1018 Dynamic Theory. 



to be in motion toward the constellation Hercules at the rate of over 

 20,000 miles an hour, at which rate we ought to get there within a 

 couple millions of years. In all probability our system travels upon a 

 vast elliptical orbit like that of a comet, which, after periods of per- 

 haps some millions of millions of years, brings us near enough to its 

 great glowing focus to turn the solid matter of our system into an in- 

 candescent gas; in which condition we are allowed to rush forward upon 

 the outbound portion of our orbit with ample leisure before us in 

 which to cool off and re-enact tne evolution of a solar system, with its 

 rings and planets and moons, with all their possibilities of revolution 

 and rotation, of land, water, and air, and of plants and animals. 



All the motions of the heavenly bodies from a two-ounce meteor or a 

 fifty-pound comet to Sirius, weighing fourteen times as much as our 

 sun, are due to the attraction of gravitation. It thus appears that the 

 Force, of Gravity alone, operating in the reduction or annihilation of 

 distances between bodies, is the cause directly or indirectly of all the 

 forms of motion and energy with which we are acquainted. 



There is no limit to human curiosity, and so we are not satisfied 

 merely to know that gravity begets molar motion, and molar motion 

 when arrested produces heat, light, sound, electricity, and other forms 

 of molecular motion; we want to know how gravity operates. 



If a cannon ball were carried up from the earth toward the moon it would 

 get lighter and lighter, till at length a point would be reached where it 

 would not weigh anything at all. Carried further, it would begin to 

 have weight, and it would have to be supported to keep it from falling, 

 not toward the earth, however, but toward the moon. At a particular 

 point, therefore, the ball has changed its allegiance from the earth 

 to the moon, and now apparently wants to go there. What has the 

 moon done to inform the ball of her whereabouts, and inspire it with 

 a desire to rush to her? Evidently she has done something, for if she 

 were moved away you might continue to cany that ball in the same 

 direction to the spot she had occupied 240,000 miles from the earth, 

 and it would still have weight which, though diminished, would cause 

 it to fall back to the earth as soon as liberated. When the moon at- 

 tracted the ball away from the earth in our hypothetical case, it looks as 

 if she threw out something like a lasso, or noose, or net, and drew it in, 

 with the ball in it. And I take it this is precisely what she did do, 

 and this is what the attraction of gravitation is. It involves a motion 

 in two ways, a reaching out, and a pulling in. Before the ball could 

 move toward the moon, some sort of connection or relationship must be 

 established between the two. Otherwise we should be compelled to sup- 

 pose some force, extraneous to both, to stand behind the ball and ad- 

 minister an impulse in the direction of the moon. But in that case 



