Such is the wonderfully accurate notice of the salient features of the coasts of Scotland given by a geographer of the second century; but his description of the tribes of the interior of the country, and the position of what he denominates towns, as compared with the physical appearance of the country, is no less so. To these tribes Ptolemy assigns definite names, and to some the possession of what he terms πόλεις in Greek, and in Latin ‘oppida.’ That these towns were not exclusively Roman stations is plain from their being mentioned in a part of the country to which the Roman arms had not yet penetrated; neither could they have been simply the rude hill-forts, or primitive shelters in the woods, such as are mentioned by Cæsar; for they are only to be found in the southern and eastern districts, and none are noticed as we approach the rude tribes of the hill country. They certainly implied a regularly fortified town, in which the habitations of the natives were collected together, and formed the great defences of their territories, as we almost invariably find them placed near the frontiers of each tribe, or the great passes from one district to another. They would naturally form the main points of attack in any assault upon the tribe; and accordingly we usually find, within the sphere of the Roman operations, a Roman camp placed in the immediate vicinity of the remains of these towns; and the Roman stations or roads are useful in assisting the accurate identification of these within the range of their campaigns. A line drawn from the Solway Firth across the island to the eastern sea exactly separates the great nation of the Brigantes from the tribes on the north; but this is obviously an artificial line of separation, as it closely follows the course of the Roman wall shortly before constructed by the Emperor Hadrian, otherwise it would imply that the southern boundary of three Barbarian tribes was precisely on the same line where nature presents no physical line of demarcation. There is on other grounds reason to think that these tribes, though apparently separated from the Brigantes by this artificial line, in reality formed part of that great nation.[63] These tribes were the Otalini or Otadeni and Gadeni, extending along the east coast from the Roman wall to the Firth of Forth. They had three towns—on the south ‘Curia’ and ‘Bremenium,’ whose situations correspond with Carby Hill in Liddesdale, where there is a strong native fort, and opposite to it a Roman station, and High Rochester, in Redesdale. Their northern frontier was guarded by the town of Alauna, which is placed by Ptolemy in the Firth of Forth, and corresponds in situation with the island of Inchkeith.[64]