[1] This series of articles is based on the Cantor Lectures delivered
before the Society of Arts, London, in March, 1903. The lectures were
attended by many of the leading British scientific men and electrical
engineers, and attracted wide attention as the most complete and
authoritative statement hitherto made of wireless telegraphy. In writing
the articles for the "Popular Science Monthly," the author has omitted
advanced technicalities in order that the substance may be suitable for
the general reader.--EDITOR.
[2] For a more detailed account of this hypothesis, the reader is
referred to an article by the present writer, entitled "The Electronic
Theory of Electricity," published in the "Popular Science Monthly" for
May, 1902.
[3] See J. J. Thomson, "Recent Researches in Electricity and Magnetism,"
chap. I., p. 16.
[4] See O. Heaviside, "Electromagnetic Theory," Vol. I., p. 54.
[5] Wiedemann's _Annalen_, 36, p. 1, 1889; or in his republished Papers,
"Electric Waves," p. 137, English translation by D. E. Jones.
[6] The fraction 7/22 here denotes a stranded wire formed of seven
strands, each single wire having a diameter expressed by the number 22
on the British standard wire gauge.
[7] G. Marconi, "Syntonic Wireless Telegraphy," _Journal_ of the Society
of Arts, Vol. XLIX., p. 501, 1901.
[8] Instruction for the manufacture of large induction coils may be
obtained from a "Treatise on the Construction of Large Induction Coils,"
by A. T. Hare. (Methuen & Co., London.)
Also see Vol. II. of "The Alternate-Current Transformer," by J. A.
Fleming, chap. I. ("The Electrician" Printing and Publishing Co., 1, 2
and 3, Salisbury-court, Fleet-street, London, E.C.)
[9] See "The Alternate-Current Transformer," by J. A. Fleming. Vol. I.,
p. 184.
[10] Du Moncel states that MacGauley of Dublin independently invented
the form of hammer break as now used. See "The Alternate-Current
Transformer," Vol. II. chap. I. J. A. Fleming.
[11] See Professor J. Trowbridge, "On the Induction Coil" _Phil. Mag._,
April, 1902 Vol. III., Series 6, p. 393.
[12] See Dr. Wehnelt's article in the _Elektrotechnische Zeitschrift_,
January, 1899.
[13] See _The Electrician_, Vol. XLII., 1899, pp. 721, 728, 731, 732 and
841; communications from Mr. Campbell Swinton, Professor S. P. Thompson,
Dr. Marchant, the author and others; also p. 864, same volume, for a
leader on the subject; also p. 870, letters by M. Blondel and Professor
E. Thomson. See also _The Electrician_, Vol. XLIII., p. 5, 1899,
extracts from a Paper by P. Barry; _Comptes Rendus_, April, 1899. See
also the _Electrical Review_, Vol. XLIV., p. 235, 1899, February 17.
[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.
[24] The "earth" itself probably only conducts electrolytically. All
such materials as sand, clay, chalk, etc., and most surface soils are
fairly good insulators when very dry, but conduct in virtue of moisture
present in them.
[25] _The Electrician_, Vol. XL., p. 86 (leader).
[26] British Patent Specification, C. and S. A. Varley, No. 165, 1866.
[27] See also _Journal de Physique_, Vol. V., p. 573, 1886.
[28] See _Comptes Rendus_, Vol. CXI., p. 785; Vol. CXII., p. 112, 1891;
or _La Lumiere Electrique_, Vol. XL., pp. 301, 506, 1891; or _The
Electrician_, Vol. XXVII., 1891, pp. 221, 448.
[29] See _The Electrician_, Vol. XXIX., 1892, pp. 397 and 432.
[30] Mr. W. B. Croft, _Proc._ Phys. Soc., Vol. XII., p. 421. Report of
meeting on October 27, 1893.
[31] See Professor Minchin, _Proc._ Phys. Soc., November 24, 1893; or
_The Electrician_, Vol. XXXII., 1893, p. 123. See also Professor
Minchin, _Phil Mag._, January, 1894, Vol. XXXVII., p. 90, "On the Action
of Electromagnetic Radiation on Films containing Metallic Powders."
[32] This lecture was afterwards published as a book, the first edition
bearing the same title as the lecture--viz., "The Work of Hertz and Some
of His Successors." In the second edition, published in 1898, an
appendix was added (p. 59) containing "The History of the Coherer
Principle," and the original title of the work had prefixed to it
"Signalling Without Wires."
[33] See _The Electrician_, Vol. XXVII., p. 222, 1891. E. Branly,
"Variations of Conductivity under Electrical Influence."
[34] See _The Electrician_, Vol. XL., p. 90. Sir Oliver Lodge, "The
History of the Coherer Principle."
[35] See Professor E. Branly, "A Sensitive Coherer," _Comptes Rendus_,
Vol. CXXXIV., p. 1,187, 1902; or _Science Abstracts_, Vol. V., p. 852,
1902.
[36] This device of making the inter-electrode gap in a tubular filings
coherer wedge-shaped has been patented again and again by various
inventors. See German patent No. 116,113, Class 21a, 1900. It has also
been claimed by M. Tissot.
[37] See _The Electrician_, Vol. XXVII., 1891, p. 448.
[38] _Journal_ of the Russian Physical and Chemical Society, Vol.
XXVIII., Division of Physics, Part I., January, 1896.
[39] See British Patent Specification No. 12,039, June 2, 1896.
[40] British Patent Specification No. 19,710 of 1899.
[41] _Comptes Rendus._, Vol. CXXVIII., p. 1,225, 1889; _Science
Abstracts_, Vol. II., p. 521.
[42] _Il Nuovo Cimento_, Vol. X., p. 279, 1899.
[43] _Wied Ann._, Vol. LXVIII., p. 594, 1899; _Science Abstracts_, Vol.
II., p. 757.
[44] _Comptes Rendus_, Vol. CXXX., p. 902, 1900; _Science Abstracts_,
Vol. III., p. 615.
[45] See _Proc._ Roy. Soc., London, Vol. LXXI., p. 402.
[46] See Report by Capt. Quintino Bonomo, "Telegrafia Senza Fili," Rome,
1902; _L'Elettricista_, Ser. II., Vol. I., pp. 118, 173.
[47] See Royal Institution, Friday evening discourse, by Mr. Marconi,
June 13, 1902; also _The Electrician_, Vol. XLIX., p. 490; also a letter
to _The Times_ of July 3, 1902, by the Marchese Luigi Solari.
[48] See U.S.A. Patent Specification No. 700,161, May 24, 1900.
[49] See E. Marx, _Phys. Zeitschrift_, Vol. II., p. 249; _Science
Abstracts_, Vol. IV., p. 471. See also German Patent Specification No.
121,663, Class 21a.
[50] See "The Scientific Writings of Professor Joseph Henry."
[51] _Phil. Trans._ Roy. Soc., London, 1897, Vol. CLXXXIX.A, p. 1.
[52] See _Proc._ Roy. Soc., London, June 12, 1902. "Note on a Magnetic
Detector for Electric Waves which can be employed as a Receiver for
Space Telegraphy," by G. Marconi.
[53] See U.S.A. Patent Specification No. 716,000, Application of July 5,
1901.
[54] See the _Electrical Review_, Vol. XLIV., 1899, May 26; _Wied Ann._,
Vol. LXVIII., p. 92; or German Patent Specification No. 107,843.
[55] U.S.A. Patent Specification No. 706,742, 1902.
[56] See British Patent Specification, G. Marconi, No. 12,039, June 2,
1896.
[57] See G. Marconi, British Patent Specification No. 12,326, of June 1,
1898.
[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 mass or inertia. Hence capacity and
inductance are qualities of an electric circuit which are analogous 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, Class 21a, No. 7,452 of 1900, and
also No. 8,087 of 1901.
[65] See German Patent Specification, Class 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
Institution, 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.
* * * * *
[Detailed Transcriber's Notes
The text has been made to match the original text as much as possible
retaining all apparent printer's errors and inconsistencies. The
following, detail the apparent printer's errors etc. identified in
the original text.
Variation in spelling, Strasburg and Strassburg for Strasbourg.
There are a number of inconsistencies in hyphenation present in the
original text. Those concerned with the variation between one word or
a hyphenated word are detailed below. Those concerned with the
variation between multiple words and hyphenated words are too
numerous to detail individually.
Inconsistent hyphenation of word, 'anti-node' and 'antinode' both
present in original text.
Inconsistent hyphenation of word, 'electro-dynamic' and
'electrodynamic' both present in original text.
Inconsistent hyphenation of word, 'horse-shoe' and 'horseshoe' both
present in original text.
Inconsistent hyphenation of word, 'over-blowing' and 'overblowing'
both present in original text.
Page 5, possible printer's error, a for at, 'consisting when a rest'.
Page 6, printer's error, comma rather than full stop at end of
sentence, 'ether constituting electric radiation,'.
Page 10, printer's error, millmetre for millimetre, 'three thousand
volts per millmetre,'.
Page 13, possible printer's error, set for sets, 'there are three set
of phenomena'.
Page 13, printer's error, duplicate word, 'detached and and travel
away.'.
Page 13, brackets added to in-line equation to aid clarity, 'F =
(3/8)CV^{2}/10^{6}.'.
Page 13, both equations originally multi-line fraction, rendered into
one line for clarity.
Page 15, both equations originally multi-line fraction, rendered into
one line for clarity.
Page 22, printer's error, correponding for corresponding,
'correponding to this frequency'.
Page 22, printer's error, consist for consists, 'due to Braun, consist
of attaching'.
Page 24, printer's error, one-hundreth for one-hundredth, 'capacity of
one-hundreth of a microfarad,'.
Page 28, printer's error, missing full stop at end of sentence added,
'in the case of the hammer break.'.
Page 33, printer's error, supppse for suppose, 'Let us supppse'.
Page 44, equation originally multi-line fraction, rendered into one
line for clarity.
Page 46, printer's error, comma rather than full stop at end of
sentence, 'to the transmitting aerial,'.
Page 48, possible printer's error, alterations for alternations,
'alterations of electric strain'.
Page 54, printer's error, Banly for Branly, 'proved that in a Banly
tube,'.
Page 56, variation in spelling, unsensitive for insensitive, 'wounded
and unsensitive.'.
Page 59, possible printer's error, sensive for sensitive 'to work a
sensive recording apparatus'.
Page 59, possible printer's error, arragement for arrangement, 'most
interesting arragement'.
Page 61, printer's error, missing letter i, 'as shown n Fig. 18,'.
Page 70, equation originally multi-line fraction, rendered into one
line for clarity.
Page 71, printer's error, osciilating for oscillating, 'to that of the
osciilating circuit'.
Page 71, printer's error, impluse for impulse, 'the period of that
impluse'.
Page 74, possible printer's error, extra comma in date, 'on May, 17,
1901.'.
Page 76, printer's error, arangements for arrangements, 'variation of
the above arangements'.
Page 77, printer's error, systonic for syntonic, 'the systonic
transmitting'.
Page 86, printer's error, interpositon for interposition, 'effect of
the interpositon of land'.
Page 87, printer's error, signaling for signalling, 'the usual
maximum signaling'.
Footnote 17, printer's error, missing letter t, 'must be _solid_
metal and no hollow,'.
Footnote 31, printer's error, missing full stop after abbreviation,
'_Phil Mag._'.
Footnote 41, printer's error, extra full stop after reference,
'_Comptes Rendus._'.
]