavy crops when irrigated. The eastern plateau, however, consists largely of arid plains covered
