the changeable Stars. * j £ 
firft : ftill their fudden appearance, and no certainty of a pe- 
riod, or at lead: infinitely longer, are, I think, fufficient rea^ 
fans to feparate them. 
Laftly, Algol, y\ Antinoi, (2 Lyrae, and S Cephei, are fo 
fimilar to each other, and fo different from the above, that 
there can be but little or no hefitation in diftinguifhing them ; 
alfo the caufe of their changes feem in general to be attributed 
to fpots, and a rotation on their axis. This property of the 
fixed ftars, though often fufpefted, was far from being evident 
till within thefe two years ; and we are not only indebted to 
Mr. Goodrtcke for the difcovery of the firft, but alfo for 
three of the only four known. 
Further may be added, that all thofe of the firft order 
(Ma yer’s 420 being yet fo little known remains doubtful) 
attain in different periods different degrees of brightnefs when 
at their full ; alfo the progreffive increafe of brightnefs of 
that in Hydra, that in the Swan’s breaft, of 0 Ceti, (2 hyrx 9 
t\ Antinoi, and $ Cephei, is not fimilar to their decreafe. This 
peculiarity with regard to Algol is yet uncertain, owing to the 
rapidnefs of its changes, fo that there is only one that feems to 
have thefe points uniform, viz the variable in the Swan’s 
neck. 
I ihall now conclude with the obfervations from which fome 
refults, given in this Paper, have been deduced ; they are here 
collefted together, in order to avoid confufion. 
Obfervations 
