MAGNETISM AND CIRCULATION OF THE ATMOSPHERE, m 
in the relation of a condenser to a grand steam machine 120), 
the boiler of which is in the region of the southeast trade-winds, 
and to consider the trade-winds of this hemisphere as performing 
the like office for the regions beyond Capricorn. 
199. The calm zone of Capricorn is the duplicate of that of 
Cancer, and the winds flow from it as they do from that, both 
north and south ; but with this difference : that on the polar side 
of the Capricorn belt they prevail from the northwest instead of 
the southwest, and on the equatorial side from the southeast in- 
stead of the northeast. 
Now if it be true that the vapor of the northeast trade-winds 
is condensed in the extra-tropical regions of the southern hemi- 
sphere, the following path, on account of the effect of diurnal ro- 
tation of the earth upon the course of the winds, would represent 
the mean circuit of a portion of the atmosphere moving according 
to the general system of its circulation over the Pacific Ocean, 
viz., coming down from the north as an upper current, and ap- 
pearing on the surface of the earth in about longitude 120° west, 
and near the tropic of Cancer, it would here commence to blow 
the northeast trade-winds of that region. 
200. To make this clear, see Plate VII., on which I have mark- 
ed the course of such vapor-bearing winds ; A being a breadth or 
swath of winds in the northeast trades ; B, the same wind as the 
upper and counter-current to the southeast trades ; and C, the 
same wind after it has descended in the calm belt of Capricorn, 
and come out on the polar side thereof, as the rain winds and pre- 
vailing northwest winds of the extra-tropical regions of the south- 
ern hemisphere. 
This, as the northeast trades, is the evaporating wind. As the 
northeast trade-wind, it sweeps over a great waste of waters lying 
between the tropic of Cancer and the equator. 
201. Meeting no land in this long oblique track over the tepid 
waters of a tropical sea, it would, if such were its route, arrive 
somewhere about the meridian of 140° or 150° west, at the belt 
of equatorial calms, which always divides the northeast from the 
southeast trade-winds. Here, depositing a portion of its vapor as 
it ascends, it would, with the residuum, take, on account of diurnal 
rotation, a course in the upper region of the atmosphere to the 
southeast, as far as the calms of Capricorn. Here it descends 
