DISCOVERY OF THE LAW OF GRAVITY ANTICIPATED. 177 



the Earth, and the Earth upon them, but that Mercury, 

 Venus, Mars, Jupiter, and Saturn also, by their attractive 

 powers, have a considerable influence upon its motion, 

 as in the same manner the corresponding attractive power 

 of the Earth hath a considerable influence upon every one 

 of their motions also. The 2nd supposition is this: 

 that all bodies whatsoever that are put into a direct and 

 simple motion will so continue to move forward in a 

 straight line till they are by some other effectual powers 

 deflected and sent into a motion describing a circle, 

 ellipsis, or some other compounded curve line. The 3rd 

 supposition is : that those attracting powers are so much 

 the more powerful in operating, by how much nearer the 

 body wrought upon is to their own centres. Now what 

 these several degrees are, I have not yet experimentally 

 verified, but it is a notion which, if fully prosecuted, as it 

 ought to be, will mightily assist the astronomers to reduce 

 all the celestial motions to a certain rule, which I doubt 

 will never be done without it. He that understands the 

 nature of the circular pendulum and circular 'motion will 

 easily understand the whole of this principle, and will 

 know where to find directions in nature for the true stating 

 thereof. This I only hint at present to such as have 

 ability and opportunity of prosecuting this inquiry, and 

 are not wanting of industry for observing and calculating, 

 wishing heartily such may be found, having myself many 

 other things in hand which I would first complete, and 

 therefore cannot so well attend to it. But this I do 

 promise the undertaker, that he will find all the great 

 motions of the world to be influenced by this principle, 

 and that the true understanding thereof will be the true 

 perfection of astronomy.' 1 



1 Baden-Powell, History of ^Natural Philosophy, p. 264-. 

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