246 GERARDIREGNERIFOCKENS 



« greally weakened, and Ihis more recent enatninalion has reduced ils force comparati- 

 « vely to almost nothing." 



« An unsleadiness evidontly cxisla in Ihf; Greenwicli instrument, and it is impossilile 

 « to say to what exlent it niay have gone in opposile seasons. Circiimslances would lead 

 « lo tlie suppositioii that some cause diminishes the measure of the inlercepted arc Iie- 

 « tween y Draconis aud a Lyrae in winter, and so conccnls the paraüax of a Lyrae. " 

 _« The effect of some existing cause of error will appear still more plainly if we lake 

 « au exact nican of all the observations in July, made during the five years, and com« 

 « pare Ihem wiih the mcan of all the observations in August. 



« By 83 days of Observation in July . . . 12^ 53' 56",33 

 « « 63 ■« « « (I August . , 5ß, 84. 



<( Now it is irapossible, if there were no cause for Ihe difference of the results oh- 

 « lained under such favourable circumstances , but the ordinary errors of Observation, 

 « that it should have been so grcat. Parallax being admitted, would only do away" 

 « part of the discordauce . . . Part of' the above difference of half a second in July 

 i( and August, must arise from some change in the measure of the arc, and the chatigri 

 V may take place to a much greater exieut beiween winter and summer. " 



In allero auiem capite omnibus rursus considcratis atcpje pondcraiis, eventus recalli- 

 guntur, qui fuerant. exhibiti in alia scriptione , ediia anno 1822 (»). 



« 333 Observations of « J.pae, reduced by the meihod of making the sum of the 

 « Squares of the errors a minimum , give: 



(I the constant of aberraiion = 20",35 



« the constant of solar nutalioa = 0, 51 

 « the constant of parallax = 1, 14." 



Concludit aulcm Brinkleius his verbis: 



« If it should appear bereafter, by any decisive observations, that I have been mista» 



« ken in having attributed the differences of the zenith distances which I have met with 



« in several slars , to parallax , I trust I shall not be found to persevere in the opinion 



« I at present hold. Recent circumstances have led me lo adhere more strongly to that 



« opinion. The alleged permanency of the arc beiween y Draconis nnd « Lyrae , see» 



<i med to furnish a powerful argument against me , and I have heretofore represented it 



« as such; now I consider the Greenwich observations of this arc, if not favourable, 



« certainlv not adverse lo parallax." 



«The 



(*) Transactions of the Royal Irish Academjr, 1822. Vol, XIV. Titiilus est; On solar nutation. 



