already seen that the apparent time of sunset would be the same from
all stations if the earth were flat. When Ptolemy, therefore,
demonstrated that the time of sunset was not the same at various
places, he showed conclusively that the earth was not flat.

As the same arguments applied to all parts of the earth where Ptolemy
had either been himself, or from which he could gain the necessary
information, it followed that the earth, instead of being the flat
plain, girdled with an illimitable ocean, as was generally supposed,
must be in reality globular. This led at once to a startling
consequence. It was obvious that there could be no supports of any
kind by which this globe was sustained; it therefore followed that
the mighty object must be simply poised in space. This is indeed an
astonishing doctrine to anyone who relies on what merely seems the
evidence of the senses, without giving to that evidence its due
intellectual interpretation. According to our ordinary experience,
the very idea of an object poised without support in space, appears
preposterous. Would it not fall? we are immediately asked. Yes,
doubtless it could not remain poised in any way in which we try the
experiment. We must, however, observe that there are no such ideas
as upwards or downwards in relation to open space. To say that a
body falls downwards, merely means that it tries to fall as nearly as
possible towards the centre of the earth. There is no one direction
along which a body will tend to move in space, in preference to any
other. This may be illustrated by the fact that a stone let fall at
New Zealand will, in its approach towards the earth's centre, be
actually moving upwards as far as any locality in our hemisphere is
concerned. Why, then, argued Ptolemy, may not the earth remain
poised in space, for as all directions are equally upward or equally
downward, there seems no reason why the earth should require any