[14] See The Electrician, Vol. XLII., 1899.
[15] For a discussion of the function of the condenser in an ordinary induction coil, see "The Alternate-Current Transformer," by J. A. Fleming. Vol. II., p. 51.
[16] See Lord Rayleigh, Phil. Mag., December, 1901.
[17] It has sometimes been stated that the spark balls [must be solid metal and no hollow,] but this is a fallacy, and has been disproved by Mr. C. A. Chant. See "An Experimental Investigation into the Skin Effect in Electrical Oscillators," Phil. Mag., Vol. III., Sec. 6, p. 425, 1902.
[18] See Proc. Roy. Soc., London, February 23 and April 12, 1860; or reprint of Papers on electrostatics and magnetism, p. 247.
[19] See Phil. Mag., August, 1902, Vol. IV., p. 224, 6th Series. Mr. Jervis-Smith has also described an experiment to show how much the use of compressed air round a spark gap is of advantage in working an ordinary Tesla coil. In his British specification, No. 12,039 of 1896, Mr. Marconi had long previously mentioned the use of compressed air round the spark gap.
[20] This energy storage is at the rate of 44 foot-pounds per cubic foot of glass. This figure shows what a relatively small amount of energy is capable of being stored up in the form of electric strain in glass. In the case of an air condenser, it is only stored at the rate of 1 foot-pound per cubic foot.
[21] See British specification No. 7,777 of 1900.—G. Marconi. "Improvements in Apparatus for Wireless Telegraphy."
[22] That this number really does represent the order of this oscillation frequency in an aerial has been shown by C. Tissot, Comptes Rendus, 132, p. 763, March 25, 1901, by photographs taken of the oscillatory spark of a Hertzian wave telegraphic transmitter. (See Science Abstracts, Vol. IV., Abs. 1,518.) He found frequencies from 0·5 million to 1·6 million.
[23] The term "jigger" is one of those slang terms which contrive to effect a permanent attachment to various arts and crafts. Similarly, the word "booster" is now used for a step-up or voltage-raising transformer or dynamo, inserted in series with an electric supply main. The word "boost" is a slang term signifying to raise or lift up. "To give a real good boost" is an expression for lending a helping hand. The term "jigger," in the same manner, is an adaptation of a seaman's term for hoisting tackle or lift.