int is clear to
the perception of the most average understanding. However, we may show
summarily that the earth is spheroidal, from the consideration that
all things, however distant, tend to its centre, and that every body is
attracted towards its centre by gravity. This is more distinctly proved
from observations of the sea and sky, for here the evidence of the
senses and common observation is alone requisite. The convexity of the
sea is a further proof of this to those who have sailed, for they cannot
perceive lights at a distance when placed at the same level as their
eyes, and if raised on high they at once become perceptible to vision
though at the same time farther removed. So when the eye is raised it
sees what before was utterly imperceptible. Homer speaks of this when he
says:

"'Lifted up on the vast wave he quickly beheld afar.'

"Sailors as they approach their destination behold the shore continually
raising itself to their view, and objects which had at first seemed low
begin to lift themselves. Our gnomons, also, are, among other things,
evidence of the revolution of the heavenly bodies, and common-sense
at once shows us that if the depth of the earth were infinite such a
revolution could not take place."(1)

Elsewhere Strabo criticises Eratosthenes for having entered into a long
discussion as to the form of the earth. This matter, Strabo thinks,
"should have been disposed of in the compass of a few words." Obviously
this doctrine of the globe's sphericity had, in the course of 600 years,
become so firmly established among the Greek thinkers as to seem almost
axiomatic. We shall see later on how the Western world made a curious
recession from this seemingly secure position under stimulus of an
Oriental misconception. As to the size of the globe, Strabo is disposed
to accept without particular comment the measurements of Eratosthenes.
He speaks, however, of "more recent measurements," referring in
particular to that adopted by Posidonius, according to which the
circumference is only about one hundred and eighty thousand stadia.
Posidonius, we may note in passing, was a contemporary and friend
of Cicero, and hence lived shortly before the time of Strabo. His
measurement of the earth was based on observations of a star which
barely rose above the southern horizon at Rhodes as compared with the
height of the same star when observed at Alexandria. This measurement
of Posidonius, together with the eve