The name assigned by the ancients to those simple substances of which, by combination, all bodies were supposed to be formed. These principles were supposed to be four in number, viz. fire, water, earth, and air; but the researches of modern chemistry have completely overturned this classification, showing that each of these supposed elements is in reality composed of two or more substances, and extending the number of simple substances to nearly fifty; at the same time it is to be observed that these substances are not pronounced to be absolutely simple, but are merely so in respect to the present state of the art of analyzing bodies. For a list of the simple or undecompound substances, see Chemistry.