176 Dr. Herschei/s Method of observing the 
letters, at least the numerical magnitudes affixed to the stars 
by astronomers, point out an order of brightness ; and there- 
fore contain my method already established. A succession of 
the marks 1, 2, 3, 4, 5, &c. and other intermediate notations, 
which are to be found in the British, and other catalogues, 
give us a long list of stars that are (or should be) in a regular 
order of brightness, from a star of the first magnitude down to 
one of the eighth or ninth. 
That these marks, denoting the magnitudes of the stars, are 
of some use every astronomer will readily perceive ; but if we 
would apply them to the purpose of detecting a change in the 
lustre of some suspected star, the defect of this method will 
easily appear, and has already been shewn in the instance of a- 
Leonis. It was hinted before that the subject would recur 
again, I shall therefore mention two other instances, in the 
first of which the common notation is sufficiently expressive. 
It will be so in all cases where a very considerable change 
takes place. Thus, (3 Persei being marked 2.3m, and ^ of the 
same constellation 4m, there could be no doubt of a change in 
the light of Algol when it was found to be not brighter than 
But let us in the next place take an observation recorded 
in my journal. 
“ May 12, 1782. (3 Lyras is much less than y.” 
Now, examining the British catalogue, we find /3 3m, and 
y 3m. Had the method of orders been adopted by Flam- 
steed, we should at once have pronounced this star to be 
changeable. For it would have been (3 y in his time, and y(3 
at the time of observation ; but since we have shewn that no 
inference can be drawn from the order of the letters, we have 
only the magnitudes to refer to. And here again the deviation 
