CORRESPONDENCE. 617 Dr James's reasonings, and particularly his method of introspective conclusion, afford further strong arguments in favour of the acceptance of this wider law. HENRY KUTGERS MARSHALL. NEW YORK, 22nd July, 1884. VISUAL SPACE-PERCEPTIONS IN THE DARK. In my Space and Vision published in 1872, I contended that our per- ception of Space depends on Sight only, the perceived object being the sensitive surface of the retina. One of my arguments in favour of this view was founded on the Space-perceptions which we experience in the dark, in relation to which I mentioned some observations of my own at pp. 37-38. I have recently met with a strong confirmation of this vk-w by one who on this subject is both a high and unprejudiced authority, and would ask for permission to insert the passage as Mr. Galton's observations are in striking accord with my own. In his recent work, Inquiries into Human Faculty and its Development, pp. 158-9, he writes thus : "When in perfect darkness, if the field of view be carefully watched, many persons will find a perpetual series of changes to be going on automatically and wastefully in it. I have much evidence of this. I will give my own ex- perience first which is striking to me because I am very unimpressionable in these matters. I visualise with effort ; I am peculiarly inapt to see ' after-images,' ' phosphenes,' ' light-dust,' and other phenomena due to weak sight or sensitiveness ; and again before I thought of carefully trying I should have emphatically declared that my field of view in the dark was essentially of a uniform black, subject to an occasional light-purple eloudi- 1 other small variations. Xow, however, after habituating myself to examine it with the same sort of strain that one tries to decipher a signpost with in the dark, I have found out that this is by no means the case but that a kaleidoscopic change of patterns and forms is continually going on, but they are too fugitive and elaborate for me to draw with any approach to truth. I am astonished at their variety and cannot guess in the re- motest degree the cause of them. They disappear out of sight and memory the instant I begin to think about anything, and it is curious to me that they should often be so certainly present and yet be habitually over- looked." Mr. Galton finds in these phenomena an explanation of the hallucinations of visionaries, on which topic they no doubt throw much light. W. H. S. MONCK.
