§ Of Eldamar and the Princes of the Eldalië The Silmarillion

Now Ulmo, by the counsel of the Valar, came to the shores of Middle-earth and spoke with the Eldar who waited there, gazing on the dark waves; and because of his words and the music which he made for them on his horns of shell their fear of the sea was turned rather to desire. Therefore Ulmo uprooted an island which long had stood alone amid the sea, far from either shore, since the tumults of the fall of Illuin; and with the aid of his servants he moved it, as it were a mighty ship, and anchored it in the Bay of Balar, into which Sirion poured his water. Then the Vanyar and the Noldor embarked upon that isle, and were drawn over the sea, and came at last to the long shores beneath the Mountains of Aman; and they entered Valinor and were welcomed to its bliss. But the eastern horn of the island, which was deep-grounded in the shoals off the mouths of Sirion, was broken asunder and remained behind and that, it is said, was the Isle of Balar, to which afterwards Ossë often came.