C s 93 3 
XIII. A Third Catalogue of the comparative Brightness of the 
Stars; with an introductory Account of an Index to Mr. 
Flamsteed’s Observations of the fixed Stars contained in 
the second Volume of the Historia Coelestis. To which are 
added , several useful Results derived from that Index. By 
William Herschel, LL.D. F.R.S. 
Read May 18, 1797. 
In my earliest reviews of the heavens, I was much surprised 
to find many of the stars of the British catalogue missing. 
Taking it for granted that this catalogue was faultless, I sup- 
posed them to be lost. The deviation of many stars from the 
magnitude assigned to them in that catalogue, for the same 
reason, I looked upon as changes in the lustre of the stars. 
Soon after, however, I perceived that these conclusions had 
been premature, and wished it were possible to find some me- 
thod that might serve to direct us from the stars in the British 
catalogue, to the original observations which have served as a 
foundation to it. The labour and time required for making a 
proper index, withheld me continually from undertaking the 
construction of it : but when I began to put the method of 
comparative brightness in practice, with a view to form a ge- 
neral catalogue, I found the indispensable necessity of having 
this index recur so forcibly, that I recommended it to my Sister 
to undertake the arduous task. At my request, and according 
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