Chapter 22 - Page 2

the sun, once in twenty-four hours; the last to the
oblique manner in which its rays struck this orb, in all places but near
its centre.

But the globe ought not to be made to move around the table with its axis
perpendicular to its surface, or to the "plane of the earth's orbit." In
point of fact, the earth is inclined to this plane, and the globe should
be placed at a corresponding inclination. Let the globe be brought to the
edge of the table, at its south side, and with its upper or north pole
inclining to the sun, and then commence the circuit, taking care always to
keep this north pole of the globe pointing in the same direction, or to
keep the globe itself in what we have termed a fixed attitude. As one half
of the globe must always be in light, and the other half in darkness, this
inclination from the perpendicular will bring the circle of light some
distance beyond the north pole, when the globe is due-south from the
light, and will leave an equal space around the opposite pole without any
light at all, or any light directly received. Now it is that what we have
termed the _fixed attitude_ of the globe begins to tell. If the north pole
inclined towards the orbit facing the rim of the table, the light would
still cut the poles, the days and nights would still be equal, and there
would be no changes in the seasons, though there would be a rival
revolution of the globe, by causing it to turn once a year, shifting the
poles end for end. The inclination being to the surface of the table, or
to _the plane_ of the orbit, the phenomena that are known to exist are a
consequence. Thus it is, that the change in the seasons is as much owing
to the fixed attitude of the earth in space, as we have chosen to term its
polar directions, as to the inclination of its axis. Neither would produce
the phenomena without the assistance of the other, as our experiment with
the table will show.

Place, then, the globe at the south side of the rim of the table, with its
axis inclining towards its surface, and its poles always pointing in the
same general direction, not following the circuit of the orbit, and set it
in motion towards the east, revolving rapidly on its axis as it moves.
While directly south of the light, it would be found that the north pole
would be illuminated, while no revolution on the axis would bring the
south pole within the circle of the light. This is when a line drawn from
the axis of the globe would cut the lamp, were the inclination brought as
low as the surface of the table. Next set the globe in motion, following
the rim of the table, and proceeding to the east or right hand, keeping
its axis always looking in the same general direction, or in an attitude
that would be parallel to a north