ABSTRACT
THAT the making of color-theories goes on apace is a most healthy sign of intellectual activity—a sign that there is a widespread feeling of the utter inadequacy of the theories of Helmholtz and of Hering. These are both theories which served a useful purpose in their day, as a means of holding together the vastly complicated facts of colour vision, but they are both wholly inadequate to represent our present knowledge of the subject. The theory of Ebbinghaus met certain logical requirements which must be made of any theory in a very satisfactory fashion, but it was unfortunately wholly in discord with facts discovered immediately after it was brought out, and it has now been withdrawn by its author. 1 It is much to be regretted that Professor von Oppolzer has not been any more successful in meeting the conditions of a satisfactory theory.
