Chapter VI: Part 6

The observations of Captain Jackson, however, only confirm the already well-known fact that Hertzian waves, as employed in the Marconi system of wireless telegraphy, within a certain range of wave-length, are considerably weakened by their passage through land, over land or round land. In some cases he noticed that quite sharp electric shadows were produced by rocky promontories projecting into the line of transmission. His attention was also directed (_loc. cit._) to the more important matter of the effect of atmospheric electrical conditions upon the transmission. The effect of all lightning discharges, whether visible or invisible, is to make a record on the telegraphic receiver. On the approach of an atmospheric electrical disturbance towards the receiving station on a ship, the first visible indications generally are the recording of dots at intervals from a few minutes to a few seconds on the telegraphic tape. Captain Jackson states that the most frequent record is that of three dots, the first being separated from the other two by a slight interval like the letters E I on the Morse code, and this is the sign most frequently recorded by distant lightning. But in addition to this, dashes are recorded and irregular signs, which, however, sometimes spell out words in the Morse code. He noted that these disturbances are more frequent in summer and autumn than in winter and spring, and in the neighbourhood of high mountains more than in the open sea. In settled weather, if present, they reach their maximum between 8 p.m. and 10 p.m., and frequently last during the whole of the night, with a minimum of disturbance between 9 a.m. and 1 p.m. Another important matter noted by Captain Jackson is the shorter distance at which signals can usually be received when any electrical disturbances are present in the atmosphere, compared with the distance at which they can be received when none are present. This reduction in signalling distance may vary from 20 to 70 per cent, of that obtainable in fine weather. It does not in any way decrease with the number of lightning flashes, but rather the reverse, the loss in signalling distance generally preceding the first indications on the instrument of the approaching electrical disturbance. It is clear that these observations fit in very well with the theory outlined above, viz., that the atmosphere when impregnated with free electrons or negatively-charged gaseous ions is more opaque to Hertzian waves than when they are absent. Captain Jackson gives an instance of ships whose normal signalling distance was 65 miles, failing to communicate at 22 miles when in the neighbourhood of a region of electrical disturbance. These effects in the case of wireless telegraphy have their parallel in the disturbances caused to telegraphy with wires by earth currents and magnetic storms.

Another effect which he states reduces the usual maximum signaling distance is the presence of material particles held in suspension by the water spherules in moist atmosphere. The effect has been noticed in the Mediterranean Sea when the sirocco wind is blowing. This is a moist wind conveying dust and salt particles from the African coast. A considerable reduction in signalling distance is produced by its advent.

Another interesting observation due to Captain Jackson is the existence of certain zones of weak signals. Thus, for instance, two ships at a certain distance may be communicating well; if their distance increases, the signalling falls off, but is improved again at a still greater distance. He advances an ingenious theory to show that this fact may be due to the interference between two sets of waves sent out by the transmitter having different wave-lengths.

Finally, in the Paper referred to, he emphasises the well-known fact that long-distance signalling can only be accomplished by the aid of an aerial wire and a "good earth." Summing up his results, he concludes: (1) That intervening land of any kind reduces the practical signalling distance between two ships or stations, compared with that which would be obtainable over the open sea, and that this loss in distance varies with the height, thickness, contour, and nature of the land; (2) material particles, such as dust and salt, held in suspension in a moist atmosphere also reduce the signalling distance, probably by dissipating and absorbing the waves; (3) that electrical disturbances in the atmosphere also act most adversely in addition to affecting the receiving instrument and making false signals or _strays_, as they are called; (4) that with certain forms of transmitting arrangement, interference effects may take place which have the result of creating certain areas of silence very similar to those which are observed in connection with sound signals from a siren.

It is clear, therefore, from all the above observations, that Hertzian-wave telegraphy taking place through the terrestrial atmosphere is not by any means equivalent to the propagation of a wave in free or empty space; and that just as the atmosphere varies in its opacity to rays of light, sometimes being clear and sometimes clouded, so it varies from time to time in transparency to Hertzian waves, the cause of this variation in transparency probably being the presence in the atmosphere of negatively-charged corpuscles or electrons. If there are present in the atmosphere at certain times "clouds of electrons" or "electronic fogs," these may have the effect of producing a certain opacity, or rather diminution in transparency to Hertzian waves, just as water particles do in the case of sunlight.

We may, therefore, in conclusion, review a few of the outstanding problems awaiting solution in connection with Hertzian wave wireless telegraphy. In spite of the fact that this new telegraphy has not been accorded a very hearty welcome by the representatives of official or established telegraphy in Great Britain, it has reached a point, unquestionably owing to Mr. Marconi's energy and inventive power, at which it is bound to continue its progress. But that progress will not be assisted by shutting our eyes to facts. Many problems of great importance remain to be solved. We have not yet reached a complete solution of all the difficulties connected with isolation of stations. In the next place, the question of localising the source of the signals and waves is most important. Our kumascopes and receiving appliances at present are like the rudimentary eyes of the lower organisms, which are probably sensitive to mere differences in light and darkness, but which are not able to _see_ or _visualise_, in the sense of locating the direction and distance of a radiating or luminous body. Just as we have, as little children, to learn to see, so a similar process has to be accomplished in connection with Hertzian telegraphy, and the accomplishment of this does not seem by any means impossible or even distant. We are dealing with hemispherical waves of electric and magnetic force, which are sent out from a certain radiating centre, and in order to localise that centre we have to determine the position of the plane of the wave and also the curvature of the surface at the receiving point. Something, therefore, equivalent to a range finder in connection with light is necessary to enable us to locate the distance and the direction of the radiant point.

Lastly, there are important improvements possible in connection with the generation of the waves themselves. At the present moment, our mode of generating Hertzian waves involves a dissipation of energy in the form of the light and heat of the spark. Just as in the case of ordinary artificial illuminants, such as lamps of various kinds, we have to manufacture a large amount of ether radiation of long wave length, which is of no use to us for visual purposes--in fact, creating ninety-five per cent, of dark and useless waves for every five per cent. of luminous or useful waves--so in connection with present methods of generating Hertzian waves, we are bound to manufacture by the discharge spark a large amount of light and heat rays which are not wanted, in order to create the Hertzian waves we desire. It is impossible yet to state precisely what is the efficiency, in the ordinary sense of the word, of a Hertzian wave radiator; how much of the energy imparted to the aerial falls back upon it and contributes to the production of the spark, and how much is discharged into the ether in the form of a wave.

Nothing is more remarkable, however, than the small amount of energy which, if properly utilised in electric wave making, will suffice to influence a sensitive receiver at a distance of even one or two hundred miles. Suppose, for instance, that we charge a condenser consisting of a battery of Leyden jars, having a capacity of one seventy-fifth of a microfarad, to a potential of 15,000 volts; the energy stored up in this condenser is then equal to 1.5 joules, or a little more than one foot-pound. If this energy is discharged in the form of a spark five millimetres in length through the primary coil of an oscillation transformer, associated with an aerial 150 feet in height, the circuits being properly tuned by Mr. Marconi's method, then such an aerial will affect, as he has shown, one of Mr. Marconi's receivers, including a nickel silver filings coherer tube, at a distance of over two hundred miles over sea. Consider what this means. The energy stored up in the Leyden jars cannot all be radiated as wave energy by the aerial, probably only half of it is thus radiated. Hence the impartation to the ether at any one locality of about half a foot-pound of energy in the form of a long Hertzian wave is sufficient to affect sensitive receivers situated at any point on the circumference of a circle of 200 miles radius described on the open sea. Hertzian wave telegraphy is sometimes described as being extravagant in power, but, as a matter of fact, the most remarkable thing about it is the small amount of power really involved in conducting it. On the other hand, Hertzian wave manufacture is not altogether a matter of power. It is much more dependent upon the manner in which the ether is struck. Just as half an ounce of dynamite in exploding may make more noise than a ton of gunpowder, because it hits the air more suddenly, so the formation of an effective wave in the ether is better achieved by the right application of a small energy than by the wrong mode of application of a much larger amount. If we translate this fact into the language of electronic theory, it amounts simply to this. It is the electron alone which has a grip of the ether. To create an ether wave, we have to start or stop crowds of electrons very suddenly. If in motion, their motion implies energy, but it is not only their energy which is concerned in the wave making, but the acceleration, positive or negative--_i.e._, the quickness with which they are started or stopped. It is possible we may discover in time a way of manufacturing long ether waves without the use of an electric spark, but at present we know only one way of doing this--viz., by the discharge of a condenser, and in the discharge of large condensers of very high potentials it is difficult to secure that extreme suddenness of starting the discharge which we can do in the case of smaller capacities and voltages.

How strange it is that the discharge of a Leyden jar studied so profoundly by Franklin, Henry, Faraday, Maxwell, Kelvin and Lodge should have become an electrical engineering appliance of great importance!

Whilst there are many matters connected with the commercial aspect of Hertzian wave telegraphy with which we are not here concerned, there is one on which a word may properly be said. The ability to communicate over long distances by Hertzian waves is now demonstrated beyond question, and even if all difficulties are not overcome at once, it has a field of very practical utility, and may even become of national importance. Under these circumstances, we may consider whether it is absolutely necessary to place the signalling stations so near the coast. The greater facility of transmission over sea has already been discussed and explained, but in time of war, the masts and towers which are essential at present in connection with transmitting stations could be wrecked by shot or shell from an enemy's battleship at a distance of five or six miles out at sea, and would certainly be done within territorial waters. Should not this question receive attention in choosing the location of important signalling stations? For if they can, without prejudice to their use, be placed inland by a distance sufficient to conceal them from sight, their value as a national asset in time of war might be greatly increased.

It has been often contended that whilst cables could be cut in time of war no one can cut the ether; but wireless telegraph stations in exposed situations on high promontories, where they are visible for ten to fifteen miles out at sea and undefended by any forts, could easily be destroyed. The great towers which are essential to carry large aerials are a conspicuous object for ten miles out at sea; and a single well-placed shell from a six-inch gun would wreck the place and put the station completely out of use for many months. Hence if oceanic telegraphy is ever to be conducted in a manner in which the communication will be inviolable or, at any rate, not be capable of interruption by acts of war, the careful selection of the sites for stations is a matter of importance. A small station consisting of a single 150-foot mast and a wooden hut can easily be removed or replaced, but an expensive power station, the mere aerial of which may cost several thousand pounds, is not to be put up in a short time.[76]

Meanwhile, whatever may be the future achievements of this new _supermarine_ wireless telegraphy conducted over long distances, there can be no question as to its enormous utility and present value for intercommunication between ships on the ocean and ships and the shore. At the present time, there are some forty or more of the transatlantic ocean liners and many other ships equipped with this Hertzian wave wireless telegraph apparatus on the Marconi system. Provided with this latest weapon of applied science, they are able to chat with one another, though a hundred miles apart on the ocean, with the ease of guests round a dinner table, to exchange news or make demands for assistance.

Ships that pass in the night, and speak each other in passing--
Only a signal shown, and a distant voice in the darkness;
So, on the ocean of life, we pass and speak one another,
Only a look and a voice, then darkness again, and a silence.

Abundant experience has been gathered to show the inexpressible value of this means of communication in case of accident, and it can hardly be doubted that before long the possession of this apparatus on board every passenger vessel will be demanded by the public, even if not made compulsory. Although the privacy of an ocean voyage may have been somewhat diminished by this utilisation of ether waves, there is a vast compensation in the security that is thereby gained to human life and property by this latest application of the great energies of nature for the use and benefit of mankind.

GEO. TUEKER, PRINTER, SALISBURY COURT, FLEET STREET, LONDON.

[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._'. ]