PROPERTIES OF MATTER. 3 
air in the tumbler. This property of air is taken advantage of in the 
diving-bell. That a liquid cannot occupy the same space with any other 
body, is clear from the fact, that if anything be put into a vessel full of 
water, the water will flow over, so as to make room for the body put in. 
3. Divisibility.— The nature of matter is such that it can be divided to an 
extent far beyond the limits perceptible to the senses. A grain of gold, 
the bulk of which is one five-thousandth part of a cubic inch, can be 
beaten out so as to cover 57 square inches. The leaf thus formed is so 
thin that a pile an inch thick would contain 282,000 leaves. The 
microscope has revealed the existence of animals, a million of which 
would not occupy more space than a grain of sand. Yet these animalcules, 
as they are called, have members and organs, and display all the appear- 
ances of vitality. How shall we conceive, the smallness of the tubes or 
vessels in which their fluids circulate, and the minuteness of the particles 
of matter composing these tubes and fluids! It must not, however, be 
supposed that there is no limit to. the divisibility of matter. On the 
contrary, there are many reasons for believing that there is a limit 
- somewhere ; and that there are ultimate particles of a determinate size 
and shape, incapable of further subdivision. These assumed particles 
are called atoms [Gr. atomos, from a, not, temmnd, to cut}. 
4, Cohesion.—Cohesion is the property by which the particles of matter 
_stick together and form masses or bodies. Without this force to bind its 
particles together, matter would only exist in the shape of sand or powder. 
There is another kind of attraction, called the Attraction of Gravitation, 
by which one body acts upon every other body at any distance, how- 
ever great ; but cohesion acts only when the particles are in contact, 
or when the distances between them are imperceptible. Thus, when a 
stone is broken, the fragments cannot be made to adhere, although placed 
together again; in other words, the cohesion which existed between the 
particles before will not operate after they have been separated. The 
degree of cohesion in all bodies, however, is not the same; and this 
gives rise to what are called states of aggregation of particles, of which | 
there are three—the solid, the liquid, and the gaseous. 
When the air has been entirely drawn out of a vessel by an air-pump, 
and a small quantity of gas introduced, the gas does not remain of the 
same bulk, but spreads itself throughout the whole vessel. This proves 
that there is in the gas itself a force repelling the particles with a power 
sufficient to overcome their own weight. This force was formerly called 
Repulsion, but it is now known that it is not an essential property, but 
the effect of heat, which is a form of motion. among the particles. In 
addition to the cohesive force which binds the particles of matter 
together, there is thus another which repels them from each other. 
When the cohesion is greater than the repulsion, the body is firm and 
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