The question next arises, What becomes of comets in the end? Kepler long ago asserted his belief that they perished, as silkworms perish by spinning their own thread, exhausting themselves by the very efforts of tail-production which render them sometimes so brilliant to observation; and this seems to be pretty much the case. Thus Halley's comet, which was once so brilliant and excited so much attention, was at its last visit a very inconspicuous object indeed. At its apparition in 1845-1846 Biela's comet was found to have split into two separate bodies, which were found at their return in 1852 to have parted company widely. Since that year it has never been observed again in the form of a comet, though, as we shall see, it has presented itself in a different guise. The same fate has overtaken the comets of De Vico (1844), and Brorsen (1846). The former should have returned in 1850, but failed to keep its appointment; and the latter, after having established a character for regularity by returning to observation on four occasions, failed to appear in 1890, and has never since been seen. The mystery of such disappearances has been at least partially dispelled by the discovery, due to Schiaparelli and other workers in the same field, that various prominent meteor-showers travel in orbits precisely the same as those of certain comets. Thus the shower of meteors which takes place with greater or less brilliancy every year from a point in the constellation Perseus has been proved to follow the orbit of the bright comet of 1862; while the great periodic shower of the Leonids follows the track of the comet of 1866; the orbit of the star-shower of April 20--the Lyrids--corresponds with that of a comet seen in 1861; and the disappearance of Biela's comet appears to be accounted for by the other November shower whose radiant point is in the constellation Andromeda. In fact, the state of the matter is well summed up by Kirkwood's question: 'May not our periodic meteors be the débris of ancient but now disintegrated comets, whose matter has become distributed round their orbits?' The loosely compacted mass which forms the nucleus of the comet appears to gradually lose its cohesion under the force of solar tidal action, and its fragments come to revolve independently in their orbit, for a time in a loosely gathered swarm, and then gradually, as the laggards drop behind, in the form of a complete ring of meteoric bodies, which are distributed over the whole orbit. The Leonid shower is in the first condition, or, rather, was when it was last seen, for it seems to be now lost to us; the Perseid shower is in the second. The shower of the Andromedes has since confirmed its identity with the lost comet of Biela by displays in 1872, 1885, and 1892, at the seasons when that comet should have returned to the neighbourhood of the sun. It appears to be experiencing the usual fate of such showers, and becoming more