Element

Element. According to the doctrines of Empedocles and Aristotle there were four elements, earth, air, water, and fire, to which was also subsequently added a fifth, the quinta essentia, the ether. It seems probable, however, that these ideas did not originate with the Greek philosophers, but were borrowed from earlier sources, perhaps from the Indians. The term element as used by them, however, did not convey the same meaning as it does at the present time. It then implied a property or complexion, rather than a form, of matter. Thus the properties of cold and moisture were associated with water, cold and dryness with earth, etc. Later, the alchemist Geber supposed all metals consisted of varying quantities of mercury and sulphur, and forthe transmutation of metals what was necessary was but the addition or abstraction of one or other of these substances. Basil Valentine added salt as the third elementary substance, which, with the two previous ones, formed all bodies. It appears, however, that this sulphur, etc., were not identical with what we know now by the terms, and were possessed of many more or less mythical properties. Boyle first gave a distinct definition of the term element, stating that those substances are to be considered as elements which are not capable of further separation into simpler components. He did not, however, specify what substances he considered as elementary. At the present day about 70 simple bodies are recognised by chemists, a list of which is given under Atomic Theory. Besides those there given, a few others may be regarded as doubtful, as, for instance, holmium, and masrium, whose existence was only indicated in 1892. Further, it is always possible that some of the substeuices regarded as elementary may be proved to consist of two or more simple bodies. Thus didymium is very probably not a true element, while the elementary nature of cobalt and nickel is also disputed. The first classification of the elements was that oi metals and non-metals, and although it is impossible to draw a definite line of demarcation between these two classes the division is still a convenient one for many purposes. The sole basis, however, upon which a scientific classification can be founded is the Periodic Law (q.v.). Of the elements but few (about 20) ave found free in nature, as oxygen, nitrogen, sulphur, carbon, and some metals, while most of these are far more common in'combination. Compounds of carbon are known as organic matter. The crnst of the earth consists almost entirely of 13 elements only, of which oxygen is the most abundant. What the composition of the interior may be, is, however, still a matter of conjecture. The question whether the various elements are distinct forms of matter or whether they are all various products of evolution from one primordial matter is one that affordsgreat scope for theorising. .Until recently the first view was that almost universally accepted, but of, late. years the second, an evolutionary idea, has been finding favour with many chemists. In the present state of knowledge, however, all theories upon this subject must be regarded as purely speculative. (See also Atomic Theory, Chemistry, Periodic Law, and the articles on the separate elements.)