MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 125 



CHAPTEE VL 



ON THE PEOBABLE EELATION BETWEEN MAGNETISM AND THE 

 CIECULATION OF THE ATMOSPHEEE. 



Faraday's Discoveries, <$» 299. — Is there a crossing of Air at the Calm Belts'! 301. — 

 Whence comes the Vapor for Rains in extra-tropical Regions 1 305. — Significant 

 Facts, 310. — Wet and dry Winds, 311. — Regions of Precipitation and Evaporation, 

 312. — What guides the Wind in his Circulations 1 313. — Distribution of Rains and 

 Winds not left to Chance, 315. — A Conjecture about Magnetism, 318. — Circum- 

 stantial Evidence, 323. — More Evaporating Surface in the Southern than in the 

 Northern Hemisphere, 326. — Whence come the Vapors that feed the great Rivers 

 with Rains 1 329. — Rain and Thermal Maps, 330. — The Dry Season in California, 

 the Wet in the Mississippi Valley, 332. — Importance of Meteorological Observations 

 in British America, 333. — Importance of extending the System from the Sea to the 

 Land, 334. — Climate of the Interior, 335. — The extra-tropical Regions of the North- 

 ern Hemisphere Condenser for the Trade-winds of the Southern, 336. — Plate VII., 

 339. — Countries most favorable for having Rains, 343. — How does the Air of the 

 Northeast and Southeast Trades cross in the Equatorial Calms, 350. — Rain for the 

 Mississippi Valley, 357. — Blood Rains, 372. — Track of the Passat-Staub on Plate 

 VII., 374.— The Theory of Ampere, 378.— Calm Regions about the Poles, 380.— 

 The Pole of maximum Cold, 381. 



299. Oxygen, philosopliers say, comprises one fifth part of the 

 atmosphere, and Faraday has discovered that it is magnetic. 



This discovery presents itself to the mind as a great physical 

 fact, which is perhaps to serve as the keystone for some of the 

 grand and "beautiful structures which philosophy is building up for 

 monuments to the genius of the age. 



300. Certain facts and deductions elicited in the course of these 

 investigations had directed my mind to the workings in the at- 

 mosphere of some agent, as to whose character and nature I was 

 ignorant. Heat, and the diurnal rotation of the earth on its axis, 

 were not, it appeared to me, sufficient to account for all the cur- 

 rents of both sea and air which investigation was bringing to light. 



301. For instance, there was reason to suppose that there is a 

 crossing of winds at the three calm belts ; that is, that the south- 

 east trade-winds, when they arrive at the belt of equatorial calms 



