No one can contemplate the firmament for long on a clear moonless night without noticing one or more of those luminous objects called shooting-stars. They are particularly numerous in the autumnal months, and will sometimes attract special attention either by their frequency of apparition or by their excessive brilliancy in individual cases. For many ages little was known of these bodies, though some of the ancient philosophers appear to have formed correct ideas as to their astronomical nature. Humboldt says that Diogenes of Apollonia, who probably belonged to the period intermediate between Anaxagoras and Democritus, expressed the opinion that, “together with the visible stars, there are invisible ones which are therefore without names. These sometimes fall upon the Earth and are extinguished, as took place with the star of stone which fell at Ægos Potamoi.” Plutarch, in the ‘Life of Lysander,’ remarks :— “Falling stars are not emanations or rejected portions thrown off from the ethereal fire, which when they come into our atmosphere are extinguished after being kindled: they are, rather, celestial bodies which, having once had an impetus of revolution, fall, or are cast down to the Earth, and are precipitated, not only on inhabited countries, but also, and in greater numbers, beyond these into the great sea, so that they remain concealed.”