ear as they did. In regard to the distance of the moon they
were not more than 1/12th from the modern estimate. The possibility of
error in dealing with the sun was much greater, and their 51,000,000
miles is little more than half of what it should have been. Exactly
how far this doctrine of the sphericity of the earth was popularly
entertained we cannot tell; it was probably almost confined to those
directly interested in the question. A theory, anticipating Galileo,
that it is the earth which moves round the sun, had been mooted, but
certainly had very little currency. Nor was speculation confined to
such astronomical conclusions. In the region of physical geography
rational attempts were made to account for various phenomena, such as
the existence of deltas or the risings of the Nile, or the appearance
of sea-shells high on dry land. Strabo, in dealing with the Black Sea,
has his theories of the elevation or subsidence of land. He also
suggests previous volcanic conditions of certain districts which had
been quiescent from before the memory or tradition of the inhabitants.

[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 evidenc