Meteorological Sketches. 63 
great circuits that the peculiarities of temperature and climate per- 
taining to different countries lying in the same latitudes, are chiefly 
to be referred, as also the remarkable absence or: predominance of 
rain which is peculiar to certain regions. 
The Monsoons of the Indian Seas are but a modification of the 
same system of circulation; the regular trade wind instead of turning 
towards the higher latitudes, being here deflected across the equator, 
where it returns to the eastward in the form of the westerly mon- 
soons; the easterly monsoons being the regular trade wind. ‘The 
monsoons have, indeed, been ascribed to local rarefaction in Asia 
and New Holland, but the northwesterly monsoon, regardless of this 
hypothesis, sometimes sweeps over half the breadth of the great 
Pacific Ocean in its eastwardly progress. 
The above generalization may also be expressed in the following 
form : 
I. Between the two parallels of 30° N. and S. the atmosphere 
at the earth’s surface, for the most part revolves around the axis of 
the earth with a slower motion than the earth’s crust, or is constantly 
being left behind in the movement of rotation. 
II. The space previously occupied by the atmosphere so left be-- 
hind, is by the centrifugal action of the earth’s rotation, constantly 
supplied from the higher latitudes. 
III. That portion of the atmosphere which is left behind in the 
tropical latitudes, and passes westward by the earth’s rotation, as 
above described, is, by the force of direct gravitation, constantly 
transferred to the higher latitudes; thus preserving the equilibrium 
of distribution, so far as the same is ever maintained in these latitudes. 
IV. That portion of the atmosphere which is so transferred to the 
higher latitudes after having acquired the high rotative velocity of 
the equatorial regions, is by this previously acquired impulse, thrown 
rapidly eastward in the form of westerly winds, thus completing the 
great circuit of perpetual gravitation, which is developed in each of 
_ the oceanic basins on both sides of the equator. 
It is by the currents of these natural circuits of gravitation, that hur- 
ricanes and sterms are found to be transported from one region or lo- 
cality to another; and the track of these storms affords demonstrative 
evidence of the predominating course which these currents pursue. 
Different sections of these currents often become locally modified in 
their apparent courses from various causes, and being often stratified, 
or as it were shwmgled upon each other, they exhibit in their cross- 
