434 



GLOBE. 



These cones may be made almost as serviceable as 

 globes, and are incomparably cheaper. Some of the 

 Best modern globes are those made since 1790, at 

 Nuremberg, after the direction of the famous obser- 

 ver Bode. Adam and Cary's globes, of London, are 

 very good. Globes have been lately made in Eng- 

 land, for the use of learners, with nothing but the 

 meridians and parallels of latitude drawn indelibly 

 on them. They are covered with a substance on 

 which drawings can be made with a slate pencil, and 

 easily efl'aced. White globes are also prepared, on 

 which the pupil can draw with a black lead pencil, 

 and nib out the work at pleasure. Either sort must 

 be highly useful in schools where geography is care- 

 fully studied. Among the most remarkable globes in 

 existence, that of Gottorp, in the academy ot sciences 

 of Petersburg, is worthy of notice. This is a large 

 concave sphere, eleven feet in diameter, containing a 

 table and seats for twelve persons, to whom the 

 inside surface represents the visible phenomena of 

 the heavens. The stars are distinguised by gilded 

 nails, according to their respective magnitudes, and 

 arranged in groupes, as the different constellations 

 require. The outside is a terrestrial globe, repre- 

 senting the land and water on the surface of the 

 earth. It is called the globe of Gottorp, from being 

 substituted for one originally made in that place, 

 which, with inconceivable labour, was conducted 

 upon rollers and sledges, over snow, and through 

 forests to Riga, and thence by sea to Petersburg. In 

 1751, it was consumed by fire, and from its iron 

 plates and materials, the present globe was made. 

 But, large as these globes are, they become diminu- 

 tive when compared with the sphere constructed by 

 the late doctor Long. This is eighteen feet in dia- 

 meter ; and it will enable thirty persons to sit within 

 its concavity, without any inconvenience. The en- 

 trance is over the south pole, by six steps. This 

 wonderful machine stands in Pembroke hall, in the 

 university of Cambridge. All the constellations and 

 stars of the northern hemisphere, visible at Cam- 

 bridge, are painted upon plates of iron, which, joined 

 together, form one concave surface. Unhappily, it 

 is now very much damaged. 



The Celestial Globe. The general definitions given 

 of the terrestrial globe, apply also to the celestial, the 

 various circles of which are more aptly illustrated by 

 the armillary sphere,* which is well adapted to give 

 youth just notions of those imaginary circles, which 

 astronomers have applied to what is vulgarly called 

 the concave sphere of the heavens ; but by means of 

 these circles, we investigate, with the nicest accur- 

 acy, the motions of the celestial bodies. There 

 are six great circles of the sphere, which require par- 

 ticular attention, but which the reader is now ac- 

 quainted with : they are, the horizon, the meridian, 

 the equator, the ecliptic, the equinoctial colure, and 

 the solstitial colure. The sphere is contained in a 

 frame, on the top of which is a broad circle, repre- 

 senting the meridian. It is suspended on two pins, 

 at opposite points of the meridian. These pins 

 are a continuation of the axis of the sphere both ways, 

 and as the sphere turns round upon them, they are 

 considered as poles, north and south. The equator 

 goes round the sphere, exactly in the middle, between 

 the two poles. The ecliptic, the colures, the tropics, 

 the polar circles, have been already defined, and are 

 easily discovered. The horizon is graduated, ac- 

 cording to the division of the circle, into quadrants 

 and degrees ; and, to refer celestial objects to the 

 horizon, we have also the points of the compass laid 

 down. Hence the amplitude, or distance, of heav 



* So called because it consists of a number of rings of 

 bras*, -which the old Romans named armUUe, from their 

 resemblance, perhaps, to bracelets, or rings for the arms. 



enly bodies, from the E. and W. points, and i]\n\<- 

 azimuth, or distance from the meridian, are reckoned 

 on the horizon of the arm ill;i ry sphere. The gradu- 

 ation of the equator enables us to fix the right ascen- 

 sion of celestial, and the longitude of terrestrial 

 objects. The graduation of the ecliptic serves to indi- 

 cate, in the armillary sphere, the latitude and longi- 

 tude of celestial bodies. The colures are, in u. 

 manner, the limits of the year, pointing out the 

 seasons by their two opposite points of the ecliptic. 

 The hour circle tells us in what time any motion of 

 the earth, in the centre, is performed. In fine, 

 many details of the science may be pleasingly nod 

 popularly illustrated by this contrivance. 



The appearances of the stars in the heavens illus- 

 trated by the armillary sphere. By placing small 

 patches of paper on the different circles to represent 

 stars, we perceive, that those which are farthest 

 from the poles will describe the greatest circles ; 

 and that the greatest circles are described by those 

 stars situated in the celestial equator. A star. lias 

 acquired its greatest elevation when it comes to the 

 upper semicircle of the meridian, and its greatest 

 depression when it is at the lower circle of the meri- 

 dian: the meridian bisects its arc of apparition. 

 Some circles of revolution are wholly above, others 

 entirely below the horizon ; therefore the patches on 

 those circles show us which stars descend below, or 

 which never ascend above the horizon. And any 

 object, whose circle of revolution is on the same side 

 ofthe equator with the elevated pole, is longer visi- 

 ble than it is invisible ; the contrary holds true if it 

 be on the other side of the equator. The following 

 definitions are more immediately applicable to the 

 celestial globe: The declination of the sun, of a 

 star, or planet, is its distance from the equinoctial, 

 northward or southward. When the sun is in the 

 equinoctial, he has no declination, and enlightens 

 half the globe, from pole to pole. As he increases 

 in north declination, he gradually shines farther over 

 the north pole, and leaves the south pole in darkness : 

 in a similar manner, when he has south declination, 

 he shines over the south pole, and leaves the north 

 pole in darkness. The greatest declination the sun 

 can have, is 23 28' ; the greatest declination a star 

 can have, is 90, and that of a planet, 30 28' north 

 or south. The latitude of a star or planet, is its dis- 

 tance from the ecliptic, north or south, reckoned 

 towards the pole of the ecliptic, on the quadrant of 

 altitude. Some stars, situate in and about the pole, 

 have 90 of latitude ; the planets have only 8 ; find 

 the sun, being always in the ecliptic, has no lati- 

 tude. The longitude of a star, or planet, is reckoned 

 by the degrees of the ecliptic, from the point Aries 

 round the globe. On the celestial globe, the longi- 

 tude of the sun corresponds with the sun's place on 

 the terrestrial globe. The right ascension ofthe sun, 

 or a star, is that degree of the equinoctial which 

 rises with the sm, or a star, in a right sphere, and is 

 reckoned from the equinoctial point Aries eastward 

 round the globe. Oblique ascension of the sun, or a 

 star, is that degree of the equinoctial which rises 

 with the sun, or a star, in an oblique sphere, and is 

 likewise counted from the point Aries eastward 

 round the globe. Oblique descension of the sun, or a 

 star, is that degree of the equinoctial which sets 

 with the sun, or a star, in an oblique sphere. The 

 ascensional or descensional difference is the difference 

 between the right and oblique ascension, or the dif- 

 ference between the right and oblique descension ; 

 and, with respect to the sun, it is the time he rises 

 before six in the spring and summer, or sets before 

 six in the autumn and winter. The angle of position 

 of a star, is an angle formed by two great circles in. 

 tersecting each other in the place of the star, the one 



