412 Hastings — Optical Errors of the Htiman Eye. 



collection ; and not alone in the wonderful achievements of 

 those forgotten artists, but also in the instructive failure which 

 has attended modern restorations.* 



This is not the place to suggest reasons why so charming an 

 art should hardly have survived the thirteenth century, nor to 

 discuss certain peculiar restrictions to which the artists sub- 

 jected themselves ; but were such an extention of this paper 

 desirable, it seems to me that it would add material weight to 

 the explanation, founded upon principles of physiological optics, 

 of the acknowledged superiority of antique mosaic windows 

 over their modern imitations. 



* In two quadrif oils in the window given by the Guild of Tanners the 

 artist has chosen a red background in place of the almost universal blue ; but 

 he has reversed the order of his colors throughout the composition so that 

 the effect, to my eyes at least, was that of two charming little intaglios. It 

 was this which first suggested to me the distinction between ancient and 

 modern mosaic windows described above and which I thought abundantly 

 verified by subsequent observations. Certain very puzzling contradictions 

 to this theory — I have no means now of determining how many — were elimi- 

 nated by a subsequent discovery that considerable areas of some of the win- 

 dows are nineteenth century substitutions for the original designs which had 

 been lost. There was no suggestion of this significant fact in my hands at the 

 time of my visit. 



Yale University, May, 1905. 



