INTRODUCTION, 17 



Prob. 9. To know by the Globe what o'Clockit is in any Part of 

 the World at any Time , provided you know the Hour of the Day 

 where you are at the same Time. 



Bring the place in which you are to the brazen r \ -p a 



meridian, the pole being raised (c) according to its ^ ^ 

 latitude, and set the index of the horary circle to the hour of the 

 day at that time. Then bring the desired place to the brazen me- 

 ridian, and the index will point out the hour at that place. 



Prob. 10. A Place being given in the Torrid Zone, to find the two 

 Days of the Year in which the Sun shall be vertical to the same. 



Bring the given place to the brazen meridian, and mark what 

 degree of latitude is exactly above it. Move the globe round, and 

 observe the two points of the ecliptic that pass through the said 

 degree of latitude. Find upon the wooden horizon (or by proper 

 tables of the sun's annual motion) on what days he passes through 

 the aforesaid points of the ecliptic ; for those are the days required, 

 in which the sun is vertical to the given place. 



Prob. II, The Month and the Day being given, to find by the 

 Globe those Places of the Northern Frigid Zone, where the Sun 

 begi?is then to shine constantly without setting ; as also those 

 Places of the Southern Frigid Zone, where he then begins to be- 

 totally absent. 



The day given (which must be always one of those either be- 

 tween the vernal equinox and the summer solstice, or between the 

 autumnal equinox and the winter solstice) find (d) the ,» p 

 sun's place in the ecliptic, and, marking the same, ^ ^ 

 bring it to the brazen meridian, and reckon the like number of de = 

 grees from the north pole towards the equator, as there is between 

 the equator and the sun's place in the ecliptic, making a mark 

 where the reckoning ends. Then turn the globe round, and all the 

 places passing under the said mark are those in which the sun be- 

 gins to shine constantly without setting, upon the given day. For 

 solution of the latter part of the problem, set off the same dis- 

 tance from the south pole upon the brazen meridian towards the 

 equator, as was in the former case set off from the north ; then 

 marking as before, and turning the globe round, all places passing 

 under the mark are those where the sun begins his total disappear- 

 ance from the given day. 



Prob. 12. A Place being given in either of the Frigid Zones, to 

 find by the Globe what number of Days the Sun constantly shines 

 upon the said Place, and what Days he is absent, as also the first 

 and last Day of his Appearance . 



Bring the given place to the brazen meridian, and observing its 

 latitude (a) elevate the globe accordingly ; count ( \ p 

 the same number of degrees upon the meridian ^ ° ' * 

 from each side of the equator as the place is distant from the pole ; 

 and making marks where the reckonings end, turn the globe, and 

 carefully observe what two degrees of the ecliptic pass exactly un- 

 der the two points marked on the meridian j first for the northern 



Vol. I. D 



