W. White provides description of the translation from characters engraved in Egyptian by Urim and Thummim.
W. White, A Little Talk, Between John Robinson and his Master about Mormonism, Shewing its Origin, Absurdity, and Impiety (Bedford: W. White, 1840), 3
It is said, these plates contained the Book of Mormon engraven in the Egyptian language, and that Joseph Smith translated them into English by the help of the Urim and Thummim, which the angel gave him with the plates, and that the Book of Mormon is as much the Word of God as the Bible, and contains “the fulness of the Gospel of Christ”.