��THE SCIENTIFIC MONTHLY
��Biela's comet, to which we have referred, when last seen in 1852, as a double comet, was expected to return in 1866 and again in 1872, but it was not seen then, nor later. A meteor shower of moderate intensity was observed on November 27, 1872, moving in the orbit of the lost comet.
Not to dwell upon the remarkable identities of the orbits of the four meteor swarms, respectively, with the orbits of the four comets (Fig. 14), two of which have disappeared, and the other two, of rela- tively long periods, which may never return, we express the prevailing opinion of astronomers in saying that the meteor streams have actually resulted from the disintegration of the four comets. Alexander Her- schel has prepared a list of seventy-six meteor streams whose orbits agree fairly closely with seventy-six comet orbits. A certain propor- tion of the suspected identities probably represent facts. It is inter-
���Pia. 14. Obbits of Meteoric Swarms, which are known to be associated with
��esting to note that even as early as 1861 the truth of the situation was expressed and printed by Kirkwood :
May not our periodic meteors be the debris of ancient but now disinte- grated comets whose material has become distributed around' their orbits f
It was in this connection and at that time that Kirkwood was able to make a list of eight comets, each of which had divided into two or more parts and had wholly disappeared from the sight of observers.
The cause of the disiiite<rration of comets is not far to seek. A