CHAMBEKS'S INFORMATION FOR THE PEOPLE. 



increased brightness, and especially in that por- 

 tion of the sun which is next the planet.' We 

 have only, then, to suppose that a variable star has 

 a very large planet revolving round it at a short 

 distance ; this will cause the part next the planet 

 to be brighter than the rest ; and thus the star will 

 vary with a period equal to that of the planet. 



Double and Multiple Stars. Another variety in 

 the nature of these luminaries is their being in 

 some instances not single stars, as they appear to 

 the naked eye, but a group of two or more, evi- 

 dently, from their motions, forming one system. 

 The star Castor, one of the Twins, is found, when 

 much magnified, to consist of two stars, of between 

 the third and fourth magnitude, within five seconds 

 of each other. Upwards of 6coo such groups have 

 been observed. It is generally observed that they 

 move round each other within a certain time, and 

 in elliptical orbits; the revolution of Castor, for 

 instance, is supposed to be accomplished in 252 

 years. 



Proper Motion of Stars. When we speak of 

 the stars \x-\n% fixed, it is only as compared with 

 the planets. There is no such thing as absolute 

 fixity in the universe. Besides the revolutions of 

 the double stars, a great many stars have been 

 observed to be slowly but constantly carried away 

 from their places in the heavens. This proper 

 motion, as it is called, has in one instance shifted 

 the situation of a star in the heavens, in the course 

 of fifty years, over ^th of a degree. Founding 

 upon these displacements of the stars, it has been 

 concluded that our sun, accompanied by his 

 attendant planets, is in motion towards a region 

 of space in the direction of the constellation 

 Hercules. 



Milky-way. The stars are very unequally scat- 

 tered over the sky. We may always observe a 

 whitish band arching the heavens, called the 

 Milky-way, which appears to the eye, and still more 

 to the telescope, as a dense mass of starry dust. 

 From this appearance it is inferred that the stars 

 forming our firmament do not extend indefinitely 

 into space, but are limited in all directions, the 

 mass having a definite shape. Herschel conceived 



the stratum to be thin in proportion to the length 

 and breadth, and that looking through the mass of 

 stars forming the depth in these directions, gives 

 the appearance of the Milky- way. As the Milky- 

 way divides into two branches, there must be a 

 bifurcation of the stratum. Our place in the 

 system is conceived to be not in the centre, but 

 nearer to one end and to one surface. 



Remote Star-systems, Nebula. from, the grand 

 idea of the solar system, we thus rise to the vastly 

 grander idea of a stellar system, composed of 

 countless myriads of solar systems, many of them, 

 perhaps, surpassing our own in magnitude, and 

 held together by the universal bond of gravitation. 

 But this star-system, which we may call our own 

 universe, inconceivably vast as it is, is but an 

 item of the heavenly inventory. Far beyond its 

 bounds, the modern telescope has descried similar 

 systems in great numbers, each hanging in some 

 tolerably defined shape in the depths of space. 



A few of these remote systems are visible to 

 the naked eye, as faint luminous spots in the 

 heavens ; but by means of powerful telescopes, 

 thousands of them have been observed and cata- 

 logued. They are generally spoken of collectively 

 as nebula, from their cloud-like appearance. Many 

 of them are resolvable into individual stars, even 

 with a moderate telescope, but others were found 

 to resist even the powerful telescope of Sir 

 William Herschel ; and he accordingly made a 

 distinction between clusters of stars, or resolvable 

 nebulae, and nebulae properly so called, which 

 presented no appearance of stars. These last 

 were conceived to be elementary sidereal matter 

 in a diffused and gaseous form matter in the 

 course of being condensed to stars and systems. 

 But when the still more powerful telescope of Lord 

 Rosse shewed that several so-called nebulae, 

 hitherto irresolvable, were really groups of stars, 

 the nebular theory was thought to be overturned ; 

 for although many still resisted resolution, this 

 was attributed to extreme distance, and the want 

 of sufficient telescopic power. That wonderful 

 instrument, the spectroscope, however, has recently 

 reinstated the nebular theory, by shewing that 



Nebulae and Clusters. 



among these appearances there are real nebulae, 

 devoid of solid or liquid matter, and consisting 

 of masses of glowing gas apparently nitrogen 

 and hydrogen. 



These nebulous-looking objects, whether star- 

 clusters or true nebulae, present the most remark- 



16 



able and sometimes startling shapes, of which a 

 few specimens are represented in the figure. It 

 is believed that Lord Rosse's telescope has brought 

 within our ken objects whose light must take sixty 

 thousand years to reach us ! 



