The Greek name for amber, _elektron_, might be freely translated ‘sun-stone,’ a meaning partially preserved in the Latin term _lapis ardens_, Teutonicised into _Brennstein_, or _Bernstein_. The English _amber_ is a loan from the Arabic, negotiated at the time of the Crusades; but the original Achæan word survives in _electricity_ and its derivatives. For the first production of that still mysterious agency was by rubbing a piece of amber, the endowment of which thereby with an attractive faculty for light objects was noted with no particular emphasis by Thales, the sage of Miletus. The ‘Electrides Insulæ,’ or ‘amber-islands,’ of the ancients, corresponded, in vagueness of geographical position, with the Cassiterides or ‘tin-islands,’ of which the Phœnicians long kept the secret. The former were eventually located in the Adriatic, whither the historical Greeks succeeded in tracing the Baltic product, transported in those later days, along a second overland route from the Vistula to the Danube, and thence, by intermediary Venetian tribes, to the Istrian shore. Yet Herodotus was without any definite notion as to the derivation of amber, one of his spasmodical fits of scepticism forbidding him to admit its reported origin from a river called the Eridanus, said to flow into the sea somewhere at the back of the North wind.[408] The Eridanus, in fact, had a ‘name’ long before it had a ‘local habitation.’ Æschylus was doubtfully inclined to identify it with the Rhone, showing that he was chiefly acquainted with amber shipped at Massilia;[409] Pherecydes, knowing more of Adriatic supplies, established the ‘fluviorum rex Eridanus,’ in the bed of the Po, where it has remained. The myth of the Heliadæ, or sun-maidens, who, after their merciful transformation into poplars, continued to weep tears of amber for the fate of their brother, the lucklessly ambitious Phaethon, took definite shape in the hands of the Attic tragedians. Homer gives no hint of acquaintance with it. Footnote 408: Lib. iii. cap. 115. Footnote 409: Helbig, _Atti dell’ Accad. dei Lincei_, t. i. p, 422, ser. iii.