on Coloured Shadows. 61 



exclaimed at the striking brilliancy and beauty of the 

 blue colour of the very shadow I was observing, I 

 could not discover in it the least appearance of any 

 colour at all. But as soon as I removed my eye from 

 the tube, and contemplated the shadow with all its 

 neighbouring accompaniments, — the other shadow 

 rendered really yellow by the effect of the yellow glass 

 and the white paper, which had likewise from the 

 same cause acquired a yellowish hue, — the shadow 

 in question appeared to me, as it did to my assistant, 

 of a beautiful blue colour. 



I afterwards repeated the same experiment with the 

 apparently blue shadow produced in the experiment 

 with daylight and candlelight, and with exactly the 

 same result. 



How far these experiments may enable us to ac- 

 count for the apparent blue colour of the sky and the 

 great variety of colours which frequently adorn the 

 clouds, as also what other useful observations may be 

 drawn from them, I leave to philosophers, opticians, 

 and painters to determine. In the mean time I be- 

 lieve it is a new discovery — at least it is undoubtedly 

 a very extraordinary fact — that our eyes are not al- 

 ways to be believed, even with respect to the presence 

 or absence of colours. 



I cannot finish this paper without mentioning one 

 circumstance, which struck me very forcibly in all 

 these experiments upon coloured shadows, — and that 

 is, the most perfect harmony which always appeared to 

 subsist 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 

 blue and the other yellow. In short, the harmony of 



