EQUATOR, ETC. 



being the revolving stage by which he is carried round, so as to 

 view in succession the spectacle which surrounds him. 



These appearances vary with the position assumed by the observer 

 on this revolving stage ; or, in other words, upon his situation on 

 the earth, as will presently appear. 



16. That diameter upon which it is necessary to suppose the 

 earth to revolve in order to explain the phenomena is that which 

 passes through the terrestrial poles. 



17. If the globe of the earth be imagined to be cut by a plane 

 passing through its centre at right angles to its axis, such a plane 

 will meet the surface in a circle, which will divide it into two 

 hemispheres, at the summits of which the poles are situate. This 

 circle is called the TERRESTRIAL EQUATOR. 



18. That hemisphere which includes the continent of Europe is 

 called the XOETHEEX HEMISPHERE, and the pole which it includes 

 is called the XOETHEEX TEEEESTEIAL POLE ; the other hemisphere 

 being the SOUTHEEX HEMISPHERE, and including the SOUTHERN 



TEEEESTEIAL POLE. 



19. If the surface of the earth be imagined to be intersected 

 by planes passing through its axis, they will meet the surface 

 in circles which, passing through the poles, will be at right 

 angles to the equator. These circles are called TERRESTRIAL 

 MEEIDIAXS, and will be seen delineated on any ordinary terrestrial 

 globe. 



These observations will be more clearly comprehended by 

 reference to fig. 2, in which x is the north, and s the south pole of 

 the earth, and & Q the equator. The firmament surrounding the 

 earth is represented by the circle ncesq. The axis s x of the earth 

 being supposed to be prolonged to the heavens will meet the firma- 

 ment at n and s, the celestial north and south poles ; and in like 

 manner the plane of the terrestrial equator JE Q being continued 

 to the heavens, will meet the firmament at <z q, the celestial 

 equator. 



If an observer be stationed at o, his zenith will be at z, and his 

 horizon at h h'. As the globe revolves from west to east, the 

 heavens will be successively brought into view on the east, and 

 will disappear continually on the west. 



20. Assuming then that all the diurnal changes of appearance 

 presented by the firmament, the risings and settings of the sun, 

 moon, and stars, and their varying appearance in diiferent lati- 

 tudes, admit of being explained with equal precision and com- 

 pleteness, either by supposing the universe to revolve daily round 

 the earth, or the earth to revolve daily on its axis, the only 

 question which remains to be decided is, which of these two 

 suppositions is the more probable ? 



57 



