ON THE CONSTRUCTION OF THK HEAVENS. 91 



tation ; which is, that a telefcope with a power of penetrating 



into fpace, like my 40-feet one, has alfo, as it may be called, 



a power of penetrating into time paft. To explain this, we [™™f*™*' 



mufi: conlider that, from the known velocity of light, it may heavens, or fpacs 



be proved, that when we look at Sirius, the rays which enter containing ita.s. 



the eye cannot have been lefs than fix years and 4| months 



coming from that ftar to the obferver. Hence it follows, that Light employing 



o lix yea.s jii its 



when we fee an object of the calculated diftance at which one pa fl age from S\- 

 of thefe very remote nebulae may Hill be perceived, the rays "»>s 3 ana near 



J ... rii. tvvo mu ions or 



of light which convey its- image to the eye, mult have been >ear3 in amvijJg 

 more than nineteen hundred and ten thoufand, that is* almoft from remote 

 two millions of years on their way;, and that, confequently, fo "L^ , lilU jjT' 

 many years ago, this object mult already have had an exigence have exited { t 

 in the fidereal heavens, in order to fend out thofe rays by bn S a o°* 

 which we now perceive it. 



VIII. Of Stars with Burs, or Slcller Nebula. 

 Situated as we are, at an immenfe diftance from the remote 3 - Stellar ne- 

 parts of the heavens, it is not in the power of telefcopes to re- 

 folve many phenomena we can but juft perceive, which, could 

 we have a nearer view of them, might probably (hew ihem- 

 felves as objects that have long been known to us. A ftellar 

 nebula, perhaps, may be a real clufter of ftars, the whole light 

 of which is gathered fo nearly into one point, as to leave but 

 jufr. enough of the light of the clufter vifible to produce the 

 appearance of burs. This, however, admits of a doubt. 



IX. Of milky Nebulofity. 



The phenomenon of milky nebulofity is certainly of a molt 9*. M '% neiu - 

 interefting nature : it is probably of two different kinds ; one 

 of them being deceptive, namely, fuch as arifes from widely . 

 extended regions of clofely connected cluftering ftars, conti- 

 guous to each other, like the collections that conftruct our 

 milky-way. The other, on the contrary, being real, and pof- 

 ftbly at no very great diftance from us. The changes I have 

 obferved in the great milky nebulofity of Orion, %o years ago, 

 and which have alfo been noticed by other aftronomers, can- 

 not permit us to look upon this phenomenon as arifing from 

 immenfely diftant regions of fixed ftars. Even Huygens, the 

 difcoverer of it, was already of opinion that, in viewing it, we 



faw, 



