312 FERGUSON'S LECTURES. 



LECT. pl ace to the brazen meridian, and the hour index to XII 

 VIII.&TX. a t noon, turn back the globe, until the sun's place cuts 

 the quadrant of altitude again, and the index will shew 

 the hour. 



Any two points of the ecliptic which are equi-distant 

 from the beginning of Cancer or of Capricorn, will have 

 the same altitude and azimuth at the same hour, though 

 the months be different; and therefore it requires some 

 care in this problem, not to mistake both the month and 

 the day of the month ; to avoid which, observe, that from 

 the 20th of March to the 21st of June, that part of the 

 ecliptic which is between the beginning of Aries and 

 beginning of Cancer is to be used : from the 21st of June 

 to the 23d of September, between the beginning of 

 Cancer and beginning of Libra : from the 23d of Sep- 

 tember to the 21st of December, between the beginning 

 of Libra and the beginning of Capricorn ; and from the 

 21st of December to the 20th of March, between the 

 beginning of Capricorn and beginning of Aries. And 

 as one can never be at a loss to know in what quarter 

 of the year he takes the sun's altitude and azimuth, the 

 above caution with regard to the quarters of the 

 ecliptic, will keep him right as to the month and day 

 thereof. 



PROBLEM XXVI. 



To find the length of the longest day at any given place. 



If the place be on the north side of the equator, find 

 its latitude (by Prob. I.) and elevate the north pole to 

 that latitude ; then, bring the beginning of Cancer SB to 

 the brazen meridian, and set the hour index to XII at 

 noon. But if the given place be on the south side of 

 the equator, elevate the south pole to its latitude, and 

 bring the beginning of Capricorn yf to the brass meri- 

 dian, and the hour-index to XII. This done, turn the 

 globe westward, until the beginning of Cancer or Ca- 



