136 
VOYAGE OF THE POTOMAC. 
[Febmary, 
lets. They are also augmented by the aid of more extensive 
vapom^s and rains, which prevail on the east of the mountains; , 
while their course is rendered more steady and uniform by the less 
undulating face of the regions through which they find their way 
to the ocean. They also derive great advantages from the shelter 
and protection afforded them by the Island of Borneo, which, 
breaking the force of the ocean's swell, guards their mouth frora 
that accumulation of sand, which, in the form of bars, too fre- 
quently obstructs the navigation of rivers not thus protected. 
The rivers of the west, however, are by no means inconsider- 
able, particularly the Cattown, Indrapoor, Tabooyong, and Sinkelly^ 
The mouths of these rivers, however, lying exposed to the whole 
strength of the winds and ocean on the west, which create a con- 
tinued action of the surf, more powerful than the current of the 
streams, renders them inaccessible to vessels of any size, and 
.often dangerous even to boats. 
From what has been said respecting the location of Sumatra, 
in the very centre of the tropics, it may be inferred that an 
atmosphere of very high temperature must be the necessary con- 
sequen-ce. Such, however, is not the fact. Experience has 
shown that it is more temperate than many regions beyond the 
torrid zone. The hour of greatest heat is about two o'clock in 
the afternoon, when the thermometer fluctuates between eighty- 
two and eighty-five degrees of Fahrenheit, and seldom rises above 
eighty-six in the shade. Some few localities, influenced by pe- 
/ culiar circumstances, may perhaps form exceptions ; but the 
above is correct as a general remark applied to the coast. Fur- 
ther inland, beyond the first range of hills, the air is quite cool, 
so that even fires are not unpleasant in the morning, but often 
desirable. The thermometer there stands at about seventy, which 
in our country would not be deemed a low temperature, although 
the system, relaxed in a warm chmate, is sensibly affected by it ; 
as are also the fruits of the island, more especially the cocoanut, 
which comes more tardily to perfection in the more elevated 
situations. ; 
The formation and shape of the island naturally produce these , 
results. Being a long narrow strip of land, rising from the bosom 
the ocean, the breezes that play over its surface carry with 
them the coolness and freshness of the sea. There are no sandy 
