AN ACCOUNT OF SOME EXPERIMENTS 

 ON COLOURED SHADOWS. 



WHILE I was employed in the prosecution of my 

 experiments on the intensities of light, I was 

 struck with a very beautiful and what I then consid- 

 ered as a new appearance. Desirous of comparing the 

 intensity of the light of a clear sky, by day, with that 

 of a common wax candle, I darkened my room, and 

 letting the daylight from the north (coming through a 

 hole near the top of the window-shutter) fall at an angle 

 of about 70 upon a sheet of very fine white paper, I 

 placed a burning wax candle in such a position that 

 its rays fell upon the same paper, and, as nearly as I 

 could guess, in the line of reflection of the rays of day- 

 light from without; when, interposing a cylinder of 

 wood, about half an inch in diameter, before the centre 

 of the paper, and at the distance of about two inches 

 from its surface, I was much surprised to find that the 

 two shadows projected by the cylinder upon the paper, 

 instead of being merely shades, without colour, as I 

 expected to find them, the one of them that which, 

 corresponding with the beam of daylight, was illumi- 

 nated by the candle was yellow ; while the other, 

 corresponding to the light of the candle, and conse- 

 quently illuminated by the light of the heavens, was 

 of the most beautiful blue that it is possible to imagine. 



