There was no intention in the first instance to publish these lectures. After their delivery, many persons expressed a desire that the information they contained should be rendered accessible to such as were interested in the theory of colour vision, and in deference to that desire the lecture-notes have been re-cast in book form. For the reader’s convenience the matter is now divided into chapters instead of into lectures, and a few additions have been made in the text to explain some of the experimental work to those who have not facilities for its repetition.
The writer has to acknowledge several debts of gratitude. First, to Mr. E. Nettleship, for his kindness in looking over the proofs, and making valuable suggestions whilst the work was passing through the press; and also, as will be seen throughout its pages, for many of the interesting cases of defective colour perception which have been examined by the somewhat novel methods described. Next, the writer’s gratitude is due to Professor M. Foster for the permission he has given to use his admirable description of the Hering theory; and, lastly, to the Royal Society for the permission it accorded to use various diagrams which have served as illustrations to papers which have appeared in its “Philosophical Transactions” and “Proceedings.”
COLOUR VISION.
CHAPTER I.
I must commence this course by saying that I feel the honour that has been done me in asking me to undertake it, connected as it is with the name of Tyndall, whose recent removal from our midst has been deplored by all lovers of science, and by none more than by those who have had the privilege of listening to him at this Institution. It is my duty to speak on some subject of physics, and the subject I have chosen is Colour Vision. I hope it will not be considered inappropriate, since it was Thomas Young, the physicist, whose connection with this Institution is well known, who first propounded a really philosophical theory of the subject. Interesting as it may be to trace how old theories have failed and new ones have started, I feel that for those who, like myself, have but little time at command in which to address you, the historical side of this question must of necessity be treated incompletely.
Colour vision is a subject which enters into the domains both of physics and physiology, and it is thus difficult for any one individual to treat of it exhaustively unless he be a Helmholtz, who was as distinguished in the one branch of science as he was in the other. I am not a physiologist, and at the most, can only pretend to an elementary knowledge of the physiology of the eye, but I trust it is sufficient to prevent myself from falling into any grievous error. I shall try and show you, however, that the subject is capable of being made subordinate to physical methods of examination. I must necessarily commence by a very brief description of those parts of the eye in which it is supposed the seat of vision lies, but in terms which are not too technical. As to the mere optical properties of the eye I shall say but little, for they are not necessary for my purpose, although more particularly adapted to mathematical treatment than the other properties I have to describe.
The eye may be diagrammatically represented as in the figure which is supposed to be a horizontal section of it, the figure being reproduced from Professor Michael Foster’s Physiology.
Fig. 1.
