class.

It was scarcely to be wondered at that an idea which has been so prolific
as a stimulator of original investigation should have exerted a marked
influence on the manufacture of tar-products. All the brilliant syntheses
of colouring-matters effected of late years are living witnesses of the
fertility of Kekule's conception. In the spring of 1890 there was held in
Berlin a jubilee meeting commemorating the twenty-fifth anniversary of the
benzene theory. At that meeting the representative of the German coal-tar
colour industry publicly declared that the prosperity of Germany in this
branch of manufacture was primarily due to this theoretical notion. But if
the development of the industry has been thus advanced by the theory, it
is no less true that the latter has been helped forward by the industry.

The verification of a chemical theory necessitates investigations for
which supplies of the requisite materials must be forthcoming. Inasmuch as
the very materials wanted were separated from coal-tar and purified on a
large scale for manufacturing purposes, the science was not long kept
waiting. The laborious series of operations which the chemist working on a
laboratory scale had to go through in order to obtain raw materials, could
be dispensed with when products which were at one time regarded as rare
curiosities became available by the hundredweight. It is perhaps not too
much to say that the advancement of chemical theory in the direction
started by Kekule has been accelerated by a century owing to the
circumstance that coal-tar products have become the property of the
technologist. In other words, we might have had to wait till 1965 to reach
our present state of knowledge concerning the theory of benzenoid
compounds if the coal-tar industry had not been in existence. And this is
not the only way in which the industry has helped the science, for in the
course of manufacture many new compounds and many new chemical
transformations have been incidentally discovered, which have thrown great
light on chemical theory. From the higher standpoint of pure science, the
industry has therefore deservedly won a most exalted position.

With respect to the value of the coal-tar dyes as tinctorial agents, there
is a certain amount of misconception which it is desirable to remove.
There is a widely-spread idea that these colours are fugitive--that they
rub off, that they fade on exposure to light, that they wash out, and, in
sho