in Ancient Geography, the crux geographorum, so called from the difficulty of ascertaining its position. It would be endless to recite the different opinions concerning it, with the various reasons advanced in support of them. Three ports are mentioned by Caesar, two of them without any particular name, viz. the higher and the lower with respect to the Portus Itius. Calais, Boulogne, St Omer, and Whitsand, have each in its turn had its several advocates. Caesar gives two distinctive characters or marks which seem to apply equally to Boulogne and Whitsand, namely, the shortness of the passage, and the situation between two other ports; therefore nothing can be determined with certainty respecting the situation of the Portus Itius.