2 BROWN : 



the earth's radius — about four thousand miles, a quantity 

 which wholly vanishes in face of the other distances which 

 are under contemplation. 



As already hinted, it has hitherto been found impossible to 

 reach the neighborhood of the terrestrial pole ; and, even had 

 this extreme latitude been attained, it would be very difficult, 

 with the small, portable instruments in use, to locate precisely 

 the point on the surface of the ground about which all others 

 revolve. But there is nothing to prevent our imagining a 

 victory over all these obstacles ; and the idea entertained by 

 some men of science that owing to causes, surmised but not 

 perfectly understood, the pole of the earth undergoes a small 

 displacement so as to affect the records of latitude, is not yet 

 sufficiently rooted and grounded in general faith to detain us 

 at this stage of progress. 



The observer, then, at the pole of the earth has the pole of 

 the heavens directly above his head, and his horizon is the 

 equator of the heavens. All the fixed stars of his hemisphere 

 are, theoretically, visible to the polar observer ; not practi- 

 cally ; for there are refraction, twilight and obscured horizon 

 to take into account. ' These fixed stars constantly move 

 round him in circles parallel to the horizon-equator. He 

 never sees the stars of the other hemisphere. 



The pole of the ecliptic is at 23° 30' from the zenith- 

 pole, and revolves round it as any other point does. The 

 equinoxes are, of course, in the horizon -equator, and can 

 be only vaguely pointed out by reference to stars. The vernal 

 equinox is in the constellation Pisces ; the autumnal in the 

 constellation \^irgo. These points revolve around the pole as 

 the others do. 



It will be noticed that the equinoxes are spokeii of some- 

 times as points, sometimes as seasons of the year. Perhaps it 

 would not be amiss if the language had means of distinguish- 

 ing for us, as we go along, between the two ideas ; but, after 

 all, it matters very little. There is no great difficulty in 

 remembering that the seasons called the equinoxes come 



