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the diftance of nine Feet from the Card, the Image of 
the Card being receiv'd upon a white Paper, at the 
diftance of nine Feet on the other fide of the Lens^ at 
B, the blue half appear’d diftind, with the Image of 
the black Silk going vertically along its Plain, whilft 
no Appearance of the black Silk was perceivable on 
the red half. Then removing the Paper about two 
Inches, to R, the red half of the Image had a black 
Line very plain upon it, whilft it was invifible on the 
blue half. This was more evident, when a ftrong I- 
mage of the Candle was fucceftively thrown on that 
half of the Card, whole Image was under Examination. 
When the Paper was held in the middle between R 
and B, the black Line upon each Colour was vifiblc, 
but indiftind. 
N. B. Care muft be taken that the Colours be deep, 
becaufe having accidentally rubb’d off fome 
of the blue, the Whitenels of the Card under 
it, made its Image fly out farther, almoft as 
far as that of the red. 
V. ^urt 
