one of the northern hemisphere. (3) A circle passing through
the poles and cutting the two preceding circles at right-angles. The
northern hemisphere contains two quarters of the earth, which are
bounded by the equator and circle passing through the poles. Each of
these quarters should be supposed to contain a four-sided district,
its northern side being of one-half of the parallel next the pole, its
southern by the half of the equator, and its remaining sides by two
segments of the circle drawn through the poles, opposite to each
other, and equal in length. In one of these (which of them is of no
consequence) the earth which we inhabit is situated, surrounded by a sea
and similar to an island. This, as we said before, is evident both to
our senses and to our reason. But let any one doubt this, it makes no
difference so far as geography is concerned whether you believe the
portion of the earth which we inhabit to be an island or only admit what
we know from experience--namely, that whether you start from the east
or the west you may sail all around it. Certain intermediate spaces may
have been left (unexplored), but these are as likely to be occupied by
sea as uninhabited land. The object of the geographer is to describe
known countries. Those which are unknown he passes over equally with
those beyond the limits of the inhabited earth. It will, therefore,
be sufficient for describing the contour of the island we have been
speaking of, if we join by a right line the outmost points which, up
to this time, have been explored by voyagers along the coast on either
side."(3)

We may pass over the specific criticisms of Strabo upon various
explorations that seem to have been of great interest to his
contemporaries, including an alleged trip of one Eudoxus out into
the Atlantic, and the journeyings of Pytheas in the far north. It is
Pytheas, we may add, who was cited by Hipparchus as having made the
mistaken observation that the length of the shadow of the gnomon is the
same at Marseilles and Byzantium, hence that these two places are on the
same parallel. Modern commentators have defended Pytheas as regards this
observation, claiming that it was Hipparchus and not Pytheas who made
the second observation from which the faulty induction was drawn. The
point is of no great significance, however, except as showing that a
correct method of determining the problems of latitude had thus early
been suggested. That faulty observations