IF a map of the world be accurately delineated on a spherical ball, the surface thereof will represent the surface of the earth: for the highest hills are so inconsiderable with respect to the bulk of the earth, that they take off no more from its roundness than grains of sand do from the roundness of a common globe; for the diameter of the earth is 8000 miles, in round numbers, and no known hill upon it is three miles in perpendicular height.
For the proof of the earth's being spherical, see ASTRONOMY, p. 440.
With regard to what we call up and down, see ASTRONOMY, p. 445.
To an observer placed any where in the indefinite space, where there is nothing to limit his view, all remote objects appear equally distant from him; and seem to be placed in a vast concave sphere, of which his eye is the centre. The moon is much nearer to us than the sun; some of the planets are sometimes nearer, and sometimes farther from us, than the sun; others of them never come so near us as the sun always is; the remotest planet in our system, is beyond comparison nearer to us than any
of the fixed stars are. And yet all these celestial objects appear equally distant from us. Therefore, if we imagine a large hollow sphere of glass to have as many bright studs fixed to its inside, as there are stars visible in the heaven, and these studs to be of different magnitudes, and placed at the same angular distances from each other as the stars are; the sphere will be a true representation of the starry heaven, to an eye supposed to be in its centre, and viewing it all around. And if a small globe, with a map of the earth upon it, be placed on an axis in the centre of this starry sphere, and the sphere be made to turn round on this axis, it will represent the apparent motion of the heavens round the earth.
If a great circle be so drawn upon this sphere, as to divide it into two equal parts or hemispheres, and the plane of the circle be perpendicular to the axis of the sphere, this circle will represent the equinoctial, which divides the heaven into two equal parts, called the northern and the southern hemispheres; and every point of that circle will be equally distant from the poles, or ends of the axis in the sphere. That pole which is in the middle of the