84 Sir George Shuckburgh’s Account 
(16. ) Tab. X. figure 3, represents the plumb line and its 
frame ; it is about 5 feet long, and suspended to the roof of 
the observatory by the two hooks a, a. AB is a hollow brass 
tube, to protect the plumb line from the wind ; the line or 
wire is fixed at the top near b, and sustains the plummet in a 
glass of water at C. b and c, are two adjusting screws, mov- 
ing a sliding plate at right angular directions, to which is 
fixed the upper end of the plumb line, d is a screw, that by 
means of a pinion moves a rack e, e, to depress or raise the 
glass of water, and thereby support the plummet, (when this 
apparatus is moved about from one side of the instrument to 
the other) and prevent the wire being broken, and, by depress- 
ing it, to enable the plummet to play free, when it is to be 
used. At A and B are two apertures, at 4 feet distance, cor- 
responding with the two microscopes, covered on the back- 
side by pieces of transparent ivory, in order to exhibit an 
agreeable field of view, to observe the coincidence of the 
plumb line with the cross wires in the microscopes. 
(17.) In Tab. XI. is seen a section of the building 
in which this instrument is placed. As the equatorial is 
a machine calculated to observe the heavenly bodies in every 
part of the hemisphere, so it became necessary to construct a 
chamber, with windows opening to every quarter, north, east, 
west, and south ; and to any degree of elevation above the 
horizon. With this view I erected a building, or small turret, 
within my house, at Shuckburgh, in Warwickshire, see Tab. 
XI. where a, b, c, d, represent a section of this room, be- 
ing about 154- feet square, containing the equatorial AB, rest- 
ing on its supporters CD. s, 0, p, r, q , t , is a hollow conical 
