182 Dr. Herschei/s Method of observing the 
former. When a third star is concerned, such as 30.24. 77 
Leonis, the order of them ought not to be changed ; notwith- 
standing an equality between each member of the series has 
been strictly ascertained. The reason of this is obvious. For 
by the order in which they are placed, it appears that 30 has 
been deemed equal to 24, and 24 equal to 77; but it is not af- 
firmed that 30 has been compared to 77. There will be a great 
probability that these two last stars do not differ sensibly or 
materially ; but since actual comparison is what we are tc go 
by, the order in which the stars are given must remain. 
When two stars are so nearly alike in their lustre that they 
may be almost called equal, and even now and then leave us 
doubtful to which to give the preference ; but when upon a 
longer inspection of them we always return to decide it in 
favour of the same, I separate the numbers that denote these 
stars by a comma. For instance, 41 ,94 Leonis. This ex- 
pression can certainly not be changed to 94 , 41 Leonis; much 
less can the order of three such stars, as 20 , 40 , 39 Libras, 
admit of a different arrangement. If ever the state of the 
heavens should be such as to require a different order in these 
numbers, we need not hesitate a moment to declare a change 
in the brightness of one or more of the stars that are con- 
tained in the series to have taken place. 
When two stars differ but very little in brightness, but so 
that even a doubt cannot arise to which the preference ought 
to be given, I separate the numbers by which they are to be 
found in the catalogue by a short line. For instance, 17- 70 
Leonis; or 68-17-70 Leonis. If, in the former instance, 
a breaking in upon the order is to be looked upon as a proof 
that at least one of the stars has undergone a change in its 
