The fact that the maximum number of meteors is always observed in the morning hours, supports the hypothesis of the cosmic origin of the shooting-stars, since the regions of the Earth where it is morning are precisely those fronting the regions towards which our globe is moving in space, and accordingly encounter more directly the meteors moving in their orbit. The greater abundance of falling stars at that time may thus be accounted for. The number of meteors penetrating our atmosphere must be very great; there is not an hour and probably not a minute during which none fall. From various considerations, some astronomers have estimated at from 65,000,000,000 to 146,000,000,000 the total number of shooting-stars yearly penetrating in our atmosphere. The actual number is undoubtedly great, yet the fact that the meteors are rarely seen through the telescope while employed in observing various celestial objects, does not indicate that they are so numerous as these figures imply. It is only occasionally that one is seen traversing the field of the instrument. Even when the sky is observed with a low power eye-piece for several hours in succession, many nights may pass without disclosing one, although an observer, sweeping the sky more freely with the naked eye, may often perceive four or five during an ordinary night. About the true nature of these bodies nothing is known with certainty. From spectrum analysis it seems to be established that most of them contain sodium and magnesium, while a few indicate the presence of strontium and iron, and in some rare cases there are traces of coal-gas. Some of the nuclei give a continuous spectrum, and others a spectrum of lines. The trail always gives a spectrum of bright lines which indicates its gaseous state. The traces of coal-gas rarely seen in meteors are, however, of great importance, as it identifies them more closely with the comets, which generally show a similar spectrum. The continuous spectra exhibited by some nuclei would indicate that they are incandescent and either solid or liquid; but it is difficult to conclude from their spectra what is their true nature, since we do not know exactly what part the terrestrial atmosphere may play in producing the results. The mass of the shooting-stars is not known with certainty, but the fact that during great meteoric showers, none are seen to reach the surface of the Earth, all being consumed in a few seconds, sufficiently indicates that it must be very small. It has been calculated that those equal to Venus in apparent size and brilliancy may weigh several pounds, while the faint ones would weigh only a few grains.