726 Hi ley. — On the Value of Different Degrees of 
(F, Text-fig. 1). The back of the box is lined with sheet cork, to which the 
seeds can be pinned. The box is strengthened by a brass strip i-8 cm. 
broad, which is bent into the form | | clasping the box on the 
back and at each side. To each of the shorter arms of this strip is. attached 
a steel axis ( AA , Text-fig. 2), which fits into the above-mentioned Vs in the 
•uprights KK' . The axis is prevented from rising out of the V s by a hinged 
cross rod which fits above the gap, thus V- The whole box is thus free to 
rotate on the axis A A. 
About the axis A A near one end is fitted a cog-wheel C y which is 
0-65 cm. in radius to the ‘ clutch ’ of the cogs, and has eighteen cogs. Fitting 
into this is another cog-wheel C (Text-figs. 1 and 2), which turns about a 
second axis A x A x . This cog-wheel is 4-7 cm. in radius, and only the upper 
part is cogged, having twenty-seven cogs. To the axis A 1 A x is firmly fixed 
a bar D , which hangs vertically downwards and bears a lead weight W at 
the bottom. Thus, as the weight W is swung backwards and forwards, the 
box B rotates about the axis AA and in the opposite direction from the 
weight. 
Fixed to the rider 5 are two brass bars L,M, one on each side; and 
through them are screwed bolts which limit the swing of the bar D in the 
two directions. When the weight W is hanging vertically, the bar rests 
against the bolt on Z, and the bolt on M prevents the weight from swinging 
outwards beyond a certain point. Now when the bar RR is still, the weight 
Whangs vertically and the box B is upright, as shown in the black line 
drawing in Text-fig. 1. But when the rod RR is rotating a centrifugal force 
acts on the weight W, causing it to swing outwards until the bar D is pressed 
firmly against the bolt on M. This causes the cog-wheel C r to rotate 
through a small angle, which in its turn reacts on the cog-wheel C, which is 
attached to the box. The weight W y the bar Z>, the cog-wheels C and C\ 
and the box B have now taken up the positions shown by the dotted lines in 
Text-fig. 1. The actual angle which the back of the box makes with the ver- 
tical can be altered at will by adjusting the bolt on M y which determines the 
limit of swing of the bar D. The position which the box is allowed to 
take during experiments is arranged so that the back will lie along 
the line of the resultant of the centrifugal force acting horizontally and 
gravity acting vertically. 
When, however, the rod RR ceases to rotate and comes to rest, the 
centrifugal force no longer acts on W , so that the bar D sinks back to the 
black-line position and the box above becomes vertical. Thus the box B 
has two fixed positions : vertical when the rod RR is still, and in the line 
of resultant of the centrifugal force and gravity when the rod is rotating. 
For the accurate measurement of the angle which the box makes with the 
vertical in the second position a protractor is fixed to the end of the box P 
(Text-fig. 2, not shown in Text-fig. 1), and by means of the pointer, p, the 
