It should be added also that the Grecian philosophers, though little fond of observation, but rejoicing rather in framing systems for the explanation of phenomena of which they possessed but the faintest glimpse, have left us some ideas about the nature of shooting stars and aerolites that come very close to those that are now accepted. "Some philosophers think," says Plutarch in his life of Lysander, "that shooting stars are not detached particles of ether which are extinguished by the atmosphere soon after being ignited, nor do they arise from the combustion of the rarefied air in the upper regions, but that they are rather heavenly bodies which fall, that is to say, which escaping in some way from the general force of rotation are precipitated in an irregular manner, sometimes on inhabited portions of the earth, but sometimes also in the ocean, where of course they cannot be found." Diogenes of Apollonius expresses himself still more clearly: "Amongst the stars that are visible move others that are invisible, to which in consequence we are unable to give any name. These latter often fall to the earth and take fire like that star-stone which fell all on fire near AEgos Potamos." These ideas were no doubt borrowed from some more ancient source, as he believed that all the stars were made of something like pumice-stone. Anaxagoras, in fact, thought that all the heavenly bodies were fragments of rocks which the ether, by the force of its circular motion, had detached from the earth, set fire to, and turned into stars. Thus the Ionic school, with Diogenes of Apollonius, placed the aerolites and the stars in one class, and assigned to all of them a terrestrial origin, though in this sense only, that the earth, being the central body, had furnished the matter for all those that surround it. Plutarch speaks thus of this curious combination:--"Anaxagoras teaches that the ambient ether is of an igneous nature, and by the force of its gyratory motion it tears off blocks of stone, renders them incandescent, and transforms them into stars." It appears that he explained also by an analogous effect of the circular motion the descent of the Nemaean Lion, which, according to an old tradition, fell out of the moon upon the Peloponnesus. According to Boeckh, this ancient myth of the Nemaean Lion had an astronomical origin, and was symbolically connected in chronology with the cycle of intercalation of the lunar year, with the worship of the moon in Nemaea, and the games by which it was accompanied. [Illustration: PLATE VI.--THE NEMAEAN LION.]