TO FIND THE LATITUDE. 



the distance from Z to n, we can infer at once the distance from 

 P to E, and hence can discover the latitude of the place. 



It is apparent, theii, if we can observe the distance of the 

 zenith of any place from the celestial pole, that will give us the 

 distance in degrees of the place itself from the terrestrial pole, 

 and by subtracting that from 90, we shall obtain the distance of 

 the place itself from the equator, or what is the same, its lati- 

 tude. As an example of this, let us suppose that in' measuring 



Fig. 2. 



\ 



the distance from Z to n we find it to be 50, we infer, therefore, 

 that since the distance of the zenith from the pole is 50, the dis- 

 tance of the place from the terrestrial pole is also 50. 



But since the terrestrial pole is 90 from the equator, it 

 follows that the distance of the place from the equator must be 

 40, and it is north or south, according as the zenith of the place 

 is in the northern or southern hemsiphere of the firmament. 



Thus, then, it appears that the latitude of a place can always 

 be found, provided we can measure the distance of its zenith 

 from the celestial pole ; and this, of course, can always be done 

 by the use of proper instruments, provided that the zenith and 

 the pole can be distinctly seen. Now the direction of the zenith 

 can always be determined by the plumb line ; but although the 



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