The Plants designed for this Operation are to be gathered when their Leaves are at full Growth, and a little before the Flowers appear, or, at least, before the Seed comes on; because the Virtue of the Simple expected in these Waters is often little, after the Seed or Fruit is formed, at which Time Plants begin to languish: The Morning is best to gather them in, because the volatile Parts are then condensed by the Coldness of the Night, and kept in by the Tenacity of the Dew, not yet exhaled by the Sun.
This is to be understood, when the Virtue of the distilled Water resides principally in the Leaves of Plants; as it does in Mint, Marjoram, Penny-royal, Rue, and many more; but the Case differs when the aromatic Virtue is only found in the Flowers, as in Roses, Lillies of the Valley, &c. in which Case we choose their flowery Parts, whilst they smell the sweetest, and gather them before they are quite opened, or begin to shed, the morning Dew still hanging on them.
In other Plants the Seeds are to be preferred, as in Anise, Caraway, Cumin, &c. where the Herb and the Flower are indolent, and the whole resides in the Seed alone, where it manifests itself by its remarkable Fragrance, and aromatic Taste. We find that Seeds are more fully possessed of this Virtue, when they arrive at perfect Maturity.
We must not omit that these desirable Properties are found only in the Roots of certain Plants, as appears in Avens and in Orpine, whose Roots smell like a Rose. Roots of this Kind should be gathered, for the present Purpose, at that Time when they are richest in these Virtues; which is generally at that Season of the Year, just before they begin to sprout, when they are to be dug up in a Morning.
If the Virtues here required be contained in the Barks or Woods of Vegetables, then these Parts must be chosen for the Purpose.
The Subject being chosen, let it be bruised, or cut, if there be occasion, and with it fill two thirds of a Still, leaving a third Part of it empty, without squeezing the Matter close; then pour as much Rain or River Water into the Still as will fill it to the same Height; that is, two thirds together with the Plant: Fit on the Head, luting the Juncture, so that no Vapour may pass through; and also lute the Nose of the Still-head to the Worm. Apply a Receiver to the Bottom of the Worm, that no Vapour may fly off in the Distillation; but that all the Vapour being condensed in the Worm, by cold Water in the Worm-tub, may be collected in the Receiver.
Let the Plant remain thus in the Still to digest for twenty-four Hours, with a small Degree of Heat. Afterwards raise the Fire, so as to make the Water in the Still boil; which may be known by a certain hissing Noise, proceeding from the breaking Bubbles of the boiling Matter; as also by the Pipe of the Still-head, or the upper end of the Worm, becoming too hot to be handled; or the smoaking of the Water in the Worm-tub heated by the Top of the Worm; and, lastly, by the following of one Drop immediately after another, from the Nose of the Worm, so as to form an almost continual Stream. By all these Signs we know that the requisite Heat is given; if it be less than a gentle Ebullition, the Virtues of the Simple, here expected, will not be raised: On the contrary, when the Fire is too strong, the Water hastily rises into the Still-head, and fouls both the Worm and the distilled Liquor; and the Plant being also raised, it blocks up the Worm; for which Reason it is no bad Caution to fasten a-piece of fine Linen before the Pipe of the Still-head; that, in case of this Accident, the Plant may be kept from stopping up the Worm: But, notwithstanding this Precaution, if the Fire be too fierce, the Plant will stop up the Pipe of the Still-head; and, consequently, the rising Vapour finding no Passage, will blow off the Still-head, and throw the boiling Liquor about the Still-house, so as to do a great deal of Mischief, and even suffocate the Operator, without a proper Caution; and the more oily, tenacious, gummy, or resinous the Subject is, the greater the Danger, in case of this Accident; because the Liquor is the more frothy and explosive.
Let the due Degree of Fire therefore be carefully observed, and equally kept up, as long as the Water, distilling into the Receiver, is white, thick, odorous, sapid, frothy and turbid; for this Water must be carefully kept separate from that which follows it. The Receiver, therefore, should be often changed, that the Operator may be certain that nothing but this first Water comes over; for there afterwards arises a Water that is transparent, thin, and without the peculiar Taste and Flavour of the Plant, but generally somewhat tartarish and limpid, though somewhat obscured and fouled by white dreggy Matter: And if the Head of the Still be of Copper, and not tinned, the Acidity of this last Water corrodes the Copper, so as to become green, nauseous, emetic and poisonous to those who use it, especially to Children, and Persons of weak Constitutions.
The first Water above-described, principally contains the Oil and presiding Spirit of the Plant; for the Fire by boiling the Subject, dissolves its Oil, and reduces it into small Particles, which are carried upwards by the Assistance of the Water, along with those Parts of the Plant that become volatile with their Motion. And, if the Vessels are exactly closed, all these being united together, will be discharged without Loss, and without much Alteration, into the Receiver; and, consequently, furnish us with a Water richly impregnated with the Smell, Taste, and particular Virtues of the volatile Parts of the Plants it was extracted from.
The Water of the second Running, wants the volatile Part above described, and has scarce any other Virtue than that of cooling.