THE USE OP THE TERRESTRIAL GLOBE. 303 



zone pass directly under that mark ; for they are the LECT. 



. , VIIL&IX. 



places required. 



The like may be done for the south frigid zone, from 

 the 23d of September to the 21st of March, during 

 which time the sun shines constantly on the south 

 pole. 



PROBLEM XIV. 



To find the place over ichich the sun is vertical, at any hour 

 of a given day. 



Having found the sun's declination for the given day 

 (by Prob. IX.) mark it with chalk on the brazen meri- 

 dian ; then bring the place where you are (suppose Lon- 

 don) to the brazen meridian, and set the index to the 

 given hour ; which done, turn the globe on its axis, until 

 the index points to XII at noon ; and the place on the 

 globe, which is then directly under the point of the sun's 

 declination marked upon the meridian, has the sun that 

 moment in the zenith, or directly overhead. 



PROBLEM XV. 



The day and hour at any place being given, to jind ail 

 those places where the sun is then rising, or setting, or on 

 the meridian: consequently, all those places which me 

 enlightened at that time, and those which are in the 

 dark. 



This problem cannot be solved by any globe fitted up 

 in the common way, with the hour circle fixed upon 

 the brass meridian ; unless the sun be on or near some 

 of the tropics on the given day. But by a globe fitted 

 up according to Mr. Joseph Harris's invention (already 

 mentioned) where the hour-circle lies on the surface of 

 the globe, below the meridian, it may be solved for any 

 day in the year, according to his method ; which is as 

 follows. 



