Changes that happen to the fixed Stars. 181 
In the next place, the letters themselves became trouble- 
some ; for a star cannot be found so readily in a catalogue or 
in an atlas by a letter, as it may be by a number. 
The inconveniences attending the above different ways of 
notation having now been sufficiently pointed out, it remains 
only to lay down the method upon which, after many trials, 
I have fixed, in order to avoid them. 
Setting aside the letters entirely I use only numbers in all 
my observations, and these numbers are such as I have added 
with red ink both to the edition of 1725 of the British cata- 
logue, and to the Atlas Coelestis taken from that catalogue, 
and printed in 1729. When I use other stars than what are 
contained in the British catalogue, the authors who have 
given them, and their numbers in the catalogues from whence 
they are taken, are particularly mentioned. 
In the choice of the stars which are to express the lustre of 
any particular one, my first view is directed to a perfect equa- 
lity. When two stars are perfectly alike in brightness, so that 
by looking often and a long while at them, I either cannot tell 
which is the brightest, or occasionally think one the largest, 
and sometimes, not long after, give the preference to the other, 
I put down their numbers together, only separated by a point. 
For instance, 30 . 24 Leonis. However, it can happen but very 
seldom that the equality in the lustre of two neighbouring 
stars is so perfect as not to leave an inclination to prefer one 
to the other; therefore I place that first which may probably be 
the largest, even though I do not particularly judge it to be so. 
But this preference is never to be understood to extend so far 
as to make it improper to change the order of the two stars ; 
and the expression 24 . 30 Leonis will be equally good with the 
