14 PHYSICAL GEOGR.lPnY OF THE SEA, AND ITS METEOROLOGY. 



is released from tlio pressure of its own superincumbent mass. 

 Its upper surface cannot "be nearer to us than fifty, and can 

 scarcely be more remote than five hundred miles. It surrounds 

 ns 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 down, more im- 

 palpable than the finest gossamer, it leaves the cobweb undis- 

 turbed, and scarcely stirs the lightest flower that feeds on the 

 dew it supplies ; jet it bears the fleets of nations on its wings 

 around the world, 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 turns the earth and the living creatures that inhabit it. It 

 draws up vapours from the sea and land, retains them dissolved 

 in itself or suspended in cisterns of clouds, and throws them 

 down 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 twinkling of an eye, removing us in 

 an instant from midnight darkness to the blaze of noon. We 

 should have no twilight to soften and beautify the landscape, no 

 clouds to shade us from the scorching heat ; but the bald earth, 

 as it revolved on its axis, would turn its tanned and weakened 

 front to the full and unmitigated rays of the lord of day. 



39. Its functions. — " The atmosphere affords the gas which 

 vivifies and warms our frames ; it receives into itself that which 

 has been polluted by use, and is thrown off as noxious. It feeds 

 the flame of life exactly as it does that of the fire. It is in both 

 cases consumed, in both cases it affords the food of consumption, 

 and in both cases it becomes combined with charcoal, which 

 requires it for combustion, and which removes it when com- 

 bustion is over. -It is the girdling encircling air that makes the 

 whole world kin. The carbonic acid with which to-day our 

 breathing fills- the air, to-morrow seeks its way round the world. 

 The date-trees that grow round the falls of the Nile will drink it 

 in by their leaves ; the cedars of Lebanon will take of it to add 



