out. The press is an iron vessel of immense strength, varying in size
from six inches in diameter, and twelve deep, and upwards, to contain
one hundred weight or more; it has a small aperture at the bottom to
allow the expressed material to run for collection; in the interior is
placed a perforated false bottom, and on this the substance to be
squeezed is placed, covered with an iron plate fitting the interior;
this is connected with a powerful screw, which, being turned, forces the
substance so closely together, that the little vessels containing the
essential oils are burst, and it thus escapes. The common tincture press
is indeed a model of such an instrument. The oils which are thus
collected are contaminated with watery extracts, which exudes at the
same time, and from which it has to be separated; this it does by itself
in a measure, by standing in a quiet place, and it is then poured off
and strained.

[Illustration: Pipette to draw off small portions of otto from water.]

2. _Distillation._--The plant, or part of it, which contains the
odoriferous principle, is placed in an iron, copper, or glass pan,
varying in size from that capable of holding from one to twenty gallons,
and covered with water; to the pan a dome-shaped lid is fitted,
terminating with a pipe, which is twisted corkscrew fashion, and fixed
in a bucket, with the end peeping out like a tap in a barrel. The water
in the still--for such is the name of the apparatus--is made to boil;
and having no other exit, the steam must pass through the coiled pipe;
which, being surrounded with cold water in the bucket, condenses the
vapor before it can arrive at the tap. With the steam, the volatile
oils--_i.e._ perfume--rises, and is liquefied at the same time. The
liquids which thus run over, on standing for a time, separate into two
portions, and are finally divided with a funnel having a stopcock in the
narrow part of it. By this process, the majority of the volatile or
essential oils are procured. In some few instances alcohol--_i.e._
rectified spirit of wine--is placed upon the odorous materials in lieu
of water, which, on being distilled, comes away with the perfuming
substance dissolved in it. But this process is now nearly obsolete, as
it is found more beneficial to draw the oil or essence first with water,
and afterwards to dissolve it in the spirit. The low temperature at
which spirit boils, compared with water, causes a great loss of
essential oil,