The same germ-idea underlying these doctrines is to be found much later in Stahl’s phlogistic theory (eighteenth century), which attempted to account for the combustibility of bodies by the assumption that such bodies all contain “phlogiston”--the hypothetical principle of combustion (see § 72)--though the concept of “phlogiston” approaches more nearly to the modern idea of an element than do the alchemistic elements or principles. It was not until still later in the history of Chemistry that it became quite evident that the more obvious properties of chemical substances are not specially conferred on them in virtue of certain elements entering into their constitution. Alchemistic Elements and Principles. § =19.= The alchemists combined the above theories with Aristotle’s theory of the elements. The latter, namely, earth, air, fire and water, were regarded as more interior, more primary, than the principles, whose source was said to be these same elements. As writes Sendivogius in Part II. of _The New Chemical Light_: “The three Principles of things are produced out of the four elements in the following manner: Nature, whose power is in her obedience to the Will of God, ordained from the very beginning, that the four elements should incessantly act on one another so, in obedience to her behest, fire began to act on air, and produced Sulphur; air acted on water, and produced Mercury; water, by its action on the earth, produced Salt. Earth, alone, having nothing to act upon, did not produce anything, but became the nurse, or womb, of these three Principles. We designedly speak of three Principles; for though the Ancients mention only two, it is clear that they omitted the third (Salt) not from ignorance, but from a desire to lead the uninitiated astray.”[28] [28] _The New Chemical Light_, Part II., _Concerning Sulphur_ (see _The Hermetic Museum_, vol. ii. pp. 142-143). Beneath and within all these coverings of outward properties, taught the alchemists, is hidden the secret essence of all material things. “. . . the elements and compounds,” writes one alchemist, “in addition to crass matter, are composed of a subtle substance, or intrinsic radical humidity, diffused through the elemental parts, simple and wholly incorruptible, long preserving the things themselves in vigour, and called the Spirit of the World, proceeding from the Soul of the World, the one certain life, filling and fathoming all things, gathering together and connecting all things, so that from the three genera of creatures, Intellectual, Celestial, and Corruptible, there is formed the One Machine of the whole world.”[29] It is hardly necessary to point out how nearly this approaches modern views regarding the Ether of Space.