t 3 75 ]

stance, which has little disposition to unite with freshoil any more than with water, as if the gummy and oilymatter were in such proportions, that one defends theother from the menstruum that would otherwise dissolveit : essential oils on the contrary, being free from gum,harden into a merely resinous mass, brittle like otherresins, and which dissolves,, like the oil at first, in fresli oilor in spirit of wine. The differences observed in differentexpressed oils, in regard to the drying quality, may de-pend on the different quantities of gummy matter andthe difference of old oil from new, on the gum beingin the latter more intimately combined, so as not to sepa-rate in the burning and boiling. When these oils are firstpressed out from the subjects, they abound with muci-lage, great part of which is only superficially mixed, so asto give a turbidness and opacity to tlTe'fluid : in keeping,a part of this loose mucilage is thrown off, and the re-mainder may be presumed to become at the same timemore intimately incorporated with the oil. The repug-nance which we observe between oil and gum does not inthe least invalidate these conjectures, any more than therepugnance between oil and water can be an argumentagainst the existence of water in oils : indeed we haveplain proofs of the coalition of oil with gum, in the ana-lysis of the purest gums, gum arabic, senica, tragacanth,from which an actual oil is obtained by distillation. Thedistillation of expressed oils themselves seems to favourthe opinion here proposed : from all of them there re-mains in the distilling vessel a large quantity, though fromsome more than from others, of a gross coaly matter; andthere arises a fluid oil, which does not dry or grow thickin the air as the oils did at first; and which is thereforefound to answer for certain purposes, as in the lapidaries

business,