THE FORCE OF GRAVITATION 



15 



therefore, is to draw a line, A B, corresponding with the 

 string, and we shall find that the centre of gravity is some- 

 where in that line. But where? To find that out, all we 



have to do is to take another place for the awl (Fio. 4), 

 hang the plumb-line, and make the same experiment, and 

 there [at the point C] is the centre of gravity, there where 

 the two lines which I have traced cross each other; and if 

 I take that pasteboard and make a hole with the bradawl 

 through it at that point, you will see that it will be supported 

 in any position in which it may be placed. Now, knowing 

 that, what do I do when I try to stand upon one leg ? Do you 

 not see that I push myself over to the left side, and quietly 

 take up the right leg, and thus bring some central point 

 in my body over this left leg? What is that point which I 

 throw over? You will know at once that it is the centre of 

 gravity that point in me where the whole gravitating force 

 of my body is centred, and which I thus bring in a line 

 over my foot. 



Here is a toy I happened to see the other day, which will, 

 I think, serve to illustrate our subject very well. That toy 

 ought to lie something in this manner (FiG. 5), and would 

 do so if it were uniform in substance; but you see it does 

 not ; it will get up again. And now philosophy conies to our 

 aid, and I am perfectly sure, without looking inside the 

 figure, that there is some arrangement by which the centre 



