PARTICLE, in Physics, the minute part of a body, an assemblage of which constitutes all natural bodies.
In the new philosophy, particle is often used in the same sense with atom in the ancient Epicurean philosophy, and corpuscle in the latter. Some writers, however, distinguish them; making particle an assemblage or composition of two or more primitive and physically indivisible corpuscles or atoms; and corpuscle, or little body, an assemblage or mass of several particles or secondary corpuscles. The distinction, however, is of little moment; and, as to most purposes of physics, particle may be understood as synonymous with corpuscle. Particles are then the elements of bodies: it is the various arrangement and texture of these, with the difference of the cohesion, &c. that constitute the various kinds of bodies, hard, soft, liquid, dry, heavy, light, &c. The smallest particles or corpuscles cohere, with the strongest attractions, and always compose larger particles of weaker cohesion; and many of these cohering compose larger particles, whose vigour is still weaker; and so on for divers successions, till the progression end in the largest particles, on which the operations in chemistry, and the colours of natural bodies, depend, and which, by cohering, compose bodies of sensible bulks.
The cohesion of the particles of matter, according to the Epicureans, was effected by hooked atoms; the Aristotelians thought it managed by rest, that is, by nothing at all. But Sir Isaac Newton shows it is by means of a certain power, whereby the particles mutually attract or tend towards each other, which is still perhaps giving a fact without a cause. By this attraction of the particles he shows that most of the phenomena of the lesser bodies are effected, as those of the heavenly bodies are by the attraction of gravity. See ATTRACTION and COHESION.