437 
How the variability of the nebula and astar closely adjacent is to be 
explained, it is not easy to say in the actual state of our mtn of 
y of 
might account for apparent extinction of the former; but in this case it 
j oon possible to conceive that the nebula can have a stellar consti- 
on. 
It is at least curious that several variable stars have been detected in 
ithout exception, having been si in or near 
borders of the Milky Way—the star-cluster to wi 
of sun and planets belon In the latter class are included the memo- 
rable star of B. C. 134, which led Hipparchus to fo is e 
munication. Continuity of observation is often most important, and 
can only be secured—and that not always in the uncertainty of weather 
—by a strong force of observers in different localities. 
I am, Sir, your most obedient servant, 
J. R. Hip. 
Mr. Bishop’s Observatory, Regent's Park, Feb. 3. 
P.S. Since writing the above, I have received a letter from Professor 
Secchi, the able and energetic director of the Observatory of the Colle- 
. | gio Romano at Rome, by which it appears that in one of the proverbially 
clear skies of that city, and with the large telescope at his command, he 
was unable on the 27th ult., to discern the least vestige of the nebula.” 
