Changes that happen to the fixed Stars. 169 
necessity to introduce such subdivisions ; but how very vague 
must be the expressions 5m, 5.6m, 6.5m, 6m ! I11 vain have 
I endeavoured to find a criterion for a star of any one of these 
magnitudes. On looking over, for instance, the stars of the 
fifth order, I found that in the list of other stars which ought 
to be less bright because they were marked 5.6m, 6.5m, or 6m, 
there were many that exceeded the former in brightness, while 
among those that are put down 5.4m, 4.5m, or even 4m, 
which ought to be more bright, I found several of a lustre not 
equal to some of this fifth magnitude, which I was desirous to 
ascertain. I may therefore justly call the method that has 
been hitherto in use to point out the lustre of stars, a reference 
to an imaginary standard. 
The inconvenience arising from this unknown, or at least 
ill ascertained type to which we are to refer, is such, that now 
our most careful observations labour under the greatest disad- 
vantage. If any dependence could be placed upon the me- 
thod of magnitudes, it would follow, that no less than eleven 
stars in the constellation of the Lion, namely, ( 2 <r ir% Ab c d 
54 48 72, had all undergone a change in their lustre since 
Flamsteed's time. For if the idea of magnitudes had been 
a clear one, our author, who marked / 3 1.2m, and y 2m, ought 
to be understood to mean that (3 is larger than y ; but we now 
find that actually y is larger than ( 3 . Every one of the ele- 
ven stars I have pointed out may be reduced to the same con- 
tradiction ; and as the subject is of some consequence, I shall 
give a few other instances of them. 
<r by Flamsteed is 4.5m, < <p u x v. tt f are all marked 4m, 
and therefore ought to be larger ; but <r is larger than any of 
them. 
MDCCXCVI. 
Z 
