92 OERARDI REGNER! FOCKENS 



micrometrum lampaclicum , quo distanlias slellarum dupliciutn accurale possit mensura-- 

 le. Imo longius etiam cxspatiatiir in amplificaliones lelescopiorum. 



« As soon as I was fully salisüed tljat in Ihe investigation of parallax the melhod of 

 « double slars would have maiiy advanlages above any olher , it became necessnry to , 

 « look öut for proper stars. This introduccd a new series of obscrvalions. I rcsolved 

 <( toexamine every Star in the heavens with the utmost attention and a very high power, 

 « that I might collect such materials for this research as would enable me to fix my ob- 

 « servations lipon those tliat would best answer my end. The subject has already pro- 

 « ved so extensive , and still promises so rieh a harvest to those who are inclined to he 

 « diligcnt in the pursuit , that I cannot help inviting every lover of astronomy to join 

 « with me in observations that must inevitably lead to new discoveries. " 



Memoiat, quid alii (Cassini, Huyghens, Pigolt, Maskelyne, Hornsby ) in hoc geuere 

 fecerint , quid ipse praestiterit. 



In dislantiis consignandis aut aestimatione , quae valde exacta fuit in pervicinis , aut 

 micrometro usus est. 



Eiliibet distributionem satis uotam duplicium in sex classes. De tribus poslremis «^ 

 quae 15'' — 120" distantes coutinet , haec monet : 



(i Though these will hardly be of any Service for the purpose of parallax , I ihought il 

 « not amiss to give an accounl of such as I have observed ; Ihey may, perhaps, answer 

 e anolher very important end, which also requires a great deal of accuracy, though 

 « not quite so much as ihc investigation of the parallax of the fixed stars. I will just 

 « mention it, though foreign to my present purpose. Several stars of the first magni- 

 « lüde have already been observed , and others suspected , to have a proper motioa pf 

 « Iheir own : hence wc may surmise, tliat our sun , with all its planets and comels , 

 « may also have a motion towards some particular pari of the heavens , on account of 

 « a greater quantily of matter coUected in a numher of stais and their surrounding pla- 

 « nets liiere situated, which may perhaps occasion a gravitalion of our whole solar. 

 «System towards it. If tlii». surmise should have any foundation, it will shew itself in 

 « a series of some years ; as from tljat motion will arise another kind of hitherto un- 

 « known parallax , (see the note in the rev. Mr. Mi Ich ell's papcr on tlie Parallax of the 

 « Fixed btars , Phil. Trans, vol. LVII. p. 252. ) the investigation of wiiich may account 

 « for some part of the motions already observed in some of the principal stars ; and for 

 « the purpose of determining the direction and quantity of such a motion , accurate ob- 

 # servations of the dislance of stars tliat are near enough to be mcasured with a mi- 

 « crometer, and a very high power of lelescopes may be of considerable use , as they 

 <c Will undoubtedly give us the relative placcs of tliosc stars to a much greater degree of 

 « accuracy tlian they can be had by transit instrumenta or seclors, and thereby muoh. 



« soo»- 



