266 Mr. W. G. Horner on the Vascular Spectrum. 



actions, which contain the original paper (vol. ii. p. 313.) not 

 being attainable here. 



My remarks being brought down to these numerical con- 

 clusions, my present purpose is accomplished. On the lumin- 

 ous fringes of the shadows, the cause of the peculiar apparent 

 structure of the centre of the retina, the nature of the vessels 

 themselves, as well as on phenomena connected with another 

 kindred experiment of C. W.'s, and the relation which exists 

 between these vascular images and the more regularly tessel- 

 lated spectra observed by Purkinje, Mrs. Griffith and others, 

 I may venture to offer an opinion hereafter, unless (as I confi- 

 dently hope) my purpose shall have been anticipated by a 

 more accomplished investigator of the phaenomena of light. 

 I am, dear Sir, yours, &c. 

 Bath, Jan. 14, 1834. W. G. HoRNER. 



P.S. In my paper on the Dccdaleum, the following errata 

 {not due, I believe, to the printer,) require correction. On 

 p. 37, last line, omit "Oo"; on p. 38, 1. 15, for x = CD 

 read x = Cq; on p. 39, 1. 14, for " outer" read "entire." 



Jan. 16— T. S. D. 



Additional Remarks. (February 1st.) 

 The contents of the preceding paper will sufficiently de- 

 clare for what reason I send it in its original state, and coun- 

 tersigned by my friend Mr. Davies on the day when he 

 perused it. You will perceive that, excepting the corrected 

 calculations in Arts. 11. and 12. no alteration has been made 

 since that day. For the purpose of correcting those calcula- 

 tions by reference to Dr. Young's publications, the paper was 

 detained. 



The new [February] Number of the Magazine and Journal 

 has just now reached me, and I have the pleasure of perceiving 

 that there is yet room for my contribution, partly as remarkably 

 confirming some of Sir D. Brewster's statements, and partly 

 as adding something new. By the aid, particularly of my 

 3rd and 4tth remarks, I flatter myself that Sir David will find 

 the difficulty mentioned in the note (p. 118.) to be completely 

 obviated ; and that the performance of the experiment being 

 now reduced to a state of precision and certainty, my rough 

 approximations will be corrected, and further conjectures 

 superseded, by persons who have more available leisure for 

 such inquiries. 



Respecting the figures which accompany the paper, I ought 

 to state that the vessels which are comparable to the larger 

 ones in fig. 2. are in fact more numerous than could be re- 

 presented in fig. 1. without confusion ; and that some branches 



