action of light varies somewhat with the different coloring matters,
according to their chemical constitution and the fiber upon which they
are applied.

With respect to this last point, Chevreul actually found that colors
are faster to light on some fibers than on others, and this fact,
which is generally known to practical men, is abundantly shown in the
diagrams on the wall. As a rule we may say that colors are most
fugitive on cotton and most permanent on wool, those on silk holding
an intermediate position. Still there are many exceptions to this
order, especially as between silk and wool.

Since the time of Chevreul, the action of light on dyed colors has not
been seriously and exhaustively studied. From time to time, series of
patterns dyed with our modern colors have been exposed to light, e.g.,
by Depierre and Clouet, Joffre, Muller, Kallab, Schmidt, and others;
but the published results must at best be considered as more or less
fragmentary. Under the auspices of the British Association, and a
committee appointed at its last meeting in Leeds, I hope to have the
pleasure during the next few years of studying this interesting
subject.

To-night I propose to give you some of the prominent results already
obtained in past years, in the dyeing department of the Yorkshire
College, where it has been our custom to expose to light and other
influences the patterns dyed by our students. Further, I wish to give
you an ocular demonstration of the action of light or dyed colors, by
means of these silk, wool, and cotton patterns, portions of which have
been exposed for 34 days and nights on the sea coast near Bombay,
during the month of February of this year.