JOURNAL 



OF 



NATURAL PHILOSOPHY, CHEMISTRY 



AN© 



THE ART S. 



MAY, 1807. 



ARTICLE I. 



Description of a New Astrometer for finding the Rising 

 and Setting of the Stars and Planets, and their Position 

 in the Heavens. By David Brewster, A. M. 



To Mr. NICHOLSON, 

 SIR, 



J^N astrometer for finding the rising and setting of the Description of 

 stars, was invented about thirty years ago, by M. Jeurat, ^^j. detemin- 

 of the Academy of Sciences at Paris, and is described in the ing the appa- 

 Memoirs of that learned body. The utiiity of this instru-,^ jj^g^j^^g'^;,, 

 ment in abridging the computation of semidiurnal arcs, 

 where great precision is unnecessary, renders It highly in- 

 teresting to those who are engaged in the study or practice 

 of astronomy, and has induced me to send you the descrip- 

 tion of a new astrometer, more simjiie in its construction, 

 and more extensive in its application, than that invented 

 iry M. Jeurat. 



This astrometer, represented in Plate 11. Fig. 1. consists 

 of four divided circumfereaces. The innermost of these is 

 moveable round the center A, and is divided into twenty- 

 4'our hours, which are again subdivided into quarters and 

 minutes, when the circle is sufficiently large. The secoad 

 circumference is composed of four quadrants of declination, 

 divided by means of a table of semidiurnal arcS; adapted 



Vol. XVL-r^MAYj 1807. 3 C to . 



