Water was believed to be an element from the very-earliest times down to only a few decades ago.

Moses mentions, in the first chapter of his Genesis, water as one of the first created elementary bodies. The Hindoos and Egyptians regarded it the basis of most of the other bodies. Among the Greeks, Thales - 600 B. c. - defended the opinion that water was the only true element, and that all other bodies, plants and animals included, were formed out of it.

Diodorus, about the year 30 B. C, suggested that rock-crystal developed from the purest water, not under the influence of cold, but under that of the heavenly fire. This opinion of the development of the stone, the characteristic ingredient of which is silex, is affirmed by its Greek name, krystallos, or ice.

Soon others got up and declared rock-crystal was not formed out of water by heat, but by long-lasting cold. Pliny, after he has spoken of solids and their formation out of warmth and cold, says:

"Contraria huic causa crystallum facit, gelu vehe-mentiore concreto. Non aliubi certe reperitur quam ubi maxirne hibernae nives rigent, glaciemque esse certum est, unde et nomen Graeci dedere." Seneca Minor and other contemporaries express the same opinion, as does also Isodorus of the seventh century.

Agricola of the sixteenth century is the first philosopher who is opposed to it; in his book De Ortu et Can-sis Subterraneorum he says: "If the crystal was formed out of water, it naturally would have to be lighter than water, for ice floats on water. He denies emphatically that any stony material might be formed of water without any additional ingredients: "Satis intellegimus, ex sola aqua non gigni lapidem ullum"

In the seventeenth century alchemists believed that an occult chemical transformation of water to stone was possible, and similar fables and humbug were still believed in during the last century.

An exception of this rule was Becher, who taught that crystals could not be formed of ice, as they are found also in localities where neither severe nor long-lasting cold reigns.

Le Roy, in the year 1767, tried to demonstrate before the Academy of Paris, that all experiments made until then did not prove the possibility of changing water into earth. He meant, earth was mixed to the water in a suspended form; that it was not formed anew by each and every distillation, but that only a part of the suspended earth was precipitated, while the greater part of it was distilled over; that by continuous distillation it would be possible to precipitate more and more of the suspended earth, but that the same result could not be obtained with the entire quantity.

It was Lavoisier who proved the true origin of this much-disputed earth; the report of his experiments in this direction is contained in the annals of the Academy of Paris for the year 1770. He showed beyond any doubt, that water, even after long boiling in glass vessels, was not transformed into earth, but that the earth which was found therein after boiling owed its existence to the glass vessel.

The opinion that water was an element was maintained to the close of the eighteenth century.

Cavendish first, in the year 1781, saw that water was produced when hydrogen was burned in the flame of oxygen. In 1783 Watt expressed the opinion that water consisted of oxygen and phlogiston, by which name he very likely meant hydrogen. The undoubted proof for the water's composition of oxygen and hydrogen was given by the great Lavoisier in the same year; the quantitative analysis was first determined by Gay-Lussac, and Humboldt in the year 1805. By numerous exact experiments it is shown that water contains one volume of oxygen and two volumes of hydrogen, or, to express the same fact in weight, it consists of eight parts of oxygen and one part of hydrogen.