Generally the laws of the conservation of mass, weight and elements are expressed as the "law of the conservation of matter." But this expression lacks scientific exactness because the term "matter" is generally not defined exactly, and because only the above-named properties of ponderable objects do not change, while all other properties do to a greater or less extent. Considered in the most general way, we may define matter as a complex of gravitational, kinetic and chemical energies, which are found to cling together in the same space. Of these energies the capacity factors, namely, weight, mass and elements, are conservative as described, while the intensity factors, potential, velocity and affinity, may change in wide limits. To explain why we find these energies constantly combined one with another, we only have to think of a mass without gravity or a ponderable body without mass. The first could not remain on earth because every movement would carry it into infinite space, and the second would acquire infinite velocity by the slightest push and would also disappear at once. Therefore only such objects which have both mass and weight can be handled and can be objects of our knowledge. In the same way all other energies come to our knowledge only by being (at least temporarily) associated with this combination of mass and weight. This is the true meaning of the term "matter." In this line of ideas matter appears not at all as a primary concept, but as a complex one; there is therefore no reason to consider matter as the last term of scientific analysis of chemical facts, and the idea of a primordial matter appears as a survival from the very first beginning of European natural philosophy. The most general concept science has developed to express the variety of experience is _energy_, and in terms of energy (combined with number, magnitudes, time and space) all observed and observable experiences are to be described. (W. O.) ELEMI, an oleo-resin (Manilla elemi) obtained in the Philippine Islands, probably from _Canarium commune_ (nat. ord. Burseraceae), which when fresh and of good quality is a pale yellow granular substance, of honey-like consistency, but which gradually hardens with age. It is soluble in alcohol and ether, and has a spicy taste with a smell like fennel. In the 17th and 18th centuries the term elemi usually denoted an oleo-resin (American or Brazilian elemi) obtained from trees of the genus _Icica_ in Brazil, and still earlier it meant oriental or African elemi, derived from _Boswellia Frereana_, which flourishes in the neighbourhood of Cape Gardafui. The word, like the older term _animi_, appears to have been derived from _enhaemon_ (Gr. [Greek: ênaimon]), the name of a styptic medicine said by Pliny to contain tears exuded by the olive tree of Arabia.