at the Cape of Good Hope. 97 
minating at 5542. 'The particulars respecting each are arranged 
in five columns, giving, for the epoch of 1830, the right ascen- 
sion, the north polar distance, the angle of position, the distance 
of the separate members from each other, and their comparative 
magnitudes ; and, in a broader column on the right, are append- 
ed copious remarks on each. Among these double stars, as might 
be expected, several binary systems were detected, indicating, in 
some cases, a rapid revolution of the members around a common 
centre of gravity. 
_ One of the most interesting of the binary systems is that of 
Gamma Virginis. Sir John Herschel had previously made this 
a particular object of research, and predicted the perihelion pas- 
sage of the smaller star. He had, however, assigned to it too 
large an orbit, requiring 625 years to complete a revolution, 
whereas its period he now finds to be only 1822 years. The 
iirst person, so far as we are informed, who discovered that the 
period formerly assigned must be greatly reduced, was Mr. E. P. 
Mason. On this subject, our distinguished countryman, Mr. S. 
©. Walker, remarks as follows: “In an interview with Mason in 
his short stay in Philadelphia, while on his way to his final rest- 
mg place in Virginia, he showed me a list of his measurements 
the positions and distances of several of the binary systems, 
(as 7 Virginis, Castor, « Corone, &c.) and mentioned that a dis- 
cussion of all the observations published to the date of 1838, 
With his own of the spring of 1840, on the graphic method of 
the younger Herschel, had given him an ellipse of a period of 
71 years for y Virginis; and that the date of 1840-4 with his 
elements, furnished an angle of position of 254 degrees. I have 
since received the Astronomical Notices from Altona, and there 
find a similar value for the same date, in the measurements of 
Struve at the great Pulkova Observatory, and of Kaiser at the 
Leyden Observatory.”* In the work before us, Sir John Her- 
schel has the following remarks on this subject. “The apparent 
perihelion passage of this interesting double star, took place in 
the first half of 1836, and the appulse of the two stars proved, 
as predicted, so very close as to cause it to appear as a single star 
to all but the most powerful and perfect existing telescopes, under 
the most favorable circumstances. In no part of the interval 
from 1835-971, to 1937-545, both dates inclusive, was it possible 
to observe any certain elongation of the united disks with the 
_ Seven-feet equatorial, capable of being, in the smallest degree, re- 
lied on for a measure.” As an apology for having so much mis- 
taken the period of revolution, our author shows by a diagram that 
‘ing the period of observation from 1782 to 1835, the orbit of 
625 years would in fact almost coincide with the orbit of 182 
Ba 
SP) oe oe Memoir of E. Pi Mason; p30. 
Scop Series, Vol. V, No. 13—Jan., 1848. 13 
