GLOBE. 



arch contained between it and the hori- 

 zon will give the degrees of altitude re- 

 quired. 



7. *' To find the sun's azimuth for any 

 hour of the day." Every thing before 

 done as in the last problem, the arch of 

 the horizon contained between the north 

 point and that where the quadrant of al- 

 titude cuts it, is the azimuth east or west, 

 as required. 



8. " To find the time when the sun ri- 

 ses or sets." Find the sun's place for the 

 given day ; bring it to the meridian, and 

 set the hour-hand to xii; then turn the 

 globe till the sun's place touches the 

 east part of the horizon, the index will 

 shew the hour of its rising ; after that 

 turn the globe to the west part of the ho- 

 rizon, and the index will shew the time 

 of its setting for the given day. 



9. " To find the length of any given 

 day or night " This is easily known by 

 taking the number of hours between the 

 rising and setting of the sun for the 

 length of the day ; and the residue, to 

 twenty -four, for the length of the night. 



10. " To find the hour of the day, hav- 

 ing the sun's altitude given.'* Bring the 

 sun's place to the meridian, and set the 

 hour-hand to xii ; then turn the globe in 

 such a manner, that the sun's place may 

 move along by the quadrant of altitude 

 (fixed in the zenith) till it touches the 

 degree of the given altitude, where stop 

 it, and the index will shew on the horary 

 circle the hour required. 



11. " To find the place of the moon, or 

 any planet, for any given day." Take 

 White's ephemeris, and against the given 

 day of the month you will find the degree 

 and minute of the sign which the moon 

 or planet possesses at noon, under the ti- 

 tle of geocentric motions. The degree 

 thus found being marked, in the ecliptic 

 on the globe by a small mark, or other- 

 wise, you may then proceed to find the 

 declination, right ascension, latitude, lon- 

 gitude, altitude, azimuth, rising, south- 

 ing, setting, &c. in the same manner as 

 has been shewn for the sun. 



12. " To explain the phenomena of the 

 harvest-moon." In order to this we need 

 only consider* that when the sun is in the 

 beginning of Aries, the full moon on that 

 day must be in the beginning of Libra ; 

 and since when the sun sets, or moon ri- 

 ses, on that day, those equinoxal points 

 will be in the horizon, and the ecliptic 

 will then be least of all inclined thereto, 

 the part or arch which the moon describes 

 in one day, viz. 13, will take up about 

 an hour and a quarter ascending above 



the horizon ; and therefore, so long will 

 be the time after sunset, the next night, 

 before the moon will rise. But at the 

 opposite time of the year, when the sun 

 is in the. autumnal, and the full moon in 

 the vernal equinox, the ecliptic will, when 

 the sun is setting, have the greatest incli- 

 nation to the horizon ; and therefore, 

 13 will in this case soon ascend, viz. in 

 about a quarter of an hour , and so long 

 after sun-set will the moon rise the next 

 day after the full : whence, at this time of 

 the year, there is much more moon-light 

 than in the spring ; and hence this au- 

 tumnal full moon came to be called the 

 harvest-moon, the hunter's or shepherd's 

 moon : all which may be clearly shewn 

 on the globe. 



13. " To represent the face of the star- 

 ry firmament for any given hour of the 

 night." Rectify the globe and turn it 

 about, till the index points to the given 

 hour; then will all the upper hemisphere 

 of the globe represent the visible half of 

 the heavens, and all the stars on the 

 globe will be in such situations as exactly 

 correspond to those in the heavens ; 

 which may therefore be easily found, 

 as will be shewn in the sixteenth pro- 

 blem. 



14. " To find the hour when any 

 known star will rise, or come upon the 

 meredian." Rectify the globe, and set 

 the index to xii ; then turn the globe till 

 the star comes to the horizon or meri- 

 dian, and the index will show the hour 

 required. 



15. " To find at what time of the year 

 any given star will be on the meridian at 

 xii at night." Bring the star to the meri- 

 dian, and observe what degree of the 

 ecliptic is on the north meridian under 

 the horizon ; then find in the calendar on 

 the horizon the day of the year against 

 that degree, and it will be the day re- 

 quired. 



16. To find any particular star." 

 First find its altitude in the heavens by a 

 quadrant, and the point of the compass it 

 bears on ; then, the globe being recti- 

 fied, and the index turned to the given 

 hour, if the quadrant of altitude be fixed 

 on the zenith, and laid towards the point 

 of the compass on which the star was ob- 

 served, the star required will be found at 

 the same degree of altitude on the said 

 quadrant, as it was by observation in the 

 heavens. 



The invention of globes is of great an- 

 tiquity. Some allusions to the celestial 

 globe may be found as early as Hippar- 

 chus's time, in the writings of Pliny and 



