Prevailing Currents of the Atmosphere. 309 
chart of 1835,* and so as to impinge with equal weight and sur- 
face on all sides of the pin or axis, and the incumbent body will 
be found to revolve from right to left, in the manner of the storms 
of the northern hemisphere. 
This experiment requires delicate management, and is more 
difficult because of the necessary rigidity of the incumbent sur- 
face, causing one part partially to counteract another; but in the 
case of a fluid, where all the particles move freely upon each oth- 
er, no such impediment exists. 
As it is chiefly the lower stratum of wind which is thrown into 
gyration from this cause, it must be evident, as above suggested, 
that within the geographical limits of the trade winds the great 
circuit of aerial revolution must be a nearly horizontal one, and 
that the storm tracks mark distinctly the usual course of this rev- 
olution. Consequently, the main outflowing course of the trade 
wind from the equatorial latitudes is not in the upper regions of 
the atmosphere. 
It was my design to have followed these general remarks with 
a detailed explanation of the delineations of the several systems 
of prevailing winds which I have placed on the maps before re- 
ferred to. ‘This was particularly my intention as relates to the ex- 
tensive developments of the monsoons, and the several belts of 
light winds and calms which may be viewed as the anticlinal and 
synclinal axes, so to speak, of the several systems of general 
winds. But the lateness of the call and my necessary avocations 
have prevented me from fulfilling this labor, in time for the expe- 
dition. 
This imperfect summary of the results of inquiries which I 
have pursued with no little interest, is now commended to the 
gentlemen of the expedition for their impartial examination ; and 
with the expectation, and desire, that truth only, as apart from 
any favored theories, will be the object of their researches in nat- 
ural science. 
*'This chart may be found in this Journal, Vol. xxx1, for October, 1836; also 
in London Nautical Magazine, April, 1836, and Col. Reid’s work on the Law of 
Storms. 
t This is also shown by the extraordinary heat of the summers in countries 
near the western boundaries of the great oceans, this heat being conveyed horizon- 
tally by the surface winds from the lower latitudes; while in winter the results 
are modified and an opposite state of temperature induced, by causes which are 
peculiar to continental meteorology. 
