114 COHESION. 



it ; and the substance which thus occupies space 

 must have some consistency, in order that we may 

 know by muscular resistance that it exists ; and 

 its consistency must depend not only on what has 

 been already noticed as its gravitation of quantity 

 of matter and position, by which it keeps its 

 place among other substances, but it must have 

 a consistency of its own, by means of which it 

 preserves its shape. That is called the cohesion of 

 the body, which means the tendency that the still 

 smaller bodies, of which we must suppose even 

 the very smallest that we can examine to be made 

 up, have to stick together. And this last pro- 

 perty, of which there are many varieties, has no 

 necessary connexion with universal gravitation. 

 The same bulk of water is, under ordinary circum- 

 stances, much heavier than cork, for cork swims 

 on the surface of water ; but water can be held up 

 in a vessel made of cork. Indeed, the cork is 

 really heavier than water ; for it may be so soaked 

 in water that it will sink like a stone t and at the 

 same time be larger than before. But the water 

 cannot possibly be heavier than itself ; and so the 

 cork must be heavier than water. Quicksilver too 

 is much heavier than glass; and yet it can be 

 contained in a glass vessel ; but still quicksilver, 

 though when laid or poured on the table, it spreads, 

 yet shows that it has still the property of cohesion, 

 though only to a limited extent. That principle 

 or property cannot resist the action of a pound or 

 an ounce; but the little beads of it are quite round, 

 and they dance about like small balls of polished 

 steel. 



It is necessary that the observer of nature, if he 

 is to be any thing higher than a mere " unmeaning 



