According to other theories meteorites may be fragments of shattered worlds that have chanced to come too near to a larger body and have been disrupted, or they may possibly be the larger fragments of the disintegrated comets of which the meteoric swarms are the smaller. Interplanetary space is not altogether a void. Our own planet sweeps up in the course of a single day, it has been estimated, approximately twenty million shooting stars or meteors of sufficient size to be visible to the naked eye, while the estimate for the telescopic particles runs up to four hundred million. Meteorites on the other hand are comparatively rare. On the average it has been estimated about one hundred meteorites strike the earth in the course of a year, of which number only two or three are actually seen. According to _Bulletin 94, U. S. National Museum_, approximately six hundred and fifty falls and finds of meteorites have been reported, representatives of which appear in museums and private collections. Meteorites, as well as shooting stars and meteors, frequently appear in showers. In such instances the fall usually consists of several hundred or thousand individual stones and the area over which they fall is several square miles in extent and roughly ellipsoidal in shape. One of the most remarkable of such falls [...] hundred thousand stones, varying in weight from fifteen pounds to a small fraction of an ounce, fell near Pultusk, Poland. Another remarkable fall of meteorites occurred at L'Aigle, France, in 1803. Between two thousand and three thousand stones fell over an ellipsoidal area of six and two-tenths miles in greatest diameter, the aggregate weight of the stones being not less than seventy-five pounds. This fall of stones is of particular interest since it took place at a time when men were still very doubtful as to whether or not stones actually fell to earth from the heavens. After this fall had occurred in a most populous district of France in broad daylight and attended by violent explosions that lasted for five or six minutes and were heard for a distance of seventy-five miles, no reasonable doubt could longer be held as to the actuality of such phenomena. Meteorites are without exception of an igneous nature, that is, they are rocks that have solidified from a molten condition. They can be classified into three groups, Aerolites or Stony Meteorites, Siderolites or Stony-iron Meteorites, and Siderites or Iron Meteorites. More iron meteorites seem to have fallen in Mexico and Greenland than in any other part of the world--at least of its land surface.