Can we learn whether the luminous matter in such nebul is more diffused or less diffused, than that of the comet of encke?
An explanation of these irregularities was suggested by encke long ago.
Look at the orbit of Jupiter, to which encke's comet approaches so nearly when it retreats from the sun.
This proved to be identical with the third comet of 1819, whose period was computed by encke to be about 5½ years.
A huge comet (encke's, I believe) was flaring all over the sky.
Mercury's mass is found by its disturbing effects on encke's comet whenever it approaches very near.
encke's comet loses in thirty-three years a thousandth part of its velocity.
But while Olbers became a mathematician because he was an astronomer, encke became an astronomer because he was a mathematician.
This object was seen in 1786, and at some subsequent returns, before it was discovered by encke in 1819 to be a periodic comet.
encke's comet, of which we have just spoken, appears to be describing such a spiral curve towards the sun.