Comets--Their small inclinations--Their motions chiefly direct--Comet of
1770 and 1844--Cause of acceleration in the case of Encke--Anomalous
motions of the comet of 1843--Change of diameter at different
distances of a comet from the sun--Cause of this change--Nature of the
nebulosity--Formation of the tail--Compound nature of a comet's
light--motion and direction of a comet's tail--Phenomena presented by
the great comet of Halley--Mass of a comet--The Zodial light--Nebulous
stars--Shooting stars--Periodic showers--Periodicity doubtful--Cause
of the apparent periodicity--Cause for being more numerous in Autumn
than in Spring. 187