HERSCHEL THE DISCOVERER. 41 



distinct from each other. In the first system, one 

 telescope was used on different regions of the 

 heavens ; whereas in the second method, various 

 telescopes were used on identical regions. The 

 principle was that the telescopic power necessary 

 to resolve groups of stars indicates the distance 

 at which the stars of the groups lie. This, 

 however, also assumed an equal distribution of 

 stars, and as the late Mr Proctor says, "I 

 conceive that no question can exist that the 

 principle is unsound, and that Herschel would 

 himself have abandoned it had he tested it 

 earlier in his observing career. ... In ap- 

 plying it, Sir W. Herschel found regions of 

 the heavens very limited in extent, where the 

 brighter stars (clustered like the fainter) were 

 easily resolved with low powers, but where his 

 largest telescopes could not resolve the faintest. 

 These regions, if the principle were true, must 

 be long, spike-shaped star groups, whose length 

 is directed exactly towards the astronomer on 

 Earth, an utterly incredible arrangement." 



Herschel, at the time of his death, left un- 

 solved the problem of the construction of the 

 heavens. It is still unsolved, and will doubtless 

 remain so until astronomers know more about 

 the distances and motions of the stars. His 

 last observation of the Galaxy showed that even 



