Presently it was shown by the Italian astronomer
Schiaparelli that one of these meteor swarms moves
in the orbit of a previously observed comet, and other
coincidences of the kind were soon forthcoming. The
conviction grew that meteor swarms are really the
debris of comets; and this conviction became a practical
certainty when, in November, 1872, the earth
crossed the orbit of the ill-starred Biela, and a shower
of meteors came whizzing into our atmosphere in lieu
of the lost comet.

And so at last the full secret was out. The awe-
inspiring comet, instead of being the planetary body
it had all along been regarded, is really nothing more
nor less than a great aggregation of meteoric particles,
which have become clustered together out in space
somewhere, and which by jostling one another or
through electrical action become luminous. So widely
are the individual particles separated that the cometary
body as a whole has been estimated to be thousands of
times less dense than the earth's atmosphere at sea-
level. Hence the ease with which the comet may be
dismembered and its particles strung out into streaming
swarms.

So thickly is the space we traverse strewn with this
cometary dust that the earth sweeps up, according to
Professor Newcomb's estimate, a million tons of it each
day. Each individual particle, perhaps no larger than
a millet seed, becomes a shooting-star, or meteor, as it