FIRST LAW OF GRAVITATION. Ill 



has to gravitate, or, as it is termed, to fall, is exactly 

 in proportion to the quantity of matter in that piece; 

 and though its effects may be varied by circum- 

 stances, in itself it remains unaltered. So that, if 

 the piece were broken into the greatest number of 

 smaller pieces, the amount of gravitation in them 

 would be exactly the same as that in the large piece 

 before it was broken. So also, if any piece or 

 pieces of matter be joined to another piece or other 

 pieces, the gravitation of the collection is always 

 exactly equal to the sum of all the gravitations of 

 the individual parts. 



This property is indestructible; and not only 

 forms part of the constitution of matter, but is the 

 property by means of which alone we acquire any 

 knowledge of matter at all. That which the tongue 

 tastes, or the nose scents, we cannot measure, or in 

 anywise know but by inference ; and it is by infer- 

 ence that we know what the ear hears, and even 

 what the eye sees, though after long practice we take 

 no notice of, and therefore forget, the process of 

 inferring. Our knowledge of extension or magni- 

 tude, too, is an inference ; and it is impossible for 

 any one to say how many millions of feelings a 

 child must sum up before it can feel the length of 

 its own finger, or make sure of touching the finger 

 of the left hand with the finger of the right. It is 

 clear, however, that in this dawn and birth of know- 

 ledge this fountain and day-spring of all ingenuity 

 and of all action, we borrow nothing from the eye ; 

 for we can lay our finger upon any reachable point 

 of our own body with our eyes shut as accurately 

 as we can with the eyes open, if, indeed, not more 

 accurately. 



Any one may be convinced of the truth of this, 

 by extending his arms, clinching his hands, except 

 the forefingers, and then bringing these to touch 

 each other, in front where he sees them, and behind 

 him, or over his head, where he sees them not ; and, 



