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THE GEOGRAPHICAL POSITION

where the outer hills, rising to high elevations near the plains, intercept the south-east monsoon, and is markedly exemplified in the valleys of Hah, Paro, Tashi-cho-jong and Bya-gha (otherwise known as Pumthang) in Bhutan and in Chumbi.

But in the deep-cut valleys of the River Teesta in Sikhim, and the Lobrak or Kuru River in Bhutan, the above division does not apply. The outer hills are lower, the monsoon current penetrates much further north, through deep valleys which run nearly to the foot of the highest mountains, and consequently the wet zone extends as far as the snows. In the case of the Teesta the elevation of the valley a few miles from Kangchen is not more than 2400 feet above mean sea level, while the Lobrak cuts through the barrier of the Himalayas, at an elevation of only 10,000 feet.

Sikhim, owing to its proximity to Kangchenjunga, to the fact that it lies in the direct path of the monsoon and to the direction of its valleys, is much the wettest portion of the whole area, and has a heavy annual rainfall, about 50 inches even in the dry upper valleys of Lachung and Lachen, increasing to about 140 inches in other districts.

In eastern Bhutan the rainfall is appreciably less as the monsoon current is diverted up the Assam Valley and does not strike the hills directly. Consequently there is a diminished rainfall, and the effect is noticeable in the vegetation which is not nearly so dense.

These hill states are drained:

Sikhim by the Teesta and its tributaries, the chief of which are the Rungeet, the Rungnu-chhu joining at Ringen, and the Lachen and Lachung rivers.

Bhutan by:

(1) The Am-mo-chhu or Torsa draining the Chumbi Valley;

(2) The Wang-chhu or Raydak with its tributaries the Hah-chhu and the Par-chhu draining the valleys of Hah, Paro, and Tashi-cho-jong;

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