74

1908 Nov 8
Logic 19

particular way from among the many which my idea might be
realized. Suppose, then, that the cones alone give the color-sensations,
the rods alone those of visual place. I suppose that the cones either because they contain
three changing chemical mixtures, or for some other reason, are capable
of three modes of natural vibration, one with a period about equal to
that of green light near E, of wave-length 525 millimicrons, one of a
period like that of red light, somewhat below C, and the third with a
period of violet-blue light a little above G, and that vibrations
of these substances or whatever they may be are set up, by resonance,
that is by forced vibrations, when light strikes upon them, giving each
by itself the sensations of vermillion, of green near E, and of blue or
violet seen (these last according to circumstances.) I suppose that
the cones likewise contain three vibrating substances, or otherwise