only as a tanning substance, or for forming rustic
work in ferneries, conservatories, &c. Subsequently the bark is removed
every eight or ten years, the quality of the cork improving with each
successive stripping; and the trees continue to live and thrive under
the operation for 150 years and upwards. The produce of the second
barking is still so coarse in texture that it is only fit for making
floats for nets and for similar applications. The operation of stripping
the trees takes place during the months of July and August. Two cuts are
made round the stem--one a little above the ground, and the other
immediately under the spring of the main branches. Between these three
or four longitudinal incisions are then made, the utmost care being
taken not to injure the inner bark. The cork is thereafter removed in
the sections into which it has been cut, by inserting under it the
wedge-shaped handle of the implement used in making the incisions. After
the outer surface has been scraped and cleaned, the pieces are flattened
by heating them over a fire and submitting them to pressure on a flat
surface. In the heating operation the surface is charred, and thereby
the pores are closed up, and what is termed "nerve" is given to the
material. In this state the cork is ready for manufacture or
exportation.

Though specially developed in the cork-oak, the substance cork is an
almost universal product in the stems (and roots) of woody plants which
increase in diameter year by year. Generally towards the end of the
first year the original thin protective layer of a stem or branch is
replaced by a thin layer of "cork," that is a layer of cells the living
contents of which have disappeared while the walls have become thickened
and toughened as the result of the formation in them of a substance
known as suberin. Fresh cork is formed each season by an active
formative layer below the layer developed last season, which generally
peels off. Where the formation is extensive and persistent as in the
cork-oak, a thick covering of cork is formed. In some cases, as on young
shoots of the cork-elm, the development is irregular and wing-like
outgrowths of cork are formed. In northern Russia a similar method to
that used for obtaining cork from the cork-oak is employed with the
birch.

Cork possesses a combination of properties which peculiarly fits it for
many and diverse uses, for some of which it alone is found applicable.
The leading purpose f