Hlectric Waves along Spiral Wires. 433 
From the above values the inductance L of each helix was 
calculated from the formula 
2 
L=na() l, where m?=9°87. 
Hence Inductance of helix A=32°07 x 10° cms., 
and Inductance of helix B=31°93 x 10° cms. 
The capacity of each helix with respect to the earth was 
measured with the helix supported horizontally and at a 
height of 50 cms. above the table. 
The values were as follows :— 
Capacity of helix A=0°000045 microfarad. 
Capacity of helix B=0-0000462 microfarad. 
From these figures the velocity of propagation of the wave 
along each helix was calculated as above described and found 
to be :— 
Velocity along helix A=174°8 x 10° ems./sec. 
Velocity along helix B=172°9 x 10° cms./sec. 
Hence it may be taken as 174 million centimetres per 
second. 
The above-described spirals were supported on insulating 
stands in a horizontal position, and one end was connected 
to an oscillating circuit consisting of a condenser made of 
sheet ebonite covered with tinfoil, an inductance-coil, and a 
spark-oap. ‘The condenser consisted of 24 ebonite plates 
immersed in vaseline oil, the plates being grouped in six 
sections of four plates each. The capacity of the sections 
s me asured, and found to be as follows :— 
meemum 17) 80 20 2. 0:001030 microfarad. 
Becton 2 ee... 0:001005 oF 
Beenom ofa. 2.0. 0:000913 , 
Beenon 46) .! 2217.2. 0:000919 a 
Beetiom. Ooo... uals! 0-000994 5 
mecunam Oo 200! 2.2 0:000974 < 
Total capacity ...... 0005835 5 
Sections 4+5-+6... 0°002887 n 
Sections 1+2+43... 0°002948 x 
Sections 1+2+4+3 in series with sections 4+5+6 
=()'001461 méfd. 
The variable inductance used with the condenser had been 
previously calibrated by comparing certain parts of it with 
the calculated inductance of squares of wire of known size. 
The inductance and capacity were then arranged so as to 
Piul. Mag. 8. 6. Vol. 8. No. 46. Océ. 1904. 2 
