ON THE ESSENTIAL PROPERTIES OF MATTER. 60/ 



supposing a previous knowledge of many other departments of natural phi- 

 losophy. 



We may distinguish the general properties of matter into two principal 

 classes, those which appear to be inseparable from its constitution, and those 

 which are. only accidental, or which are not always attached to matter of 

 all kinds. The essential properties are chiefly extension and divisibility, 

 density, repulsion, or impenetrability, inertia, and gravitation ; the acci- 

 dental properties are in great measure dependent on cohesion, as liquidity, 

 solidity, symmetry of arrangement, cohesive elasticity, stiffness, toughness, 

 strength, and resilience. 



The extension of matter can scarcely be considered as a property separate 

 from its impenetrability, unless we conceive that it can occupy space, without 

 excluding other bodies from it. This opinion has indeed been maintained 

 by some philosophers, who hav^e imagined that the minute particles which 

 they suppose to constitute light, may penetrate the ultimate atoms of other 

 matter without annihilating or displacing them; and if this hypothesis were 

 admitted, it would be necessary to consider each particle of matter as a sphere 

 of repulsion, extended without being impenetrable. 



The divisibility 6f matter is great beyond the power of imagination, bat 

 wc have no reason for asserting that it is infinite; for the demonstrations, 

 which have sometimes been adduced in favour of this opinion, are obviously 

 applicable to space only. The infinite divisibility of space seems to be essen- 

 tial to the conception that we have of its natur^; and it may be strictly de- 

 monstrated, that it is mathematically possible, to draw an infinite number of 

 circles between any given circle and its tangent, none of which shall touch 

 either of them, except at the general point of contact; and that a ship, following 

 always the same oblique course with respect to the meridian, for example, sailing 

 north eastwards, would continue perpetually to approach the pole without 

 ever completely reaching it. But when Ave inquire into the truth of the 

 old maxim of the schools, that all matter is infinitely divisible, we are by no 

 means able to decide so positively. Newton observes, that it is doubtful 

 whether any human means may be sufficient to separate the particles of mat- 

 ter beyond a certain limit; and it is not impossible that there may be some. 



