272 Mr. H. J. Elwes’ catalogue of the 
south by the plains of Bengal. That part of it which is 
included in British territory, and which alone has been 
well explored by Europeans, is less than forty miles wide, 
and extends from the Singalelah range, which forms the 
Nepal boundary, to the great Tista river, which separates 
it from British Bhotan ; and is not more than twenty or 
thirty miles from the Rangit river, which separates it 
from independent Sikkim, to the plains. Its highest eleva- 
tion is on the north-western frontier, where the mountain 
called Sundukpho exceeds 12,000 ft. Sikkim consists 
for the most part of steep hills covered with virgin forest 
above 6000 ft., but cleared for tea and native cultivation 
down to about 1500 or 2900 ft., except in those places 
where the slopes are very steep, and in the bottoms of 
the deep tropical valleys which everywhere intersect the 
country. In the interior the mountains rise to the 
highest elevation in the world, none of the passes into 
Tibet being much under 15,000 ft. in elevation, and 
some over 18,000 ft.; but of this part of Sikkim we 
know comparatively little, owing to the many natural 
and political obstacles which still exist, and which have 
prevented this part of the Himalaya from being as well 
known as the north-western part of the range. 
The forest consists of tall trees, varying very much 
in character according to the elevation, and mostly 
accompanied by a luxuriant undergrowth of shrubby 
and herbaceous vegetation or bamboos, which make it 
in many places almost impenetrable.* 
The deep valleys of the Rangit and Tista, with their 
numerous tributary streams, are extremely hot and 
damp during the greater part of the year, and unhealthy, 
except in the dry season. The Kastern Himalayas have 
been divided by Hodgson (see Journal of the Asiatic 
Society of Bengal for 1835) into three zones of elevation, 
each of which has a very distinct fauna and flora; and, 
when writing on the distribution of Asiatic birds (Proc. 
Zool. Soc., 1873, p. 65), I showed that these three zones 
are perfectly characteristic of three different zoological 
provinces. The lower or tropical zone extending up to 
about 5000 ft., which is inhabited by plants, birds, and 
insects characteristic of the Indo-Malay region. The 
* The character of the forest in different parts of Sikkim is very 
well described by Mr. Gamble in the first volume of the ‘ Indian 
Forester,’ Caleutta, Central Press Co., 1876, where there is an 
excellent map of the district. 
