82 Sir George Shuckburgh’s Account 
will be obtained,*' and consequently its true place in the 
heavens. 
(14.) Before I proceed, it may be necessary to say some- 
thing of the remaining parts of this apparatus, such as are 
either necessary to it, or concomitant in the use of it. These 
are, 1. The lamp to illuminate the cross wires. 2. The re- 
fraction piece. 3. The plumb line. 4. The moveable roof. 
5. The regulator. 6 . The meridian mark. And these will 
be best understood by inspection of the plates, where Tab. X. 
figure 1, represents the lamp fixed to the farther end of 
the declination axis. AB is the brass case or lantern, sus- 
pended on two centres C and D, within the frame E and F, 
which is attached to the pillars of the equatorial (IK, GH, 
and that one hidden behind E F ) by the cylindrical braces a, 
b , c , d. e is the lamp or vessel containing the oil, swinging 
upon the centres/ and g, at right angles to C and D ; and by 
means of this cross axis, and the counterpoise h, the lamp is 
kept constantly in an upright position, whatever may be the 
situation of the declination axis. G is a chimney to carry off 
the smoke from the instrument, and prevent its heating it. 
1, is a convex lens, that collects the rays from the flame 
upon the extremity of the declination axis, U, V, which, be- 
ing hollow, conveys all the light to the perforated speculum 
before mentioned, within the centre of the axis and of the 
telescope ; and this is assisted by another convex lens at the 
end of the axis, before which occasionally is screwed a pale 
green glass, of which there are three, of different shades, to 
temper the light of the lamp, if necessary, to the light of the 
* The adjustments which T have just now mentioned, together with some others, 
will be duly explained in their proper places. 
