i86 HISTORY OF PHYSICAL ASTRONOMY. 



published two Standard Catalogues ; that of the Royal Astronomical 

 Society, containing 2881 stars; and that of the British Association, 

 containing 8377 stars. I omit other Catalogues, as those of Argel- 

 ander, &c., and Catalogues of Southern Stars. 



Of the Berlin Maps, fourteen hours in Right Ascension have been 

 published ; and their value may be judged of by this circumstance, 

 that it was in a great measure by comparing the heavens \vith these 

 Maps that the new planet Astraea was discovered. The Zone observa- 

 tions made at Konigsberg, by the late illustrious astronomer Bessel, 

 deserve to be mentioned, as embracing a vast number of stars. 



The common mode of designating the Stars is founded upon the 

 ancient constellations as given by Ptolemy ; to which Bayer, of Augs- 

 burg, in his Uranometria, added the artifice of designating the bright- 

 est stars in each constellation by the Greek letters, a, j3, y, &c., applied 

 in order of brightness, and when these were exhausted, the Latin let- 

 ters. Flamsteed used numbers. As the number of observed stars in- 

 creased, various methods were employed for designating them ; and the 

 confusion which has been thus introduced, both with regard to the 

 boundaries of the constellations and the nomenclature of the stars in 

 each, has been much complained of lately. Some attempts have been 

 made to remedy this variety and disorder. Mr. Argelander has recently 

 recorded stars, according to their magnitudes as seen by the naked 

 eye, in a Neue Uranometrie. 



Among representations of the Moon I may mention Hevelius's Sele- 

 nographia, a work of former times, and Beer and Madler's Map of the 

 Moon, recently published.] 



I have already said something of the observations of the two Her- 

 schels on Double Stars, which have led to a knowledge of the law of 

 the revolution of such systems. But besides these, the same illustrious 

 astronomers have accumulated enormous treasures of observations of 

 JVcbulce ; the materials, it may be, hereafter, of some vast new general- 

 ization with respect to the history of the system of the universe. 



[2d Ed.] [A few measures of Double Stars are to be found in pre- 

 vious astronomical records. But the epoch of the creation of this part 

 of the science of astronomy must be placed at the beginning of the 

 present century, when Sir William Herschel (in 1802) published in the 

 Phil. Trans, a Catalogue of 500 new Nebula of various classes, and in 

 the Phil. Trans. 1803, a paper " On the changes in the relative situa- 

 tion of the Double Stars in 25 years." In succeeding papers he pur- 

 sued the subject. In one in 1814 he noticed the breaking up of the 



