THE FORCE OF GRAVITATION f 



lac [a stick of shell-lac about 12 inches long and i 1-2 

 in diameter], and rub it with flannel, and hold it an inch 

 or so in front of the upper part of this upright sheet, the 

 paper is immediately moved towards the shell-lac, and by 

 now drawing the latter away, the paper falls over without 

 having been touched by any thing. You see, in the first 

 illustration I produced an effect than which nothing could 

 be commoner; I pull it over now, not by means of that 

 string or the pull of my hand, but by some action in this 

 shell-lac. The shell-lac, therefore, has a power wherewith it 

 acts upon the sheet of paper; and, as an illustration of the 

 exercise of another kind of power, I might use gunpowder 

 with which to throw it over. 



Now I want you to endeavor to comprehend that when 

 I am speaking of a power or force, I am speaking of that 

 which I used just now to pull over this piece of paper. 

 I will not embarrass you at present with the name of that 

 power, but it is clear there was a something in the shell-lac 

 which acted by attraction, and pulled the paper over; this, 

 then, is one of those things which we call power, or force; 

 and you will now be able to recognize it as such in whatever 

 form I show it to you. We are not to suppose that there are 

 so very many different powers ; on the contrary, it is wonder- 

 ful to think how few are the powers by which all the phe- 

 nomena of nature are governed. There is an illustration of 

 another kind of power in that lamp; there is a power of 

 heat a power of doing something, but not the same power 

 as that which pulled the paper over ; and so, by degrees, we 

 find that there are certain other powers (not many) in the 

 various bodies around us; and thus, beginning with the 

 simplest experiments of pushing and pulling, I shall gradually 

 proceed to distinguish these powers one from the other, 

 and compare the way in which they combine together. 

 This world upon which we stand (and we have not much 

 need to travel out of the world for illustrations of our 

 subject; but the mind of man is not confined like the matter 

 of his body, and thus he may and does travel outward, for 

 wherever his sight can pierce, there his observations can 

 penetrate) is pretty nearly a round globe, having its sur- 

 face disposed in a manner of which this terrestrial globe 



