Tropical Forests 
Such colonies as Sierra Leone are amongst the oldest 
possessions of Great Britain, so that it does seems strange 
that, in spite of the extraordinary fertility of the soil, or 
rather on account of it, plantations have very seldom 
been successful. The abundant vegetation and moist 
atmosphere produces a climate which is quite unsuitable 
for Europeans and even for natives. Both management 
and labour are apt to become expensive and unprofitable 
under such conditions. Nor has any planter any reason- 
able expectation of living until his plantations pay. 
The improvement during the last few years has been, 
however, of the most astonishing character. 
The fact that a mosquito carries the germ of malaria 
from one fever-stricken patient to those as yet unaffected, 
has made it possible almost to exterminate malaria in 
some places, and to reduce the death-rate enormously. 
Perhaps the most striking instance of the advantage of 
Sir Patrick Manson’s great discovery is the fact that the 
death-rate at the works for the Panama Canal has been 
reduced amongst the white employees to 16.71 per 
thousand.’ This district was notorious as amongst the 
most deadly to Europeans of all climates in the world. 
Besides this great discovery, the history of sleeping 
sickness is beginning to be understood. The tsetse-fly 
is said to convey the blood-parasite or trypanosome from 
man to the crocodile, and possibly back from the croco- 
dile to man. There has not, however, as yet been 
devised any method of exterminating either tsetse or 
crocodiles.® 
Even in West Africa, the mere fact that the land is 
steadily coming under real control by the white man, 
enormously alters the prospects of the future. When 
there is real security for life and property, both the 
native population and the amount of cultivation will 
increase enormously. 
The first destruction of virgin forest for crops of any 
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