VOL. LXX1I.] PHILOSOPHICAL TRANSACTIONS. 205 



to find how far our endeavours, to render the first image perfect, have been 

 successful. 



As soon as I was fully satisfied that, in the investigation of parallax, the 

 method of double stars would have many advantages above any other, it became 

 necessary to look out for proper stars. This introduced a new series of observa- 

 tions. I resolved to examine 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 observations on those that would best answer my end. 

 The subject has already proved so extensive, and still promises so rich a harvest, 

 to those who are inclined to be diligent 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. I took some pains to find out what double stars had 

 been recorded by astronomers; but my situation permitted me not to consult 

 extensive libraries, nor indeed was it very material : for as I intended to view the 

 heavens myself, Nature, that great volume, appeared to me to contain the best 

 catalogue on this occasion. However, I remembered that the star in the head 

 of Castor, that in the breast of the Virgin, and the first star in Aries, had been 

 mentioned by Cassini as double stars. I also found the Nebula in Orion was 

 marked in Huygens' Systema Saturnium as containing 7 stars, 3 of which (now 

 known to be 4) are very near together. With this small stock 1 began, and in 

 the course of a few years' observations have collected the stars contained in my 

 catalogue. I find, with great pleasure, that a very excellent observer, whom I 

 have the honour to call my friend,* has also, though unknown to me, met with 

 3 of those stars that will be found in my catalogue: and on this occasion I also 

 beg leave to observe, that the Astronomer Royal, when I was at Greenwich last 

 May, with his usual politeness, showed me, among other objects, a. Herculis as 

 a double star, which he had discovered some years ago. The Rev. Mr. Hornsby 

 also, when I had the pleasure of seeing him at Oxford, in a conversation on the 

 subject of the stars of the first magnitude that have a proper motion, mentioned 

 7r Bootis as a double star. It is a little hard on young astronomers to be obliged 

 to discover over-again what has already been discovered; however, the pleasure 

 that attended the view when I first saw these stars has made some amends for not 

 knowing they had been seen before. 



If I should mention, in my list of observations, a few that may be found 

 difficult to be verified by other telescopes, I must beg the indulgence of the 

 observers. I hope it will sufficiently appear, that I have guarded against optical 

 delusions; and every astronomer, I make no doubt, will find, by those observa- 



* Phil. Trans., for the year 1781, double stars discovered in 1779, at Frampton-house, Glamor- 

 ganshire, by Nat. Pigott, Esq., f. r.s., &c. 



