NEW CONCEPTIONS IN SCIENCE 



tradictory to every-day experience than this law of 

 equal attraction. There is nothing in nature to 

 lead us, a priori, to believe that a ton of air and a 

 ton of gold pull each other with the same force. 

 Yet it is precisely because of this that the blanket 

 of air we call the atmosphere presses down upon 

 the earth with a force, everywhere, of fifteen 

 pounds to every square inch. The earth is plough- 

 ing through space at the rate of nineteen miles 

 per second; the reason the earth's atmosphere has 

 not disappeared in the depths of space long ago is 

 because of the Newtonian attraction between the 

 earth and the farthest particles of the air. This 

 attraction still subsists, even when the air is mill- 

 ions of times more rarefied than at the earth's 

 surface, and where single particles may have a 

 free path of miles, instead of thousandths of an 

 inch, as at ordinary pressures. 



We are accustomed to think of the sun as a 

 molten mass, implying a fiery liquid. It is more 

 likely a ball of incandescent gas, so that the force 

 which holds the earth to its customary revolution 

 is exerted by the particles of a gas, like the air. 

 The same is probably true of all the stars ; they are 

 balls of gas. Some of them are moving at the 

 rate of three or four hundred miles a second. This 

 speed is generated by the pull of one gas-ball, or 

 set of them, on another. Some of these flaming 



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