366 FERGUSON'S LECTURES. 



LECT 



Tojind the latitude of any place by observation. 



The latitude of any place is equal to the elevation of 

 the pole above the horizon of that place. Therefore it 

 is plain, that if a star was fixed in the pole, there would 

 be nothing required to find the latitude, but to take the 

 altitude of that star with a good instrument. But 

 although there is no star in the pole, yet the latitude 

 may be found by taking the greatest and least altitude of 

 any star that never sets : for if half the difference between 

 these altitudes be added to the least altitude, or sub- 

 tracted, from the greatest, the sum or remainder will 

 be equal to the altitude of the pole at the place of obser- 

 vation. 



But because the length of the night must be more 

 than 12 hours, in order to have two sucli observations ; 

 the sun's meridian altitude and declination are generally 

 made use of for finding the latitude, by means of its 

 complement, which is jqual to the elevation of the equi- 

 noctial above the horizon ; and if this complement be 

 subtracted from 90 degrees, the remainder will be the 

 latitude ; concerning which, I think, the following rules 

 take in all the various cases. 



1. If the sun has north declination, and is on the 

 meridian, and to the south of your place, subtract the 

 declination from the meridian altitude (taken by a good 

 quadrant) and the remainder is the height of the equi- 

 noctial or complement of the latitude north. 



EXAMPLE. 



c cThe sun's meridian altitude 42^ 2T;' Soulh 



And his declination, subt. 10 15 North 



Rem. the complement of the lat. . . 32 5 

 Which subtract from 90 



And the remainder is the latitude 57 55 North 



