THE PHOTOGRAPHIC CHART OF THE HEAVENS. 67 



seem more crowded in a great plane, and in the same plane we 

 should see certainly two, and probably many nebulae, projected 

 into straight lines, because looked at in the plane in which they 

 revolve ; in some directions the stars would appear thinner than 

 in others, because in those, the photograph shews us they do not 

 extend so far into space, and in others owing to the dark spaces 

 in the great spiral, we would see through into the infinity beyond. 

 If you look at the photograph and assume as I have done above, 

 that the whole universe of stars is spread out in the plane of the 

 photograph, you will notice that there would be no difficulty in 

 finding positions from which the observer would see through 

 some of the comparatively dark places as well as other directions 

 in which countless multitudes of stars of all magnitudes would 

 meet the gaze. In fact, his vision would be much the same as 

 ours, in one plane in the heavens, that of our universe, we see an 

 inconceivable wealth of stars, the Milky-Way, with here and 

 there dark spaces, coal sacks — so called — due to the dark rifts 

 such as those above referred to, and turning our eyes gradually 

 a, way from that plane the number of stars decreases, although 

 they are still abundant. 



Now, although even amongst the infinitude of the heavens, we 

 cannot find two star-clusters, or two nebulae alike, we can still find 

 classes, which have many points in common, and I think we have 

 reasonable ground for supposing, that we have presented to us 

 in the Nubecula Major, a universe similar to that in which we 

 are, and that instead of seeing it from within, where it is im- 

 possible to make out its form, we are here — with the aid of 

 telescopes, and the still more powerful Star Camera — able to see 

 just such a universe, to trace out a rational explanation of the 

 many puzzling features of the stars, and Milky-Way around us, 

 and to see how such a universe may be arranged. 



In reference to another well-known southern object, " the 

 nebula about Eta Argus," it will be remembered that last session 

 I exhibited a photograph of it with three hours exposure, stating 

 that it had not been exposed long enough. On April 9th, 1891, 



