[Illustration: FIG. 113.--WORLD AS CONCEIVED ABOUT A.D. 100.] Sound methods of discovering latitude and longitude were not yet in use, and therefore a map of the world according to ideas current in the first century would present a strange aspect to us. There is much error in the placing of towns or districts upon their parallels; and coasts or mountain ranges, particularly, of course, on the outskirts of the empire or in the less familiar lands beyond its bounds, are perhaps made to run north instead of north-west, or east instead of south-east. It follows that measurements of distances especially across the wider seas, were often very inaccurate, although within and about the Mediterranean there was so much traffic and such close observation of the stars that the errors were gradually reduced. The mariner, when he did not follow the coast and guide his course by familiar landmarks, steered by the stars, but of these he had a very intimate knowledge, to which he joined a close observation of the prevailing direction of the winds at the various seasons. There was a well-ordered system of lighthouses, and charts and mariners' guides were not wanting. In the winter months navigation over long distances was regularly suspended, and ships waited in port for the spring. So far as acquaintance with the world was concerned, we have sufficient evidence that the trader knew his way very well down the African coast as far as Zanzibar, and along the southern shores of Asia as far as Cape Comorin. With Ceylon his acquaintance was vague, and only by tradition did he know of Further India by way of the sea and of China by way of the land. In the interior of Africa the caravans reached the Oases, and by way of Nile or caravan there was trade with the Soudan. Outside the Straits of Gibraltar, the Canary Islands and Madeira--known indiscriminately as the "Fortunate Isles," or "Isles of the Blest"--were in touch with the port of Cadiz. The shape of Great Britain beyond England was indefinite, although it was known to be an island, with the Shetlands lying beyond. Ireland was also recognised as an island and its relative size was not greatly misconceived. The chief misconception in this corner of Europe was that of orientation, Britain being placed either far too near or far too parallel to Spain (through a large error as to the shape of the Bay of Biscay). Meanwhile the coast of the Netherlands and Germany was made to run in a line much too closely parallel to the eastern shores of Britain. Scandinavia was known from navigating explorers and from the amber trade, but was commonly regarded as a large island. Knowledge of the Baltic did not extend beyond about the modern Riga, and of the whole region thence to the Caspian only the dimmest notions were entertained.