^M GERARDI REGNERI FOCKENS 



« nor is this ilifference to be found only in Iwo obscrvalions, in which case, it may 

 (( easily be nltributed to llie account of the unavoidable errors ; but five observations in 

 « July opposed to Iwo in December and January , make the zenith distances vary 8" in 

 « the direction , whicli a parallax ought to produce. " 



« I am aware , that it may be objecled , Ihat two observatioris made in the winter 

 « season in December and January, at oue of the maxima of the parallax, are too few 

 « to determine a point of such consequence , and rcadily agree , that the argument is 

 « weakened in pioportion to llie paucity of llie observations : but then , it sliould also 

 « be considered, that the observations made in March and April concur with the rest in 

 « supporting the supposition of a parallax; and, upon the whole , the observations will, 

 « perhaps, be judged to afford a sufficient presumplion of the existence of a parallax 

 « to encourage the undertaking a carefui trial. It is upon the strength of this presump- 

 u lion, principally, that I have ventured to lay these llioughts before the Royal Society, 

 « whose members may justly claim the honour of having made the greatest altempts to- 

 « wards demonstrating this important , but yet undelermined point in aslronomy. " 



Quisnam aulcm M askelyniani propositi eventus fuerit , rogas? Ad meam quidera 

 nolitiam nihil iiervenit, quod faciat ad nostrum argumentum, 



§ 3. 



Memörandus autem est in his, qui circa paraüaxin ingenio magis quam oculis versati 

 occupatique fuerint , Johannes Mitchell, qui anno 1767 conscripsit dissertatiunculam , 

 cujus argumentum titulo egregie respondens huc fere redit (*) : 



« Though no man can al present doubt , that tlie want of a sensible parallax in the 

 « fixed Stars, is owing to their immense distance, yet it may not perhaps be disagreea- 

 « ble to See , that this distance is farther confirmed by other circumstances. For let us 

 « suppose them to be , at a medium, equal in magnitude and natural brightness to the 

 « sun , to which Ihey seem in all respects to be analogous ; and having laid this down as 

 « a foundation to build upon , let us inquire , what would be the parallax of the sun , if 

 « he were to be removed so far fr^ra us, as to make the quantity of the light , which 

 « we should then receive from hira , no more Ihan equal to Ihal of the fixed slars, " 



Indic^t , lucis quantitates , quibus a sole et stellis collustremur , comparari posse se-' 



cun- 



(*) P/iil. Trans. 1767. Vol. LVII. P. I. p. 234. Titulus est: An inquiry into the proballe Parallax 

 and Magnitude of the fixed Stars from the quantity oj light , which they afford us and the par- 

 ticular circumstances of their Situation, By the Rev, John Mitchell. B, D, F. R, S, Ca^mt : 

 Read May 7 and 14. 1767, 



