USEFUL PROJECTS. 



347 



5f many of the appearances in the 

 foregoing experiments. So far from 

 jeii'gable to observe any change in 

 he shadow iipon which my eye was 

 Sxed, I was not able even to tell 

 when the yellow glass \. as betore 

 he lamp and when it was not: and 

 though (he assistant often exclaimed 

 It the striking brillancy and brainy 

 of the blue colour of the very slia- 

 .1ow I was observing, I could not 

 discover in it the least appearance of 

 sny colour at all. But as soon as I 

 removed ray eye from the tube, and 

 contemplated the shadow with all 

 its neighbouring accompaniments, 

 the other shadows rendered really 

 yellow by the effect of the yellow 

 glass, and the while paper which 

 had likewise from the same cause 

 acquired a yellowishhuejtheshadow 

 in question appeared tome, as it did 

 to my assistant, of a beautiful blue 

 colour. I afterwards repeated the 

 same experimentwith the apparent- 

 ly blue shadow produced in the ex- 

 })eriment with day-light andcandle- 

 ight, and with exactly the same 

 result. 



How far these experiments may 

 enable us to account for the appa- 

 rent blue colour of the sky, and the 

 great variety ol colours which fre- 

 quently adorn the clouds, as also 

 wliat other useful observations may 

 be drawn from them, I leave to 

 ph:losophers,opticians, and painters, 

 to determine. In the mean time I 

 believe it is a new discovery, at 

 least it is undoubtedly a very extra- 

 ordinary fact, that the eyes are not 

 always to bo believed, even with 

 respect to the presence or absence of 

 colours. 



I cannot finish this letter without 

 mentioning onccircunistance, which 

 struck me very forcibly in all these 

 experiments upon coloured sbadoMSj 



and that is, the most perfect har- 

 niony which always appeared tosvib- 

 sist between the colours, whatever 

 they were, of the two shadows ; 

 and this harmony seemed to me to 

 be full as perfect and pleasing when 

 the shadows were of different tints 

 of brown, as when one of them was 

 bine and the other yellcw. In 

 short, the harmony of these colours 

 was in ail cases riot only very strik- 

 ing, but the appearances were al- 

 together quite enchaining j and I 

 nevtr fcund any body to whom I 

 showed these experiments whose 

 eyes were not fascinated with their 

 bewitching beanlies. It is, iiow- 

 ever, more than probable, that a 

 great part of the pleasures which 

 these experiments afforded to the 

 spectators arose from the continual 

 changes of colour, tint, and shade, 

 with which the eye was amused, 

 and the attention kept awake. We 

 are i!sed to seeing colours fixed aud 

 unalterable, hard as the solid bodies 

 Irom v\hich they come, and just as 

 motioi:!ess, consequently dead, un- 

 interesting, and tiresome to thee/e; 

 but in these experiments all is mo- 

 tion, life, and beauty. 



It appears to me very probable, 

 that a farther prosecution of these 

 experimentsupon coloured shadows 

 may not only lead to a knowledge 

 of the real nature of the harmony of 

 colours, or the peculiar circum- 

 stances upon which that harmony 

 depends : but that it may also en- 

 able us to construct instruments for 

 piodncing that harmony, for the 

 entti lainment of the eyes, in a man- 

 ner similar to that in which the ears 

 are entertained by musical sounds. 

 I know that attempts have already 

 been made for that purpose ; but 

 when I consider the means employ- 

 ed, I am not surprized that they did 



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