Which preposition to use with eau

in Occurrences 7%

He answers in the words of Murray, Weld, Pond, Smith, Adams, Kirkham, Merchant, Ingersoll, Bacon, Alger, Worcester, and others: "A triphthong is the union of three vowels, pronounced in like manner: as eau in beau, iew in view."

Which preposition to use with  eau