Prof. J. D. Forbes on tlie Classification of Colours. 177 



Mr. Hay has been kind enough to arrange for me his ex- 

 tensive suite of artificial colours according to these diagrams. 



But it must be owned to be highly desirable to possess such 

 a suite of colours in more perfect and durable materials than 

 any pigment as usually applied presents. Painted porcelain 

 and coloured enamels alone appear to possess this valuable pro- 

 perty. I'he immense collection of artificial enamels employed 

 in the Vatican fabric of mosaic pictures seenis to offer an unri- 

 valled opportunity of forming such a classification. 



This gigantic establishment was founded about two centu- 

 ries ago tor the express purpose of adorning the interior of St. 

 Peter's with the elaborate mosaic pictures and ceilings which 

 astonish every visitor. The whole interior of the stupendous 

 dome is incrusted with mosaic patterns and pictures, of coarse 

 execution indeed, but such as suits best the vast distance from 

 which alone they can be properly viewed ; whilst the finished 

 mosaic works which adorn the altars reproduce in unfading 

 colours and with consummate skill in shading the chefs- 

 c?'a?«3;r^ of Raphael, Domenichino, and other artists preserved 

 in the Vatican gallery. The material is a soft and fusible 

 enamel, and the formation of 1 8,000 tints was effected by an 

 ingenious artist named Matteoli, at the time I have mentioned. 

 The rough cakes of enamel are preserved in separate cup- 

 boards or pigeon-holes, surrounding a hall of great length ap- 

 propriated to this purpose by Pope Pius VI. But the main 

 intention of the work being completed with St. Peter's, it has 

 not been thought worth while to preserve the integrity of the 

 collection (which, indeed would be no easy matter) ; and it is 

 certain that though still reputed to contain 18,000 modified 

 colours, the effective number is vastly smaller. 



Having been fortunate enough in 1844< to make the valu- 

 able acquaintance of Monsignore de' Medici Spada, an en- 

 lightened and influential prelate residing at Rome, I entreated 

 his influence to procure a selection of specimens of the leading 

 colours of the Vatican mosaics. For a long time official slug- 

 gishness rendered the application fruitless ; at length the im- 

 portunity of my friend overcame all difficulties, but not until 

 I had long left Rome, and was therefore quite unable to 

 superintend the selection. My instructions were therefore 

 general, to prefer the most varied tints which the collection 

 presented. At last an assortment of no less than 94 1 pieces 

 of mosaic, classified in separate packets, arrived. A close 

 examination rather disappointed me. They presented a great 

 preponderance of indefinite colours, and a great deficiency of 

 many of the livelier and brighterprimary and secondary colours. 

 But particularly whole packets were composed of specimens 



Phil. Mag. S. S. Vol. 34. No. 228. March 1849. N 



