ii                                             PREFACE

colors, but the effort was successful only to the extent that it was
an improvement on its predecessors; and, although still the
standard of color nomenclature among zoologists and many other
naturalists, it nevertheless is seriously defective in the altogether
inadequate number of colors represented, and in their unscientific
arrangement. Fully realizing his failure, the author, some two or
three years later, began to devise plans, gather materials, and
acquire special knowledge of the subject, in the hope that he might
some day be able to prepare a new work which would fully meet
the needs of all who have use for it. Unfortunately, his time has
been so fully occupied with other matters that progress has neces¬
sarily been slow; but after more than twenty years of sporadic
effort it has at last been completed.

Acknowledgments are due to so many friends for helpful
suggestions that it is hardly possible to name them all, or to specify
the extent or kind of help which each has rendered; but special men¬
tion should be made of Mr. Lewis E. Jewell, of Johns Hopkins
University ; Dr. R. M. Strong, of the University of Chicago;
Prof. W. J. Spillman, of the U. S. Department of Agriculture ;
Mr. Williams Welch, of the U. S. Signal Service; Mr. Milton
Bradlev, of Springfield, Mass.; Dr. P. G. Nutting, of the U. S.
Bureau of Standards ; Mr. P. L. Ricker, of the Bureau of Plant
Industry, JJ. S. Department of Agriculture; and Mr. J. L.
Ridgway, of the U. S. Geological Survey. The late I'rofessor
S. P. LanglEY, then Secretary of the Smithsonian Institution, was
good enough to take a kindly interest in this undertaking and gave
the author assistance for which he is glad to make acknowledg¬
ment. More than to all others, however, is the author deeply
indebted to Jlr. John E. Thayer, of Lancaster, Mass., and Senor
Don Jose C. ZelEdon, of San Jos^, Costa Rica, for aid so indis-
pensible that without it the work could not have been completed.

To Dr. G. GrublER & Co., of Leipzig, Germany, the author
is under obligations for the gift of a nearly complete set of their
celebrated coal-tar dyes, which have proven quite necessary to the
work, especially in the coloring of the Maxwell disks on which the
color scheme is based.

The reproduction of the plates has been a difficult matter,
involving not only expensive experimentation, but more than three