years of unremitting labor. Vastly different from the ordinary lines of commercial color work, the correct copying of each one of the 1115 colors of the original plates developed many perplexing and often discouraging problems, which were finally solved through Mr. A. B. Hoen's expert knowledge of chemistry and pigments; the skill, industry, and patience of the firm's head colorist, Mr. Frank Portugal, and the personal interest of both these gentlemen. It is, therefore, with the greatest pleasure that the author's grateful acknowledgment is made to the firm of A. Hoen & Company for the satisfactory manner in which they have fulfilled their contract.
EXPLANATION OF PLATES XXII AND XXIV.
Reference to these plates was unfortunately overlooked when the text was going through the press.
These plates are simply extras. They were made at an early stage in the preparation of the work and discarded; but were finally inserted, merely to add to the number of colors represented.
