THE ATMOSPHERE. 



53 



depth, so that the fluid were on both sides of it, the 

 pouring in of the water would not injure the glass. If 

 it were even placed several feet below the surface, and 

 were so thin that a few grains would break it in the 

 atmosphere, it would be safe in the fluid, although it 

 might endure the pressure of several hundred weight. 

 These peculiarities depend on the uniform pressure of 

 fluids, which is equal upwards, downwards and in all 

 directions. 



RESISTANCE OF THE AIR. 



The efforts to prove the mechanical properties of the 

 air, were looked upon with contempt by many who pro- 

 fessed a great regard for science. How could it pos- 

 sess mechanical peculiarities, when it appeared to offer 

 no resistance to their motions, permitted the bird to 

 soar to the loftiest heights, and the rain to fall in gentle 

 drops on the tender plant? But the science now ex- 

 hibits the fallacy of such reasoning, and explains the 

 means by which all these purposes are effected. It 

 tells us man cannot live above a certain distance from 

 the sea; the bird cannot soar beyond a certain height; 

 and that the gentleness of the rain is caused by the re- 

 sistance the air offers to its fall. Were it not for this 

 cause birds could not rise in the atmosphere. Their 

 flight depends on the resistance the air opposes to their 

 wings. Those birds which fly a long while and far, 

 generally have small bodies and large wings. While 

 those of shorter or less frequent flight, commonly have 

 larger bodies and smaller wings in proportion. These 

 have to beat their wings more frequently in flying, to 

 preserve their velocity and height, and are consequently 

 more easily fatigued. 



The velocity of falling bodies is much resisted by the 

 air ; and the distance to which projectiles are thrown, 

 is materially affected by this principle. One of the 

 most beautiful illustrations of this resistance is shown 

 in the ascent of the sky-rocket. 



The common sky-rocket consists of a simple cylinder 

 of paper filled with gunpowder, or some other explosive 

 material, about six inches long, and about one and a 



VOL. i. NO. in. 5* 



