Mechanical Philosophy. 59 



secondary, including the minute irregularities of 

 each, with some errors indeed, but with a degree 

 of conformity to nature and subsequent observa- 

 tion, which must ever astonish and delight the in- 

 quiring mind. The British philosopher leaving 

 astronomy in this improved state, no wonder that 

 those who came after him should at once, with 

 growing ardour, and with greater ease, pursue a 

 course which he had so happily marked out. 



At the beginning of the century under review, 

 we find Flams TEAD, the first Astronomer Royal of 

 England, devoting himself to this science with 

 great zeal and success. He particularly directed 

 his attention to the ^fixcd stars y and after a series of 

 patient and most laborious observations, published, 

 in 1719, a catalogue of stars, more extensive and 

 -accurate than had ever been formed by one man. 

 To him, both in office, and in astronomical fame, 

 succeeded Dr. Halley, who made a number of 

 important discoveries, and useful publications. 

 Among many others which might be mentioned, 

 he discovered the Acceleration of the Moon, and 

 gave a very ingenious method of finding her paral- 

 lax. He composed tables of the Sun, the Moon, 

 and all the planets. He also recommended the 

 mode of ascertaining the Longitude by lAinar Ob- 

 servationss a mode which has been since much 

 improved, and generally adopted; and which is, 

 at present, the most certain guide of the mariner. 

 After him, at the head of the Royal Observatory 

 was placed Dr. Bradley, who greatly distin- 

 guished himself as a practical astronomer. He 

 was the first who made observations with sufiici- 

 ent accuracy to detect the smaller inequalities, in 

 the motions of the planets and fixed stars. By 

 means of this accuracy, he discovered, in 1727, 

 \\\c aberration of tlie stars, a phenomenon pro- 

 duced by the compound motion of the earth, and 



