THE SEA A^B THE AT:iIOSPHEEE. 13 



rain, seem rec[iiisite to deflagrate the noxious gases wliicli have 

 accumulated, to commingle in one healthful mass the polluted ele- 

 ments of the air, and restore it fitted for the ends designed for it. 

 We have hitherto dealt vrith the sea and air — the one the medium 

 through which the commerce of all nations is transported, the 

 other the means by which it is moved along — as themselves the 

 great vehicles of moisture, heat, and cold throughout the regions 

 of the vrorld — the means of secm'ing the interchange of these in- 

 estimable commodities, so that excess may be removed to where 

 deficiency exists, deficiency substituted for excess, to the un- 

 bomided advantage of all. This group of illustrations has been 

 selected because they are the most obvious, the most simple, and 

 the most intelligible and beautiful that could be chosen. 



38. " We have already said that the atmosphere forms a spheri- 

 Towers of the air. cal shcll, smTouuding the earth to a depth which is 

 unknown to us, by reason of its growing tenuity, as it is released 

 from the pressure of its own sujjerincumbent mass. Its upper 

 surface cannot be nearer to us than fifty, and can scarcely be 

 more remote than five hundred miles. It surrounds us on all 

 sides, yet we see it not ; it presses on us with a load of fifteen 

 pounds on every square inch of surface of our bodies, or from 

 seventy to one hundred tons on us in all, yet we do not so much 

 as feel its weight. Softer than the finest do^vn, more impalpable 

 than the finest gossamer, it leaves the cobweb undisturbed, and 

 scarcely stirs the lightest flower that feeds on the dew it supplies ; 

 yet it bears the fleets of nations on its wings around the v/orld, 

 and crushes the most refractory substances with its weight. When 

 in motion, its force is sufficient to level with the earth the most 

 stately forests and stable buildings, to raise the waters of the ocean 

 into ridges like mountains, and dash the strongest ships to pieces 

 like toys. It warms and cools by tmiis the earth and the living 

 creatures that inhabit it. It draws up vapours from the sea and 

 land, retains them dissolved m itseK or suspended in cisterns of 

 clouds, and throws them do"wn again, as rain or dew, when they 

 are required. It bends the rays of the sun from their path to give 

 us the aurora of the morning and twilight of evening ; it disperses 

 and refracts their various tints to beautify the approach and the 

 retreat of the orb of day. But for the atmosphere, sunshine would 

 burst on us in a moment and fail us in the t^mlding of aii eye, 

 removing us in an instant from midnight darkness to the blaze 

 of noon. We should have no tv^dlight to soften and beautify tLo 



