THE MAGELLANIC CLOUDS. 25 



The researches of modern astronomers, aided by the 

 magnificent instruments of Lord Rossc,* have, however, 

 shown that many of the most remarkable nebulae are 

 only clusters of stars ; so remote from us, that the light 

 from them appears blended into one diffused sheet or 

 luminous film. There are, however, the Magellanic 

 clouds, and other singular patches of light, exhibiting 

 changes which can only be explained on the theory of 

 their slow condensation. There is no evidence to dis- 

 prove the position that world-formation may still be 

 going on ; that a slow and gradual aggregation of par- 

 ticles, under the influence of laws with which we are 

 acquainted, may be constantly in progress, to end, even- 

 tually, in the formation of a sphere. 



May we not regard the zodiacal light as the remains 

 of a solar luminiferous atmosphere, which once embraced 

 the entire system of which it is the centre ? f Will not 



Ixxvi. ; Catalogue of another 1000, with remarks on the Heavens, vol. 

 Ixxix. ; Catalogue of 500 wiore, with remarks as above, vol. xcii. ; 

 Of such as have a cometary appearance, vol. ci. ; Of planetary 

 nebula, ibid. ; Of stellar nebulae, ibid. ; On the sidereal part of 

 the heavens, and its connection with the nebulous, vol. civ. ; On the 

 relative distances of clusters of nebulous stars, vol. cviii. 



: -' : Lord Rosse's beautiful telescopes have been formed upon 

 principles which appear to embrace the best possible conditions 

 for obtaining a reflecting surface which should reflect the greatest 

 quantity of light, and retain that property little diminished for a 

 length of time. The alloy used for this purpose consists of tin and 

 copper in atomic proportions, namely, one atom of tin to four atoms 

 of copper, or by weight 58*9 to 126'4. On the Construction of 

 large Reflecting Telescopes : by Lord Rosse. Report of the Pour 

 teeuth Meeting of the British Association, 1844, p. 79. 



f The best description of the Zodiacal Light occurs in a letter 

 furnished by Sir John Herschel to the Times newspaper in March, 

 1843: "The zodiacal light, as its name imports, invariably ap- 

 pears in the zodiac, or, to speak more precisely, in the plane of the 

 sun's equator, which is 7 inclined to the zodiac, and which plane, 

 seen from the. sun, intersects the ecliptic in longitude 78 and 258, 

 or so much in advance of the equinoctial points : in consequence 

 it is seen to the best advantage at, or a little after, the equinoxes ; 



