244 GERATVDI REÜNERI FOCKENS 



« quesiion. Tliis series began on the Ist of July 1822, and Las been coutinued to ihe 

 « present time. " . . . . 



« My obscrvalions , thus conducted , indicale in the most decided manner, that ihe 

 « parallax of » Lyrae cannot exceed a very small fraction of a second. " 



Seiiuunlur aniraadversiones quaedam de inslrumento Grenovicensi et Dublinensi. Sed 

 epilogus scriplionis pciquam memorabilis est. 



« Nolhwitstanding ihe imporiance of these inrestigaiions lo the history of astrooomy, 

 « and to cur forraing a correct noiion of the sysiem of ihe uuiverse , yet cur decision 

 « ultimalcly lurns upon so very small a quaniity, ihat our having reduced the enquiry 

 « to these narrow Hmits , ralher tends to show ihe perfection of each insirument ihati 

 « ihe defect of eiiher. " 



« On former occasions I considered the quesiion of parallax in the particular case of 

 (( « Lyrae as undecided, and as perfectly open to future ingestigation ; but the obser- 

 « ralions of the present year have produced , on my miad a conviction approching to 

 M moral certainly. The history of annual parallax appears to rae to be iliis: in propor- 

 « lion as instruments have bocn imperfect in iheir construciion , they have misled ob« 

 « Servers inlo the belief of the existence of sensible parallax. TLis has huppened in 

 « Italy to astronomers of the very first repulation. The Dublin instrument is superior 

 « 10 any of a similar construciion on the coniinenl : and accordingly , it shows a much 

 « less parallax than the Itahan astronomers imagincd they had detccied. Conceiving that 

 tt I have esiablished beyoud a doubl, ihat the Greenwich instrument approaches still 

 « nearer to perfeciion , I can come to no oiher coaclusiou, than that this is ihe reason 

 « why it discovcrs no parallax at all." 



§ 15. 



Protinus Brinkleius responsum parat et annuntiat Decembris 6, 1823 ( * ). 



« This resalt of the quesiion of the southern motion , appears adverse to the opiuion 

 « advanced by Mr. Pond, relative lo the decided superiürity of the Greenwich over the 

 « Dublin circle. If we are to judge of the Instruments by the observations , I am proba- 

 (1 bly right in the opiuion I have long entertained, of the unfi'.ness of the Greenwich 

 « circle for the accurate invcstigation of small raotions. Whereas I have generally 

 « found my insirument consistent in that respect ; unless it be said, it has deceived me 

 « in regard lo the parallax of «, Lyrae. Tliis resting on the authority of the Greenwich 



« inj 



(*) Phil. Trans. i8i4. P- I. p- So. Tom, CXIY, Titulus est: On the north polar distances of Me 

 prineipal fixed slars. By John B r i n k 1 e y. 



