280 WRITINGS OF JOSEPH HENRY. [1855- 



carry up with it the surface air of the system B, and thus 

 conspire with the downward motion at/ to produce the cir- 

 culation shown in system B. 



The upward current at g, (as in the case of the upward 

 current at the equator,) will tend to diminish the pressure of 

 the air and produce a low barometer and an abnormal fall 

 of rain, which perhaps will be more effective in helping on 

 the circulation of the system B than the mere mechanical 

 effect of the uprising of the current of C. The current 

 at the surface of the earth in the system C, as is shown 

 in Fig. 6, will curve to the westward on account of the 

 increased rotation of the earth, and will therefore be almost 

 in direct opposition to the system B. If we attentively con- 

 sider the effect of the rotation of the earth on the system B, 

 we shall find that as the 'current passes along the surface 

 to the northeast as indicated in Fig. 6, it will begin to 

 ascend when it comes near the parallel of 60°, (retaining 

 however its easterly direction,) will gently curve round and 

 pass southward as an upward current, and flow toward the 

 equator as an upper northwest current, shown in the figure 

 by the few longer arrows, indicating a northwest wind. 

 The system A is the constant circulation of the trade and 

 anti-trade winds. The system C depends upon a similar 

 cause as we have seen, and is for a similar reason permanent 

 in its character. Though but comparatively few observa- 

 tions have been made in the polar regions, the character of 

 this system does not rest upon mere inference from the gen- 

 eral principles we have given, but is conclusively established 

 by the immediate results of reliable data. Professor J. H. 

 Coffin, in his valuable memoir on "The Winds of the 

 Globe," published by the Smithsonian Institution, inferred 

 the existence of this system independently of theoretical 

 conclusions. From the reduction of all the observations 

 he was able to obtain, he conclusively proved that the 

 resultant wind from the pole is from a northeasterly 

 direction; and the same result is established by the discus- 

 sion of the interesting series of observations made during the 

 last expedition of Dr. Kane. These observations, which 



