MILKY- WAY RECENTLY TAKEN AT SYDNEY OBSERVATORY. Ill 



parts must be given. As we saw just now even the coal sack is 

 full of diamonds, so here we find no rift in the stars of the Milky- 

 Way, but the same distribution of stars as in other parts. It has 

 always seemed to me that the theories put forward to account for 

 the visible Milky- Way were most fantastic and improbable, and 

 that something must be wrong about the facts which required 

 such views to account for them, because they are so unlike the 

 arrangements which we can see amongst distant nebulous bodies. 



Of course the question at once arises, if these stars have no 

 effect on the eye why are they so conspicuous with the photographic 

 eye. In looking at the stars in these spaces with the large 

 telescope, I have always had the impression that I was looking at 

 stars through a mist, and accounted for their faintness by supposing 

 that cosmical clouds intervened, a view that has been held by many, 

 but their presence here may mean that speaking generally, the 

 stars in these regions are more powerful in photographing them- 

 selves than those in other parts. There might, for instance, be a 

 preponderance of blue or of white stars, while other parts con- 

 spicuous to the eye might have a large number of yellow and red 

 stars, and every one who has examined the bright parts of the 

 galaxy knows how these colours congregate in the brighter parts 

 of it ; such stars of course have very little power in recording 

 themselves by photography. If such be the case it would account 

 at once for the difference between the visual and photographic 

 picture. But I am disposed to think that this is not the main 

 cause, although it may have something to do with it ; what seems 

 to be the real cause is a fault in the photographic method, which 

 will have to be carefully remembered in using it, for it tends to 

 exaggerate the small stars and show them out of their true relation 

 to the larger ones. Suppose for instance a photo is taken of a 

 group of stars of various sizes, the light from the brighter stars 

 continues to shine on one part of the plate, and when it has 

 produced all the effect that can be produced on that part of the 

 film it can do no more, no matter how long the exposure is carried 

 on • during the same time that the larger star took to produce 

 its full effect, the smaller one with its feeble beams produces but 

 a very slight effect on the sensitive plate, but by continuing the 

 exposure the feeble star goes on accumulating its effect upon the 

 film until ultimately it will have done as much as the brighter 

 one. Or to put it another way, this process may be carried on 

 until the true relation of the stars is destroyed ; and in order to 

 make the camera show us what the eye sees, a series of pictures is 

 necessary, shewing first the brighter stars, then those of the next 

 magnitude, and so on. But the fact remains that in some of the 

 great dark spaces of the Milky-Way we have probably as many 

 stars, fainter though they be, as we have in the other parts. 



