ON THE TIXED STAR8. 4S>5 



It has been conjectured that all stars are disposed in nebulae, and that 

 those, which apj)ear to us to be more widely separated, are individual s ars of 

 that particular nebula in which we are placed, and of which the marginal 

 parts may be observed, in the form of a lucid zone, which is called the 

 milky way, being too distant to allow the single stars to be perceived by 

 thfe naked eye. This opinion was first suggested by Professor Kant, the 

 author of the system of metaphysics called the critical philosophy. The idea 

 was adopted by Lambert, who considers the largest stars as constituting a 

 distinct nebula placed among a multitude of others, which together produce 

 the appearance of a continued zone ; and Dr. Herschel has investigated very 

 particularly the figure of a single nebula, which would be capable of being 

 pnjected into the form of the milky way. We must not, however, suppose 

 that each of Dr. Herschel's 2500 nebulae can be at all comparable in mag- 

 nitude to this supposed nebula, since many of them are almost as much re- 

 solved by the telescope into single stars as the milky way itself; which 

 would be utterly impossible, if the stars which they contain were equally 

 numerous with those of the nebula to which the milky way belongs. Sup- 

 posing all the stars of this nebula to be as remote from each other as the 

 nearest of them are from the sun, it may be calculated that the most distant 

 are abuut 500 times as far from us as the nearest, aud that light, which is 

 probably 15 or 20 years in travelling to us from Sirius, would be nearly 

 twenty thousand in passing through the whole diameter of the milky way. 

 A nebula of the same size as this, appearing like a diffused light of a degree 

 in diameter, must be at such a distance, that its light would require a 

 million ifears to reach us. (Plate XXXI. Fig. 464.) 



The stars are not, properly speaking, absolutely fixed with respect to each 

 other, for several of t:,em have particular motions, which have been dis- 

 covered by a comparison of accurate observations, made at very <listant times. 

 Arcturus, for instance, has a progressive motion, amounting to more than 

 two seconds annually. Dr. Maskelyne found, that out of S6 stars, of which 

 he ascertained the places with great precision, 35 had a proper motion. Mr. 

 Michell and Dr. llerschcl have conjectured, that some of the stars revolve round 

 others which are apparently situat<>d very near them; and perhaps even all 

 the stars may in reality change their places more or less, although their re- 



