GLOBE. 



twenty-four hours, and the remainder is the length of tlie 

 day. 



To Jind the r'ljmg, fitting and culminating of a Jlar ; its 

 continuance above the horizon for any place and day ; toge- 

 ther ivith its oblique afcenjion and defcenjion, and its eajlern 

 and wejlern amplitude and azimuth. — i. Adjufl the globe 

 lo the ftate of the heavens at twelve o'clock that day. 



2. Bring the ftar to the caflern fide of the horizon : 

 thus will the weftern amplitude and azimuth, and time 

 of riling, be found, as already taught of the fun. 



3. Bring the fame ftar to the weftern fide of the hori- 

 zon : thus will the weftern amplitude and azimuth, and 

 the time of fetting, be found. 4. The time of rifing, 

 fubtraftcd from that of fetting, leaves the continuance 

 ■of the ftar above the horizon. 5. This continuance 

 above the horizon, fubtradled from twenty-four hours, 

 leaves the time of its continuance below the horizon. 

 6. Laftly, the hour to which the index points, when tlie 

 ftar is brought to the meridian, gives the time of its cul- 

 mination. 



To find the altitude of the fun, or flar, for any given hour 

 of the day or night. — I. Adjuft the globe to the pofttion 

 of the heavens, and turn it till the index point at the 

 given hour. 2. Fix on the quadrant of altitude, at 

 90 degrees from the horizon, and bring it to the fun's or 

 liar's place ; the degrees of the quadrant, intercepted 

 between the horizon and the fun or ftar, is the altitude 

 required. 



The altitud; of the fun by day, or of a Jlar by night, being 

 given, to find the time of that day or night. — I. Reftify the 

 globe as in the preceding problem. 2. Turn the globe 

 and quadrant, till fuch time as the ftar, or degree of the 

 ecliptic the fun is in, cut the quadrant in the given de- 

 gree of altitude ; then does the index point at the hour 

 fought. 



The azimuth ofti'e fun or a Jlar given, to find the time of 

 the day or night. — Reftify the globe, and bring the quad- 

 rant to the given azimuth in the horizon ; turn the globe, 

 till the ftar come to the fame : then will the index (liew 

 the time. 



To Jind the interval of time between the rifmgs of tivo flars, 

 or the culminations. — I. Raife the pole of the globe fo 

 many degrees above the horizon, as is the elevation of 

 the pole of the place. 2. Bring the iirft ftar to the ho- 

 rizon, and obferve the time the index points to. 3. The 

 fame do by the other ftar : then fubtrafting the former 

 time from the latter, the remainder is the interval between 

 the rifmgs. 



After the like manner is the interval between two cul- 

 minations found, by bringing both ftars to the meridian. 



The day of the month being given, to Jind luhen any Jlar audi 

 come to the meridian. — Reftify for the fun'r. place ; turn the 

 globe till the given liar comes to the meridian ; then the 

 index will point to the time fought. 



To Jind when any given Jlar will come to the meridian, at any 

 given hour oj the night. — Bring the given liar to the me- 

 ridian ; fet the index to twelve at noon ; then turn the 

 globe eaftward, till the index points to an hour as far 

 diftant in the forenoon from twelve as the given hour is 

 in the afternoon, obferve the degree of the ecliptic then at the 

 meridian, over-againft ^vhich degree, in the calendar, is the 

 day of the month, when the given ftar will be upon the 

 meridian at the given hour. 



By obfervution of a flar upon the meridian, to find the hour 



of the night Reftify for the latitude and the fun's place ; 



bring the given ftar to the meridian, and the index will 

 ftew the hour of the night. 



Vol. XVI, 



To find the beginning and ending of the crepufculum or In:. 

 l'Sht~-i Rectify the globe, and fet the index to the 

 tweltth hour, the fun's place being in tlie mcridiaa. 

 2 Note the fun's place, and turn the globe weft ward, at 

 alfo the quadrant of altitude, till the point oppofitc the 

 fun's place cut the quadrant of altitude in the eighteenth 

 degree above the horizon : the index will then ftiew the time 

 when the twilight commences in the morning. 3. Taking 

 the point oppofile to the fun, bring it to the eallern hemi- 

 fphere, and turn it, till it meet with the quadrant of altitude 

 in the eighteenth d-gree : then will the index Ihew the tiror 

 when tlie twih'ght ends. 



Given the fun's longitude and the obliquity of the ecripiic, la 



Jind the fun's right afcenjion and declination Find the fun's 



longitude or place on the ecliptic, and bring it to t.Sf 

 brazen meridian. Then the arc of the.-quator, between th- 

 iirft point of Aries and the brazen meridian, (hews the fuc's 

 right afccnfion ; and the arc of the brazen meridian between 

 the equator and the ecliptic (liews the declination. 



Given the obliquity nj the ecliptic and the fun's declinaiion, la 

 Jind the fin's longitude and right afcenjion. — Mark the fun's 

 declination on the brazen meridian, and turn the globe till 

 the ecliptic comes under the figure ; then will the diftance 

 from the meridian to the firft point of Aries fhew the fun's 

 longitude on the ecliptic, and its right afcenfion on the 

 equator. 



Given the obliquity oJ the ecliptic and the fun's right afcenjion. 

 required the fun's declination and hmgititde. — Bring the fun's 

 right afcenfion in the equator to the brazen meridian, then 

 will the intercepted arc of the ecliptic to Aries fliew the fun's 

 longitude ; and the arc of the meridian, that is between the 

 fun's right afcenfion and longitude, will fhew the declination. 

 To find on what day the fun begins tofli'ine conjlantly at any 

 g'lv'en place in either oJ the frigid zones, and how long he con- 

 tinues to Jhine without interm'iffion at the Jame place . — Subtraft 

 the latitude of the given place from 90 ', and find in what 

 two days of the year the fun's declination isexaftly equal to 

 the remainder, and of the fame kind as the latitude of the 

 place ; then on the firft of thofe days in the fpring quarter, 

 the fun ccafes to fet at the given place, and (hines withou^ 

 intermiftion there till he arrives at another point of the 

 ecliptic, as many degrees on the otlitr fide of the fummer 

 folftice, when his declination is again equal to the comple- 

 ment of the latitude : the fpace of time between thofe two 

 days is the length or duration of the longcft day. 



To Jind the latitude of thofe places in the north frigid zone, 

 where the fun begins to Jhine conjlantly on any day between tlie 

 vernal equinox and the fummer f-jl/lice, or in the fouth frigid zme 

 on any d.iy between the autumnal equinox and the winter foljlice. 

 — Find the fun's declination for the given day ; fubtraft it 

 from 90', and the remainder will be the latitude of thofe 

 places : where the fun begins to (hine conftantly the latitude 

 is of the fame kind as the fun's declination. 



To determine under what latitude ttvo given fiars rife or fet at 

 the fame injiavt. — Bring one of t!ie ftars to tl;e horizon, and, 

 keeping it there, raife or deprefs the pole till the other is on 

 the horizon at the fame time, obferving whetlier this is 

 effl'tled on the ealt or weft pofition of the horizon ; then 

 the degree of tlie meridian, inttrfeCled by the horizon, will 

 be the latitude of the place required. 



To Jin J at ri'hat place a given Jlar is vertical at any given hour 

 at London ; e. g. at what place will Capella be ifrtical 

 the 2d of M.irch at 10 o'clock afternoon, at London time. 



N B. — This problem requires the afliftance of both the 

 terreftrial and celeftial globes. 



1. Find, as above, tlie time of the meridian paflage of the 

 . Z-: ihu-: 



