Upon this hypothesis, the extraordinary length of their tails and the
fact that stars are visible through the densest portion of them is
explained; as also the fact that they so rapidly disappear from view
when moving from the sun, the light received by them from the sun
being in proportion to their distance from it, and but little of that
reflected.
JOHN M. HUGHES.
Brooklyn, N. Y.
* * * * *
[FOR THE SCIENTIFIC AMERICAN.]
ON COMETS.
When we see a comet approaching the sun with its tail following in the
orbit of the nucleus, we have no great difficulty in believing the
common theory that a comet consists of nucleus attracted toward the sun,
while the tail is repelled; and that we see the whole of it. But as it
approaches the sun, difficulties arise that make us doubt whether the
theory be true.
Let us suppose a comet with a tail 50,000,000 miles in length, and that
it will require two days to pass round the sun. Now the tail, being
always in a line drawn through the center of the sun and center of the
nucleus, will, when it reaches the long axis of the elliptical orbit,
stand perpendicularly to the orbit of the nucleus.
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