294 STUDIES OF NATURE. 



I fhall infift no longer on the other harmonic 

 (hades which may be deduced, in conformity to 

 the huvs of their generation, from colours the moft 

 oppofite ; and of which might be formed accords 

 and concerts, fuch as Father Caftel produced from 

 his celebrated Harpfichord. I muft, however, 

 remark, that colours may have a powerful influ- 

 ence on the paflions ; and that they, as well as 

 their harmonies, may be referred to the moral af- 



wlfe modified that light, on terreftrial objefts, in fuch a man- 

 ner, as to illuminate both immediately and mediately, by refrac- 

 tion and by refleftion, and to extend it's tints, and it's harmo- 

 nies, with thofe of fhade, in a way that no words can exprefs. 



J. J. Roujffcau one day made this obfervation : •' Painters. 

 *' can give the appearance of a body in relief, to a fmooth fur- 

 " face ; I fliould be very glad to fee them give the appearance of 

 *' a fmooth furface to a laifed body." I made no reply at the 

 moment ; but having fince reflecfled on the folution of this pro- 

 blem in optics, I by no means confider the thing as impoflible. 

 The whole that is neceflary, according to my idea, is to deftroy 

 one of the harmonic extremes which render bodies prominent. 

 For inftance, if the objeft aimed at were to flatten a bafs-relief, 

 it would be neceflary to paint the cavities white, or the promi- 

 nent parts black. Accordingly, as they employ the harmony of 

 the clare-obfcure, to give the appearance of a folid body to a 

 plane furface, they might employ the monotony of one fingle 

 tint, to make what is aftually raifed and folid to difappear, and 

 become to the eye a plane furface. In the firfl: cafe, painting 

 renders th-.it vifible which is not tangible ; in the fécond, we 

 fliould have a body that might be touched, without being vi- 

 fible. Thii li^ft deception would be fully as furprizing as the 

 other, 



feflions. 



