170 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
the sum of the decrements of the cymometer and antenna. A second 
experiment made with a known additional resistance inserted in the 
cymometer bar enables us to eliminate the decrement (D) of the 
cymometer itself, and thus find that of the antenna alone. When 
Strongly Damped Oscillations 
Fig, 5. 
this is done we know what percentage each oscillation in the antenna 
is of the previous one. Suppose we agree that when the oscillations 
have decayed away to 1 per cent of their initial value, the train 
shall be considered to be finished, then another simple formula 
M= (4.605+-D) /2 D enables us 
to find the number of complete 
A oscillations M in a train when 
we know the decrement D.* 
Electric oscillations are clas- 
sified into highly damped, fee- 
bly damped and undamped 
varieties corresponding to few, 
many and infinite oscillations 
iia bral. © (See ost.) wlan 
electric - wave telegraphy we 
have various kinds of transmit- 
ters or wave-makers which are 
intended to create these types of 
Fic. Se ea eae damped oscillation. In the first case, if 
we set up an antenna and con- 
nect the lower end to one of the spark balls of an induction coil, 
the other being to earth, we have an arrangement which produces 
highly damped oscillations and waves. (See fig. 6.) This is due 
to the fact that since the capacity of the antenna itself is small, 
4 See “The Principles of Electric-Wave Telegraphy,” Fleming, p. 167. 
