1^4 ^^' Goodricke's Obfervations 



inclined to think, that the extent of its variation is twelve days, 

 and nineteen hours, during which time it undergoes the fol- 

 lowing changes. 



1. It is of the third magnitude for about two days. 



2. It diminilhes in about one day and a quarter. 



3. It is between the fifth and fourth magnitude for lefs than 

 a day. 



4. It increafes in about two days. 



5. It is of the third magnitude for about three days. 



6. It diminishes in about one day. 



7. It is fomcthing larger than a ftar of the fourth magnitude- 

 for little lefs than a day. 



8. It increafes in about one day and three quarters to the firft 

 point, and fo completes a whole period. 



Thefe eight points of the variation are perhaps inaccurately 

 afcertained ; and indeed it cannot be expelled to be otherwife in 

 eflimations of this nature, where it is very poffible to err even 

 feveral hours. 



The relative brlghtnefs of jG Lyra;, at its obfcuratioii in the 

 third and feventh points, is nearly as follows. When in that of 

 the third point, it is lefs than ^and x, and nearly equal to 

 ^ Lyras ; and when in that of the feventh point, it is rather 

 lefs than J and 5 Herculis, and much brighter than ^, jc, and 

 2 Lyras. At its greatefl: brightnefs in the firfl: and fifth points^ 

 it is fometimes brighter than y Lyrae, but lefs than /3 Cygni,. 

 and fometimes only nearly equal to it 5 but in thofe points it 

 fcems to alter in its brightnefs feveral times in the fame night,, 

 and that generally in a pretty confiderable degree. However,, 

 this may perhaps be only owing to fome fallacy of obfervation ; 

 for I have often perceived, that the relative brightnefs of ftars 

 is affeded not only by the different flates of the air, but alfo by 



their 



