-1859] WRITINGS OF JOSEPH HENRY. 275 



comes less and less as we depart from the equator; hence all 

 the air which ascends at the equator could not flow entirely 

 to the pole, but the larger portion of it would descend to the 

 earth to return again to the equator, along the surface at 

 some intermediate point, which would be, on an average, 

 about the latitude of 30°, since the space included between 

 this and the equator would be nearly equal to the remaining 

 surface in each hemisphere. Again as we have seen, the 

 simplicity of this system of winds would be interfered with 

 by the rotation of the earth on its axis. On account of this 

 rotation, as a general rule, when a current moves from the 

 equator, in the northern hemisphere, for example, it would 

 gradually curve to the east, and when it moves southward 

 in the same hemisphere, it would curve to the west; the- 

 rapidity of curving in either case would increase as we ap- 

 proach the pole. On account of this curvature and deflec- 

 tion east and west of the upper and lower currents, together 

 with the disturbance produced by the evolution of the latent 

 heat, the simple system we first described will tend to sepa- 

 rate, as we shall more fully see hereafter, into three distinct 

 systems, which we have represented by A, B, and 0, in the 

 annexed figure. 



Fig. 5 is a diagram intended to represent an ideal section 



Fig. 5. 



through a meridian of the northern hemisphere, showing 

 the several systems of aerial circulation, commencing on the 

 left at E (the equator), and completing the series on the right 

 at P, — the north pcle. Fig. 6 is a bird's eye view of the 

 globe, designed to illustrate the prevailing direction of the-- 



