But liere, too, the spectroscope has come to our aid, and 

 thus analysing the light from these far distant sources ^^■e affirm 

 that many are really vast cloudy masses of incandescent gas. 

 Let us look at some of these nehute, and mark their -varied and 

 .singular forms, and note some relations between the brilliant 

 nuclei, and the gaseous matter surrounding them. Before you is 

 vrhat is called j;«/- exi'dUnce the great nebula of Orion. I cannot 

 tfll you over how many millions of square miles it stretches. 

 Tlie extent of it is almost unimaginable. In the centre is a 

 gi-oup of seven suns which belong to one system. In their 

 immediate neighljourhood is a rectangular mass of brilliant 

 cloud, in which clusteis of stars have been discerned, or we Avill 

 put it, that in certain jx^ints tlie liglit is more condensed than in 

 others. Now it is very certain, that since this nebula was first 

 discovered in 1656 it has undergone changes in form and in the 

 1 lightness of its diiferent parts. As remarkable, perhaps, as this 

 nebula in Orion, is the one in Doradus now l)efore you. This 

 belongs to the class of large, irregular neljula?, l)ut still in the 

 bright annular masses of its central portion we see the evidence 

 that its molecules are Ijeing marshalled into a definite organiza- 

 tion. On the outskirts its shapeless cloud-masses seem torn 

 into streamers and filaments, as if by the force of tempests. 

 Another remarkable nel)ula of irregular outline is that in Taurus. 

 As seen through Lord Kosse's telescope, it presents tlie form now 

 shown to you, resembling, perhaps, a gigantic lolister more than 

 anything else. The claA\'s and antennae are here star-streams. 

 But these luminous clouds often take forms much more sym- 

 metrical than those that \\^\e been sho"\TO. AVho can look at 

 this beautiful nebula of the Lion, and in the spiral concentric 

 lajei's of luminous matter in its centre, and not s^e the gathering 

 of a shapeless mass into the first outhnes of a definite form. 



But it is in what are termed the planetary nebulaj that we 

 liave this definite form most strikingly presented. Here in this 

 one, in the constellation Andromeda, we \vA\e a brilliant 

 luminous ring with a fringe of cloudy light on its exterior, and 



