456 Proceedings of Philosophical Societies. [Junk, 



in the two papers just mentioned, the most remarkable and 

 unexpected phaenomena presented themselves. The apparent 

 distances of many of the double stars were found to diftier 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 revolution 

 round each other. This was the case whether the star had a 

 considerable proper motion of its own ; or whether it was appa- 

 rently at rest with respect to the other stars around it : thus 

 showing incontestibly thai: the tvv^o stars acted on each other 

 agreeably to the universal law of gravitation. 

 . In fact, in the language of Messrs. Herschell and South, " the 

 existence of binary systems (in which two stars perform to each 

 other the office of smi and planet) has been distinctly proved ; 

 and the periods of rotation of more than one such pair ascer- 

 tained with something approaching to exactness. The immer- 

 sions 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 remarkable and regular instance of this kind is that of the 

 double star ^ Ursa Majoris: where the stars perform a revolu- 

 tion 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 Opiuchi presents also a similar phaenomenon, 

 with amotion in its orbit still more rapid. In this case the two 

 stars are very unequal in their magnitude. Castor, y Virginis, 

 C Cancri, I Bootis, J Serpe.ntis, and that remarkable double star 

 61 Cygni, together with several others, exhibit likewise the 

 same progressive increase in the angle of position. The in- 

 stances 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 nebulse, and the singular changes which 

 they seem to be undergoing, and which are too evident to admit 

 of a doubt, and too important to be overlooked, we must con- 

 fess that there is still much to learn in the science of astronomy. 

 It is true that our late illustrious President has drawn some 

 important inferences from those remarkable appearances which 



