GLOBE. 



The lesser circles, of principal use, are 

 the two tropics and two polar circles. 



Of these circles some are fixed, and al- 

 ways obtain the same position; others 

 moveable, according to the position ot the 

 observer. The fixed circles are the equa- 

 tor and the ecliptic, with their parallels 

 and secondaries ; which are usually delin- 

 eated upon the surfaces of the globes. The 

 moveabie circles are the horizon, with its 

 parallels and secondaries. 



The horizon is that broad wooden cir- 

 cle surrounding the globe, and dividing 

 it into two equal parts called the upper 

 and lower hemispheres. It has two notch- 

 es, to let the brazen meridian slip up and 

 down, according to the different heights 

 of the pole. On the flat side of this cir- 

 cle are described the twelve signs, the 

 months of the year, the points of the 

 compass, &c. The brazen meridian is an 

 annulus or ring of brass, divided inio de- 

 grees, viz. each quadrant in 90 degrees. 

 It divides the globe into two equal parts, 

 called the eastern and western hemi- 

 spheres. The quadrant of altitude is a 

 thin pliable plate of brass, answering ex- 

 actly to a quadrant ot the meridian. It is 

 divided into 90, and has a notch, nut, and 

 screw., to fix to the brazen meridian in 

 the zenith of any place ; where it turns 

 round a pivot, and supplies the room of 

 vertical circles. The hour-circle is a flat 

 ring of brass, divided into twenty-four 

 equal parts, or hour-distances ; and on 

 the pole of the globe is fixed an index, 

 that turns round with the globe, and 

 points out the hours upon the hour-cir 

 cle. Lastly, there is generally added a 

 compass and needle upon the pediment 

 of the frame. 



The surface of the celestial globe may 

 be esteemed a just representation of the 

 concave expanse of the heavens, not- 

 withstanding its convexity ; for it is easy 

 to conceive the eye placed in the centre 

 of the globe, and viewing the stars on its 

 surface ; supposing it made of glass, as 

 some globes are : also that if holes were 

 made in the centre of each star, the eye 

 in the centre of the globe, properly 

 placed, would view through each of the 

 holes the very stars in the heavens repre- 

 sented by them. 



As it would be impossible to have any 

 distinct notion of the stars, in respect to 

 their number, order, and distances, with- 

 out arranging them in certain forms, call- 

 ed constellations, this the first observers 

 of the heavens took care to do ; and these, 

 like kingdoms and countries, upon the 

 terrestrial globe, serve to distinguish the 



different parts of the superfices of the 

 celestial globe. 



The stars, therefore, are all disposed 

 in constellations, under the forms of vari- 

 ous animals, whose names and figures are 

 represented on the celestial globe; which 

 were first invented by the ancient astro- 

 nomers and poets, and are still retained, 

 for tlie better distinction of these lumina- 

 ries. We shall now give some problems 

 on both the globes, beginning with the 

 terrestrial globe. 



TERRESTRIAL GLOBE. 



PROB. 1. "To find the latitude and 

 longitude of any place." Bring the place 

 to the graduate'd side of the first meri- 

 dian : then the degree of the meridian it 

 cuts is the latitude sought ; and the de- 

 gree of the equator then under the meri- 

 dian is the longitude. 



. 2. To find a place, having a given 

 latitude and longitude." Find the degree 

 of longitude on the equator, and bring it 

 to the brass meridian ; then find- the de- 

 gree of latitude on the meridian, either 

 north or south of the equator, as the giv- 

 en latitude is north or south ; and the 

 point of the globe just under that degree 

 of latitude is the place required. 



3. " To find all the places on the 

 globe that have the same latitude and 

 the same longitude, or hour, with a given 

 place, as suppose London." Bring the 

 given place, London, to the meridian, 

 and observe what places are just under 

 the edge of it, from north to south ; and 

 all those places have the same longitude 

 and hour with it. Then turn the globe 

 round; and all those places, which pass 

 just under the given degree of latitude 

 on the meridian, have the same latitude 

 with the given place. 



4. " To find the antceci, perioeci, and 

 antipodes, of any given place, suppose 

 London." Bring the given place, Lon- 

 don, to the meridian, then count 51^ the 

 same degree of latitude southward, or 

 towards the other pole, and the point 

 thus arrived at will be the antoeci, or 

 where the hour of the day or night is al- 

 ways the same at both places at the same 

 time, and where the season and lengths 

 of days and nights are also equal, but at 

 half a year distance from each other, be- 

 cause their seasons are opposite or con- 

 trary. London being still under the me- 

 ridian, set the hour index to twelve at 

 noon, or pointing towards London ; then 

 turn the globe just half round, or till the 

 index p oint to the opposite hour, or twelve 



