THE ATMOSPHERE. 99 



discs about the poles as it does in cyclones, \az., against the hands 

 of a watch in the northern, with them in the southern hemisphere. 

 267. To act and react upon each other, to distribute moisture 

 The offices of sea and over the surfaco of the earth, and to temper the 

 economy^ ^ ^"'^^ climato of different latitudes, it would seem, are two 

 of the many offices assigned by their Creator to the ocean and the 

 ?iir. When the north-east and south-east trades meet and produce 

 the equatorial calms (§ 212), the air, by the time it reaches this 

 calm belt, is heavily laden with moisture, for in each hemisphere it 

 has travelled obliquely over a large space of the ocean. It has no 

 room for escape but in the upward direction (§ 223). It expands 

 as it ascends, and becomes cooler ; a portion of its vapour is thus 

 condensed, and comes down in the shape of rain. Therefore it is 

 that, under these calms, w^e have a region of constant precipita- 

 tion. Old sailors tell us of such dead calms of long continuance 

 here, of such heavy and constant rains, that they have scooped up 

 fi'esh water from the sea to drink. The conditions to which this 

 air is exposed here under the equator are probably not such as to 

 cause it to precipitate all the moistiu-e that it has taken up in its long 

 sweep across the waters. Let us see what becomes of the rest ; for- 

 Nature, in her economy, permits nothing to be taken away from the 

 earth which is not to be restored to it again in some form, and at 

 some time or other. Consider the great rivers — the Amazon and 

 the Mississippi, for example. We see them day after day, and year 

 after year, discharging immense volumes of water into the ocean. 

 *' All the rivers run into the sea, yet the sea is not full." — Eccl. i. 7. 

 Where do the waters so discharged go, and where do they come 

 from? They come from their sources, is the ready answer. But 

 whence are their sources supplied ? for, unless what the fountain 

 sends forth be retm-ned to it again, it will fail and be dry. We 

 see simply, in the waters that are discharged by these rivers, the 

 amount by which the precipitation exceeds the evaporation through- 

 out the whole extent of valley drained by them ; and by precipita- 

 tion I mean the total amount of water that falls from, or is de- 

 posited by the atmosphere, whether as dew, rain, hail, or snow. 

 The springs of these rivers (§ 191) are supplied from the rains of 

 heaven, and these rains are formed of vapours w^hich are taken up 

 from the sea, that " it be not full," and carried up to the mountains 

 tlu'ough the air. " Note the place whence the rivers come, thither 

 they retm-n again." Behold now the waters of the Amazon, of the 

 Mississippi, the St. Lawrence, and all the great rivers of America, 



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