SIE DAVID GILL, ON THE SIDEREAL UNIVERSE. 183 



I venture to suggest with reference to these spiral nebulae a 

 theory which, though not yet proven, seems to me to have 

 many elements of probability. My beHef is that these giant 

 spirals are distant universes not unlike our own, and that if we 

 could place ourselves on one of these — say the Great Andromeda 

 nebula — w^e should, on looking towards our stellar system, see 

 our Milky Way somewhat as we see (or rather as it has been 

 photographed) the Andromeda nebula. That we should find 

 there condensations of light having stellar spectra such as we 

 see in the great spiral nebulce, and that our own sun and the 

 stars which surround it would be represented by one of these 

 patches or condensations of light, the component stars being too 

 distant to be separately visible. 



In conclusion, the lecturer exhibited photographs of the 

 60-inch reflecting telescope with which the beautiful photo- 

 graphs of the nebulae bad been made. 



The instrument is mounted on Mount Wilson, near Pasadena, 

 in California. It was made by Mr. Eitchey there, by whom 

 also the photographs were taken, and is a marvel of exact 

 mechanical and optical workmanship. 



The lecturer explained the details of its construction, the 

 mode of its use, and made an appeal for funds to establish a 

 similar telescope on the southern hemisphere. 



Discussion. 



The Chaiiiman said : Ladies and gentlemen, ic is not very easy 

 to speak after such a mental treat as we have had, and one hardly 

 knows how best to put into words the thoughts that I am sure are 

 in all our minds. The first is that we are deeply grateful to 

 Sir David Gill for the labour and pains he has taken to make this 

 magnificent subject as simple as it could possibly be for us. Many 

 of our minds were like some, of the nebulae we have just been 

 looking at, although I am afraid not quite as clear as these nebulae 

 now are. 



I am sure we have learned two things ; one is the greatness of 

 the human mind. I take it that one of these magnificent instru- 

 ments is a sort of embodiment of mind, and as you looked at it 

 you saw the way in which the plan was carried out, and thought of 

 the quiet work, and the way in which the observer would devote 

 three nights to get an eleven hours' exposure, and you marvel at the 



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