Aerolites come singly and unexpectedly, falling actually to earth on land or sea. "Shooting stars" come usually in battalions. They travel together in swarms, and the earth may meet the same swarm again and again. They are smaller than aerolites, probably mere particles of dust, and for the most part are entirely consumed in our upper atmosphere, so that they do not actually reach the earth. The swarms travel along paths that resemble cometary orbits; they are very elongated ellipses, inclined at all angles to the plane of the ecliptic. Indeed, several of the orbits are actually those of known comets, and it is generally held that these meteorites or "shooting stars" are the _débris_ that a comet sheds on its journey. We can never see the same "shooting star" twice; its visibility implies its dissolution, for it is only as it is entrapped and burnt up in our atmosphere that we see it, or can see it. Its companions in a great meteoric swarm, are, however, as the sand on the sea-shore, and we recognize them as members of the same swarm by their agreement in direction and date. The swarms move in a closed orbit, and it is where this orbit intersects that of the earth that we get a great "star shower," if both earth and swarm are present together at the intersection. If the swarm is drawn out, so that many meteorites are scattered throughout the whole circuit of its orbit, then we get a "shower" every year. If the meteor swarm is more condensed, so as to form a cluster, then the "shower" only comes when the "gem of the ring," as it is termed, is at the intersection of the orbits, and the earth is there too.