Proceedings of the Royal Society. 251 
Thursday, January 15, - 
Messrs. J. H. Vivian and M. Faraday were respectively ad- 
mitted Fellows of the Society. 
The reading cf Messrs. Herschel and South’s paper, of which the 
following is an abstract, was resumed and concluded. 
The determination of the apparent distances and positions of 
such double stars as could be measured with micrometrical instru- 
ments, and high magnifying powers, was suggested by Sir W. 
Herschel more than forty years ago; and in his hands it led toa 
new department of physical astronomy, by the discovery of sidereal 
phenomena, referable to the agency of attractive forces. But the 
determination of the existence of annual parallax, the immediate 
object for which the inquiry was instituted, was soon lost sight of, 
in the more extensive views of the construction of the Universe, 
which gradually unfolded themselves. Nor has the investigation 
been resumed, although from the precision with which such obser- 
vations can be made, it seems in the opinion of the authors of this 
paper likely to be the mode by which the existence or non-existence 
of sensible parallax, will ultimately be determined. 
The results of Sir William Herschel’s observations from 1779 to 
1784, were published in the Philosophical Transactions for 1782 
and 1785; and a re-examination after a lapse of twenty years was 
undertaken by him in 1801-2-3 and 4; and in the Transactions 
for 1802 and 1804, unexpected phenomena were communicated. 
Instances in which two stars were performing to each other the 
offices of sun and planet were proved to exist, and to more than one 
pair the period of rotation was, according to the observations of 
the authors of this paper, assigned with considerable exactness. 
Immersions and emersions of stars behind each other had been 
witnessed, and real motions among some of them had been ob- 
served rapid enough to be detected, in very short intervals of 
time. 
But as from the novelty of the subject, and from the imperfec- 
tions of the micrometers employed in 1779 and 1780, it was likely 
hat some instances of error had occasionally crept in, it became 
