ON THE EXTERNAL CAUSES OF DISEASE. 
379 
what are called the sea and the land breeze, are of the highest 
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importance to the comfort and health of the inhabitants. And 
though the hurricanes to which these regions are exposed are 
mentions a very remarkable observation which occurred to him during the 
late prevalence of epidemic eholera:—On the 9th of February, 1832, the 
weight of the air suddenly appeared to rise above the usual standard. 
This continued for six weeks, and the increased weight of the air the 
doctor attributed to the diffusion of some gaseous body through the air 
of the city, considerably heavier than the air it displaced. When this 
phenomenon was first observed, the wind in London, which had previously 
been west, veered round to the east, and remained pretty steadily in that 
quarter till the end of the month. Now, precisely on the change of the 
wind, the first cases of epidemic cholera were reported in London; and 
from that time the disease continued to spread. The foreign body, there¬ 
fore, that was diffused through the atmosphere of London, in February 
1832, was probably a variety of malaria,—a subject which we now proceed 
to consider. 
In districts partially covered with water, and having a luxuriant vege¬ 
tation, such as marshes and fens, particularly in warm countries, or, in 
colder countries at seasons of the year when the sun is most powerful, 
noxious exhalations arise, whose nature differs, perhaps, in some degree 
according to the locality. Such exhalations have received the general 
name of malaria, and are well known to be the fertile source of various 
diseases, more or less, of the intermittent febrile type. In cold and in 
temperate climates, these diseases for the most part assume the character 
of regular ague, or of rheumatism ; but on approaching to and within the 
tropics, they appear as the more formidable remittent and continued 
fevers, the well known scourges of hot climates. 
With respect to the nature of these exhalations our knowledge is very 
imperfect. Evidently, they are in some way connected with vegetation 
not being in a state of growth, but with vegetation in a state of decay. 
It has, therefore, been thought likely that these exhalations contain 
some gaseous body, composed chiefly of hydrogen and carbon. These 
effects may arise from a gaseous compound of this description, though no 
such compound is at present known ; and the probability is, that malaria 
occasionally owes its properties to other elements, besides the hydrogen 
and carbon disengaged from decayed vegetables. 
“ With respect to foreign bodies in the atmosphere ,*’ says the doctor, 
“ it remains to observe, that though of very opposite characters, they have 
yet this resemblance, that they all apparently exist less on their own 
account, than as being the inevitable results of general laws established 
for a higher purpose ; and whatever appear to us anomalous or defective, 
may in reality be parts of some great cycle or series, too vast to be com¬ 
prehended by the human mind, and only known to beings of a higher 
order, or to the Creator himself. So the desolation of the hurricane 
or of the thunder-storm, the settled affliction of malaria, and the march 
of the pestilence, are, in truth, but so many examples of the unsearch¬ 
able ways of the Almighty. ‘He sits on the whirlwind, and directs 
the storm; 7 —a hamlet is laid waste ; a few individuals may perish, but the 
general result is good: the atmosphere is purified, and pestilence with all 
its train of evils disappear. Nay, however inscrutable the object of the 
deadly malaria itself, do we not see one end which it serves, namely, to 
stimulate the industry and reason of man ? By his reason, man has been 
