This is true or not.
I submit the following experiments to substantiate the theory advanced.
Partially fill a vial or a tumbler with water, hold it by the rim,
and move it around a lighted candle placed upon a table. A shadow
surrounding the transmitted light will be cast upon the table. As the
tumbler approaches the light, the shadow follows the tumbler, and when
receding the tumbler follows the shadow; and as the tumbler is moved
around the light, the shadow will swing round from one side to the
other. If the tumbler be held so that a puff of smoke can be blown
into the transmitted rays, the particles of smoke will reflect the
transmitted light, and will illustrate my idea of what constitutes a
comet's tail. A dark band may be observed in this stream of light, as
also in the light cast upon the table.
In these experiments, we see the effects produced by a cause which is
known; the effects are similar to those observed in the tails of comets,
the cause of which we do not know; but is it not reasonable to assume
that the cause is similar?
Assuming now that comets are transparent, can any other phenomena
peculiar to comets be accounted for upon this hypothesis? Next to
the tail itself, the curve is the most noticeable feature, and if we
consider the extraordinary length of these appendages, the astounding
velocity at which comets move in their orbits, and the time that would
elapse before a ray of light, emitted from the nucleus, would reach the
end of the tail, perhaps the curve--which, if I am not deceived in my
observations, always dips toward its orbit--can be accounted for.
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