13 



January 16, 1851. 



Lieut.-Col. SABINE, R.A., V.P. and Treasurer, in the Chair. 



The Chairman, by desire of the President, read the following 

 letter : — 



" Downing Street, Jan. 6, 1851. 

 " My Lord, — I beg to inform your Lordship, that I shall set 

 apart One Thousand Pounds, from the fund for Special Service, to 

 be applied by the Council of the Royal Society in the same manner 

 as the grant made for Scientific purposes last year. 

 " I have the honour to be, 



" Your Lordship's obedient humble Servant, 



"J. Russell." 



" The Earl of Rosse" 



The following papers were then read : — 



1. "On the Results of Periodical Observations of the Positions 

 and Distances of Nineteen of the Stars in Sir John Herschels Lists 

 of Stars favourably situated for the investigation of Parallax con- 

 tained in Part III. of the Phil. Trans, for 1 826, and in Part I. for 

 1827." By Lord Wrottesley, F.R.S. &c. Received November 14, 

 1850. 



In Sir John Herschel's papers above referred to, he shows that if 

 a double star occupy a certain position with respect to the ecliptic, 

 and one of the components be supposed to be very much nearer to 

 the earth than the others, a considerable periodical and parallactic 

 change will take place in their angle of position, and that the maxi- 

 mum variations from the mean position will occur at two opposite 

 seasons of the year, which indicate the best times of observation of 

 the parallax of the star. Sir John gives a list of stars thus favour- 

 ably situated, with the coefficients of the maximum parallactic varia- 

 tion of the angles of position, and the times of their occurrence 

 subjoined. 



Lord Wrottesley having erected at his seat in Staffordshire an 

 observatory provided with a good equatorial, determined to devote 

 the instrument to a good trial of the method, and the present paper 

 contains the results of his observations and researches. 



The equatorial employed was that formerly belonging to Mr. 

 Beaumont. Its telescope is of 10 feet 9 inches focal length, and the 

 object-glass is of 7|- inches clear aperture, and a good glass of its 

 size. The instrument is mounted according to the usual English 

 method for a fixed observatory, viz. with a long polar axis resting 

 in at each end. This polar axis is 14 feet 3 inches long, and 

 10 inches square in the middle, having pivots at the ends of hard 

 bell-metal. The Y^ above and below are attached to massive stone 

 piers, supported by a very firm and large foundation of brick-work. 

 The steadiness of the instrument is not satisfactory, compared with 

 that of some recently-established equatorials. The observations were 

 made with a parallel-wire micrometer, containing one fixed and two 



