GLOBE. 



dcfcribc srclics c, d; tliefe v.jll be twelfth parts of tlie 

 tropics. 



6. Throiigli the degree of the equator e, corrcfpondiiig 

 to the right afcenfion of any given ftar, and the poles D 

 and E, draw an arch of the circle, and taking in the com- 

 pafTes the complement of the declination from the pole D, 

 diTcribe an arcli interfee\i]ig it in / ; this point i will be the 

 place of tlrat liar. 



7. All the liars of a conftcllation being thus laid down, 

 the figure of the conllellatiou is to be drawn according to 

 T3aycr, Hevelius, or Flamfteed. 



8. Lattly, after the fame manner are the declinations and 

 right afcenlions of each degree of the ecliptic d g to be de- 

 termined. 



9. Tlic furface of the globe thus proje&ed on a plane is 

 to be engraven on copper, to fave the trouble of doing this 

 over again for each globe. 



10. A ball, in the mean time, is to be prepared of paper, 

 plalter, fee. after the manner above dlretled, and of the 

 intended diameter of the globe : on this, by means of a 

 fcmi-circle and ilyle, is the equator to be drawn : and 

 through every gotli degree a meridian. Tlie ball thus di- 

 vided into twelve parts, correfponding to the fegments be- 

 fore projeiied, t'ley are to be cut from the printed paper, 

 and palled on the ball. 



IT. Nothing now remains but to hang the globe, as be- 

 fore, in a brazen meridian and wooden liorizon ; to which 

 may be added a quadrant of altitude H I, fig. 120. made 

 of brafs, aud divided in the fame manner as the ecliptic and 

 equator. 



If the declinations and right afcenfions of the ftars be not 

 given, but their longitudes and latitudes in lieu thereof, the 

 lurface of the globe is to be projeftcd after the fame man- 

 ner as before: except that, in this cafe, D and TLyJig. 121. 

 are the poles of the ecliptic, andyi the ecliptic itlelf ; and 

 •that the pol.ir circles and tropics, with the equator g d, and 

 the parallels thereof, are to be determined from their de- 

 clinations. 



One of the fullelt catalogues of the ftars is that of Mr. 

 Flamlleed ; wherein the right afcenlions and declinations, 

 as well as the longitudes, latitudes, &c. are every where 

 cxprefled. 



Globk, ufe of the cckjl'wl. Tlie ufe of this inftrument is 

 very cxtenfive ; there being fcarcely any thing in the fpherical 

 ailronomy but may be exhibited thereby. 



The prmcipal points are contained in the following pro- 

 blems, with their folution ; which will let the reader enough 

 into the nature and rcafon of this noble inftrument, to apply 

 it, of his own accord, in any other cafes. 



To find the right ofcmfion and decUiiat'ion cf afar, rejtre- 

 fented on the furface of the globe. — Bring the ftar to the gradu- 

 ated fide of the brazen meridian : then the number of de- 

 grees intercepted between the equator, and the point on the 

 meridian cut by the flar, gives its declination ; and the de- 

 gree of the equator which comes under the meridian, toge- 

 ther with the liar, is its right afcenfion. 



To find the longitude and latitude of a flar. — Apply the 

 centre of the quadrant of altitude over the pole of the 

 ecliptic in the iame hemifpliere with the ftar, and bring 

 its graduated edge to the ftar : the degree on the quadrant 

 cut by the ftar is its latitude, reckoned from the ecliptic ; 

 and the degree of the ecliptic cut by the quadrant its lon- 

 gitude. 



To find the fun s place in the ecliptic. — Seek the day of the 

 month in the proper calendar on the horizon, and againft 

 the day in the circle of figns is the fign and degree the fun 

 i s ill for that day ; this done, find the fame fign upon the 



ecliptic, on the furface of the globe ; this is the fuu's place- 

 for that day. 



'To find the declination of the fin. — The fun's place for the 

 day given being brought to the meridian, the degrees of 

 tlic meridian intercepted between the cquinodlial and that 

 place, are the fun's declination for that day at noon. 



To fnd the place of a pdanct, ivith its right afccnf.on and 

 declination ; its longitude and latitude for the time Icing given. — 

 Apply the centre of the quadrar.t of altitude on the pole 

 of the ecliptic (the pole, we mean, of the fame denomina- 

 tion with the latitude), and bring it to I'ne given longitude 

 in theechptic : this point is the planet's place ; and bringing 

 it to the meridian, its right afcenfion and declinatio}i will be 

 found, as already fliewn of a ftar. 



To reffify the globe, or adjufl it to the place, ijfc. fo as it 

 may r.pnfent the prefent fate or fitiiation of the heavens, — 

 ! . If the place be in north latitude, raife the north pole 

 above the horizon ; if in fouth, raife the fonth pole ; 

 till the arch intercepted between the pole and horizon 

 be equal to the given elevation of the pole. 2. Fix the 

 quadrant of altitude on the zenith, i. e. on the latitude 

 of the place. 3. By means of a compafs or meridian 

 line, place the globe in fuch a manner as that the brazen 

 meridian may be in the plane of the terreftrial meridian. 

 4. Bring the degree of the ecliptic the fun is in to the me- 

 ridian, and fet the horary index to tu'elve ; thus will the 

 globe exhibit the face of tl;e heavens for the noon of that 

 day. 5. Turn the globe till the iiidex come to any other 

 given hour : thus will it fliew the face of the heavens for 

 that time. 



To ino'zv all the flars and planets by means of the globe.— 



1. Adjuft the globe to the ftate of the heavens for that 

 time. 2. Look on the globe for fome one ftar which you 

 know, e. gr. the middlemoft ftar in the tail of the Great 

 Bear. 3. Obferve the pofitions of the other more con- 

 fpicuous ftars in the fame conftellation ; and by tranf- 

 ferring the eye from the globe to the heavens, you will 

 cafily note the fame there. 4. After the fame manner may 

 you proceed from this to the neighbouring confteUations, 

 till you have learned them all. 



If the planets be reprefented on the globe, after the man- 

 ner above defcribed, by comparing them with the neigh- 

 bouring ilars you will likewife know the planets. 



To find the funs oblique afccrfiun, his eaflern amplitude, and 

 O'z.imutb, with the time of rifng. — i. Redtify the globe for 

 the hour of twelve, and bring the fun's place to the 

 eaflern fide of the horizon : then the number of degrees, 

 intercepted between that degree of the equator now come 

 to the horizon and the beffinning- of Aries, is the fun's 

 oblique afcenfion. 2. The degrees on the horizon, in- 

 tercepted between the eaft point thereof and the point 

 wherein the fun is, is the ortive or rifing amplitude. 

 3. The hour, pointed to by ths index, is the time of the 

 fun's rifing. 4. Turning the globe till the index points 

 to the prefent hour, lay the quadrant to the fun's place: 

 the degree cut by the quadrant, in the horizon, is the fun's 

 azimuth. 



To find the fun's oblique defcenfion, "jieflern amplitude, and 

 azimuth, ivith the time of flting. — The folution of tliis 

 problem is the fame as that of the former ; excepting 

 that the fun's place muft be here brought to the weftern 

 fide of the horizon, as in the former it was to the 

 eallern. 



To fnd the length of day and night. — i. Find the time 

 of the fun's rifing, which being numbered from mid- 

 night, the double thereof gives tlie length of the night. 



2. Subtradl the length of the night from the whale day, cr 



twenty- 



