By a careful study of the influence of the atomic arrangement upon the stability of colors, information useful to the color manufacturer may possibly be gained, but at present my facts are not yet sufficiently tabulated to enable one to recognize any generally pervading law in this direction. It is scarcely necessary to say that the fastness to light of a color is independent of its commercial value, this being mainly determined by the price of the raw material from which it is manufactured, the working expenses, and the profit desired by the manufacturer. Neither must we suppose that facility of application necessarily interferes with its fastness to light, for some of our fastest coal tar colors on wool, e.g., diamine fast red, tartrazin, etc., are applied in the simplest possible manner. On the other hand, the intensity or depth of a color has considerable influence on its fastness. Dark full shades invariably appear faster than pale ones produced from the same coloring matter, simply because of the larger body of pigment present. A pale shade of even a very fast color like indigo will fade with comparative rapidity. The fugitive character of many of the coal tar colors is, in my opinion, rendered more marked, because, owing to their intense coloring power, there is often such an infinitesimal amount of coloring matter on the dyed fiber. Hence it is that in the Gobelin tapestries pale shades on wool are frequently obtained by the use of more or less unchangeable metallic oxides and other mineral colors, to the exclusion of even fast vegetable dyes. It is interesting to examine what is the action of light upon compound colors. Is a fugitive color rendered faster by being applied along with a fast color? My own opinion, based upon general observation, is that it is not, and that when light acts upon a compound color the unstable color fades, while the stable color remains behind. A woaded color, for example, is only fast in respect of the vat indigo which it contains, and yet how frequent is the custom to unite with the indigo such dyes as barwood, orchil, and indigo-carmine, the fugitive character of which I have pointed out. Having thus rapidly surveyed these numerous coal tar colors, both in their dyed and exposed conditions, I again ask why are they so generally regarded as altogether fugitive? First, because we have, especially among these "direct dyes," a very large number which are undoubtedly very fugitive.