296 Astronomical Society. 
sented themselves. The apparent distances of many of the 
double stars were found to differ from what they had been at 
a former period; at the same time also that their angles of 
position were discovered to have undergone a perceptible 
variation, and evidently indicating a revoiution round each 
other. This was the case whether the star had a considerable 
proper motion of its own; or whether it was apparently at rest 
with respect to the other stars around it: thus showing incon- 
testibly that the two stars acted on each other agreeably to the 
universal law of gravitation. 
In fact, in the language of Messrs. Herschel and South, 
*‘ the existence of binary systems (in which two stars per- 
‘form to each other the office of sun and planet) has been 
‘‘ distinctly proved; and the periods of rotation of more 
“than one such pair ascertained with something approach- 
‘‘ ing to exactness. The immersions and emersions of stars 
“ behind each other have been noted; and real motions 
‘“‘ among them detected, rapid enough to become sensible and 
‘‘ measurable in very short intervals of time.” ‘The most re- 
markable and regular instance of this kind is that of the double 
star § Urse Majoris: where the stars perform a revolution 
round each other in the short space of 60 years: and already 
three fourths of the circuit has been actually observed from 
the first period of its discovery in 1781 to the present day. 
The double star p Ophiuchi presents also a similar phanome- 
non, with a motion in its orbit still more rapid. In this case 
the two stars are very unequal in their magnitude. Castor, 
y Virginis, § Cancri, § Bootis, § Serpentis and that remarkable 
double star 61 Cygnz, together with several others exhibit like- 
wise the same progressive increase in the angle of position. 
The instances are indeed too numerous for me to enlarge upon 
in this place; and I allude to them merely with a view of 
drawing your attention to this important and interesting branch 
of the science. 
These binary systems, it must be confessed, open a vast field 
of inquiry and speculation relative to the true system of the 
universe. The mind is lost in the contemplation of such im- 
mense bodies performing their revolutions round each other 
at such immeasurable distances. Our vast planetary system 
shrinks to a mere point, when compared to the orbits of these 
revolving suns. When we consider likewise the remarkable 
appearances exhibited by clusters of very minute stars, by ne- 
bulous stars and by nebulee, and the singular changes which 
they seem to be undergoing, and which are too evident to ad- 
mit of a doubt, and too important to be overlooked, we must 
confess that there is still much to learn in the science of astro- 
. nomy. 
