1290 
| 
duration +’ of effect 34, an attempt still further to shorten the 
time x would be useless. 
Counting the time from the moment of a positive reversal we 
may represent the couple acting on the cylinder in virtue of the 
first effect by a line as shown in fig. 4. The width of each of 
the peaks will be very small compared with the half period (4 7’) 
A= 
Fig. 4. 
of the pendulum. Now in developing the value of the couple in 
a Fourrer-series we may confine ourselves to the first term 
S t 
— 4 — cs 2a —, 
T AP 
as it represents the only part of the couple whose action is inten- 
sified by resonance, where S denotes the impulse of rotation 
produced by one reversal. 
The third effect (Ba and 34 taken together) is also represented 
t 
by a term with cos 27 nn the amplitude having the same or the op- 
posite sign as that in the above expression, and we may therefore 
also use an expression of the form 
Women Ee 529.3) 
7 
for the effects (1,38) combined. 
As to the second effect, we may represent the couple acting on 
the cylinder (the couple exerted on the magnet by the compen- 
sating coil being included) by fig. 5, where h may be as well 
