294 Mr. Tomlinson on the Theory of [Oct. 



here my admission of the fact that black does result from the 

 contemplation of white ; that while philosophers have been 

 so long engaged, and so profitably, in the investigation of 

 the phenomena of light, an immense field of research remains 

 still, comparatively unexplored, i. e., the immediate consider- 

 ation of the living eye, the knowledge of the phenomena of 

 which, compared with that of its rival in utility and beauty, 

 the ear, is but small. I object to the theory explanative of 

 M. Plateau's fourth proposition, conceiving that, as the 

 involuntary adjustment of a healthy eye, the function of 

 which is not abused by the individual exercising it, depends 

 upon the harmony subsisting between the retina, the pupil, 

 and the ciliary nerves ; so by the abuse of the function, 

 such as the rigid fixation of the eye upon white objects, 

 whereby a constrained voluntary adjustment is continually 

 resulting, the organ is overwrought, or overacted on, and 

 amaurotic affections result, as in my case, (7.) and if per- 

 sisted in, the power to exercise the function ceases, eventu- 

 ally, to exist. The manner in which this reasoning applies 

 to other cases, such as white resulting from the contempla- 

 tion of black, &c., together with M. Plateau's proposition, 

 [5.] I propose to consider in another paper. 



11. It affords me very sincere pleasure to state that I 

 consider the next proposition, [6.] tenable, although I think 

 M. Plateau has made the experiment in support of it some- 

 what complicated. I do not find it by any means necessary 

 ** to cover the eyes with a handkerchief," after the observa- 

 tion, or, indeed, with any thing ; nor do I find it necessary 

 to '* insulate" the coloured squares by employing a black 

 ground.* 



12. Although I agree, to a great extent, with this propo- 

 sition, yet I have found it necessary to modify it, and, as 

 the consideration of its various features will lead me to a 

 greater length than time will now allow of, I think it better 

 to offer the whole of my experiments and observations in a 

 separate paper, next month, if possible, than to leave them 

 imperfect now. I will, therefore, conclude with an account 

 of two recent experiments which I think interesting, and 

 upon which I shall enlarge hereafter. 



♦ The colours of the grounds employed with the same, and various comple- 

 mentary doublets of squares, &c., have formed the subject of an extensive series 

 of observations by Mr. Dodd, which will be published hereafter. 



