54^ DISSERTATION ON 



ter, we muft fuppofe that they would reft there *. In the fame manner. 

 iron is moved towards the magnet ; and, when it is there, it refts. In 

 like manner, the particles of metals, when they are diffolved in a men- 

 ftruum, are moved towards the menftruum, and, when they are in- 

 corporated with it, they are at reft. But a motion, in empty fpace, 

 going on in itifnitum, without any determination or purpofe, is a thing 

 altogether anomalous, and fo much out of the ordinary courfe of na- 

 ture, that it never can be fuppofed, but muft be proved by the moft 

 convincing arguments. 



But it will be faid, if the motion be not eternal, it muft laft fomc 

 determinate time. Now, what is that determinate time ? My anfwer 

 is. That, in all we know of nature, bodies are always retarded, more 

 or lefs, by the refiftence of the medium through which they pafs. We 

 are unable, therefore, by any experiment we can make, to determine 

 how long a body will contmue its motion zn -vacuo ; but, as we know 

 with great certainty, that there is nothing in nature but what is go- 

 verned by rule and meafure, ratio and proportion, we are fure that the 

 motion of bodirs m vaaw. (if there be fuch a thing as a vacuum) 

 muft be, fome way or other, determinate : And we might go a little 

 farther, and fay, without hazard of error, that the duration of the 



motion 



* I know the Newtonians maintain, that the body, when it arrives at the center of 

 the earth, would not reft there, but would pafs the center, and fwing backward and 

 forward, w.th an ofcillatory motion: Bat they proceed, upon the fuppofition imo 

 Thatgr.v.tat.on is produced by pulfation; and, 2do, That motion, fo produced con' 

 tmues forever : Whereas, I, fuppoHng that gravitation is produced immediately and 

 d.reaiy by the grand agent in nature-.>//«^, and not believing that there is any fuch 

 thmg m nature as body continuing to be moved perpetually by material neceffitv c.n 

 not conceive how body (hould be carried by Mind beyond the place of its deftination" 

 I therefore hold, th.t a body, when it arrives at the center of the earth, refts as iron 

 does when u comes to the loadflcne. As to the motion of a pendulum here on earth 

 It .3 plamlycon^pounded of different forces, acting in differem direcl.ons, viz bod,lv 

 rmpulfe and gravitation : Whereas, the n,otion of a body towards the center of the 

 earth zs perfectly fimple , fo that there can be no argument drawn from the ouc to the 

 other. ^ ""^ 



