Centrifugal Force as Geotropic Stimuli. 727 
angle in question can be read off. Before performing an experiment the 
centrifugal force is theoretically calculated, and the appropriate angle for the 
second position is obtained by screwing the bolt in M, till the bar D swings 
to the right extent. 
Fig. 4, PL LVII, shows the ‘ wheel 5 entire. It is propelled by a h. p. 
electric motor which rotates at about 4,000 revolutions per min. By means 
of two pulleys the rotation of the wheel itself is geared down to about 
200 per min. The actual number of rotations made by the e wheel ’ is 
indicated by the rotation recorder, shown below the central pulleys. 
The intermittent apparatus is diagrammatically shown in Text-fig. 3. 
To the minute axis of a clock C is fixed a pulley round which is wound about 
three yards of angler’s twine. The free end of the twine is passed round 
one of the pulleys at D and then round the fixed pulleys pj eventually 
round the free pulley / 3 (to which a weight W is attached), ending up at the 
3 D 2 
