THE CAMPHOR-TREE OF SUMATRA. 69 
mediately at the foot of high mountains ; secondly, the uninterrupted 
dense forests, with which not only the mountain-chain itself, but the 
coast-plain, is covered. These circumstances produce a greater humi- 
dity, and at the same time a greater coolness of the air, at an inferior 
elevation than in Java. 
At the eastern foot of the Sumatra mountain-chain, there are exten- 
sive arid and barren plains, only overgrown with Alang-alang (e. g., 
at Pertibi). Over the heated soil of these plains the air becomes ex- 
traordinarily rarefied: the cooler sea-air rushes in, coming from the 
ocean on the western side of Sumatra, where the sea is deep, and where 
no land exists for a great distance; and a west wind arises, which, 
partly kept back by the obliquely situated mountain-chains, changes 
into a north-western one. This wind carrries the humidity of the sea 
towards the mountains, by the summits of which the moisture is soon 
condensed and changed into clouds. These, during the whole year, at 
intervals almost daily, at regular hours, but chiefly in the afternoon, 
shed heavy showers over the land, while the thunder roars in the moun- 
tains. The dampness of the air is then so great, that mist and clouds 
are for many days seen hanging immoveably even over the woods of 
` the lower coast-lands. Frequently, too, the wind blows by reverberation, 
` in an opposite direction, like a hurricane, from the mountains to the 
“coast. 
Thus the Camphor-tree grows in a very changeable and generally — 
moist climate, where extreme states of heat and coolness by storm > 
quickly follow each other. About eleven in the morning, in the 
serenest weather, there is frequently an oppressive warmth, while at 
noon heavy showers, driven on by a north-west wind and accompanied | 
by thunder and lightning, seem to cover the land. p 
Surrounding Vegetation.—One consequence of the unsettled charac- 
ter of the climate, of the low elevation of the clouds, and of the cooler 
temperature in general, is the occurrence of some trees and plants near 
the sea-coast, which in Java are met with only at a greater height. 
Thus the Camphor-tree grows often in company, not only with species 
of Acacia, Anona, Michelia, and Dipterocarpeæ, but also with Oaks; 
and itis found with marsh Ozsuarine, with the Nipong Palm (Onco- 
sperma filamentosum), and with Benzoin-trees. Amidst the underwood. 
of the forest are seen species of Melastoma, Elettaria, and other Scita- 
mineæ, With Vitex trifoliata (which occurs most frequently), and several 
