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ASTRONOMY. 



[UEMNITIOXS. 



they deflect no shadow, luid are hence ntyled ancii, mean 

 ing shadowlesa. At other time* their shadows fall a 

 noon, north or south, according as the sun ia north o 

 south of them. They are then called amjihucii, sign 

 fying that their shadows fall both ways. 



The variation in the temperature has led to the div 

 ion of the earth into zones. Between the latitud 

 60 32" north and south, the sun rises and nets every da) 

 In all higher latitudes, however, there are certain period 

 of the year when the sun never rises, and others when i 

 never sets. The two parallels of latitude A A', B B 

 (Fig 3), which correspond to the latitude 60 32", divid 



the surface of th 

 earth in three parts 

 The two zones a 

 A P A', B Q B' are 

 called the frozen 

 zones. The circle 

 A A', B B' are the polai 

 circles; A A' ia thi 

 urctic; while the other 

 ia the antarctic circle 

 in the points between 

 these two are th 

 several zones, in whicl 

 the sun sets and rises 

 daily. 



Those who dwell in 

 the temperate zones have their shadows at noon always 

 cast towards the north in the north temperate zone, and 

 towards the south in the south temperate zone. They are 

 styled heteroscii, meaning, that they have their shadows 

 at noon, either north or south. 



The inhabitants of the frigid zones are called jvrixii, 

 signifying a shadow turning about, as, during a revolu- 

 tion of the earth on its axis, their shadows are projected 

 towards every point of the compass. 



The Due of a planet is its apparent face, seemingly 

 perfectly flat, though really spherical. The planets ex- 

 hibit discs as seen with the telescope. The diameter of 

 the disc of the sun and moon is considered to be divided 

 into twelve parts called digits. 



The Orbit of a planet is the path described by it in 

 one revolution round the sun. 



The Plane of a planet's orbit is an imaginary surface 

 cutting through the centre of the sun and the planet, and 

 reaching out to the stars. 



Figure 4 shows the plane of the earth's orbit. The 

 tars to which it extends form the constellations of the 

 odiao. The circle A, B, C, D, is the ecliptic, the sun's 

 place in the heavens, as seen from the earth, and the 

 earth s place as seen from the sun. 



Tht /rv fnw/K-n of the orbit of a planet is its plane 

 referred to the plane of the earth's orbit, to which it is 

 inclined. 



If we suppose the shaded part of the diagram to be a 

 furfac* of water, a ring hoop held inclined so at to be 



half immersed, will describe the relation of the planetary 

 orbits to that of the earth. They are all inclined towards 

 it, one half Wing Wlow, and tho other half above it. 

 The angle of inclination varies, but exhibits, at tho 

 greatest, only a slight divergence. 



Mercury . 

 Venus 



Mars 



r v o" 



3 23 28 

 1 51 6 



Jupiter 



Siiturn . 

 Uranus 



1 18' 



4-. 



51' 



The Node* of a pknet are the two opposite points 

 where its orbit appears to cut the orbit of the ean 

 the ecliptic. Where the planet appears to rise above 

 the orbit of the earth, it is called the ascending node ; the 

 opposite point, where it appears to go below it, is called 

 the descending node. 



Conjunction and Opposition are terms used to denote 

 certain situations of the planets with respect to the sun 

 and to each other. 



A planet directly between the earth and the sun, is said 

 to be in inferior conjunction with tho sun. This can 

 only take place in the case of Mercury and Venus, but 

 along with them the earth may be in inferior con- 

 junction with the sun to Mars, and with Mars to Jupi- 

 ter, A-C. 



A planet with the sun directly between it and the 

 earth, is said to be in superior conjunction with tho 

 sun. The terms inferior and superior refer to 

 smaller or greater distance of the planet from the 

 earth. 



A planet, with the earth directly between it and the 

 sun, is said to be in opposition. This can never take 

 place in the case of Mercury and Venus, whose orbits 

 are included in that of the earth. 



Planets are said to be in conjunction with each other 

 when they are in the same sign and degree. This is a 

 common occurrence in the case of two ; but the very rare 

 phenomenon of Mercury, Venus, Mars, Jupiter, and 

 Saturn Wing in conjunction Wtween tho wheat ear of 

 Virgo and Libra, took place, September 15, 1186. It 

 will be ages Wfore they cluster again in that part of the 

 deavens. Venus, Jupiter, and the moon, wore in con- 

 junction in Leo in 1801. 



The aspect of the planets to each other is said to be 

 sextile, when they are two signs apart, or the si xtli part 

 of the zodiac ; quartile, when they are three signs dis- 

 :ant, the fourth part of the zodiac ; trine, when they are 

 'our sL;iis distant, tho third of tho zodiac. ; and in oppo- 

 sition, when they are six signs, or half t.ho zodiac, from 

 each other. 



Ajioyee is that point of the moon or a planet's orbit 

 which is farthest from the earth. 

 1'eri'je.e is that which is nearest 



Aphelion is that point of the orbit of the earth, or of 

 iny planet and comet, which is farthest from the sun. 



7i. /ion is that which is nearest. A straight line 

 oiuing the points of aphelion and perihelion, is 

 he line of the apsides. 



Culmination is the act of coming to tho meridian in 

 he case of any star or planet, when it attains, on any 

 given day, its greatest altitude in tho heavens. 



Daily Acceleration is the interval of timo that the stars 

 rise, culminate, and set, sooner every succeeding <\-.\\ 

 han on the one preceding. It amounts to about four 

 iiinutes daily, or two hours a month. 



l!<>t:itkiH. Besides the apparent diurnal motion of the 

 tJirs, caused by the earth's rotation upon its axi.-. 



i to have a motion westward, in consequence of 

 !m earth's orl.iial course eastward. They #iin, tliere- 



>re, on the sun, rising, culminating, and setting MH r, 



iy after day. Thus, those stars and constell; 

 n any given evening, rise at ten o'clock, will, at the 

 ame hour, a month afterwards, W 30 above the hori- 

 011 ; and three months afterwards, they will be advanced 

 ver our heads ; and six months afterwards W setting in 

 10 west, having accomplished half of their apparent 

 annual revolution. 



Hence tho same constellations are not always visible 

 us through the year. Some, not visible before, suo- 

 ively me to view in the east ; while others sink in the 



