Scotland during the Roman Empire of the geography of Scotland had extended to the "Hebudes" (The Hebrides), "Dumna" (probably the Outer Hebrides), the Caledonian Forest, and the Caledonians. Ptolemy, possibly drawing on earlier sources of information as well as more contemporary accounts from the Agricolan invasion, identified 18 tribes in Scotland in his "Geography", but many of the names are obscure. His information becomes much less reliable in the north and west, suggesting early Roman knowledge of these area was confined to observations from the sea. Famously, his coördinates place most of Scotland north of Hadrian's Wall bent at a right angle, stretching due eastward
Planetrees (Hadrian's Wall section) he must have a mean opinion of me, who would travel six hundred miles to see it; and if it was, he could never merit my thanks for destroying it." The eastern part of the surviving section (approximately in length) is built as Broad Wall, 10 Roman Feet wide. The eastern section (approximately in length is built as Narrow Wall, 8 Roman Feet wide, yet still on foundations clearly installed for a Broad Wall. The join is archeologically interesting, as it suggests a change in plan during construction. Also present on the narrow wall stretch is a culvert. The stones