4. In chemistry are found a certain number of elementary substances, such as: —oxygen, hydrogen, nitrogen, carbon, chlorine, iodine, fluoride, sulfur, phosphorus, and all the metals. By their combination they form compound bodies: — the oxides, acids, alkalize, salts, and innumerable varieties resulting from combinations of these.
By the combination of two bodies, in order to form a third, a particular concurrence of circumstances is exacted, — either a determined degree of heat, dryness or humidity, movement or repose, or an electric current, etc. If these conditions do not exist, the combination does not take place.