actital observation of the heavens. On the surface of 
the celestial globe are represented the fixed stars, in 
their true relative positions, distinguished according to 
their magnitudes, and arranged in constellations. 
Besides the parts already described, there are other 
’ appendages common to/both globes, which yet remain 
‘0 to be explained. The principal of these are the horary 
or hour circle, the quadrant of altitude, and the 53. 
The horary is a small brass circle, generally fixed on 
the north pole of the globe, and divided into 24 equal 
parts, representing the hours of the day. The divisions 
are numbered from 1 to 12 along the first semicircle, 
and again from 1 to 12 along the next, in the contrary 
direction to that in which the globe naturally revolves. 
The circle is moveable separately by the hand, so that 
any given hour may be brought to the brazen meridian; 
but when left to itself, itturns with the globe, and thus 
serves to measure the whole, or any part of a revolution. 
The quadrant of aliitude is a graduated slip of brass, 
so thin and flexible, as to be easily applied to the sur- 
face of the globe. It is furnished at one extremity with 
a nut and serew, by which it may be fastened to any 
rt of the meridian. When this extremity is fixed on 
the zenith of the globe, the zero, or commencement of 
the graduation, coincides with the horizon, thus form- 
ing the fourth part of a vertical circle. The ua- 
‘tion is also continued to the other extremity of the qua- 
drant, which is generally about 18 or 20 degrees, It 
takes its name from being applied to measure the alti- 
tude of heavenly bodies. 
The compass consists of a magnetic needle, suspend- 
ed over the centre of a circle, on the circumference of 
which are marked the 32 points or rhumbs of the hori- 
zon. It is, in fact, the simplest form of the mariner’s 
compass, fixed in the under part of the frame or mount- 
ing, and used for placing the brazen meridian in the 
meridian of the place. 
It would be tedious, even to enumerate the various 
improvements and alterations, that have been from time 
to time recommended, in the construction and use of 
the globes, as well as of their appendages. Such an 
“enumeration, however, is we conceive unnecessary, be- 
cause any body who understands the general principle 
of the globes, as we have now explained it, will find no 
difficulty in using any of the instruments, with which 
they may be accompanied ; and because more informa- 
tion will be acquired, in half an hour, from inspecting 
the globe itself, than we could communicate in a whole 
volume of descriptions and drawings. While, there- 
fore, we have endeavoured, in the preceding short 
sketch, and by help of the representations, Figs, 5 and 
6. Plate CCLXV. to convey some idea of the nature 
of the globes, we would conclude, by recommending to 
such of our readers as wish to become thoroughly ac- 
teenie with the subject, to draw their information 
rom the instrument itself. 
The most natural, as well as the most correct method 
of tracing out the circles of a globe, may easily be dedu- 
ced from the preceding description. Suppose, for ex- 
ample, it is required to delineate on the surface of a 
spherical body, the various lines and figures of the ter- 
restrial globe. From either of the points that represent 
the poles, with a radius equal to Pat the distance be- 
tween them, a circle is described to represent the equa- 
tor, and divided into degrees. From the 90th degree of 
‘the equator with the same radius, another circle is 
described, passing through the poles, and representing 
the first meridian. Other meridians are described in a 
similar manner, by taking for a centre every fifth, tenth, 
ant of 
GEOGRAPHY. 
155 
or fifteenth degree of the equator, according to the num- Mathemait. 
ber required, The first, or any other meridian, being “ — 
divided into degrees, from the equator towards the poles, ey 
the tropics aly polar circles may be described from the 
poles as centres, with radii extending to 23}° and 663° 
respectively. Other parallels of latitude are described 
in a similar manner. The ecliptic is described, by ta- 
king as a centre the point which is in 90° west longi- 
tude, and 663° north latitude, and for a radius one- 
fourth of the circumference of the globe. Having thus 
described all the circles, it only remains to lay down 
the different places of the earth, according to their re- 
spective longitudes and latitudes, as determined by ob- 
servation, and described in books of geography. 
But though this method of delineating globes is in Method 
itself simple, and capable of being carried to almost any commonly 
degree of exactness, those whose business it is to con- adopted. 
struct them for sale, have found it necessary, in order 
to furnish them at a moderate price, to adopt another 
method, less accurate perhaps, but much more expedi- 
tious, This method consists in delineating, on separate 
pieces of paper of the form /ENQS, (Fig. 7.) called cee 
gores, separate portions of the earth or the heavens, ac- pi rt 
cording as they are intended for a terrestrial or celestial” 
globe, and afterwards fixing them in order on the surface 
of the sphere, when N and S coincide with the poles, 
NES, NMS, and NQS become meridians, and ZMQ 
an arch of the equator. Strictly speaking, indeed, no 
portion of paper can be accurately fitted to a spherical 
surface; but if AiQ be very small compared to the 
whole circumference, the portion of the sphere, covered. 
by the segment AZNQS, will not sensibly differ from a 
plane in the direction AEQ; that is, the arches of 
the equator AEM, QM, and of the parallel of latitude 
ab, cb, may be considered as straight lines perpendicu- 
lar to NS. The number of segments necessary to co- 
ver the globe, will depend on the length of the arch 
ZEQ ; but when the whole have been once carefully 
designed and accurately fitted to the sphere, it is only 
necessary to make correct engravings of the originals, 
in order to construct, with comparatively little labour, 
any number of globes of the same dimension. Some- 
times the segments are truncated at each extremity 
AB, CD, so as to leave a small circular space about the 
poles. These spaces are considered as plane surfaces, 
and are accordingly covered with one circular piece of 
paper, on which the portions of the meridians form ra- 
dii of a circle. The method of delineating the gores 
will be explained when we come to the projection of 
maps, 
Having thus shortly noticed the different methods of 
constructing globes, we should now proceed to what more 
properly constitutes the object of this Chapter, the appli« 
cation of these instruments to the solution of problems. 
Before concluding this Section, however, we would ob- 
serve, that in perusing the terrestrial globe, the eye of the 
observer is in its natural position ; but in the case of the 
celestial globe, he must conceive himself situated’in the 
centre, and looking towards the concave surface. This 
will perhaps be better understood by referring to the 
Mis sphere, as represented Fig. 8. Plate CCLXV. Armillary 
This mstrument consists of a number of metallic rings, sphere. 
so connected as to represent the circles of the sphere, Prats 
and at the same time to exhibit the apparent relative CCLXV. 
positions of the earth and heavens. As delineated in Fis ® 
the figure, N and S represent the poles, and the line 
NS the axis of the world, with the earth G in the cen- 
tre; HR the horizon, ASQ the equinoctial, EL the eclip- 
tic, ENQS the solstitial colure, KM the equinoctial ¢o« 
