48 INTRODUCTION. 



arch of the circle, namely, that comprehended between the two de- 

 grees marked, which, being reduced to time, will give the number 

 of days that the sun constantly shines above the horizon of the giv- 

 en place ; and the opposite arch of the said circle will, in like 

 manner, give the number of days in which he is totally absent, and 

 also will point out which days those are. And in the intervals he 

 daily will rise and set.* 



Prob. IS. The Month and Day being given, to find those Places 

 on the Globe, to which the Sun, when on the Meridian, shall be ver- 

 tical on that Day. 



, ,. p - The sun's place in the ecliptic being found (b) 



* ' ' bring the same to the brazen meridian, on which 



make a small mark exactly above the sun's place. Then turn the 

 globe ; and those places which have the sun vertical in the meri- 

 dian, will successively pass under the said mark. 



Prob. 14. The Month and Day being give?i, to find ufion what 

 Point of the Compass the Sun then rises and sets in any Place. 



Elevate the pole according to the latitude of the place, and, find- 

 ing the sun's place in the ecliptic at the given time, bring the 

 same to the eastern side of the horizon, and it will show the point 

 of the compass upon which he then rises. By turning the globe 

 till his place coincides with the western side of the horizon, you 

 may also see upon that circle the exact point of his setting. 



Prob. 15. To know by the Globe the Length of the longest and 

 shortest Days and Mights in any Part of the World. 



Elevate the pole according to the latitude of the given place, 

 and bring the first degree of Cancer, if in the northern, or Capri- 

 corn, if in the southern hemisphere, to the eastern side of the ho<- 

 rizon. Then, setting the index of the horary circle at noon, turn 

 the globe about till the sign of Cancer touches the western side of 

 the horizon, and observe upon the horary circle the number of 

 hours between the index and the upper figure of XII, reckoning 

 them according to the motion of the index ; for that is the length 

 of the longest day, the complement of which to 24 hours is the ex- 

 tent of the shortest night. The shortest day and longest night are 

 only the reverse of the former. 



Prob. 16. The Hour of the Day being given at any Place, to find 

 those Places of the Earth where it is either Noon or Midnight, or 

 any other particular Hour, at the same time. 



Bring the given place to the brazen meridian, and set the index 

 of the horary circle at the hour of the day in that place. Then 

 turn the globe till the index points at the upper figure of XII, and 

 observe what places are exactly under the upper semicircle of the 

 brazen meridian ; for in them it is midday at the time given. 

 Which done, turn the globe- till the index points at the lower fi- 

 gure of XII, and whatever places are then in the lower semicircle 

 of the meridian, in them it is midnight at the given time. After 

 the same manner we may find those places that have any other 



