128 Mr.ViGorr^ChfervaUons 



At its greateft brightnefs 44 ± hours. 



In decreafing - - 62 zt hours. 



At its leaft brightnefs 30 rt hours. 



In increafing - - 3^ ± hours. 



All thefe changes, which hitherto feem to be regular and con- 

 flant, are performed in 7 days 4 hours 38 — minutes; this Ifhall 

 ftlle its period, and hereafter will fhew how it is determined 

 with fuch exadlnefs. 



The ftars to which t] Antinoi was compared are in order 

 thus : ^ Aquilae third magnitude, j6 Aquil^ and Q Serpentis 

 fourth magnitudes, i Antinoi fourth or fifth magnitude, and ^ 

 Aquilse a bright fifth. I find, by feveral years obfervation, 

 that /3 AquiliE retains the fame brightnefs. ; Antinoi, which 

 has been examined with particular attention by Mr. Good- 

 RiCKE and myfelf, is fufpeded by us both to be fubjecl to a 

 fmall variation, but not fufficiently apparent, fo as to afFcd: 

 materially thefe comparifons, and poffibly it may be only the 

 effect of fome optical illufion ; for I have frequently remarked, 

 that both in the twilight and moon-light, or when the air is in 

 the leaft hazy, there is a greater difference between the bright- 

 nefs of many of the ilars, than in a dark night and clear Iky. 

 In the following journal of obfervations of ri Antinoi, the 

 Greek letters i3, (J, ^, belong to Aquila, and /, i/, to Antlnous ; 

 fecondly, the magnitudes marked in column the third are by 

 eflimation, and can be of no further ufe than merely to give, 

 at firft fight, an idea of the flares brightnefs ; and laftly, the 

 lines diftinguifhed by inverted commas, are extradls from Mr. 

 Goodricke's journal, whofe friendly afliftance I have often ex- 

 perienced, and was the more welcome on this occafion, becauie 

 repeated attention and great exadtnefs were requifite. 



c Dates. 



