174 -D r . Herschel's Method of observing the 
time assured that those other stars remain still in their former 
unaltered lustre. But if the star D will no longer stand in its 
former order CDE, it must have undergone a change ; and if 
that order is now to be expressed by CED, the star has lost 
some part of its lustre ; if on the contrary, it ought now to be 
denoted by DCE, its brightness must have had some addition. 
Then, if we should doubt the stability of C and E, we have 
recourse to the orders BCD, and DEF, which express their 
lustre ; or even to ABC, and EFG, which continue the series 
both ways. Now having before us the series BCDEF, or if 
necessary even the more extended one ABCDEFG, it will be 
impossible to mistake a change of brightness in D, when every 
member of the series is found in its proper order, except D. 
Here I have used the letters of the alphabet merely to ex- 
plain my way of fixing the order of brightness of the stars. 
In the journal or catalogue itself, which gives this order of 
brightness, each star must bear its own proper name, or 
number. For instance, the brightness of the star <$“ Leonis may 
be expressed by j3 $ s Leonis, or better by 94 — 68 — 17 
Leonis; these being the numbers which the three above stars 
bear in the British catalogue of fixed stars. 
Perhaps it may be thought that the known introduction of 
letters, added to the magnitudes of the stars, seems to be that 
very method which I now recommend, as different from what 
has already been used. And certainly if letters had been an- 
nexed to stars with a strict view to their order of brightness, 
they would now be of considerable service ; but the intention 
of the astronomers who lettered the stars seems only to have 
been to give them a name, whereby to call them more readily, 
than by the descriptive method of pointing out their situation. 
