On the Nebula around Eta Argus. 23 



tliis character was one discovered by Mr. Hind in 1852 ; it was ob- 

 served rather bright by D'Arrest in 1853, by M. Auwers in 1858 

 fainter, and in 1861 he could not find it with the same telescope, 

 4-|-inch, or with a 6-inch. AVith the large refractor at Pulkowa 

 it was seen, but very faint indeed. Another one in Coma 

 Berenices, discovered by Sir William Herschel, was missed in 

 1862. D'Arrest having found two nebula which he thought new, 

 Sir John Herschel pointed out that his father found three in the 

 same place ; subsequently M. Foucalt's large reflector revealed 

 the missing object, but it was very faint indeed. 



The extent of these faded nebula near Eta, if assumed to be at 

 the distance of the nearest known fixed star is so great; that 

 space for thousands of solar systems such as ours would be found 

 without the orbits of the most distant members overlapping ; yet 

 all has to our senses ceased to be in about thirty years — perhaps 

 had done so when the Cape drawing was made, with light which 

 may have been still streaming in from space. 



What can be the constitution of such systems we naturally 

 ask ? and science answers, wait ! But before such facts, we 

 must speculate. 



Are they gas which has ceased to shine and now forms a dark 

 veil obscuring the light of the stars ? Are they innumerable 

 suns, the centres of minor systems, which have used up all their 

 stores of meteoric and cometic fuel, and are now frozen in dark- 

 ness ? Are they accumulations of meteors, such as we know are 

 revolving round our own sun and at irregular periods darkening 

 his surface, as in 1090, when it was during daytime dark for three 

 hours — 1208, for six hours — 1547, for three days — 1706, dark 

 enough at 10 a.m. to light candles ; and 1777, when " Messier" 

 saw innumerable dark bodies passing over the sun at noon ? Were 

 they once incandescent, but now cooled down, still revolving 

 round their common centre of gravity, now more and now less 

 between us and it, making for us as the ages roll on a variable 

 star, hazy at its minimum, like Eta is at the present time, and 

 bright beyond measure at its maximum ? 



Or ; are they inexplicable difficulties in the path of astronomers 

 which no speculation will ever solve ? 



List of Recoeded Magnitudes of Eta Aegus. 



1677 



4 



Halley 



1858 2.3 Powell 



1751 



2 



Lacaille 



(made in same year 



1811 



4 



Burchell 



2.1 by Abbott) 



to 







1859 3.1 Powell 



1815 



4 



Burchell 



(made in same year 



