a42 NATURAL THEOLOar. 



I. Air is essentially different from earth. There appears 

 to be no necessity for an atmosphere's investing our globe, 

 yet it does invest it ; and we see how many, how various, 

 and how important are the purposes which it answers t*» 

 every order of animated, not to say of organized beings, 

 which are placed upon the terrestrial surface. I think that 

 ^very one of these uses will be understood upon the first 

 mention of them, except it be that of rejlecting light, which 

 may be explained thus : If I had the power of seeing only 

 by means of rays coming directly from the sun, whenever I 

 turned my back upon the luminary I should find myself in 

 darkness. If I had the power of seeing by reflected light, 

 yet by means only of light reflected from solid masses, these 

 masses would shine indeed, and glisten, but it would be in 

 the dark. The hemisphere, the sky, the world, could only 

 be illuminated, as it is illuminated, by the light of the sun 

 being from all sides, and in every direction, reflected to the 

 eye by particles as numerous, as thickly scattered, and as 

 widely diffused, as are those of the air. 



Another general quality of the atmosphere is the powei 

 of evaporating fluids. The adjustment of this quality to oui 

 use is seen in its action upon the sea. In the sea, water and 

 salt are mixed together most intimately ; yet the atmosphere 

 raises the water and leaves the salt. Pure and fresh as drops 

 of rain descend, they are collected from brine. If evapora- 

 tion be solution — ^which seems to be probable — then the air 

 dissolves the water, and not the salt. Upon whatever it be 

 founded, the distinction is critical : so much so, that when 

 M'e attempt to imitate the process by art, we must regulate 

 our distillation with great care and nicety, or, together with 

 the water, we get the bitterness, or at least the distasteful- 

 ness of the marine substance ; and, after all, it is owmg tc 

 this original elective power in the air, that we can effect the 

 separation which we wish, by any art or means whatever. 



By evaporation, water is carried up into the air ; by the 

 converse of evaporation, it falls down upon the earth And 



