[58] See the _Electrical Review_, September 26, 1902, Vol. LI., p. 543.

[59] There is a good deal of contradiction between various inventors on this point, some saying that "earthed" aerials obviate atmospheric electrical disturbances, and others that insulated aerials are in this respect superior. The truth appears to be that, neither form is absolutely free from risk of disturbance by this cause.

[60] The capacity of an electrical circuit corresponds to the elastic pliability, or what is commonly called the elasticity, of a material substance, and the inductance to ma.s.s or inertia. Hence capacity and inductance are qualities of an electric circuit which are a.n.a.logous to the elasticity and inertia of such a body as a heavy spring.

[61] See Cantor Lectures, on "Electrical Oscillations and Electric Waves," delivered before the Society of Arts, London, November 26, December 4, 10, 17, 1900. Lecture I., p. 12, of reprint.

[62] A fuller account of these experiments was given by the author in a letter to the London _Times_ published on April 14, 1903.

[63] See _Journal_ of the Society of Arts, Vol. XLIX., p. 505. "Syntonic Wireless Telegraphy," by G. Marconi.

[64] See German Patent Specifications, Cla.s.s 21a, No. 7,452 of 1900, and also No. 8,087 of 1901.

[65] See German Patent Specification, Cla.s.s 21a, No. 7,498 of 1900, applied for November 9, 1900. The above-mentioned patent is subsequent in date to Mr. Marconi's experiments on the same subject.

[66] See _The Electrician_, January 18, 1900, Vol. XLVI., p. 475. Also reprint of a Paper of Professor A. Slaby, "Abgestimmte und mehrfache Funkentelegraphie."

[67] See British Specification No. 11,348 of 1901.

[68] See _Comptes Rendus_, May 21, 1900; Rapports du Congres International d'Electricite, Paris, 1900, p. 341.

[69] See _The Electrician_, Vol. XLVI., p. 573, February 8, 1901.

[70] See _The Electrician_, Vol. L., p. 418, January 2, 1903.

[71] See Mr. Marconi's Friday evening discourse at the Royal Inst.i.tution, June 13, 1902; also _The Electrician_, Vol. XLIX., p. 390.

[72] See _Proc._ Roy. Soc., June 12, 1902. "A Note on the Effect of Daylight upon the Propagation of Electromagnetic Impulses over Long Distances," by G. Marconi.

[73] See _Phil. Mag._, Vol. IV., p. 253, Series 6, August, 1902. J. J.

Thomson, "On Some Consequences of the Emission of Negatively-electrified Corpuscles by Hot Bodies."

[74] The opinion that ionisation of the air by sunlight is a cause of obstruction to Hertzian waves propagated over long distances has also been expressed by Mr. J. E. Taylor. See _Proc._ Roy. Soc., Vol. LXXI., p. 225, 1903. "Characteristics of Earth Current Disturbances and their Origin."

[75] See _Proc._ Roy. Soc., May 15, 1902. "On Some Phenomena affecting the Transmission of Electric Waves over the Surface of the Sea and Earth," by Captain H. B. Jackson, R.N., F.R.S.

[76] Mr. Marconi has informed the writer that these strategic questions have received attention in selecting the sites for large Marconi power stations in Italy.