Royal Astronomical Society. 209 



It will be seen that the second line in each group is identical, 

 and depends solely on E, F, &c. ; that is on A, B, C, and D. This 

 therefore could be tabulated in the Ephemeris for the day, under one 

 symbol K. The third lines depend on a, 6, &c. and«', 6', &c. ; and 

 therefore admit of tabulation in the Catalogue as k and k' respectively 

 for each star. The corrections could now be in this form : — 



In R.A. =J20'-0+Ee+F/ + Gg+H/i-(K + A-J 

 InN.P.D.=120"-0+Ee'+F/'+Gg'+H//-(K+A'). 



The greatest possible value of K is about 182, and the greatest 

 values of k and k' are about 170. Let 



L=190-K, /=170-^-, l'=nQ-k'; 

 then substituting these values in the last equations, the corrections 



In R.A. =Ee + F/+Gg + HA+L+/— 240'-00 

 In N.P.D.=Ee'+F/'+Gg'-f HA'+L+/'-240"-0 



in which every symbol is necessarily positive. 



The Astronomer Royal finds that logarithms M'ith five decimal 

 places would be wanted for the corrections in R.A., and that four 

 would be sufficient in N.P.D. 



An additional column would thus be required for the Ephemeris 

 and two columns for the Star Catalogue, but there would be no sign 

 employed either in the tabulation or computation. The trouble of 

 deducing E, F, &c., e,f, &c., L, /, &c. is trifling, and might be made 

 still Ccisier by subsidiary tables. The change proposed is not recom- 

 mended for uncatalogued stars observed only once. Stars which 

 are nearer the pole than 3° 45' require special treatment- 

 Orbits of Double Stars. Computed by Capt. W. S. Jacob, B.E. 



These orbits have been computed from all the observations acces- 

 sible to the author, including his own for the current year. The 

 orbit of Castor has only been roughly deduced, as the observations 

 are not yet sufl[icient to define the elements with precision. It was 

 undertaken by Captain Jacob for the purpose of ascertaining what 

 alteration was required in Mr. Hind's elements to make them repre- 

 sent his own observations, and those of Captain Smyth in 1838 and 

 1843. 



In computing the orbits of the other stars, the method of least 

 squares has been employed to correct the elements which were ob- 

 tained in Sir J. Herschel's manner. 



The stars which Captain Jacob has computed are Castor, ^ Ursae, 

 y Virginis, and 70 Ophiuchi. 



Notice respecting a pair of Chinese Planispheres brought from 

 Chusan, and presented to the Society by Captain Sir E. Home, Bart. 

 R.N. By Mr. Woolgar. 



The hemispheres are of twenty-five inches internal diameter, pro- 

 jected stereographically on the j)lane of the ecliptic. The magni- 

 tudes of the stars arc represented conventionally by a method which 

 makes a star of the first magnitude less conspicuous than one of the 

 third or fourth. There are six magnitudes. The principal stars are 



