172 Dr. Herschei/s Method of observing the 
comparison, we can only refer to the general, imaginary one; 
and here the rules we have laid down will be of considerable 
service. The magnitude of this star given by Flamsteed 
is 1.2m ; but as we have shewn that there is some ground to 
admit that 1.2m, even in this coarse way of reference, may be 
distinguished from what the same author seems to have taken 
for 2m, we conclude that the star has probably lost some of 
its former brightness. Again, he gives /81.2m, and y 2m. 
This notation may be taken to imply, though indirectly, that 
(3 is larger than y ; which not being the case, we have an ad- 
ditional reason to suspect a change. De la Caille puts 
down 13 2m. Now the difference between the notation 1.2m 
of Flamsteed and 2m of the latter author, can add nothing 
to the force of the argument for a change ; as we have ob- 
served before, that a considerable allowance must be made for 
nominal varieties in different authors. Nor can we draw any 
support from the magnitude itself, because the star will pass 
very well for one of that order, when compared with other 
stars which are marked 2m by the same author. But when 
De la Caille marks (3 2m, and y 3m, we may then conclude 
that he estimated (3 to be larger than y, though we do not 
know that he compared these two stars together ; because a 
whole magnitude in the second class, as we have said, cannot 
well be mistaken, coarse as is the type to which the reference 
is made. Upon the whole, therefore, we conclude that (3 
Leonis is now less brilliant than it was formerly. 
In this manner, with proper circumspection, we may get at 
some certainty, even by the method of magnitudes ; the im- 
perfection of it, however, in other cases is very obvious. <r 
Leonis, for instance, being marked by Flamsteed 4.5m, the 
