600 
ON CORAL REEFS AS A CAUSE OF THE FEVER 
all exposed coral reefs malaria emanates, and the intensity of the 
malaria depends on the non diffusion of the poison from want of 
ventilation , or it may be modified by solution with the surround¬ 
ing atmosphere, so that ivhen it reaches a ventilated locality it is 
innocuous ; as a drop of concentrated sulphuric acid will burn, but 
mingle it with a pint of water and its effect is lost . This latter 
part of the deduction is more applicable to localities which will be 
examined in Part three, as the Cocos Islands and some islands of 
the Pacific, than any locality near Singapore. My third deduction 
is that mere proximity to a coral reef does not necessarily imply 
that the locality is obnoxious to fever ; for instance kampong Kopit 
on Pulo Brain, is within a mile of Ayer Bandera where remittent 
fever is endemic, yet is it only subject to epidemic fever ; kampong 
Serapong is seldom or never subject to fever and is only ^ a mile 
inland from Ayer Bandera; detached houses on the same island are 
only separated from the source of fever by a belt of mangroves, this 
also occurs in other islands as Pulo Sikra, and the inhabitants of these 
houses are healthy. I am therefore entitled to draw, from these 
facts previously enlarged upon, my third deduction, that mere prox¬ 
imity to a coral reef, does not necessarily imply, that the locality 
is obnoxious to fever, as the interposition of high land, or a belt 
of trees, as the primitive jungle or mangrove swamp, may act as 
an effectual barrier. 
It has been stated that fresh water kills the coral polyps,* and in 
my opinion even more quickly than exposure to the air or sunshine, 
for if a reef when exposed receives a fall of rain, the corals imme¬ 
diately blacken and a most intense stench is given forth. The de¬ 
tritus of coral and the sand from broken up land, destroy by me¬ 
chanical means the delicate polyps : a fourth deduction may therefore 
be drawn that when a large river opens into the sea, or when the 
sea is gaining on the land, but little living coral will be exposed, 
as the first prevents the formation of coral, and the second quick¬ 
ly destroys what is formed, covering it up so that at low tide sand 
and dead coral only are visible, and from which no malarious in¬ 
fluence proceeds. Instances of the effects of rivers will be given in 
* See Darwin fon coral formations page 66,) who has entered minutely 
into this point, from whose work I first received the information which 
forms this my fourth deduction and which not being based on original data, 
cannot be considered as asserted fur the first lime, but the reader will on 
examining Darwin see a point of difference bciwixt us regarding the de¬ 
gree of importance of fresh water and sandy detritus as destructive agents. 
