The Celtic Apollo
From Apollonius Rhodius' Argonautica

(ll. 592-626) Thus Argo cried through the darkness; and the sons of Tyndareus uprose, and lifted their hands to the immortals praying for each boon: but dejection held the rest of the Minyan heroes. And far on sped Argo under sail, and entered deep into the stream of Eridanus; where once, smitten on the breast by the blazing bolt, Phaethon half-consumed fell from the chariot of Helios into the opening of that deep lake; and even now it belcheth up heavy steam clouds from the smouldering wound. And no bird spreading its light wings can cross that water; but in mid-course it plunges into the flame, fluttering. And all around the maidens, the daughters of Helios, enclosed in tall poplars, wretchedly wail a piteous plaint; and from their eyes they shed on the ground bright drops of amber. These are dried by the sun upon the sand; but whenever the waters of the dark lake flow over the strand before the blast of the wailing wind, then they roll on in a mass into Eridanus with swelling tide. But the Celts have attached this story to them, that these are the tears of Leto's son, Apollo, that are borne along by the eddies, the countless tears that he shed aforetime when he came to the sacred race of the Hyperboreans and left shining heaven at the chiding of his father, being in wrath concerning his son whom divine Coronis bare in bright Lacereia at the mouth of Amyrus. And such is the story told among these men. But no desire for food or drink seized the heroes nor were their thoughts turned to joy. But they were sorely afflicted all day, heavy and faint at heart, with the noisome stench, hard to endure, which the streams of Eridanus sent forth from Phaethon still burning; and at night they heard the piercing lament of the daughters of Helios, wailing with shrill voice; and, as they lamented, their tears were borne on the water like drops of oil.

(ll. 627-658) Thence they entered the deep stream of Rhodanus which flows into Eridanus; and where they meet there is a roar of mingling waters. Now that river, rising from the ends of the earth, where are the portals and mansions of Night, on one side bursts forth upon the beach of Ocean, at another pours into the Ionian sea, and on the third through seven mouths sends its stream to the Sardinian sea and its limitless bay. (3) And from Rhodanus they entered stormy lakes, which spread throughout the Celtic mainland of wondrous size; and there they would have met with an inglorious calamity; for a certain branch of the river was bearing them towards a gulf of Ocean which in ignorance they were about to enter, and never would they have returned from there in safety. But Hera leaping forth from heaven pealed her cry from the Hercynian rock; and all together were shaken with fear of her cry; for terribly crashed the mighty firmament. And backward they turned by reason of the goddess, and noted the path by which their return was ordained. And after a long while they came to the beach of the surging sea by the devising of Hera, passing unharmed through countless tribes of the Celts and Ligyans. For round them the goddess poured a dread mist day by day as they fared on. And so, sailing through the midmost mouth, they reached the Stoechades islands in safety by the aid of the sons of Zeus; wherefore altars and sacred rites are established in their honour for ever; and not that sea-faring alone did they attend to succour; but Zeus granted to them the ships of future sailors too. Then leaving the Stoechades they passed on to the island Aethalia, where after their toil they wiped away with pebbles sweat in abundance; and pebbles like skin in colour are strewn on the beach; (4) and there are their quoits and their wondrous armour; and there is the Argoan harbour called after them.

SOURCE
Apollonius Rhodius. Argonautica. edited and translated by R.C. Seaton. Loeb Classical Library. Cambridge, MA: Harvard University Press, 1912. URL: http://classics.mit.edu/Apollonius/argon.4.iv.html