Strabo had much to tell us concerning zones, which, following
Posidonius, he believes to have been first described by
Parmenides. We may note, however, that other traditions assert
that both Thales and Pythagoras had divided the earth into zones.
The number of zones accepted by Strabo is five, and he
criticises Polybius for making the number six. The five
zones accepted by Strabo are as follows: the uninhabitable torrid
zone lying in the region of the equator; a zone on either side of
this extending to the tropic; and then the temperate zones
extending in either direction from the tropic to the arctic
regions. There seems to have been a good deal of dispute among
the scholars of the time as to the exact arrangement of these
zones, but the general idea that the north-temperate zone is the
part of the earth with which the geographer deals seemed clearly
established. That the south-temperate zone would also present a
habitable area is an idea that is sometimes suggested, though
seldom or never distinctly expressed. It is probable that
different opinions were held as to this, and no direct evidence
being available, a cautiously scientific geographer like Strabo
would naturally avoid the expression of an opinion regarding it.
Indeed, his own words leave us somewhat in doubt as to the
precise character of his notion regarding the zones. Perhaps we
shall do best to quote them:

"Let the earth be supposed to consist of five zones. (1) The
equatorial circle described around it. (2) Another parallel to
this, and defining the frigid zone 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 and faulty application
of the correct principle should have been made is not surprising.
Neither need we concern ourselves with the details as to the
geographical distances, which Strabo found so worthy of criticism
and controversy. But in leaving the great geographer we may
emphasize his point of view and that of his contemporaries by
quoting three fundamental principles which he reiterates as being
among the "facts established by natural philosophers." He tells
us that "(1) The earth and heavens are spheroidal. (2) The
tendency of all bodies having weight is towards a centre. (3)
Further, the earth being spheroidal and having the same centre as
the heavens, is motionless, as well as the axis that passes
through both it and the heavens. The heavens turn round both the
earth and its axis, from east to west. The fixed stars turn round
with it at the same rate as the whole. These fixed stars follow
in their course parallel circles, the principal of which are the
equator, two tropics, and the arctic circles; while the planets,
the sun, and the moon describe certain circles comprehended
within the zodiac."[4]

Here, then, is a curious mingling of truth and error. The
Pythagorean doctrine that the earth is round had become a
commonplace, but it would appear that the theory of Aristarchus,
according to which the earth is in motion, has been almost
absolutely forgotten. Strabo does not so much as refer to it;
neither, as we shall see, is it treated with greater respect by
the other writers of the period.


TWO FAMOUS EXPOSITORS--PLINY AND PTOLEMY

While Strabo was pursuing his geographical studies at Alexandria,
a young man came to Rome who was destined to make his name more
widely known in scientific annals than that of any other Latin


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