4lil Life of the Rev. John Flamsteed, [Dec. 



angle of 5 degrees. Then br^inging the threads in the fixed 

 telescope to the beginning of the divisions, and forming it 

 close, he moved the screw, and carrying the moveable 

 index along the limb, noted what revolutions and parts 

 were marked by it, when the threads covered the divisions 

 of the 5 next degrees. 



During the building of the Observatory, the instruments 

 were kept at the Queen's house, where he observed the 

 appulses of the moon to the planets and fixed stars. In 

 July and August, he took the elevation of the Observatory 

 from two stations in Friar's Road, and found it 182 feet 

 above the Thames. He was anxious for a mural arc, but 

 the sextant having cost more than was expected, a 10 feet 

 quadrant was fitted up by Mr. Hook, at the instance of Sir 

 Jonas Moore, but no dependence could ever be placed 

 on it. 



When he went to reside at Greenwich, the only instru- 

 ments provided for him, were a sextant and two clocks. 

 The sextant was of iron, the limb covered with brass half 

 an inch thick ; its fiducial edge, by a peculiar contrivance 

 received a male screw fixed on the end of the moveable 

 index, which by the help of a crown wheel and handle it 

 easily turned round, and thereby carried the index gently 

 along the limb, and held it immoveable in any place. The 

 revolutions of the screw were numbered on the face of the 

 limb, and were readily turned into degrees and parts of a 

 circle, by means of a table made for that purpose, by trial at 

 land angles, before it was mounted on its axis and semi- 

 circles, in September, 1676. 



In December, 1677, he took the sextant down and 

 divided the limb into degrees and minutes, in the mode 

 adopted by Hevelius and Tycho. His pendulum clocks 

 were made by Mr. Tompion, the pendulums 13 feet long 

 made one vibration in two seconds, and their weights re- 

 quired to be drawn up only once in twelve months. He 

 had a quadrant to rectify these, with which he could 

 take the sun or a star's height so exactly, as to be within 

 10" of the clock. This quadrant he used till June, 1678, 

 when Sir Jonas Moore procured him one from the Royal 

 Society, which he employed till October, 1679, " when the 

 ill nature of Mr. Hook forced it out of his hands." This 



