108 Count Rumford j s Account of some 
corresponding to the light of the candle, and consequently il- 
luminated by the light of the heavens, was of the most beau- 
tiful blue that it is possible to imagine. This appearance, 
which was not only unexpected, but was really in itself in the 
highest degree striking and beautiful, I found, upon repeated 
trials, and after varying the experiment in every way I could 
think of, to be so perfectly permanent, that it is absolutely im- 
possible to produce two shadows at the same time from the 
same body, the one answering to a beam of daylight, and the 
other to the light of a candle or lamp, without these shadows 
being coloured, the one yellow and the other blue. 
The experiment may very easily be made at any time by 
day, and almost in any place, and even by a person not in the 
least degree versed in experimental researches. Nothing 
more is necessary for that purpose than to take a burning 
candle into a darkened room in the day time, and open one 
of the window-shutters a little, about half or three quarters of 
an inch for instance ; when the candle being placed upon a table 
or stand, or given to an assistant to hold, in such a situation 
that the rays from the candle may meet those of daylight 
from without, ac an angle of about 40°, at the surface of a sheet 
of white paper, held in a proper position to receive them, any 
solid opaque body, a cylinder, or even a finger, held before the 
paper, at the distance of two or three inches, will project two 
shadows upon the paper, the one blue, and the other yellow. 
If the candle be brought nearer to the paper, the blue 
shadow will become of a deeper hue, and the yellow shadow 
will gradually grow fainter ; but if it be removed farther olfi, 
the yellow shadow will become of a deeper colour, and the 
blue shadow will become fainter ; and the candle remaining 
