1836.] Results at the Madras Observatory, 49 



gravity, conforming to the Newtonian laws of gravity, equally with the 

 bodies which compose our system. Among the several stars which 

 have been examined, some have been found which perform their revo. 

 lutions in the comparatively short periods of 40 or 50 years, whilst 

 others, again, there are, that take up fifteen hundred years, to perform 

 their circuit. 



Of one of these (7 1 Virginis) the Astronomer just mentioned* (who 

 has lately removed to the Cape of Good Hope, where he is now devot- 

 ing a most particular attention to this class of observations) was pleas- 

 ed to give me, in a letter dated Cape, 7th January 1836, the following 

 information : 



" I made an interesting observation here a few days ago on 7 Virginis. 

 That star is now single ; the two individuals are yet so close, that no 

 magnifying power I can apply to the seven feet equatorial, shews the 

 disc otherwise than round — not even elongated — yet, as the star pre- 

 serves its apparent " magnitude" to the naked eye, it is clear that no 

 part of the body of one star is hidden behind the body of the other." 



The same individual has lately been occupied in verifying the places 

 of the satellites of Uranus. It is well known triat the late Sir William 

 Herschel (the discoverer of this planet) has assigned to it six satel- 

 lites. But, from the circumstance of Sir William Herschel being the 

 only individual who has ever seen these satellites, and from his having 

 obtained but a very limited number of observations of them ; added to 

 the fact of his having assigned to them a motion perpendicular to the 

 plane of the ecliptic (a motion different from that observed in the other 

 twelve secondaries) ; it has been suspected that he might have mistaken 

 some minute stars for the satellites. 



The observations, lately made, have shewn, with regard to two of 

 these satellites, that the motions assigned to them by Sir William 

 Herschel were very nearly correct, differing, in the case of the first 

 satellite, less than half a minute for the period of its revolutions ; and, 

 for the second satellite, agreeing to about one minute and three quar* 

 iers. 



Other observers we find who are variously engaged — In observing, 

 for instance, the position of stars near the moon's path, for determin- 

 ing the longitude form occultations ; or in observing stars near the 

 planet Mars, for the determination of his parallax ; or in sweeping 

 the heavens, night after night, for the purposes of laying down the 

 places of nebulae, or discovering comets. The steady pursuit of this 

 latter class of observation, has made us acquainted, during the last 

 ten years, with the comets of Biela and Encke, as forming a part of 

 our system ; the former traversing its orbit in three years and a half, 

 and the latter in six years and eight months. 



Sir John Herschel, 



