Philalethes says, in _A Brief Guide to the Celestial Ruby_: "The Philosopher's Stone is a certain heavenly, spiritual, penetrative, and fixed substance, which brings all metals to the perfection of gold or silver (according to the quality of the Medicine), and that by natural methods, which yet in their effects transcend Nature.... Know then that it is called a stone, not because it is like a stone, but only because, by virtue of its fixed nature, it resists the action of fire as successfully as any stone. In species it is gold, more pure than the purest; it is fixed and incombustible like a stone, but its appearance is that of very fine powder, impalpable to the touch, sweet to the taste, fragrant to the smell, in potency a most penetrative spirit, apparently dry and yet unctuous, and easily capable of tinging a plate of metal.... If we say that its nature is spiritual, it would be no more than the truth; if we described it as corporeal, the expression would be equally correct." The same author says: "There is a substance of a metalline species which looks so cloudy that the universe will have nothing to do with it. Its visible form is vile; it defiles metalline bodies, and no one can readily imagine that the pearly drink of bright Phoebus should spring from thence. Its components are a most pure and tender mercury, a dry incarcerate sulphur, which binds it and restrains fluxation.... Know this subject, it is the sure basis of all our secrets.... To deal plainly, it is the child of Saturn, of mean price and great venom.... It is not malleable, though metalline. Its colour is sable, with intermixed argent which mark the sable fields with veins of glittering argent." In trying to attach definite meanings to the alchemical accounts of Principles, Elements, and the One Thing, and the directions which the alchemists give for changing one substance into others, we are very apt to be misled by the use of such an expression as _the transmutation of the elements_. To a chemist that phrase means the change of an element into another element, an element being a definite substance, which no one has been able to produce by the combination of two or more substances unlike itself, or to separate into two or more substances unlike itself. But whatever may have been the alchemical meaning of the word _element_, it was certainly not that given to the same word to-day. Nor did the word _transmutation_ mean to the alchemist what it means to the chemist.