DEPOPULATION OF THE MISSIONS. QA) 
ters contained in the rocks themselves. The In- 
dians and missionaries assert, that the exhalations 
from these rocks are unwholesome, and consider it 
dangerous to sleep on granite near the river; and our 
travellers, without entirely crediting this assertion, 
usually took care to avoid the black rocks at night. 
But the danger of reposing on them, Humboldt 
thinks, may rather be owing to the very great de- 
gree of warmth they retain during the night, which 
was found to be 85:°5°, while that of the air was 78°8°. 
In the day their temperature was 118:4°, and the 
heat which they emitted was stifling. 
Among the causes of the depopulation of the 
missions, Humboldt mentions the general insalu- 
brity of the climate, bad nourishment, want of pro- 
per treatment in the diseases of children, and the 
practice of preventing pregnancy by the use of dele- 
terious herbs. Among the savages of Guiana, when 
twins are produced one is always destroyed, from 
the idea that to bring more than one at a time into 
the world is to resemble rats, opossums, and the 
vilest animals, and that two children born at once 
cannot belong to the same father. When any phy- 
sical deformity occurs in an infant, the father puts 
it to death, and those of a feeble constitution some- 
times undergo the same fate, because the care which 
they require is disagreeable. ‘Such,’ says Hum- 
boldt, “‘ is the simplicity of manners,—the boasted 
happiness of man, in the state of nature! He kills 
his son to escape the ridicule of having twins, or to 
avoid travelling more slowly,—in fact, to avoid a 
little inconvenience.” 
The two great cataracts of the Orinoco are form- 
ed by the passage of the river across a chain of gra- 
P 
