Tie a piece of muslin or gauze over a glazed earthern pot, whose
mouth is just large enough to receive the bottom of a warming-pan;
on this cloth lay the herb, clipped; then place upon them the
warming-pan, with live coals in it, to cause heat just enough to
prevent burning, by which means as the steam issuing out of the herb
cannot mount upwards, by reason of the bottom of the pan just fitting
the brim of the vessel below it, it must necessarily descend, and
collect into water at the bottom of the receiver, and that strongly
impregnated with the essential oil, and the salt of the vegetable
thus distilled; which, if wanted to make spirituous or compound
water, is easily done, by simply adding some good spirits, or French
brandy to it, which will keep good for a long time, and be much
better than if the spirits had passed through a still, which must,
of necessity, waste some of their strength. Care should be taken not
to let the fire be too strong, lest it scorch the plants; and to
be made of charcoal, for continuance and better regulation, which
must be managed by lifting up and laying down the lid, as wanted to
increase or decrease the degrees of heat. The deeper the earthen pan,
the cooler the season, and the less fire at first (afterwards to be
gradually raised), in the greater perfection will the distilled water
be obtained.
As the more moveable, or volatile parts of vegetables, are the
aqueous, the oily, the gummy, the resinous, and the saline, these are
to be expected in the waters of this process; the heat here employed
being so great as to burst the vessels of the plants, some of which
contain so large a quantity of oil, that it may be seen swimming on
the surface of the water.
Although a small quantity only of distilled waters can be obtained
at a time by this confined operation, yet it compensates in strength
what is deficient in quantity. Such liquors, if well corked up from
the air, will keep good a long time, especially if about a twentieth
part of any spirits be added, in order to preserve the same more
effectually.