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POPULAR ASTRONOMY. 



IN giving a brief sketch of the principal phenomena of Aslroauiny, it will be de- 

 sirable to commence with a description of the Solar System. 



^THE SOLAR SYSTEM comprises the sun, eight principal planets, and thirty-five 

 minor planets ; all of -which revolve round the sun as their centre, and are termed 

 primary planets ; in addition to these, it also comprises a number of secondary 

 planets or moons, which revolve round some of the primary planets ; and an unknown 

 number ot bodies called comets. 



THE SUN. 



The Sun forms the centre of the planetary system, and is a round opaque body, 

 surrounded by a luminous atmosphere, adapted to supply heat and light to all the 

 planets. The sun is distant from the earth about ninety-five million miles ; his dia- 

 meter is 882,000 miles ; and Jus vojumeor bulk. 1,?QO,QOO times greater than that of 

 the earth. The sun rotates updn/his axJ ifl IJwOqty-fivf days eight hours. 



Upon looking at the sun thrbugh'a telescope; h^vnig* coloured glasses, a number 

 of dark spots are usually seen upon its surface. If these spotsbe repeatedly watched, 

 they will be found not to b slatiorjaay^o"^ ttte! sun's ."dis fot'*any long period of time, 

 nor to remain of the sasae shap'ei haf fc> vary'tlleir pogitipn, to contract or enlarge^ 

 and at times suddenly to *dfsap*pfeaf ; ' while 'otters* brea*k* out in places where none 

 beforeexisted. The size of some of the spots is immense; in the year 1758, one 

 was observed which measured 45,000 miles across : indeed, the least possible spot 

 which can be seen by our best glasses, cannot be less than 465 miles in diameter. 

 The result of the investigations into this subject is, that the solar spots are believed 

 to be spaces or openings through the luminous matter, exposing to view portions of 

 the solid body of the sun. By an attentive observer it will be remarked, that such 

 of the spots as remain stationary for a considerable time, have a gradual motion, 

 apparently across the sun's disk. This motion of the spots can only arise from the 

 rotation of the sun on his axis; and they serve to mark the time of this rotation. 

 These spots also prove that the sun is a spherical body ; for a spot makes its appear- 

 ance on the western edge of the sun as a fine line, which gradually increases n 

 breadth tiil it approaches the centre. As it passes on to the eastern edge, its dia- 

 meter gradually lessens into a fine line, before it entirely vanishes from view. 



With regard to the question, whether or not the sun is inhabited, astronomers are 

 undecided. Sir William Hershel, from what he had observed in that luminary, 

 states as follows : " The sun appears to be nothing else than a very eminent, large,. 

 and lucid planet ; evidently the first, or rather, the only primary one of our system, 

 all the rest being secondary to it. Its similarity to the other globes of the solar 

 system, with regard to its solidity, its atmosphere, and its diversified surface, leads 

 us to suppose that it is most probably also inhabited, like the rest of the planets, by 

 beings whose organs are adapted to the peculiar circumstances of that vast globe." 



Owinj* to the great difference in the distances of the various planets from toe sun 

 and which will be described presently, it will be evident that he must present to their 

 various inhabitants different degrees of magnitude. Thus, to Mercury, he appears 

 as a globe far larger than he does to us, while to the inhabitants of Neptune, he 

 must appear little larger than a star point. The former planet being only 37 mil 

 lions of miles distant from him, while the latter view him from the enormous distance 

 of 2,800 millions. 



THE PLANETS 



Round the sun revolve tne planets, in orbits not circular, but more or less ellip- 

 tical or oval. The planets are opaque, solid, globular bodies, which receive their 

 light and heat from the sun ; they all rotate upon their axis, and consequently, all 

 enjoy the alternations of day and night. Their axis is also more or less inclined to 

 the plane of their orbit ; they therefore experience, to a greater or less degree, the 



