177 
Changes that happen to the fixed Stars. 
of (3 from its usual brightness not being so considerable, but 
that a star such as it appeared to be at the time of observation 
might pass for one of the third magnitude, we are left in the 
dark ; notwithstanding which a few years after, this star was 
actually found to be not only changeable, but periodical.* 
M. de la Lande in mentioning the change of $ Ursae ma- 
joris arranges the seven bright stars of that constellation as 
they appeared to him ; and remarks that sometimes y and e 
should stand before (3, and sometimes after it. Here we have 
something like an order of seven remarkable stars ; but as it 
happens, the stars themselves are not favourable to the forma- 
tion of a regular series. Mr. Pigott and Mr. Goodericke 
also compared the stars whose changes they were examining 
to other neighbouring stars that were proper to be estimated 
with them, and were in a manner forced to lay aside the me- 
thod of magnitudes.-f These instances contribute to support 
the arguments I have used, to shew that another method of 
ascertaining the lustre of the stars is required, while at the 
same time they sufficiently indicate that the comparative 
brightness of stars is the only safe one to which we can have 
recourse. 
It will be necessary now to enter into a full display of my 
proposed method ; for simple as it is in its principle, it is not 
only difficult but very laborious in its progress. I began to 
put it into execution about 14 years ago ; but other very in- 
teresting astronomical pursuits have broken in upon the re- 
gular continuation of it. By relating the difficulties or incon- 
veniences as they happened, it will appear that my present 
* Phil. Trans. Vol. LXXVI. Parti, page 197. 
+ Phil. Trans. Vol. LXXV. Part I. page 127 and 154, 
mdccxcvi. A a 
