250 A Short History of Astronomy [Cn. x. 



office of Astronomer Royal, with a salary of ^100 a year, 

 and the warrant for building an Observatory at Greenwich 

 was signed on June i2th, 1675. About a year was occupied 

 in building it, and Flamsteed took up his residence there 

 and began work in July 1676, five years after Cassini 

 entered upon his duties at the Observatory of Paris 

 (chapter vin., 160). The Greenwich Observatory was, 

 however, on a very different scale from the magnificent 

 sister institution. The King had, it is true, provided 

 Flamsteed with a building and a very small salary, but 

 furnished him neither with instruments nor with an assist- 

 ant. A few instruments he possessed already, a few more 

 were given to him by rich friends, and he gradually made 

 at his own expense some further instrumental additions of 

 importance. Some years after his appointment the Govern- 

 ment provided him with " a silly, surly labourer " to help 

 him with some of the rough work, but he was compelled 

 to provide more skilled assistance out of his own pocket, 

 and this necessity in turn compelled him to devote some 

 part of his valuable time to taking pupils. 



198. Flamsteed's great work was the construction of a 

 more accurate and more extensive star catalogue than any 

 that existed ; he also made a number of observations of 

 the moon, of the sun, and to a less extent of other bodies. 

 Like Tycho, the author of the last great star catalogue 

 (chapter v., 107), he found problems continually presenting 

 themselves in the course of his work which had to be 

 solved before his main object could be accomplished, and 

 we accordingly owe to him the invention of several improve- 

 ments in practical astronomy, the best known being his 

 method of finding the position of the first point of Aries 

 (chapter n,, 42), one of the fundamental points with 

 reference to which all positions on the celestial sphere are 

 defined. He was the first astronomer to use a clock 

 systematically for the determination of one of the two 

 fundamental quantities (the right ascension) necessary to 

 fix the position of a star, a method which was first suggested 

 and to some extent used by Picard (chapter vin., 157), 

 and, as soon as he could get the necessary instruments, 

 he regularly used the telescopic sights of Gascoigne and 

 Auzout (chapter vin., 155), instead of making naked-eye 



