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Show 52 STEPPES AND JJESERTS. ral equatorial current of the waters of the ocean1 and opposes a barrier to the more rapid commercial intercourse of Europe and Western Africa with the eastern parts of Asia. North of the 17th degree of latitude and the celebrated isthmus of Tehuantcpec1 the mountain87 quitt.ing the coast of the Pacific, and following a more direct northerly course, become an inland Cordillera. In North Mexico, the" Crane Mountains" (Sierra de las Grullas) form part of the Rocky Mountain chain. Here rise, to the west, the Columbia and the Rio Colorado of California j and, to the east1 the Rio Roxo de Natchitoches, the Candian1 the Arkansas, and the Platte or shallow river1 a name which has latterly been ignorantly transformed into that of a silver-promising river Plate. :Between the sources of these rivers (from N. lat. 37° 20' to 40° 13') rise three lofty summits (formed of a granite containing much hornblende and little mica), called Spanish Peak, James's or Pike's Peak, and :Big Horn or Long's Peak. (See my Essai Politique sur la Nouvelle Espagne, 2me edit. t. i. pp. 82 and 109.) The elevation of these peaks exceeds that of any of the summits of the Andes of North Mexico, which, indeed, from the 18th and 19th parallels of latitude, or from the group of Orizaba and Popocatepetl (respectively 2717 toises or 17,374 English feet, and 2771 toiscs or 17,720 English feet), to Santa Fe and Taos, ne~er reach the limits of perpetual snow. James's Peak, in lat. 38° 40'1 is supposed to be 1798 toises, or 11;497 English feet j but of this elevation only 1335 toises (8537 English feet) has been measured trigonometrically, the remaining 463 toises, or 2960 English feet, being dependent, in the absence of barometrical observations, on uncertain estimations of the declivity of streams. As a trigonometrical measurement can hardly ever be undertaken from the level of the sea, measurements of inaccessible heights must generally be partly trigonometrical, and partly barometrical. Estimations of the fall of rivers, of their rapidity1 and of the length of their course1 are so deceptive1 that the plain at the foot of the Rocky Mountains1 nearest to the summits above spoken of, was estimated, previous to the important expedition of Capt. Fremont, sometimes at 8000, and sometimes at 3000 feet. (Long's Expedition1 vol. ii. pp. 36, 3621 3821 App. p. xxxvii.) It was from a similar deficiency of barometrical measurcn1ents that the |