2A ON THE NEWTONIAN CONSTANT OF GRAVITATION. 
DESCRIPTION OF PLATES 1 AND 2. 
PLATE 1. 
Fig. 1 is a vertical section, and fig. 2 a sectional plan of the apparatus. Fig. 3 is a front view of a 
portion of it. Figs. 4, 5, 6 show details of the lid, pillars, and ball-holders on a larger scale. Fig. 7 
represents the beam-mirror, counterweight, and eye-hooks full size. Figs. 8 to 10 show the window 
apertures in the central tube, beam raiser, &c., on a larger scale. Figs. 11 and 12 are the front and 
back windows used when deflections and periods are being observed. Figs. 13 and 14 show the back 
window for use with the optical compass. Fig. 15 represents the tubular screens; figs. 16 and 17, the 
mould for pressing the 44-inch lead balls. 
PLATE 2. 
Figs. 18, 19, 20, and 21 are plan, side, and end elevations of the cellar with the apparatus in position. 
Fig. 22 is a horizontal section of the octagon house, the position of the apparatus being shown in dotted 
lines. Fig. 23 is an isometric projection of the geometrical clamps holding the scale and dummy. 
Figs. 24, 25, 26 are plan, front and side views, of the rotating and focussing slides and scale of the 
optical compass in position on the lid of the instrument, which is represented in chain lines. Figs. 27, 
28, 29 are plan, front and side views, of the traversing slides and microscopes of the optical compass in 
position on the focussing slide, which is represented in chain lines. 
ScALE oF Fries. PLATES 1 AND 2. 







| 
Scale . : | t a 3 1 | + inch to foot. | 
Figure hrhal 1 4 7 18 
16 2 5 | 19 | 
17 3 6 20 
22 | 24 8 21 
23 | 25 | 9 | 
26 10 
| 27 11 
28 12 
| 29 | 3 | 
| | 14 


