356 Sir David Brewster on the Law of Visible Position 



intestinal concretions consisted of the small setae attached to 

 the coreopsis of the seed of the oat. I have discovered in the 

 Museum several concretions from the lower animals, consist- 

 ing also of the vegetable hairs from the different parts of 

 plants. 



The nature of the so-called lithofellinic acid calculus, for 

 which I shall propose the name of resino-bezoardic acid, and 

 also of the oxalate of lime concretion, was described in a report 

 read before the Committee in January 1841, but the statements 

 of Professor Goebel, and other eminent foreign chemists, have 

 compelled me carefully to re-examine these calculi. 



I trust soon to have an opportunity of sending you in detail 

 the results of my investigation of this subject, but until the 

 Catalogue is published the Committee are desirous that only 

 the above brief notice of a few of the leading facts should 

 appear. 



I remain, my dear Sir, 



Yours very truly, 



91 Fleet Street. Thomas Taylor. 



LIII. On the Law of Visible Position in Single and Bi- 

 nocular Visioft, and on the representation of Solid Figures 

 by the union of dissimilar Plane Pictures on the Retina*. By 

 Sir David Brewster, K.H^D.C.L., F.R.S., and V.P.R.S. 

 Edin. f 



TN the course of an examination of Bishop Berkeley's New 

 Theory of Vision, the foundation of the Ideal Philosophy, 

 I have found it necessary to repeat many old experiments, and 

 to make many new ones, in reference to the functions of the 

 eye as an optical instrument. I had imagined that many points 

 in the physiology of vision were irrevocably fixed, and placed 

 beyond the reach of controversy ; but though this supposition 

 may still be true in the estimation of that very limited class of 

 philosophers who have really studied the subject, yet it is mor- 

 tifying to find that the laws of vision, as established by expe- 

 riment and observation, are as little understood as they were 

 in the days of Locke and Berkeley. Metaphysicians and phy- 

 siologists have combined their efforts in substituting unfounded 

 speculation for physical truth; and even substantial discove- 

 ries have been prematurely placed in opposition to opinions 

 of which they are the necessary result. 



In prosecuting this subject, my attention has been particu- 



* A second paper on this subject will appear in an early Number of this 

 Journal. 



f From the Transactions of the Royal Society of Edinburgh, vol. xv. 

 part 3; having been read January 23 and February 26, 1843. 



