470 
ON THE MEDICAL TOPOGRAPHY OF SINGAPORE. 
agricultural produce lias for some time ceased to be cultivated 
these vallies are now occupied with rank vegetation, such as species 
of Graminacese, Cyperacem and other plants that court a boggy soil. 
The principal part of the rain that falls sinks into the ground and 
lodges there, for the under soil is of a clayey consistence; the rest 
goes to the nourishment of these plants, which spring up to the 
height of 6 feet, vigorous, healthy, and strong, till their time of 
decay comes, when their decomposed state gives stimulus, and 
strength, and nourishment, to those plants that take their place. The 
sun shines down with its full brilliancy and effect, having no high 
trees to ward it off, raising into existence many forms of organic 
life with an alarming celerity. The hills around protect the 
vallies from breezes or gales, giving the atmosphere a heavy, 
warm, and sickly feeling, while the absence of currents of air and' 
the presence of much moisture, retain undiluted the pernicious ma¬ 
laria. A few Bugis and Malays are seen located on the sides of the 
hills, but the visible living in the vallies are confined to frogs and 
snakes, some, as the Ular Sawa or Python, reaching the enormous 
length of 30 feet, the snipe in its season is to be met with, but our 
wild animals as Deer, Pigs, and Tigers, limit their peregrinations to 
its borders. These fresh water vallies may be called the vallies of 
death, and furnish incontestable proofs of the malarious influence of 
decomposing vegetable matter. 
In the high jungles we have vegetation undergoing somewhat the 
same decomposition that occurs in the vallies, but not to such an 
extent, owing to the height of the trees, and the denseness of the un¬ 
der brushwood preventing the action of the sun. A tree that falls, 
or leaves that cover the soil, in a dry situation merely undergo a slow 
process of combustion, by which the Carbon unites with oxygen ve¬ 
ry slowly, and elicits carbonic acid. In marshes again where there 
is free moisture, and access to air and sunshine, instead of a mere 
decay of vegetable matter, there is a decomposition, the carbon not 
only unites with oxygen to form carbonic acid, but the water con¬ 
tained in the plant is decomposed,—its oxygen uniting in a certain 
proportion to form carbonic acid, while its hydrogen [unites with 
