138 Mr. Pigott on the periodical Changes of 
its various changes as follows : in six weeks it had increased to 
its full brightness, the middle time of which was August 11th, 
1795. At its full brightness it was of the 6.7th magnitude, and 
remained the same without any perceptible alteration for about 
three weeks : it then was three weeks and a half in decreasing 
to the 9.10th magnitude, and disappeared a few days after. 
Having reappeared in the following April, 1796, it was on the 
7th of May again of the 9.10th magnitude, and increasing 
nearly in a similar manner as on the 20th of June the pre- 
ceding year ; which completes all its changes, and gives a pe- 
riod of ten months and a half. 
Very remarkable and perplexing it was, that just after I had 
made out the periods of these two variable stars, their changes 
should appear different from those before observed ; the par- 
ticulars concerning that in Sobieski’s Shield have been noticed: 
as for this in the Northern Crown , it shews at present (being 
the computed time of its full brightness), great unsteadiness, 
more so, I think, than any of the variables whose periods have 
been settled with certainty ; for having increased as before, 
with tolerable regularity, till it attained the 7.8th magnitude, it 
then kept wavering between those magnitudes, and is still so 
at the present time (August) that I am closing my account of 
it. I nevertheless hope to add a few more remarks in the Jour- 
nal, as I have done for the other variable. Future observations 
will determine how far the period of ten months and a half is 
rightly settled. I am greatly inclined to think it the true one, 
as the star went through all its changes progressively and 
steadily. Many of the variables are occasionally liable to un- 
expected changes, particularly at the attainment of their full 
brightness in different periods ; such perturbed periods may 
