aas GERARDl REGNERI FOCKEPfS 



Dein, 26 Junii 1817 # refert teriio (*), qualis fuerit telescopii in Cygni » fixi eventus. 



« U appcars lo rae Ihat the observaliozis alrcady obtained , afford a proof sufEcieritly 

 « salisfactory, Ihat tlie discordances , which formed Ihe subject of my last commuiuca- 

 « lion , must bave had some other cause tlian parullax. " 



Tum methodum explicat, qua stellam « non.cum libella aul linea plumbea corapara- 

 verit , sed cum Aurigae ß, declinationem eandem , sed longe diversam adscensionem 

 liabenie, et sa'.is lucida , ut interdiu conspiciatur. Observationum 54, inde ab 21 Ja- 

 nuarii usque ad 16 Äugusti 1817 instiiutarum, eventus hi sunt: 



Cygni fls — Aurigae ß. Medium ex 18 observaiionibus. 



8',249 + 9",757 = 18' ,006 



8, 133 + 9, 861 = 17, 994 



7, 604 + 10, 473 = 18, 077 



Sed postquam ad 21 Septembris continuasset observationes, hoc exhibuit scema : '* 



Observationes hyemales 25, Cygni « = 24' + 8",173 * 



« 28, Aurigae /3 = 35 + 9, 81^ ' ' ' '^""" + I7".984 



« neutrales 26, Cygni « = 24 + 7, 920 



« «29, Aurigae /3 = 35 + 10, 044 * * ' *'' ^^^ 



u aesiivae 32, Cygni « = 24 -f- 3, 340 



« 22, Aurigae ß = 35 + 14, 825 * ' * 



« I da not consider tbe small discordance of 0",2 in the total distance of the tWO 

 ■« Stars in a direclion contrary to the efifect of parallax as accidental , but trust that in 

 « time I shaU discover the cause. For the present , however, I am willing to attribüte 

 « it to error of Observation. Now, even in this most unfavourable poiat of view, I think 

 « we may venture to infer, that (supposing the proportion of parallax of each star not 

 « to differ greatly from their degree of brightness ) tlie mean place of either of them is 

 « never deranged by parallax above one tenfh of a second , because such a deviation 

 « would produce , by ils double effect on each star, a total discordance of nearly 0",3, 

 « which 1 really think exceeds the limits of my uncertainty. " 



<i Should the parallax of « Cygni be admitled to be insensible, it would follow Crom 

 « the observations wilh the mural circle,. that it was equally so in a, Lyrae and y Dra- 

 « conis, as these stars have assiduously been observed during a period of 5 or 6 years, 

 « without any perceplible difference at opposite seasons. " 



Difc 



(•) Ibidem p. 353. Titulus est: On tie parallax of the fixed Stars, By Jahn Pond, Esij. As- 

 Ironomer Uojal, 



I 



