732 
Hi ley. — On the Value of Different Degrees of 
But as determined by the control clock and rotation recorder the stimu- 
lation was 22*9 mg. acting for thirty seconds, which represents 687 Ct units. 
I now assume that the stimulating power as reckoned by the method 
of summation of the stimulating force for each five seconds is more accurate 
than that reckoned from the total number of revolutions and the time the 
current was flowing. In this case a more accurate value for the stimulating 
force is obtained by multiplying the recorded centrifugal force by 
5 74*5 
68 7 
or 0-84. 
This correction I call the Mechanical error correction , and this will be 
quoted by saying M.E.C. — 0*84. 
The example here taken is one in which the mechanical error correction 
makes a very great difference. This is due to the fact that in this experi- 
ment (i) the bands were very slack so that a considerable amount of slipping 
was possible, which made the ‘ wheel ’ both slow in getting up speed and 
slow in stopping, (ii) the period of running was short, so that the starting and 
stopping took up a greater amount of time in proportion to the time of 
normal running ; and (iii) the rider was far out on the rod RR so that the 
wheel acquired a great momentum. 
Specimen Experiment. 
July 29, 1912. Helianthus annnus radicles. 
Total period (/+ T) = 11 min. where / is the length of one period still, and T 
the length of one period of rotation. 
Temp. = 20 0 C. 
9 = angle made with vertical by back of box when rotating = 96°. 
Distance of middle of box from centre of rotation = 20 cm. 
Time. 
Control 
Time 
Rotation 
Rotations 
Clock. 
rotating. 
recorder. 
per sec. 
h. m. 
s. 
h. 
m. s. 
m. s. 
July 29 
10 20 
0 p.m. 
5 
5 
4 53} 
5 49) 
54 1 
y 
47,772) 
47,973) , 
3*59 2 
59 x 7 = 3,557 s. 
3-69 
July 30 
9 2 4 
8 a.m. 
6 
6 
5 8) 
6 8j 
) 
60 1 
61,096} ' 
61,39! 1 ) 
3*75 
\ 5 59 = 359 s. 
.... 
3-7 1 
10 40 o 
From the above 
/+ T 
6127' 62,654 
Total time of experiment 
Time recorded by control clock 
2 2^ 40 m — I oh 20 m 
6 h 1 2 m 7 s — gh 4111 58 s 
44,400 s 
4,034 s 
11*0 
t 
T 
io«o. 
1 This is the actual length of a period of rotation. It could not be kept quite constant. 
2 This figure is obtained by dividing the number of revolutions by the number of seconds 
during which the ‘ wheel ’ was revolving, 
i,e, it = 47, 973-47, _ 7^ = 3 , S9- 
54 
