Orosius, Histories against the Pagans 1.2.75-78
A new translation of this work has recently come out in Liverpool’s Translated Texts for Historians series; I haven’t yet seen it though, so I apologise for any howlers in the following version!
et quoniam Oceanus habet insulas, quas Britanniam et Hiberniam vocant, quae in aversa Galliarum parte ad prospectum Hispaniae sitae sunt, breviter explicabuntur.
Britannia Oceani insula per longum in boream extenditur; a meridie Gallias habet. cuius proximum litus transmeantibus civitas aperit, quae dicitur Rutupi Portus; unde haud procul a Morinis in austro positos Menapos Batavosque prospectat. haec insula habet in longo milia passuum DCCC, in lato milia CC.
a tergo autem, unde Oceano infinito patet, Orcadas insulas habet, quarum XX desertae sunt, XIII coluntur.
deinde insula Thyle, quae per infinitum a ceteris separata, circium versus medio sita Oceani, vix paucis nota habetur.
And since the Ocean contains the islands which they call Britain and Hibernia, which are situated in the region opposite the Gauls and looking towards Spain, they will be briefly described.
Britain, an island in the Ocean, extends a long way into the north; the Gauls are to the south. A city, which is called Rutupus’ Port, offers the nearest landing-place for those who make the crossing. It looks out from there towards the Menapi and Batavi, who are not far from the Morini to the south. This island is 800 miles in length, 200 miles in breadth.
But behind it, where the boundless Ocean extends, there are the Orcades islands, 20 of which are deserted, 13 inhabited.
Then the island of Thule, which is separated from the rest by a vast distance, and is situated to the north-west towards the middle of the Ocean, is known only to a few.