RULES FOR FINDING THE LATITUDE. 369 



If you observe the sun beneath the pole, subtract his 

 declination from 90 degrees, and add the remainder to 

 his altitude ; and the sum is the latitude. 



EXAMPLE. 



Sun's declination 20 30 



Subtract from 90 



Remains 69 30> 



Sun's altitude below the pole . . . 10 20) add 



The sum is the latitude . . , . . 79 50 



Which is north or south, according as the sun's de- 

 clination is north or south : for when the sun has south 

 declination, he is never seen below the north pole ; nor 

 is he ever seen below the south pole, when his declina- 

 tion is north. 



7. If the sun be in the zenith at noon, and at the same 

 time has no declination, you are then under the equi- 

 noctial, and so have no latitude. 



8. If the sun be in the zenith at noon, and has decli- 

 nation, the declination is equal to the latitude, north or 

 south. These tvyp cases are so plain, that they require 

 no examples. 1 " 



Xote 112. The method here detailed is subject to any error which 

 n;ay exist in the tables of the declination of the sun. A series of 

 altitudes of the pole-star observed constantly on the meridian both 

 above and below the pole appears to offer the method least liable to 

 error. Ferguson objects to this method, because one of the observa- 

 tions must be made in the day time, but it is well known that the 

 stars which are above the horizon, are visible- at all times, 

 through a telescope, even of moderate power. Several corrections are 

 necessary in each of these methods, if accuracy is required, as for re- 

 fraction, &c. 



24. i; i, 



