[footnote] *On 'méteoric dust', see Arago, in the 'Annuaire' for 1832, p. 254. I haave very recently endeavored to show, in another work ('Asie Centrale', t. i., p. 408). how the Scythian saga of the sacred gold, which fell burning from heaven, and remained in the possession of the Golden Horde of the Paralatæ (Herod., iv., 5-7), probably originated in the vague recollection of the fall of an aërolite. The ancients had also some strange fictions (Dio Cassius, lxxv., 1259) or silver which had fallen from heaven, and with which it had been attempted, under the Emperor Severus, to cover bronze coins; metallic iron was however, known to exist in meteoric stones. (Plin., ii., 56.) The frequently-recurring expression 'lapidibus pluit' must not always be understood to refer to falls of aërolites. In Liv., xxv., 7, it probably refers to pumice ('rapilli') ejected from the volcano, Mount Albanus (Monte Cavo), which was not wholly extinguished at the time. (See Heyne, 'Opuscula Acad.', t. iii., p. 261; and my 'Relation Hist.', t. i., p. 394.) The contest of Hercules with the Ligyans, on the road from the Caucasus to the Hesperides, belongs to a different sphere of ideas, being an attempt to explain mythically the origin of the round quartz blocks in the Ligyan field of stones at the mouth of the Rhone, which Aristotle supposes to have been ejected from a fissure during an earthquake, and Posidonius to have been caused by the force of the waves of an inland piece of water. In the fragments that we still possess of the play of Æschylus, the 'Prometheus Delivered', every thing proceeds, however, in part of the narration, as in a fall of aërolites, for Jupiter draws together a cloud, and causes the "district around to be covered by a shower of round stones". Posidonius even ventured to deride the geognostic myth of the blocks and stones. The Lygian field of stones was, however, very naturally and well described by the ancients. The district is now known as 'La Crau.' (See Guerin, 'Mesures Barométriques dans les Alpes, et Météorologie d'Avignon', 1829, chap. xii., p. 115.) p 116 We can ascertain by measurement the enormous, wonderful, and wholly planetary velocity of shooting stars, fire-valls and meteoric stones, and we can gain a knowledge of what is the general and uniform character of the phenomenon, but not of the genetically cosmical process and the results of the metamorphoses. If meteoric stones while revolving in space are already consolidated into dense masses,* less dense, however, p 117 than the mean density of the earth, they must be very small nuclei, which surrounded by inflammable vapor or gas, form the innermost part of fire-balls, from the height and apparent diameter of which we may, in the case of the largest, estimate that the actual diameter varies from 500 to about 2800 feet.