own to the ancients, but we can
not find whether they were used as a dyeing agent. Wilkinson says that
tanning was in Egypt a subdivision of dyeing, and it is mentioned that
copperas with galls dyed leather black; and there can be little doubt
that galls were used for a similar purpose in ordinary dyeing. The
_Myrobollans_ and several sorts of barks and pods of the _Acacia
nilotica_ were also used for tanning, from their astringent
properties, and may have been similarly used for dyeing.

These are a few of the principal coloring matters used by dyers in
ancient times. There is a little confusion with respect to some of the
salts mentioned as having been used by them, especially the alkaline
salts--a circumstance, however, not to be wondered at. In more modern
times there is a similar confusion on this same head.

When nitre, for instance, is burned with carbonaceous matter, the
product is carbonate of potash. The ashes left by burning wood contain
the same salt. The ashes left by burning sea-weed produce carbonate of
soda. When nitre is burned with sulphur, the product is sulphate of
potash, etc. These have all been called generically, even in modern
times, nitre, having each a certain prefix well understood by the
adept, or chemist, of the day.

We think it probable that all these processes for making the different
salts were practiced in ancient times, but now having only the generic
name _nitre_ given us by historians, we can not understand exactly
when nitre is mentioned which of the nitres is meant.

When Solomon speaks of the action of vinegar upon nitre, the chemist
understands that the salt referred to is a carbonate, but when the
nature of the action or application is not given, we have no idea what
particular salt is meant. There is no doubt, however, that the
ancients were well acquainted with the alkaline salts of potash and
soda, and applied them in the arts. The metallic salts of iron,
copper, and alumina were well known, and their application to dyeing
was generally the same as at the present day. That they were used both
as mordants and alterants is evident from several references.

A very suggestive statement is made by Pliny about the ancient
Egyptians. "They began," says he, "by painting or drawing on white
cloths with certain drugs, which in themselves possessed no color, but
had the property of attracting or absorbing coloring matter, after
which these cloths were immersed in a heated dyeing l