HIMALAYA MOUNTAINS 731 der 13,000 ft. To this succeeds the central belt or axis of the chain, from 20 to 30 m. hroad, its mean elevation perhaps 18,000 ft., at least in the middle Himalaya, and the main ridge or watershed seldom below 17,000 ft. ex- cept at the extremities ; the surface is rocky and often precipitous. The northern belt is a region of mountains and valleys little explored, constituting the slope toward Thibet. Its cli- mate is temperate, but of excessive vicissitudes, subject to drought, and the hills lack the luxu- riant forest growth which covers those of cor- responding elevations upon the other side. Skirting the southern foot of the Himalaya lies a tract of part forest, part jungle and marsh, from 10 to 20 m. in breadth. It is due to the humidity of the climate and to copious springs, as well as to the fact that this belt of pestilen- tial waste is slightly depressed below the level of the plain to the south of it, thus allowing the collected waters to stagnate, and to pro- duce beneath the tropical sun a rank and dense vegetation. This tract is called Terrai or Tar- ragani, "passage through," and its outer habi- table region Kadir. It gradually narrows away as it gains in height toward the central portion of the chain, and disappears W. of the Sutlej. Back of this tract Dr. Hooker says that " the mountains rise more or less suddenly, though seldom in precipices." They are reached sometimes by difficult paths that follow up the narrow and pestilential gorges of the rivers, or more commonly by the roads that ascend into the healthier atmosphere upon the summits of the secondary ridges. These ridges present to the traveller toward the axis of the chain a Mount Everest, seen from above Darjeeling. succession of ascents and descents ; in each valley his progress is interrupted by a stream tributary to the nearest river to the right or left, or by the deep gorges of the larger branch- es themselves; and upon the slopes his course is impeded by forests and rocky precipices. No plain anywhere opens out before him ; and during the warmer portion of the year cloud and fog shut in the view from the commanding points he reaches. So rugged are the moun- tains that 12 or 14 days are usually required for the journey of about 100 m. to the axis of the chain upon the main routes from India to Thibet. The difficulties thus opposed to ex- ploration or settlement are not compensated by the presence either of great mineral wealth or of large tracts favorable to culture. On the other hand, it would be unjust to adopt the descriptions of occasional travellers. It takes a long time, even for one acquainted with mountain regions, to trace correctly the va- rious positions of ridges and spurs, of valleys and river courses, in any large area of an al- pine aspect ; but this difficulty is nowhere so formidable as among the huge masses and laby- rinthine windings of the Himalaya. By most travellers the secondary ridges on the S. side, particularly of the E. portion of the chain, are represented as spurs leaving this at right an- gles, though as seen from the plains at a dis- tance they present the appearance of longitu- dinal ridges. The strike of the rocky forma- tions of which the chain is composed the metamorphic slates and granitic rocks of the central portion, and the Silurian sandstone of the southern ridges is described as every- where with the general course of the moun- tains, thus suggesting a resemblance of the system to that of the Appalachians of the United States in its parallel ridges and valleys,
