GLOBE. 



483 



iwiith, r.nd sun's place Rule. For the latitude: 

 elevate the pole above the horizon according to the 

 latitude of the place, and the globe will be adjusted 

 for the latitude. For the zenith : screw the quadrant 

 of altitude on the meridian, at the given degree 

 of latitude, counting from the equator towards the 

 elevated pole, and the globe will be rectified for the 

 zenith. For the sun's place :* find the sun's place 

 on the horizon, and then bring the place which 

 corresponds thereto, found on the ecliptic, to the 

 meridian, and set the hour index to twelve at noon ; 

 then will the glol>e be adjusted for the sun's place. 



Problem 9. To find the sun's declination. Rule. 

 Bring the sun's place for the given day to the brass 

 meridian, nnd the degree over it will be the decli- 

 nation sought ; or bring the day of the month marked 

 on the analemma, to the brass meridian, and the 

 degree over it will be the declination, as before. 1. 

 The declination of the sun being its distance north 

 or south from the equator, this Problem is exactly 

 thfi same as that for finding the latitude of a place. 

 2. The greatest north declination, 23 28', is when 

 the sun enters Cancer, June 21st. The greatest 

 south declination, 23 28', is when it enters Capri- 

 corn, December 21st. 



Problem 10. To find the sun's rising and setting 

 for a given day, at a given place. Rule. Elevate 

 the globe for the sun's declination ; bring the given 

 place to the meridian ; set the index to twelve, and 

 turn the globe till the given place comes to the 

 eastern edge of the horizon ; then the index will 

 show the time of the sun's rising. Next bring the 

 given place to the western edge of the horizon, and 

 the index will show the hour at which the sun sets. 

 If the hour circle have a double row of figures, make 

 use of that which increases towards the E. ; the 

 sun's rising and setting may then be found at once, 

 by bringing the place only to the eastern edge of the 

 horizon ; for the index will point on one row to the 

 hour of rising, and on the other (that which increases 

 towards the \V.) to the hour of setting. By this 

 problem may be found the length of the day and night, 

 Double the time of the sun's setting, and it will give 

 the length of the day. Double the time of the sun's 

 rising, and it will give the length of the night. 



Problem 11. To find all those places in the torrid 

 zone to which the sun is vertical on a given day. Rule. 

 Find the sun's place for the given day, bring it to 

 the meridian, mark the declination, and turn the 

 globe round, when all those places which pass under 

 that mark of the meridian, will have the sun vertical 

 on the given day. By the analemma, bring the day 

 of the month, marked upon the analemma, to the 

 brazen meridian, and mark the declination ; then the 

 places will be found as above. 



Problem 12. The day, hour and place being given, 

 to find at what places of the earth the sun is then rising 

 and setting ; where it is noon and midnight. Rule. 

 Find the place to which the sun is vertical at the 

 given hour, bring the same to the meridian, and 

 adjust the globe to a latitude equal to the sun's de- 

 clination. Then, to all places under the western side 

 of the horizon, the sun is rising ; to those above the 

 eastern horizon, the sun is setting ; to all those under 

 the upper half of the brazen meridian, it is noon ; and 

 to all those under the lower half, it is midnight. 



Problem 13. To show, by the globe, the cause of 

 day and night. The sun shines upon the earth, and 

 illuminates that half only which is turned towards 

 him : the other half is in darkness. But, as the earth 

 turns round on its axis, from W. to E., once in twen- 

 ty-four hours, every meridian upon the earth, will, in 



Find the day of the month on the horizon, and against 

 it in the adjoining circle, will be found the sign and degree 

 in which the sun in for that day. 



that time, successively be presented to the sun, and 

 be deprived of its light again. Rule. Elevate thf 

 globe for the sun's declination, so that the sun may 

 be in the zenith, and the horizon will be the termina- 

 tor, or boundary circle, of light and darkness : that 

 half of the earth above the horizon enjoys light; that 

 half below the horizon will be in darkness. Put a 

 patch upon the globe, to represent any place, turn the 

 globe round from W. to E., and when the place comes 

 to the western side of the horizon, the sun appears to 

 the inhabitants of that place to be rising in the E. ; 

 but it is more properly the inhabitants of that place 

 rising in the W. Go on to turn the globe round, and 

 the place will ascend higher towards the meridian in 

 a contrary direction. When the place has arrived 

 at the meridian, it will then be noon there, and the 

 sun will be at his greatest altitude for that day. Con- 

 tinue to turn the globe, and the place will gradually 

 recede from the meridian, and decline towards the 

 eastern horizon, which will cause the appearance of 

 the sun descending towards the W. When the place 

 has arrived at the eastern horizon, as it is then going 

 below the boundary of light and darkness, the sun 

 will appear to be setting in the W. The place, being 

 now at a greater distance than 90 from that point 

 where the sun is vertical, is deprived of his light, and 

 continues in darkness till, by the revolution of the 

 earth, it arrives again at the western horizon,when the 

 sun will appear to rise as before. The sun is obviously 

 rising, at the same time, to all places on the western 

 side of the horizon, and setting, at the same time, to 

 all places on the eastern side of the horizon. 



Problem 14.. To show, by the globe, the cause of 

 the variety of the seasons. When the sun is in the 

 equator, the horizon will represent the terminator, or 

 boundary circle of light and darkness ; and, the poles 

 being made to coincide with it, we shall have a fail- 

 representation of the two seasons, spring and autumn; 

 for, its rays then extending 90 every way from the 

 vertical point, both poles will be illuminated. When 

 the sun is in the tropic of Cancer, being 23 farther to 

 the N. than before, his rays will extend 23^ beyond 

 the north pole, on the opposite meridian: they will not, 

 however, reach the south pole by 23^; they will ex- 

 tend to the antarctic only, being 90 distant from the 

 tropic of Cancer : hence, to make the horizon the 

 terminator in this case, the north pole must be ele- 

 vated 23^ above the horizon, and we shall have the 

 summer season to Europeans. When the sun is in 

 the tropic of Capricorn, the reverse of this takes 

 place ; for the sun's rays then extend 23 beyond 

 the south pole, on the opposite meridian, and only as 

 far north as the arctic circle : hence, to make the 

 horizon the terminator in this case, the south pole 

 must be elevated 23^ above the horizon, and we 

 shall have the winter season to Europeans. 



The problems thus given are only to be considered 

 as specimens of what may be performed. On the 

 terrestrial globe, Butler describes fifty-seven ; while, 

 on the celestial sphere, the number and variety are 

 still much greater. It is said that Anaximander of 

 Miletus, a pupil of Thales, who flourished about the 

 fiftieth Olympiad (580 B. C.), invented the terres- 

 trial globe. That Ptolemy had an artificial globe, 

 with the universal meridian, appears from his Al- 

 magest. The ancients likewise made celestial globes. 

 Among the moderns, several have distinguished them- 

 selves in the construction of globes. The Vene- 

 tian Coronelli, (who died 1718) prepared, in 1683, 

 with the assistance of Claudius Molinet, and other 

 Parisian artists, a terrestrial globe, for Louis XIV. 

 twelve Parisian feet in diameter. The same artist 

 made a celestial globe of the same size. Funk, in 

 Leipsic, published, in 1780, models in the form of 

 cones (coniglobia), as substitutes for celestial globes. 



2H? 



