420 Prof. J. A. Fleming on the Propagation of 
The means of the closely concordant results, obtained by three 
independent observers, were as follows :— 
ar to. a) 2. ee 0:001531 microfarad. 
ar INO 2 6.0... ae ():001256 Es 
Both jars in parallel ...... 0:002783 
Both jars in series [ieee 0:000712 _ 
The variable inductance-coil was calibrated in microhenrys*. 
The inductance of the thick connecting wires joining up the 
jars, variableinductance, and spark-gap was also measured,and 
as first used was found to be 2600 centimetres. Subse- 
quently, however, these connexions were shortened so as to 
make the inductance of the connexion almost negligible. 
The next step was to measure the inductance and capacity 
of the long helix in the position in which it was to be used 
with the earth-wire at various distances. The inductance 
was measured by the modified form of Anderson’s Bridge 
method, employing a telephone as a detector as described by 
the author. (See loc. cit., Phil. Mag. May 1904.) 
The following nine values were obtained for the inductance 
of this helix on different occasions :— 
TABLE I. 
Inductance measurements of long Helix of 5000 turns, 200 
centims. in length and 4°096 centims. in mean diameter. 
minations=19°9 x 10° centims. 
20°3 X 10° centimetres. 19:2 x 106 centimetres. 
19-2 ,, “ | 206 ,, i | 
193, : es a : 
AOL, i : | 203 5 ¥ 
BU.) ee al | Mean of the above nine deter- 
| 
The capacity of the Helix with respect to the earth was then 
taken by means of the Fleming and Clinton Commutator t+. 
The earth-wire was arranged parallel to the helix and at 
* For a description of this inductance-coil see J. A Fleming, “ A Note 
on the Measurement of Small Inductances and Capacities”; and ‘‘ On a 
Standard of Small Inductance,” Phil. Mag. May 1904. It consisted of a 
coil of No. 14 S.W.G. copper wire wound in a groove in a boxwood 
cylinder. The diameter of this cylinder was 10 cms., its length 45 cms., 
and it had 2:4 turns of wire per centimetre of length. The total inductance 
of the coil was 227,000 cms. 
+. For a description of this instrument and mode of using it see Phil. 
Mag. May 1903. J.A. Fleming & W. C. Clinton, ‘“ On the Measurement - 
of Small Capacities and Inductances.” 
