68 I'RACTirAL EXERCISES IN GEOGRAPHY 



Star circles remains fixed wherever the observer goes and liowever 

 much his horizon changes from the position that it had at the pole. 

 As the observer moves along any meridian toward the e<iuator ids 

 horizon must progressively tilt from the position that it had at the 

 pole ; and the amount of tilting may be measured by tlie angle l)e- 

 tween the tilted horizon and any one of the star or sun circles. This 

 is, in essence, the method of Eudoxus, already referred to. A third 

 way from pole to equator the angle would be 30°; half way, 45° ; 

 two-thirds way, 60° ; at the equator, 90°. The rotation of the earth 

 is tiius of great assistance in determining the relative positions of 

 places. Bearing these principles in mind, let the sun-circle be de- 

 termined and represented l)y a series of stakes in a school yard, as in 

 fii,Muv 1. Stand about .']0 feet to one side of the stakes, in such a posi- 



Vu.\ UK 1 



tion that the tops of all of them fall into a slanting, straight line when 

 the observer's head is lowered to the height of the highest stake ; 

 estimate or measure the angle, CAD, by which the horizon is de- 

 pressed beneath this slanting line* ; and as the angle thus deter- 

 mined is to 90°, so is the distance from the pole (measured along a 

 meridian from the jiole to the observer) to the entire quadrant of the 

 meridian from pole to equator. Latitude is counted from thee(iuator 

 toward the pole; it will therefore be the complement of the angle 

 just measured. It should be noted that latitude may l)e thus de- 

 termined at any time of year and without knowledge of the sun's 

 angular distance from the sky equator (declination). 



* The pivot docs not lie iu the piano of the suu-eirele, and the slanting line does not measure 

 the sun's noon altitude, except at the equinoxes. The noon altitude of the sun varies tiirough 

 the year, but the slanting line (the slant of the plane of the sun-eircle) is constant through the 

 year, whatever the declination of the sun. In all this method of determining latitu<le it is 

 assumed that the motion of the sun in decli)i.itii.n in a single day will nut lie clctcoted l.y the 

 rough methods of record here employed. 



