12 POPULAR LECTURES AND ADDRESSES. 



shore, by observation of the heavenly bodies. Look 

 at the stars, hour after hour, on a clear night, you 

 will see them all seeming to turn round one point 

 in the sky. That pivot point of the sky is called 

 the north celestial pole. You understand that you 

 are in the northern hemisphere. Any one south of 

 the equator observing the stars similarly, would 

 perceive in the southern sky another point, the 

 south celestial pole, round which the stars there 

 would seem to turn. 



12. The north and south terrestrial poles are 

 those points on the earth's surface where the north 

 celestial pole and the south celestial pole are exactly 

 overhead, that is to say, they are the two points 

 of the earth's surface whose verticals are precisely 

 parallel to the axis of the earth's rotation. It is by 

 finding the pivot point of the stars vertically over 

 his head, that Captain Nares will recognise the 

 north pole when he comes to it. 



13. There is no distinctly visible star exactly at 

 the north celestial pole ; but there is one star of the 

 second magnitude which nowadays is at a dis- 

 tance of i 2 1' from it. This star is therefore now 



