§ 2G0. THE ATMOSPHERE. 97 



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

 traveled 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 vapor is thus 

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

 that, under these calms, we 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 fresh 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 moisture 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, 

 you will say. But whence are their sources supplied ? for, unless 

 what the fountain sends forth be returned 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 throughout the whole extent of valley drained by 

 them ; and by precipitation I mean the total amount of water that 

 falls from, or is deposited by the atmosphere, whether as dew, 

 rain, hail, or snow. The springs of these rivers (§ 191) are sup- 

 plied from the rains of heaven, and these rains are formed of va- 

 pors which are taken up from the sea, that "it be not full," and 

 carried up to the mountains through the air. "Note the place 

 whence the rivers come, thither they return again." Behold now 

 the waters of the Amazon, of the Mississippi, the St. Lawrence, 

 and all the great rivers of America, Europe, and Asia, lifted up by 

 the atmosphere, and flowing in invisible streams back through the 

 air to their sources among the hills (§ 191), and that through chan- 

 nels so regular, certain, and well defined, that the quantity thus 

 conveyed one year with the other is nearly the same : for that is 

 the quantity which we see running down to the ocean through 



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