GLOBE. 



481 



called seconds, &c. ; a degree is therefore only a re- 

 lative idea, and not an absolute quantity, except 

 when applied to a great circle of the earth, as to the 

 equator or to a meridian, in which cases it is sixty 

 geographical miles, or sixty-nine and a half English 

 miles. A degree of a great circle in the heavens is 

 a space nearly equal to twice the apparent diameter 

 of the sun ; or to twice that of the moon, when con- 

 siderably elevated above the horizon. Degrees are 

 marked with a small cipher, minutes with one dash, 

 seconds with two, thirds with three, &c. ; thus, 

 25 14' 22" 35"' are twenty-five degrees, fourteen 

 minutes, twenty-two seconds, thirty-five thirds. In 

 the upper semicircle of the brass meridian, these de- 

 grees are numbered ten, twenty, &c., to ninety, from 

 the equator towards the poles, and are used for find- 

 ing the latitudes of places. On the lower semicircle 

 of the brass meridian, they are numbered ten, twenty, 

 &c., to ninety, from the poles towards the equator, 

 and are used in the elevation of the poles. (See De- 

 gree.) Great circles, as the equator, ecliptic, and 

 the colures, divide the globe into two equal parts. 

 Small circles, as the tropics, polar circles, parallels 

 of latitude, &c., divide the globe into two unequal 

 parts. Meridians, or lines of longitude, are semi- 

 circles, extending from the north to the south pole, 

 and cutting the equator at right angles. Every place 

 upon the globe is supposed to have a meridian pas- 

 sing through it, though there be only twenty-four 

 drawn upon the terrestrial globe ; the deficiency is 

 supplied by the brass meridian. When the sun 

 comes to the meridian of any place (not within the 

 polar circles), it is noon or mid-day at that place. 

 The first meridian is that from which geographers 

 begin to reckon the longitudes of places. In English 

 maps and globes, the first meridian is a semicircle, 

 supposed to pass through London, or the royal ob- 

 servatory at Greenwich. The equator (q. v.), a great 

 circle of the earth, equidistant from the poles, divides 

 the globe into two hemispheres, northern and 

 southern. The latitudes of places are reckoned 

 from the equator northward and southward, and the 

 longitudes are reckoned upon it eastward and west- 

 ward. The equator, when referred to the heavens, 

 is called the equinoctial, because, when the sun ap- 

 pears in it, the days and nights are equal all over the 

 world, viz., twelve hours each. The declination of 

 the sun, stars, and planets, is counted from the equi- 

 noctial northward and southward; and their right 

 ascensions are reckoned upon it eastward round the 

 celestial globe, from to 360 degrees. The ecliptic 

 (q. v.) is a great circle in which the sun makes his 

 apparent annual progress among the fixed stars. It 

 is the real path of the earth round the sun. The 

 points at which the ecliptic intersects the equator, at 

 an angle of 23 28', are called the equinoctial points : 

 the ecliptic is situated in the middle of the zodiac. 

 The apparent path of the sun is either in the equi- 

 noctial, or in lines nearly parallel to it, and his ap- 

 parent annual path may be traced in the heavens, by 

 observing what particular constellation in the zodiac 

 is on the meridian at midnight ; the opposite con- 

 stellation will show, very nearly, the sun's place at 

 noon on the same day. The zodiac (q. v.), on the 

 celestial globe, is a space which extends about 8 on 

 either side of the ecliptic. Within this belt the 

 motions of the planets are performed. 



Signs of the Zodiac. The ecliptic and zodiac are 

 divided into twelve equal parts, called signs, each 

 containing 30 ; and the sun makes his apparent 

 annual progress through the ecliptic, at the rate of 

 nearly a degree in a day. The names of the signs, 

 and the days on which the sun enters them, are given 

 in the article Ecliptic. The colures, two great 

 circles passing, one through the points Aries and 

 in. 



Libra and the poles of the world, the other through 

 Cancer and Capricorn and the poles of the world, 

 have their uses in mechanical geography. That 

 passing through Aries and Libra is called the equi- 

 noctial colure ; that passing through Cancer and 

 Capricorn, the solstitial colure. The tropics are two 

 smaller circles, each 23 28' from the equator, with 

 which they are parallel ; the northern is called the 

 tropic of Cancer, the southern the tropic of Capricorn. 

 The tropics are the limits of the torrid zone, north- 

 ward and southward ; and within these boundaries 

 alone is the sun ever seen vertical. The polar circles 

 are two small circles, parallel to the equator (or equi- 

 noctial), at the distance of 66 32' from it, and 

 23 28' from the poles. The northern is called the 

 arctic, the southern the antarctic circle. Parallels 

 of latitude are small circles drawn through every ten 

 degrees of latitude, on the terrestrial globe, parallel 

 to the equator. Every place on the globe is supposed 

 to have a parallel of latitude drawn through it, though 

 there are generally only sixteen parallels of latitude 

 drawn on the terrestrial globe. The hour circle, of 

 the artificial globe, is a small circle of brass, with an 

 index or pointer fixed to the north pole. The hour 

 circle is divided into twenty-four equal parts, corre- 

 sponding to the hours of the day ; and these are again 

 subdivided into halves and quarters. The horizon 

 (q. v.) is a great circle, which separates the visible 

 half of the heavens from the invisible ; the earth 

 being considered as a point in the centre of the sphere 

 of the fixed stars. Horizon, when applied to the 

 earth, is either sensible or rational. The sensible or 

 visible horizon is the circle which bounds our view, 

 where the sky appears to touch the earth or sea. 

 The sensible horizon extends only a few miles ; for 

 example, if a man of six feet high were to stand on a 

 large plane, or on the surface of the sea, the utmost 

 extent of his view, upon the earth or the sea, would be 

 only a very few miles. The rational or true horizon, 

 is an imaginary plane, passing through the centre of 

 the earth, parallel to the sensible horizon. It deter- 

 mines the rising and setting of the sun, stars, and 

 planets. The wooden horizon, circumscribing the 

 artificial globe, represents the rational horizon on the 

 earth. This horizon is divided into several concen- 

 tric circles, arranged in the following order : One 

 contains the thirty-two points of the compass, divided 

 into half and quarter points. The degrees in each 

 point are to be found in the amplitude circle. 

 Another contains the twelve signs of the zodiac, with 

 the figure and character of each sign ; and another 

 contains the days of the month, answering to each 

 degree of the sun's place in the ecliptic, and the 

 twelve calendar months. The cardinal points of the 

 horizon are east, west, north and south. The Cardi- 

 nal points in the heavens are the zenith, the uadir, 

 and the points where the sun rises and sets. The 

 cardinal points of the ecliptic are the equinoc- 

 tial and solstitial points, which mark out the four 

 easons of the year ; and the cardinal signs are, Y* 

 Aries, <xo Cancer, ^ Libra, and $ Capricorn. The 

 zenith is a point in the heavens exactly over head, 

 and is the elevated pole of our horizon. The 

 nadir is a point hi the heavens exactly under 

 our feet, being the depressed pole of our horizon, 

 ;uid the zenith, or elevated pole, of the horizon of 

 our antipodes. The pole of any circle is a point on 

 the surface of the globe, 90 distant from every part 

 of the circle. Thus the poles of the world are 90 C 

 Voin every part of the equator ; the poles of the 

 ecliptic (on the celestial globe) are 90 from every 

 part of the ecliptic, and 23 28' from the poles of the 

 equinoctial ; consequently they are situated in the 

 arctic and antarctic circles. Every circle on the 

 globe, whether real or imaginary, has two poles dia- 

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