COMMENTATIO ÄSTRONOMICA. 2?9 



t tities furnished by othei-s ? A conaiderable negalire parallax would have been decisive. 

 « Agaiii, mig'it it not hare beea cspected Ihat slars, ia which the effect of parallas ia 

 t declination is oiily a small part of the whole , would have showa a great paralJai of 

 « declination as well as otliers , if Ihe appearence of parallax ia to be aUributed to some 

 « other cause? Aldebaran , /3 Tauii^ «Orionis, Castor, Procyon, Pollux., ele. are so 

 « situate , that only a »mall part of tbe wLole parallax could affcct the declination , 

 « and therefore if these Stars had exhibited a chaoge of place of a second or Iwo, it 

 « could not arise from parallax." 

 tjusque verosimilitudinem ita: 



« The results, contained in the three first tables, have been deduced frota so many 

 « observations, that it is impossible that the principal conclusions , although relative to 

 « such minute quantities , can be materially affecled by the variable errors of observa» 

 V tion. If error exist , it must be from some cause not to be eontroUed by mere obser- 

 « valions. Two causes suggested themselves , which seemed to require particular consi , 

 « deralioa. " 



Temperaturam autem opinatur , scilicel diversa anni lempestate diversam , aerisque 

 interai diversam ab exlerni aeris temperatura. 

 Peroratio est haec fere s 



« Having thus given a detaiied accouut of observations that have been prmcipally in- 

 \t stituted with a view of obtaining an explanation of the source of the difference of the 

 « results of my former observations and of those of Mr. Pond, relative to parallax, it 

 « is with concem I State , that it contains not a trace of amj such explanation. I ha- 

 & ve been unable to obtain any result that is opposed to my former conclusions. " 



Sequuntur autem tres animadversiones de Pondianis observationibus. Tandem ob- 

 servationum suarum tractat probabilitalem et reduclionum verosimiles valores. 

 Epilogus scriptionis totius hujusmodi est : 



« The discordances between my observations and those made at Greenwich may , by 

 « some, be considered as showing the great precision of modern observations, when it 

 « is understood, that the whole extent of the absolute difference betweea the results of 

 « the observations of the Astronomer Royal , and of those made here , is only about one 

 « second. But independently of Ibe interest of the question of parallax, it is highly im-. 

 « porlant to ascertain the origin of Ihis small difference. It may instruct as to the limil 

 « of accuracy actually to be attained to , when apparently there should exist no limit. " 

 # It will also appear, should any of the results that I have found be inexact, that 

 « the delicacy of an Instrument cannot be appreciated by giving correctly some of the 

 « analler motions , real or apparent , that oecur, because the same Instrument may, as 

 « to others, eatirely mislead. Whalever may be the ultimale detenninatioa», it is ho- 



«ped,- 



