ATTRACTION. 15 



containing unequal quantities of matter, were 

 placed at any distance, and left in the same manner 

 at liberty, they would fall towards one another 

 with velocities which would be in an inverse pro- 

 portion to their respective quantities of matter; 

 and moving faster and faster in their mutual ap- 

 proach, would at last meet in a point as much 

 nearer to the place from which the heavier body 

 began to fall, than to the place from which the 

 lighter began to fall, as the quantity of matter in 

 the former exceeded that in the latter. 



The earth attracts all bodies on its surface, and 

 they are all drawn towards the center of the earth ; 

 consequently bodies fall every where peqiendicular 

 to its surface, and therefore in opposite directions 

 on opposite sides of the earth. As it acts upon 

 all bodies in proportion to their quantities of mat- 

 ter, it is this attractive force that constitutes the 

 weight of bodies. 



In all places equidistant from the center of the 

 globe, the force of gravity is equal: but this 

 power is greatest at the earth's surface, from 

 whence it decreases both upwards and downwards, 

 but not both ways in the same proportion; for, 

 upwards, the force of gravity decreases as the 

 square of the distance from the centre increases; 

 so that at a double distance from the. centre above 

 the surface, the force would be only one fourth 

 of what it is at the surface : but below the surface 

 of the earth, the power decreases in such a manner 

 that its intensity is directly as the distance from 

 the centre, and not as the square of the distance; 

 so that at the distance of half a semi-diameter 

 from the centre, the force would be but half what 

 it is at the surface; at one third of the semi- 

 diameter, the force would be one third, and so on. 



