ELEMENTARY PHYSICS. CHAPTER I. Somatology DEFINITIONS AND GENERAL PROPERTIES OF MATTER. 1. Physics Physical Agents. - NATURAL PHILOSOPHY, OR PHYSICS, treats of the general properties of bodies, and of the causes that modify these properties without altering their constitution. The principal causes that modify the properties of bodies are: Gravitation, Heat, Light, and Electricity. These causes are called Physical Agents or Forces. 2. A Body is a collection of material particles; as a stone, or a block of wood. A body which is exceedingly small is called a Material Point. 3. Molecules and Atoms. Bodies are made up of small particles, called Molecules, and these again are composed of still smaller elements, called Atoms. A molecule is the smallest particle of matter that can exist by itself. An atom is the smallest particle of matter that can exist in combination. A molecule may consist of two or more atoms of the same kind of matter, or it may be composed of several atoms of different kinds; thus, a molecule of sulphur is a combination of two atoms of sulphur, |