1835.] First Astronomer- Royal. 413 



some vehemence, *' He must have them anew observed, 

 examined and corrected, for the use of his seamen ; " and 

 further, (when it was urged to him how necessary it was to 

 have a good stock of observations taken for correcting the 

 motions of the moon and planets), with the same earnest- 

 ness ** he must have it done." And when he was asked 

 Who could, or who should, do it? '* The person (says he) 

 that informs you of them." Whereupon I was appointed to 

 it, with the incompetent allowance aforementioned : but 

 with assurances, at the same time, of such further additions 

 as thereafter should be found requisite for carrying on the 

 work. 



[For the site of the Observatory, Hyde Park and'Chelsea 

 College were proposed, but, at the suggestion of Sir Chris- 

 topher Wren, Greenwich Hill was chosen. The King 

 allowed £500, with bricks from Tilbury Fort, where there 

 was a spare stock, and some wood, iron, and lead from a 

 gatehouse which had been demolished in the Tower. In 

 July, he removed to Greenwich to look after the workmen. 

 The foundation of the building was laid 10th August, 1675, 

 and the roof was finished by Christmas. 



While living with Sir Jonas Moore, he contrived the 

 large sextant of 6 feet 9 inches radius ; and Sir Jonas had 

 it constructed of wood at his own expense, by the Tower 

 smiths. The frame of the sextant was soon finished with 

 the axis and semicircle ; the brass limb being fitted on it 

 with the telescopes, and the limb screwed to carry the 

 moveable index gently upon the limb, by Mr. Tompion. 

 This was the first instrument of such a size. 



Mr. Hook claims to be the inventor of the mode of 

 screwing the limbs of instruments ; but according to Flam- 

 steed, this contrivance is due to the Emperor Ferdinand. 

 Flamsteed now determined how many revolutions and 

 parts of the screw would answer to any number of degrees, 

 minutes and seconds. He erected a frame parallel to the 

 plane of the terrace at the bottom of the Hill. On this 

 frame the instrument was placed, and from its centre, 8762 

 inches were measured off towards the other end of the walk, 

 where a strong flat rail was placed. " Having computed 

 how many feet answered to a degree, he marked them off 

 on this rule which was made so long, as to subtend an 



