Experiments upon coloured Shadozvs . ng 
a manner before the candle, that only a part of the paper, half 
of it for instance, be affected by it, the other half of it re- 
maining white. 
To make these experiments with more convenience, the 
paper, which may be about 8 or 10 inches square, should be 
pasted or glued down upon a flat piece of board, furnished with 
a ball and socket upon the hinder side of it, and mounted upon 
a stand ; and the cylinder should be fastened to a small arm 
of wood, or of metal, projecting forward from the bottom of 
the board for that purpose. A small stand, capable of being 
made higher or lower as the occasion requires, should likewise 
be provided for supporting the candle ; and if the board with 
the paper fastened upon it be surrounded with a broad black 
frame, the experiments will be so much the more striking and 
beautiful. For still greater convenience, I have added two 
other stands, for holding the coloured glass through which the 
light is occasionally made to pass, in its way to the white sur- 
face upon which the shadows are projected. It will be hardly 
necessary to add, that in order to the experiments appearing 
to the greatest advantage, all light, which is not absolutely ne- 
cessary to the experiment, must be carefully shut out. 
Having fitted up a little apparatus according to the above 
directions, merely for the purpose of prosecuting these in- 
quiries respecting the coloured shadows, I proceeded to make 
a great variety of experiments, some with pointed views, and 
others quite at random, and merely in hopes of making some 
accidental discovery that might lead to a knowledge of the 
causes of appearances which still seemed to me to be enve- 
loped in much obscurity and uncertainty. 
Having found that the shadows corresponding to two like 
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