"The iron quadrant of Graham continued to be attached to the eastern face of the wall erected for its support in 1725, and was employed both by Halley and Bradley in observing the celestial bodies which passed the meridian to the south of the . Bradley however was desirous of extending the plan of his observations and... presented a memorial to the Government in the year 1740, soliciting another quadrant, by means of which the stars that passed the meridian to the north of the zenith might be observed. The Government... at once acceded... and in the following year the observatory was furnished with a magnificent brass quadrant of eight feet radius constructed by Bird, who now took the place of Graham, as the most skilful divider of instruments in his day. ...these were finally subdivided by the micrometer screw to every 1″. The Government at the same time furnished the observatory with a new transit telescope by Bird, eight feet long, besides an excellent clock by Shelton...They also purchased of Bradley the famous zenith sector with which he discovered the phenomena of aberration and nutation, and appropriated it to the use of the observatory. This noble instrument was designed by Bradley to be henceforward employed in determining the errors of collimation of the quadrants, by making observations with it when its face was turned alternately east and west."