VOL. XXXVII.J PHILOSOPHICAL TKANSACTIONS. A^^ 



An Account of Mr. James Christopher Le Blons Principles of Printing, in 

 Imitation of Painting, and of Weaving Tapestry, in the same manner as 

 Brocades. By Cromivell Mortimer, M. D., S. R. Secret. N''419, p. 101. 



Mr. Le Bloti^ endeavouring to fix the true harmony of colouring in painting, 

 found that all visible objects may be represented by the 3 primitive colours, 

 red, yellow, and blue ; for out of them, all others, even black, itself, may be 

 compounded. We are beholden to the great Sir Isaac Newton for the discovery 

 of the difference of colours contained in the rays of the sun; and that the union 

 of them all produces a white, which is light itself. 



For distinction sake, Mr. Le Blon calls those colours which are comprehended 

 in the rays of the sun, impalpable colours, and those used in painting, material 

 colours. In the material colours, a mixture of all three produces a black or 

 darkness, contrary to what is observed in the impalpable, which as above said 

 produces white. Mr. Le Blon takes this phenomenon to be owing to the body 

 or substance of which these three material colours consist, and to their particles 

 being opaque, and not transparent ; for they only reflect certain rays of light, 

 that strike on their surfaces ; and therefore, when small particles of different 

 colours are placed close together, if they are so small that each of them cannot 

 be seen separately by the eye, we do not discern the colour of each particular 

 atom, but only the blended reflected rays, proceeding from the adjoining parti- 

 cles : thus yellow and red produce an orange ; yellow and blue a green, &c. 

 which seems to be confirmed by placing two pieces of silk near together ; viz. 

 yellow and blue ; when by intermixing of their reflected rays, the yellow will 

 appear of a light green, and the blue of a dark green; which deserves the farther 

 consideration of the curious. 



M. Le Blon has reduced the harmony of colouring in painting to certain in- 

 fallible rules, built on this foundation : whereas, according to the common 

 practice of painters, their colouring is the effect of mere chance or guess-work 

 at first, but improved by experience ; all painters usually declaring that there 

 can be no certain rules given for mixing colours. Mr. Le Blon published some 

 years ago an ingenious book on this subject, entitled, Coloritto ; or, the har- 

 mony of colouring in painting. 



By these rules he discovered the manner of printing any object in its natural 

 colours, by the means of three plates, and the three primitive colours ; an art 

 attempted and sought after ever since the invention of printing, but in vain, 

 and thought impossible, till he put it in practice about 15 years since. 



The plates are engraved chiefly after the mezzotinto manner ; only the darker 



