On Malaria. 315 
ments which returned to England from Walcheren in 1809, appears 
to me a satisfactory answer. Dr. Keate states that after their arrival 
in England from that most disastrous campaign, where more lives 
were lost by disease than by the collisions of war, “ Many of the 
men fell down suddenly after the fatigue of a short march with an 
attack of the identical fever, so fatal at Walcheren,” and he has no 
doubt that the poison was imbibed there, and remained Jatent unul 
after their return. This seems to me so conclusive on this point, 
that I need not take room to repeat other instances where the effect 
of marsh effluvia had remained latent for different periods, from six 
days to six weeks and more, and where the proximate cause of its 
developement was fatigue, or a luxurious meal, night watching or 
some other casual excitement. 
It has been further suggested, that it is a mistake to attribute this 
class of maladies to a local cause, as the North American Indians 
were not affected in the same manner, although more exposed to va- 
rieties of soils and seasons than the present race of inhabitants. 
That the Indians were subject to epidemics, we are informed by 
Hutchinson, who in his “ History of Massachusetts,” remarks that 
“the Indians had been greatly weakened by an epidemic.” In Bel- 
knap’s Biography, ‘several periods of pestilence among the natives 
of New England are named.” It is mentioned, in “ Gookin’s His- 
torical Collections of the Indians in New England,” that consumption 
and fever were among the diseases of the natives, and also, that they 
invoked invisible spirits in powows, “ to lay the latter distemper.” 
These sicknesses might, or might not be owing to causes at present 
operating, but they could scarcely be as violent, because the swamps 
and low grounds were screened in a good degree from the sun b 
the almost impenetrable forests ; and the amount of humid vapors 
- would be proportionate to the degree of heat which exhaled them, al- 
though their character might be influenced by other causes. 
The severe sickness, and the violent fevers, which assailed the ear- 
ly settlers of this country, are familiarly known ; nor need we a re- 
cord of the symptoms to convince us that they were analogous to 
those which appear in every new settlement west of our Atlantic bor- 
der, where the newly cleared lands, are known to be sources of dis- 
ease to the cultivators. When the deep accumulations of autumnal 
leaves and other vegetable remains, which have been gathering for 
ages, are broken up by the plough and exposed to the sun and 
rain, those elements are necessarily disengaged and exhaled, which, 
