RAINS AND RIVERS. 119 



records for upwards of 260,000 days in the Atlantic Ocean north 

 and south (Plate XIII.), have been carefully examined for the 

 purpose of ascertaining, for comparison, the number of calms, 

 rains, and gales therein recorded for each hemisphere. Pro- 

 portionally the number of each as given is decidedly greater 

 for the north than it is for the south. The result of this ex- 

 amination is very instructive, for it shows the status of the atmo- 

 sphere to be much more unstable in the northern hemisphere, 

 with its excess of land, than in the southern, Avith its excess 

 of land. Eains, and fogs, and thunder, and calms, and storms, 

 all occur much more frequently, and are more irregular also as* to 

 the time and place of their occurrence on the north side, than 

 they are on the other side of the equator. Moisture is never ex- 

 tracted from the air by subjecting it from a low to a higher 

 temperature, but the reverse. Thus all the air w^hicli comes, 

 loaded with moisture from the other hemisphere, and is borne 

 into this with the south-east trade-winds, travels in the upper 

 regions of the atmosphere (§ 213) until it reaches the calms 

 of Cancer ; here it becomes the surface wdnd that j^revails from 

 the southward and westward. As it goes north it grows cooler, 

 and the process of condensation commences. We may now liken 

 it to the wet sponge, and the decrease of temperature to the 

 hand that squeezes that sponge. Finalty reaching the cold 

 latitudes, all the moisture that a dew-point of zero, and even 

 far below, can extract, is wrung from it ; and this air then com- 

 mences " to return according to his circuits" as dry atmosphere. 

 And here we can quote Scripture again : " The north wind 

 driveth away rain." This is a meterological fact of high au- 

 thority, and. one of great significance too. 



292. Tlw trade-winds tJie emporating winds. — By, reasoning in 

 this manner and from such facts, we are forced to the conclusion 

 that our rivers are supplied with their waters principally from 

 the trade-wdnd regions — the extra-tropical northern rivers from 

 the southern trades, and the extra-tropical southern rivers from 

 the northern trade-wdnds, for the trade-winds are the evaporating 

 winds. 



293. Tlie saltest part of the sea. — Taking for our guide such 

 faint glimmerings of light as we can catch from these facts, 

 and supposing these views to be correct, then the saltest portion 

 of the sea should be in the trade-wind regions, where the water 

 for all the rivers is evaporated; and there the saltest portions 



