L';d 
4S0 Mr. goodricke’s Account of a 
April 13. : _ ' . 
At 8 h. it was between the third and fourth magnitude; 
brighter than 0 Per lei, but not fo bright as $ Perfei. 
• At 82 h. rather brighter than a Perfei, and not fo bright ass 
Perfei. 
At 9 h. rather brighter than s Perlei. It was too low to 
ohfervd its farther variation. 
. May3 \ ■ • . . 
At 9 1 h. nearly between the third and fourth magnitude, 
and fomewhat brighter than ? Perfei ; but fo low that I coulff 
not well compare it with other ftars, or be able to oblerve the 
remainder of the variation. I believe it muft have paffed its- 
lead brightnefs not long before. 
The times of the above obfervations are nearly apparent 
4 r 
time, and were for the molt part made under favourable clr- 
cumftances. My friend Mr. edward pigott, to whom I 
am' under great obligations on this as well as on other ocea- 
fions, alfo obferved fome of the variations; and where our 
times of obfervation were the lame, always agrees with me. 
• • * ■ * a T ^ 
From an attentive comparifon of all the particulars in the 
above obfervations it appears, firlf, that this {far changes from 
the fecond to about the fourth magnitude in nearly three hours 
and a half, and from thence to the fecond magnitude again in 
the lame fpace of time ; fo that the whole duration of this 
lingular variation is only about feven hours. And, fecondly, it? 
appears alfo, that this variation probably recurs about every two 
days and twenty-one hours. This laft conclufion will be ren- 
dered more confpicuous by the following table ; the firfl co- 
lumn of which Ihews the days, and exact time of the day, 
when Algol was obferved to be very near, or at its lealt bright- 
nefs ; the fecond column marks the different intervals of time 
o elanfed 
