434 Prof. J. A. Fleming on the Propagation of 
produce the frequency of oscillation required to set up the 
fundamental or bigher harmonic oscillations in one of the 
helices, and the wave-lengths measured as already described 
with the Neon vacuum- inde? The results of these observa- 
tions are set out in the following Table VIII. 
TaBLE VIII.—Observations made with Helix A with Ebonite 
Core and with Ebonite Condenser, variable Inductance, 
and Neon Vacuum-tube, to determine the Wave-velocity 
along the Helix. 
| 
| | Capacity Inductance 
in mfds.in in ems. in | Caleulated Observed Calculated 
Osoillats | Belarttcnseart te : Wave- | wave- 
scelliatlon. conc enser conc enser | requency lencth. ) velocity. ° 
circuit. circuit. | 2 | : 
0, L. | 2. Xr. | W=mnaA. 
| Fundamental...... | 0:005835 110,000 0:197x10° (871) (172 x 10°) 
lst Harmonice...... | 0002887 25,000 |0°588 ,, 292 y2 AG 
find .<'y \ eae — 0:001461 18,000 0977 _., 175 1725 
had 3 oy cane 0001464 9,000 |1:379 ,, 124 jt 
th“. 9 ha aes | 0001461 | 6,000 |1:70_,, 95 163. ,, 
aceon 0:001461 | 5,000 |19 , 80 | 152 
From the above observed values it is seen that the wave- 
lengths of the Ist, 2nd, and 3rd harmonics are very nearly 
in the ratio of 3: 5:7 for 292x 3=876, 11dx5=819;0aee 
124x7=868. Hence the fundamental wave-length should 
be 871. If we insert the value in Table VIII. and calculate 
the wave-velocity for the fundamental frequency, we find it 
to be 172 x 10° cms. per second, or exactly the same value as 
that obtained for the three succeeding harmonics. 
Hence from the fundamental and the three succeeding 
higher harmonies, we obtain values for the wave-velocity 
which are closely identical and equal to 172 x 10°cms./sec., and 
in very near agreement with the velocity of 174 x 10° ems. ‘/see. 
calculated from the constants of the helix itself. 
There is a slight falling off in the velocity obtained from 
the 4th and 5th harmonics, but the difficulty of measuring 
the small inductance then used in the condenser circuit is 
considerable. 
Hence we may say that when a helix wound on an ebonite 
core is used, observations confirm theory substantially, and 
show us that the stationary waves are formed as predicted, 
the wave-velocity being calculable from the observed induc- 
tance and capacity of the helix. 
