sponge dipped in a jelly of white soap. If there are
spots of oil or grease, this soap will not suffice; it will be necessary
to use black soap, or perhaps a weak solution of some alkali, such as
potash or ammonia. In using such alkalis, it is best to first try them on
some odd pieces of leather of the same color or upon some part of the
bindings not likely to be noticed, because certain colors in leather are
apt to decompose or change their tint under the action of an alkali. It
has been observed that alkalis tend to darken the leather, more or less;
therefore, after employing them, a little acidified water must be applied
to neutralize their effect. Also that morocco should be moistened only
very slightly, as, otherwise, the surface grain may be smoothed away.

One might begin by trying benzine; this liquid will not attack any color
or, at least, only a color formed principally of fatty or resinous
substances. Benzine does not act like an alkali; it does not saponify the
greasy body, but it dissolves it as water dissolves a salt, a gum or
gelatine. It must be used quickly, as it evaporates much more rapidly than
ammonia, which itself is considered volatile. The latter will mix with
water, but benzine combines only with alcohol.

Thus benzine, like all other essential oils, operates only as a dissolvent
and, after having been applied, either pure or mixed with alcohol, upon
the book cover, it must be wiped off with a soft cloth before it
evaporates, so that the particles of grease which it has dissolved, but
not decomposed, will not sink again into the leather and later reappear on
its surface.

The best method, after having poured some drops of the liquid upon one
side of the book, is to turn this side toward the ground. In this position
the benzine, charged with part of the greasy substance, will run down and
accumulate upon the lowest edge of the cover, from which it can quickly be
wiped off with the substances it holds in solution. Perhaps an even better
method of operation may be discovered.

This manner of employing benzine, alcohol or turpentine as dissolvents for
the greasy body is equally applicable for removing oily spots from prints,
and I recommend it to the reader for experiment. When grease is removed
with alkaline water, it is useless to proceed in this manner; the soapy
substance which forms on the leather after rubbing should be removed with
a damp sponge, after which the book should be dried in the