3 i6 Iff STARRY REALMS. 



This marvellous structure will naturally suggest that 

 Laplace could have no more appropriate picture to illus- 

 trate his nebular theory than the photograph of the 

 nebula in Andromeda. There seems no doubt, indeed, 

 that this nebula is condensing down, but the magni- 

 tudes involved show us that the solar system bears but 

 little resemblance to the gigantic rings of the vast nebula. 

 Look at the facts of the case. It happens that we have 

 in the case of Andromeda a partial hint as to its actual 

 dimensions of which we are usually destitute in objects of 

 this description. A few years ago a variable star broke 

 out in Andromeda under circumstances which rendered it 

 in the highest degree probable that the star was actually 

 in the nebula, and not merely accidentally on the line of 

 sight. The parallax of this star was sought for by 

 astronomers myself among the number and we came 

 to the unanimous conclusion that the star, and therefore 

 presumably the nebula, was too remote for our methods of 

 survey to be successful. The diameter of the earth's orbit 

 cannot subtend an angle at the very most of more than a 

 couple of seconds at the nebula, which is itself more than a 

 couple of degrees in length. We are hence assured that 

 the diameter of the system which is being evolved in 

 Andromeda, whatever it may be, is at the very least three S 

 thousand six hundred times as great as that of the earth's 

 orbit round the sun. 



Another superb achievement in the exclusive depart- 

 ment of photography is the discovery of the nebulae which 

 surround some of the stars in the Pleiades. We may 

 look in vain for them with the ordinary telescope, but the 

 exquisite pictures of Roberts demonstrate their exist- 



