1826.] Astronomical Society/, 455 



Before he commenced his observations, however, he was 

 desirous of ascertaining what other astronomers had done be- 

 fore him in the same pursuit. But, not having the facihty of 

 reference to many works, he himself (as he emphatically ex- 

 presses it) opened the Great Book of Nature, and explored that 

 vast and splendid volume, as the best catalogue that he could 

 find for the occasion. At the time that he began his important 

 and interesting inquiries, he was not aware of more than four 

 stars that came under the description of double stars : yet, with 

 this small stock he began his pursuit ; and, in the course of a 

 few years, formed a catalogue of 269 double and triple stars, 

 which he presented to the Royal Society, and which is pub- 

 lished in the Philosophical Transactions for 1782. In this 

 Memoir, and in all his subsequent ones, he gave not only the 

 Distances between the two stars, as measured by various me- 

 thods, but also the Angle of Position, or the angle formed by 

 the parallel of declination, and an imaginary line joining the 

 tvpo stars. These records have now become of considerable 

 importance, as enabhng future observers to compare their results, 

 and thus determine the change which those quantities have 

 undergone during the interval that has elapsed since they were 

 made. 



Ever ardent in the cause of science, this distinguished astro- 

 nomer followed up his favourite pursuit by a second collection, 

 consisting of 434 additional double stars ; which was published 

 in the Philosophical Transactions for 1785. 



In the years 1803 and 1804 he communicated to the Royal 

 Society " An account of the changes that have happened 

 during the last 25 years, in the relative situation of double 

 stars : " and it was in these papers that he first made known to 

 the world those astonishing and important facts which have so 

 justly excited the admiration of astronomers. In order to set 

 this in a clearer light, I would remark that it had been hitherto 

 a commonly received opinion, that the difference in the appa- 

 rent magnitude of the fixed stars was caused by the difference 

 in their distance from the eye of the observer : that a star of 

 the first magnitude, for instance, was situated nearer to us than 

 one of the second magnitude ; and this again, nearer to us than 

 one of the third magnitude ; and so on in succession till we 

 came to the smallest point visible in the most powerful tele- 

 scopes : and moreover that those apparent combinations of stars, 

 by twos or by threes, or any larger clusters (numbers of which 

 present themselves to the eye of the observer) were merely the 

 consequence of their lying nearly in the same line of vision, 

 and that they were nevertheless separated from each other by 

 an immense and immeasurable distance. But this, however 

 much it may be true in some particular instances, is not univer- 

 sally the case : for, in the course of the observations alluded to 



