190S] Proceedings of N. C. Academy of Science 
-17 
2. With central ball representing the earth, to it is securely 
attached the horizon plane and vertical circles for, say, an 
observer in latitude 36° north. Clamping the celestial circles in 
fixed position, the earth-ball with its horizon system is easily 
rotated eastward, showing sun-rise and sun -set and the rising and 
setting of moon, stars and planets — these objects being suitably 
indicated , for any given date, in their apparent places on the 
celestial frame-works. Or clamping the horizon in its seemingly 
fixed position, the celestial circles and objects in place are readily 
rotated westward in accord with familiar appearances. 
3. Altering in latitude the attachment of the horizon plane to 
the earth-ball, the apparatus shows in turn the reality and the 
appearances to an observer at the equator; or, again, to an obser- 
ver at the north pole during his six-months’ day and his six- 
months’ night. 
4. Some circles and the celestial objects may be variously 
adjusted and placed for an indefinite number of of astronomical 
illustrations. 
5. Selected circles and objects may be duly disposed to facili- 
tate apprehension and solution of numerous celestial problems— 
and, if problems also in geodesy and navigation which involve 
the ever-recurring “astronomical triangle”. 
QUESTION AND ANSWER. 
Are the earth and sun at the centre? They are not held to be 
at the centre of the myriad stars of the visible universe. They 
are at the centre of the “celestial sphere”, conceived of as every- 
where equidistant from the earth ; so distant as to be beyond the 
remotest star. Its quasi reality is that vast shell of void space 
beyond the stars, upon which as a dark, spherical background all 
the stars appear fixed as viewed from the central earth. So 
measureless its remoteness, any point within the earth’s com- 
paratively little orbit, including the sun, is virtually its centre. 
■ This “celestial sphere”, with sun or earth as centre, is the 
basis of practical astronomy. Its standard circles in miniature 
are part of our armillary sphere. 
