[429] I have already had occasion to remark, concerning this class of phænomena, that there is no doubt of their actual occurrence, although their origin is still unexplained. [430] The life of Anaxagoras has been written by Diogenes Laërtius. We have an ample account of him by Enfield in the General Biography, _in loco_; he was born B.C. 500 and died B.C. 428. [431] There is some variation in the exact date assigned by different authors to this event; in the Chronological table in Brewster’s Encyc. vi. 420, it is said to have occurred 467 B.C. [432] Aristotle gives us a similar account of this stone; that it fell in the daytime, and that a comet was then visible at night; Meteor. i. 7. It is scarcely necessary to remark, that the authority for this fact must be referred entirely to Aristotle, without receiving any additional weight from our author. The occurrence of the comet at the same time with the aërolite must have been entirely incidental. [433] “Deductis eo sacri lapidis causa colonis, extructoque oppido, cui nomen a colore adusto lapidis, est inditum, Potidæa. Est enim ποτὶ Dorice πρὸς, ad, apud; δαίομαι, uror.” Hardouin, in Lemaire, i. 361. It was situated in the peninsula of Pallene, in Macedonia. [434] The Vocontii were a people of Gallia Narbonensis, occupying a portion of the modern Dauphiné. [435] “Manifestum est, radium Solis immissum cavæ nubi, repulsa acie in Solem, refringi.” [436] Aristotle treats of the Rainbow much in detail, principally in his Meteor. iii. 2, 3, 4, and 5, where he gives an account of the phænomena, which is, for the most part, correct, and attempts to form a theory for them; see especially cap. 4. p. 577 _et seq._ In the treatise De Mundo he also refers to the same subject, and briefly sums up his doctrine with the following remark: “arcus est species segmenti solaris vel lunaris, edita in nube humida, et cava, et perpetua; quam velut in speculo intuemur, imagine relata in speciem circularis ambitûs.” cap. 4. p. 607. Seneca also treats very fully on the phænomena and theory of the Rainbow, in his Nat. Quæst. i. 3-8. [437] _Vide supra_, also Meteor. iii. 2, and Seneca, Nat. Quæst. i. 3. [438] Aristotle, Meteor. iii. 5. p. 581, observes, that the rainbow is less frequently seen in the summer, because the sun is more elevated, and that, consequently, a less portion of the arch is visible. See also Seneca, Nat. Quæst. i. 8. p. 692. [439] Aristotle treats at some length of dew, snow, and hail, in his Meteor. i. cap. 10, 11 & 12 respectively. [440] When water is frozen, its bulk is increased in consequence of its assuming a crystalline structure. Any diminution which may be found to have taken place in the bulk of the fluid, when thawed, must be ascribed to evaporation or to some accidental circumstance.