much expanded.  He places the sources of the Nile, and the Mountains of the Moon in south latitude thirteen, instead of north latitude six or seven; but the error of latitude is not so remarkable and unaccountable as the very erroneous latitude which he assigns to Cape Aromata, on a coast which was visited every year by merchants he must have seen at Alexandria.  The most difficult point to explain in Ptolemy’s central Africa is the river Gir, which he describes as equal in length to the Niger, and running in the same direction, till it loses itself in the same lake.  What this river is, geographers have not agreed.  It is mentioned by Claudian, as resembling the Nile in the abundance of its waters.  Agethimedorus, a geographer of the third century, regards it and the Niger as the same river.

What then was the amount of the knowledge of the ancients, as it existed among the Romans, in the height of their power, respecting the form, extent, and surface of the globe?  If we view a map drawn up according to their ideas, we are immediately struck with the form they assigned the world, and perceive with what propriety they called the extent of the world from east to west longitude or length, and the extent from north to south latitude, or breadth.  In some maps, especially that drawn up from the celebrated Peutingerian Tables, which contain an itinerary of the whole Roman empire, thirty-five degrees of longitude occupy twenty-eight feet eight inches, whereas thirteen degrees of latitude are compressed within the space of one foot.  It is easy to conceive how it happened that too much space is assigned between places situated east and west of each other, as the latitude of a place is much more easily determined than its longitude.  At the same time, as the routes of the Roman armies generally were from east to west, the countries lying in that direction were better known than those lying to the north and south, though the longitudes, and general space assigned the world, in the former deviation, were erroneous.  It was the opinion of most of the ancient geographers, that there was a southern continent or hemisphere, to correspond to and balance the northern; and this they formed by cutting off the great triangle to the south.  The ancients also, while they curtailed those parts of the world with which they were unacquainted, extended the known parts.

The limit of the Roman geography of Europe to the north was the Baltic, beyond which they had some very imperfect and obscure notion of the south of Sweden, and perhaps of Norway.  They were acquainted with the countries on the eastern boundary of Europe lying on the Danube and the Vistula, and the rivers Wolga and Tanais seem also to have been tolerably well known to them.  Of the whole of the west of Europe they were well informed, with the exception of the general figure, and some part of the British isles.