But it is possible that all the chemical elements may be combinations of different quantities of one primal element. Certain facts make this supposition tenable; and some chemists expect that the supposition will be proved to be correct. If the hypothetical primal element should be isolated, we should have fulfilled the aim of alchemy, and gained the One Thing; but the fulfilment would not be that whereof the alchemists dreamed. Inasmuch as the alchemical Essence was thought of as the Universal Spirit to whose presence is due whatever degree of perfection any specific substance exhibits, it followed that the more perfect a substance the greater is the quantity of the Essence in it. But even in the most perfect substance found in nature--which substance, the alchemists said, is gold--the Essence is hidden by wrappings of specific properties which prevent the ordinary man from recognising it. Remove these wrappings from some special substance, and you have the perfect form of that thing; you have some portion of the Universal Spirit joined to the one general property of the class of things whereof the particular substance is a member. Then remove the class-property, often spoken of by the alchemists as _the life_, of the substance, and you have the Essence itself. The alchemists thought that to every thing, or at any rate to every class of things, there corresponds a more perfect form than that which we see and handle; they spoke of gold, and the _gold of the Sages_; mercury, and the _mercury of the Philosophers_; sulphur, and the _heavenly sulphur of him whose eyes are opened_. To remove the outer wrappings of ordinary properties which present themselves to the untrained senses, was regarded by the alchemists to be a difficult task; to tear away the soul (the class-property) of a substance, and yet retain the Essence which made that substance its dwelling place, was possible only after vast labour, and by the use of the proper agent working under the proper conditions. An exceedingly powerful, delicate, and refined agent was needed; and the mastery of the agent was to be acquired by bitter experience, and, probably, after many disappointments. "Gold," an alchemist tells us, "does not easily give up its nature, and will fight for its life; but our agent is strong enough to overcome and kill it, and then it also has the power to restore it to life, and to change the lifeless remains into a new and pure body."