The Himalaya system intersects various climatic belts along the approximately 1900 miles of its length. To the south-east, in Assam and Bengal as far as Bhutan, the lowlands are covered by tropical rain-forests, further west, in Sikkim and Nepal, by humid monsoon forests (Sal-forest), from west Nepal to Sutlej by drier, semihumid monsoon forests, in Pandjab by subtropical, semia rid shrub steppes. In the extreme north-west, in Ladak, Karakorum, Gilgit and Chusistan, the alpine heights rise from the floors of desert-like valleys. Thus, the arid belt of Central Asia extends over the Himalayan...