360 
DR. P. E. SHAW ON THE NEWTONIAN CONSTANT OF 
abandoned on account of the difficulty of maintaining a high vacuum in a metal 
vessel. 
(2) Next I tried, as the vacuum case, a glass tube 160 cm. long, 2’5 cm. bore. 
The small masses were wires, and the large ones, now outside the vessel, were also 
stout wires. This particular form of suspension, if in high vacuum, retains any 
vibrations it may receive with great persistency, so the apparatus was set aside. 
(3) The third form was a glass vessel provided with a window, W, and two other 
flanged openings, G, H (see elevation fig. 4, and plan section fig. 5). It was very 
H 
Figs. 4 and 5. Show the third form of apparatus used. The reason for having twin tubes is to provide 
for change in temperature of both large and small masses. The window is not shown in fig. 5. 
sensitive ; in one experiment the period was 33 mins., and the scale movement was 
560 mm. The beam is shown carrying the small masses, m, m in chain form. The 
whole suspended system was of purest aluminium. The large masses, M, M, as shown 
in fig. 5, are in front or behind tubes, C, D, according to requirement. 
