168 THE PHYSICAL GEOGRAPHY OF THE SEA. 



Cape Yerd Islands, Lyons, Genoa, and other places (§ 325) ; thus 

 confirming, as far as such evidence can, the indications of our ob- 

 servations, and increasing the probability that the general course 

 of atmospherical circulation is in conformity with the suggestions 

 of the facts gathered from the sea as I had interpreted them, viz., 

 that the trade-winds of the southern hemisphere, after arriving at 

 the belt of equatorial calms, ascend and continue in their course 

 toward the calms of Cancer as an upper current from the south- 

 west, and that, after passing this zone of calms, they are felt on 

 the surface as the prevailing southwest winds of the extra- tropical 

 parts of our hemisphere ; and that, for the most part, they bring 

 their moisture with them from the trade-wind regions of the op- 

 posite hemisphere. I have marked on Plate YII. the supposed 

 track of the " Passat-Staub," showing where it was taken up in 

 South America, as at P, P, and where it was found, as at S, S; 

 the part of the line in dots denoting where it was in the upper 

 current, and the unbroken line where it was wafted by a surface 

 current ; also on the same plate ie designated the part of the South 

 Pacific in which the vapor-springs for the Mississippi rains are 

 supposed to be. The hands (1^^) point out the direction of the 

 wind. Where the shading is light, the vapor is supposed to be car- 

 ried by an upper current. Such is the character of the circum- 

 stantial evidence which induced me to suspect that some agent, 

 whose office in the grand system of atmospherical circulation is 

 neither understood nor recognized, was at work in these calm 

 belts and other places. It may be electrical, or it may be magnet- 

 ic, or both conjoined. 



859. The more we study the workings of the atmospherical 

 Queteiet's observa- machinery of our planet, the more are we impress- 

 *'^°^" ed with the conviction that we as yet know very 



little concerning its secret springs, and the little " governors" here 

 and there which regulate its movements. My excellent friend M. 

 Quetelet, the astronomer royal at Brussels, has instituted a most 

 excellent series of observations upon atmospherical electricity. 

 He has shown that there is in the upper regions of the air a great 

 reservoir of positive electricity, which increases as the temperature 

 diminishes. So, too, with the magnetism of the oxygen in the up- 

 per regions. 



360. In the southern hemisphere, we may, by reason of its great 



