measuring the comparative Intensities of Light. 105 
the same held good, with very little variation, when three, 
and even when four candles were made use of in the experi- 
ment, instead of two. 
I even caused a lamp to be constructed with nine round 
wicks, placed in an horizontal line, and just so far asunder as to 
prevent their flames uniting, and no farther. And I found, 
upon repeating the experiment with this lamp, that the result 
was much the same as with the candles ; the intensity of the 
illumination at the field of the photometer being very nearly 
the same, whether these nine lights were placed so as to cover, 
and pass through each other, or not. 
But I afterwards found means to demonstrate the very great 
transparency of flame by a still more simple experiment. 
Suspecting that the only reason why bodies are not visible 
through a sheet of vivid flame is, that the light of the flame 
affects the eye in such a manner as to render it insensible to the 
weaker light emitted by, or reflected from the objects placed 
behind it, I conceived that a very strong light would not only 
be visible through a weak flame, but also (as all transparent 
bodies are invisible) that it might perhaps cause the flame 
totally to disappear ; to determine that fact, I took a lighted 
candle at mid-day, the sun shining moderately bright, and hold- 
ing it up between my eye and the sun, I found the flame of the 
candle to disappear entirely. It was not even necessary, in 
order to cause the flame to become invisible, to bring it to be 
directly between the eye and the body of the sun ; it was suffi- 
cient for that purpose to bring it into the neighbourhood of 
the sun, where the light was very strong : even in a situation 
in which the light was not so strong as to dazzle the eye so much 
mdccxciv. p 
