A HISTORY
OF
WIRELESS TELEGRAPHY
K J- C fc .. WitUOUCHBY
THE ARCH BUILDERS OF WIRELESS TELEGRAPHY.
A HISTORY
OF
WIRELESS TELEGRAPHY
1838-1899
INCLUDING SOME BARE-WIRE PROPOSALS
FOR SUBAQUEOUS TELEGRAPHS
BY
J. J. FAHIE
MEMBER OF THE INSTITUTION OF ELECTRICAL ENGINEERS, LONDON, AND OF
THE SOC1ETE INTERNATIONALE DBS ELECTRICIENS, PARIS J
AUTHOR OF
'A HISTORY OF ELECTRIC TELEGRAPHY TO THE YEAR 1837 ' J ETC.
WITH FRONTISPIECE AND ILLUSTRATIONS
WILLIAM BLACKWOOD AND SONS
EDINBURGH AND LONDON
MDCCCXCIX
All Rights reserved
LOAN STACK
TK51II
Betucatefc
TO
W. H. PREECE, ESQUIRE, C.B., F.R.S.,
Past President, Institution of Electrical Engineers ;
President, Institution of Civil Engineers,
&c., &c.,
The First Constructor of a Practical
Wireless Telegraph,
AS A SLIGHT TOKEN OF ESTEEM AND FRIENDSHIP,
AND IN ACKNOWLEDGMENT OF MANY
KINDNESSES
EXTENDING OVER MANY YEARS.
375
PREFACE.
in 1897 there was a great flutter in the dove-cotes
of telegraphy, and holders of the many millions of telegraph
securities, and those interested in the allied industries,
began to be alarmed for the safety of their property.
Mysterious paragraphs about the few, Wireless, or Space
Telegraphy, as it was variously called, kept appearing in
the papers ; and the electrical profession itself certainly
some leading members of it seemed disposed to accept
implicitly the new marvels, without the grain of salt usual
and proper on such occasions.
In a lecture on Submarine Telegraphy at the Imperial
Institute (February 15, 1897), Professor Ayrton said: "I
have told you about the past and about the present. What
about the future *? Well, there is no doubt the day will
come, maybe when you and I are forgotten, when copper
wires, gutta-percha coverings, and iron sheathings will be
relegated to the Museum of Antiquities. Then, when a
person wants to telegraph to a friend, he knows not where,
he will call in an electro-magnetic voice, which will be
viii PREFACE.
heard loud by him who has the electro-magnetic ear, but
will be silent to every one else. He will call, ' Where are
you 1 ' and the reply will come, ' I am at the bottom of the
coal-mine,' or ' Crossing the Andes,' or ' In the middle of
the Pacific ' ; or perhaps no reply will come at all, and he
may then conclude the friend is dead."
Soon after, in the course of a debate in the House of
Commons (April 2, 1897) on the Telephone monopoly, one
of the speakers said : " It would be unwise on the part of
the Post Office to enter into any very large undertakings in
respect of laying down telephone wires until they had as-
certained what was likely to be the result of the Eontgen
form of telegraph, which, if successful, would revolutionise
our telephonic and telegraphic systems."
When cautious men of science spoke, or should I not
say dreamt thus, and when sober senators accepted the
dream as a reality and proceeded to legislate upon it, we
can imagine the ideas that were passing in the minds of
those of the general public who gave the subject a thought.
Well, two years have now elapsed, and the unbounded
potentialities of the new telegraphy have been whittled
down by actual experiment to small practical though still
very important proportions ; and so, those interested in the
old order can sleep in peace, and can go on doing so for a
long time yet to come.
Having in the course of many years' researches in electric
lore collected a mass of materials on this subject for the
idea embodied in the new telegraphy is by no means new
and having been a close observer of its recent and startling
developments, I have thought that a popular account of its
PREFACE. IX
origin and progress would not now be uninteresting. This
I have accordingly attempted in the following pages.
At an early stage in the evolution of our subject, objec-
tion was taken to the epithet Telegraphy without Wires,
or, briefly, Wireless Telegraphy, as a misnomer (e.g., the
'Builder/ March 17, 1855, p. 132), and in recent times
the objection has been repeated. Induction, Space, and
Ethereal Telegraphy have been suggested, but though
accurate for certain forms, they are not comprehensive
enough. A better name would be Telegraphy without
Connecting Wires, which has also been suggested, but it is
too cumbrous an awkward mouthful. Pending the dis-
covery of a better one, I have adhered to the original
designation Wireless Telegraphy, which actually is the
popular one, and for which, moreover, I have the high
sanction of her Majesty's Attorney-General.
In the course of a discussion on Mr W. H. Preece's
paper on Electric Signalling without Wires (' Journal
Society of Arts,' February 23, 1894), Sir Eichard Webster
laid down the law thus : " I think the objection to the
title of the paper is rather hypercritical, because ordinary
people always understand telegraphing by wire as meaning
through the wire, going from one station to the other ; and
these parallel wires, not connected, would rather be looked
upon as parts of the sending and receiving instruments. I
hope, therefore, that the same name will be adhered to in
any further development of the subject." If thus the name
be allowable in Mr Preece's case where, to bridge a space
of, say, one mile, two parallel wires, each theoretically one
mile long, are requisite, or double the amount required in
X PREFACE.
the old form of telegraphy, it cannot be objected to in any
of the other proposals which are described in these pages,
certainly not to the Marconi system, where a few feet of
wire at each end suffice for one mile of space, or, to put it
accurately, where the height of the vertical wires varies as
the square root of the distance to be signalled over.
At the outset of my task I was met with the difficulty
of arranging my materials whether in simple chronological
order, or classified under heads, as Conduction, Induction,
Wave, and Other or Miscellaneous Methods. Both have
their advantages and disadvantages, but after consideration
I decided to follow in the main the chronological order as
the better of the two for a history which is intended to be
a simple record of what has been done or attempted in the
last sixty years by the many experimenters who have
attacked the problem or contributed in any way to its
solution.
Having settled this point, the further question of sub-
division presented itself, and as the materials did not lend
themselves to arrangement in chapters I decided to divide
the text into periods. The first I have called The Possible
Period, which deals with first suggestions and empirical
methods of experiment, and which, by reason of the want
of delicacy in the instruments then available, may not
inaccurately be compared with the Palaeolithic period in
geology. The second is The Practicable (or Neolithic)
Period, when the conditions of the problem came to be
better understood, and more delicate instruments of research
were at hand. The third The Practical Period brings
the subject up to date, and deals with the proposals of
PREFACE. XI
Preece (Electro - Magnetic), of Willoughby Smith (Con-
ductive), and of Marconi (Hertzian), which are to-day in
actual operation.
The whole concludes with five Appendices, containing
much necessary information for which I could not conveni-
ently find room in the body of the work. Appendix A
deals with the philosophic views of the relation between
electricity and light before and after Hertz, who, for the
first time, showed them to be identical in kind, differing
only in the degree of their wave-lengths. Appendix B
gives in a popular form the modern views of electric
currents consequent on the discoveries of Clerk-Maxwell,
Hertz, and their disciples. Appendix C reproduces the
greater part of Professor Branly's classic paper on his
discovery of the Coherer principle, which is one of the
foundation-stones of the Marconi system. Appendix 1)
contains a very interesting correspondence between myself
and Prof. Hughes, F.K.S., which came too late for insertion
in the body of the work, and which is too important from
the historical point of view to be omitted.
In Appendix E Mr Marconi's patent specification is
reproduced, as, besides being historically interesting as the
first patent for a telegraph of the Hertzian order, it is in
itself a marvel of completeness. As the apparatus is there
described, so it is used to-day after three years' rigorous
experimentation, the only alterations being in points of
detail a finer adjustment of means to ends. This says
much for the constructive genius of the young inventor,
and bodes well for the survival of his system in the
struggle for existence in which it is now engaged.
Xll PREFACE.
In the presentation of my materials I have allowed, as
far as possible, the various authors to speak in their own
words, merely condensing freely and, where necessary,
translating obsolete words and phrases into modern technical
language. This course in a historical work is, I think,
preferable to obtruding myself as their interpreter. For
the same reason I have given in the text, or in footnotes
thereto, full references, so that the reader who desires to
consult the original sources can readily do so.
I seem to hear the facetious critic exclaim, " Why, this
is all scissors and paste." So it is, good sir, much of it;
and so is all true history when you delete the fictions with
which many historians embellish their facts. What one
person said or what another did is not altered by the pres-
ence or absence of quotation marks. However, the only
credit I claim is that due to collecting, condensing, and pre-
senting my facts in a readable form no light task, and if
my critics will award me this I will be satisfied.
Since the following pages were written, two excellent
contributions have been made by Prof. Oliver Lodge
and Mr Sydney Evershed in papers read before the Insti-
tution of Electrical Engineers, December 8 and 22, 1898.
These will be found in No. 137 of the 'Journal,' and,
together with the discussion which followed, should be
studied by all interested in this fascinating subject. Mr
Marconi has followed up these papers with one on his own
method, which was read before the Institution on the 2nd
of March last, and was repeated by general request on the
16th idem. He does not carry the matter farther than I
have done in the text, but still the paper is worth reading
PREFACE. Xlll
if only as an exposition in a nutshell of his beautiful
system.
As a Frontispiece I give a group of twelve portraits of
eminent men who may be fitly called the Arch-builders of
Wireless Telegraphy. At the top stands Oersted (Den-
mark), who first showed the connection between electricity
and magnetism. Then follow in order of time Ampere
(France), Faraday (England), and Henry (America), who
explained and extended the principles of the new science of
electro-magnetism. Then come Clerk-Maxwell (England)
and Hertz (Germany), who showed the relation between
electricity and light, the one theoretically, and the other
by actual demonstration. These are followed by Branly
(France), Lodge (England), and Eighi (Italy), whose dis-
coveries have made possible the invention of Marconi.
The last three are portraits of Preece and Willoughby
Smith (England) and Marconi (Italy), who divide between
them the honour of establishing the first practical lines of
wireless telegraph each typical of a different order.
ST HELIER'S, JERSEY,
September 1899.
CONTENTS,
FIRST PERIOD THE POSSIBLE.
PACK
PROFESSOR C. A. STEINHEIL 1838 . . . 1
EDWARD DAVY 1838 . . 6
PROFESSOR MORSE 1842 .... 10
JAMES BOWMAN LINDSAY 1843 . . . .13
j. w. WILKINS 1845 ..... 32
DR O'SHAUGHNESSY (AFTERWARDS SIR WILLIAM o'SHAUGH-
NESSY BROOKE) 1849 . . . .39
E. AND H. HIGHTON 1852-72 . . . .40
G. E. DERING 1853 ..... 48
JOHN HAWORTH 1862 . . . . .55
J. H. MOWER 1868 ..... 70
M. BOURBOUZE 1870 ..... 71
MAHLOX LOOMIS 1872 . ... 73
SECOND PERIOD THE PRACTICABLE.
PRELIMINARY : NOTICE OF THE TELEPHONE IN RELATION
TO WIRELESS TELEGRAPHY . . . .79
PROFESSOR JOHN TROWBRIDGE 1880 85
xvi CONTENTS.
PROFESSOR GRAHAM BELL 1882 . . \ . 96
PROFESSOR A. E. DOLBEAR 1883 . . . .99
T. A. EDISON 1885 '. . . .103
W. F. MELHUISH 1890 . . . ..- .114
C. A. STEVENSON 1892 . . * " . 122
PROFESSOR ERICH RATHENAU 1894 ". 130
THIRD PERIOD THE PRACTICAL.
SYSTEMS IN ACTUAL USE.
w. H. PREECE'S METHOD . . . . ; . 136
WILLOUGHBY SMITH'S METHOD . . . . " 162
G. MARCONI'S METHOD .... . '. . .177
APPENDIX A.
THE RELATION BETWEEN ELECTRICITY AND LIGHT
BEFORE AND AFTER HERTZ . . . 246
APPENDIX B.
PROF. HENRY ON HIGH TENSION ELECTRICITY BEING
CONFINED TO THE SURFACE OF CONDUCTING BODIES,
WITH SPECIAL REFERENCE TO THE PROPER CON-
STRUCTION OF LIGHTNING-RODS . . . 261
ON MODERN VIEWS WITH RESPECT TO THE NATURE OF
ELECTRIC CURRENTS ..... 264
APPENDIX C.
VARIATIONS OF CONDUCTIVITY UNDER ELECTRICAL IN-
FLUENCE 276
CONTENTS. Xvii
APPENDIX D.
RESEARCHES OF PROF. D. E. HUGHES, F.R S., IN ELECTRIC
WAVES AND THEIR APPLICATION TO WIRELESS TELEG-
RAPHY, 1879-1886 -. . . .... 289
APPENDIX E.
REPRINT OF SIGNOR G. MARCONI'S PATENT . . 296
+-
INDEX . 321
A HISTOEY OF
WIRELESS TELEGRAPHY.
1838-1899.
FIKST PERIOD THE POSSIBLE.
"Awhile forbear,
Nor scorn man's efforts at a natural growth,
Which in some distant age may hope to find
Maturity, if not perfection. "
PROFESSOR C. A. STEINHEIL 1838.
JUST mentioning en passant the sympathetic needle and
sympathetic flesh telegraphs of the sixteenth and seven-
teenth centuries, a full account of which will be found in
my 'History of Electric Telegraphy to 1837' (chap, i.),
we come to the year 1795 for the first glimmerings of
telegraphy without wires. Salva, who was an eminent
Spanish physicist, and the inventor of the first electro-
chemical telegraph, has the following bizarre passage in
his paper " On the Application of Electricity to Teleg-
raphy," read before the Academy of Sciences, Barcelona,
December 16, 1795.
After showing how insulated wires may be laid under
2 FIRST PERIOD THE POSSIBLE.
the seas, and the water used instead of return wires, he
goes on to say : "If earthquakes be caused by electricity
going from one point charged positively to another point
charged negatively, as Bertolon has shown in his ' Elec-
tricite des Meteores ' (vol. i. p. 273), one does not even want
a cable to send across the sea a signal arranged beforehand.
One could, for example, arrange at Mallorca an area of
earth charged with electricity, and at 'Alicante a similar
space charged with the opposite electricity, with a wire
going to, and dipping into, the sea. On leading another
wire from the sea-shore to the electrified spot at Mallorca,
the communication between the two charged surfaces would
be complete, for the electric fluid would traverse the sea,
which is an excellent conductor, and indicate by the spark
the desired signal." l
Another early telegraph inventor and eminent physi-
ologist, Sommerring of Munich, has an experiment which,
under more favourable conditions of observation, might
easily have resulted in the suggestion at this early date
of signalling through and by water alone. Dr Hamel 2
tells us that Sommerring, on the 5th of June 1811, and
at the suggestion of his friend, Baron Schilling, tried the
action of his telegraph whilst the two conducting cords
were each interrupted by water contained in wooden tubs.
The signals appeared just as well as if no water had been
interposed, but they ceased as soon as the water in the
tubs was connected by a wire, the current then returning
by this shorter way.
Now here we have, in petto, all the conditions necessary
1 Later on in these pages we shall see that Salve's idea is after
all not so extravagant as it seems. We now know that large spaces
of the earth can be electrified, giving rise to the phenomenon of
"bad earth," so well known to telegraph officials.
2 Historical Account of the Introduction of the Galvanic and
Electro-magnetic Telegraph into England, Cooke's Keprint, p. 17.
PROFESSOR C. A. STEINHEIL. 3
for an experiment of the kind with which we are dealing,
and had it been possible for Sommerring to have employed
a more delicate indicator than his water-decomposing appar-
atus he would probably have noticed that, notwithstanding
the shorter way, some portion of the current still went the
longer way ; and this fact could hardly have failed to suggest
to his acute and observant mind further experiments, which,
as I have just said,' might easily have resulted in his recog-
nition of the possibility of wireless telegraphy.
Leaving the curious suggestion of Salva, which, though
seriously meant, cannot be regarded as more than a jeu
d'esprit a happy inspiration of genius and the what-
might-have-come-of-it experiment of Sommerring, we come
to the year 1838, when the first intelligent suggestion of a
wireless telegraph was made by Steiuheil of Munich, one of
the great pioneers of electric telegraphy on the Continent.
The possibility of signalling without wires was in a
manner forced upon him. While he was engaged in estab-
lishing his beautiful system of telegraphy in Bavaria, Gauss,
the celebrated German philosopher, and himself a telegraph
inventor, suggested to him that the two rails of a railway
might be utilised as telegraphic conductors. In July 1838
Steinheil tried the experiment on the Nurmberg-Furth
railway, but was unable to obtain an insulation of the rails
sufficiently good for the current to Teach from one station
to the other. The great conductibility with which he
found that the earth was endowed led him to presume that
it would be possible to employ it instead of the return wire
or wires hitherto used. The trials that he made in order
to prove the accuracy of this conclusion were followed by
complete success ; and he then introduced into electric teleg-
raphy one of its greatest improvements the earth circuit. 1
1 For the use of the earth circuit before Steinheil's accidental dis-
covery, see my 'History of Electric Telegraphy to 1837,' pp. 343-345.
4 FIRST PERIOD THE POSSIBLE.
Steinheil then goes on to say : " The inquiry into the
laws of dispersion, according to which the ground, whose
mass is unlimited, is acted upon by the passage of the
galvanic current, appeared to be a subject replete with in-
terest. The galvanic excitation cannot be confined to the
portions of earth situated between the two ends of the wire ;
on the contrary, it cannot but extend itself indefinitely, and
it therefore only depends on the law that obtains in this
excitation of the ground, and the distance of the exciting
terminations of the wire, whether it is necessary or not to
have any metallic communication at all for candying on
telegraphic intercourse.
" An apparatus can, it is true, be constructed in which
the inductor, having no other metallic connection with the
multiplier than the excitation transmitted through the
ground, shall produce galvanic currents in that multiplier
sufficient to cause a visible deflection of the bar. This is a
hitherto unobserved fact, and may be classed amongst the
most extraordinary phenomena that science has revealed to
us. It only holds good, however, for small distances ; and
it must be left to the future to decide whether we shall ever
succeed in telegraphing at great distances without any
metallic communication at all. My experiments prove that
such a thing is possible up to distances of 50 feet. For
greater distances we can only conceive it feasible by aug-
menting the power of the galvanic induction, or by ap-
propriate multipliers constructed for the purpose, or, in
conclusion, by increasing the surface of contact presented
by the ends of the multipliers. At all events, the phe-
nomenon merits our best attention, and its influence will not
perhaps be altogether overlooked in the theoretic views we
may form with regard to galvanism itself." l
In another place, discussing the same subject, Steinheil
1 Sturgeon's Annals of Electricity, vol. iii. p. 450.
PROFESSOR C. A. STEINHEIL. 5
says : " We cannot conjure up gnomes at will to convey
our thoughts through the earth. Nature has prevented
this. The spreading of the galvanic effect is proportional,
not to the distance of the point of excitation, but to the
square of this distance ; so that, at the distance of 50 feet,
only exceedingly small effects can be produced by the most
powerful electrical effect at the point of excitation. Had
we means which could stand in the same relation to elec-
tricity that the eye stands to light, nothing would prevent
our telegraphing through the earth without conducting wires ;
but it is not probable that we shall ever attain this end." l
Steinheil proposed another means of signalling without
wires, which is curiously apropos of Professor Graham
Bell's photophone. In his classic paper on "Telegraphic
Communication, especially by Means of Galvanism," he
says : " Another possible method of bringing about
transient movements at great distances, without any inter-
vening artificial conductor, is furnished by radiant heat,
when directed by means of condensing mirrors upon a
thermo-electric pile. A galvanic current is called into play,
which in its turn is employed to produce declinations of a
magnetic needle. The difficulties attending the construc-
tion of such an instrument, though certainly considerable,
are not in themselves insuperable. Such a telegraph,
however, would only have this advantage over those
[semaphores] based on optical principles namely, that it
does not require the constant attention of the observer;
but, like the optical one, it would cease to act during
cloudy weather, and hence partakes of the intrinsic defects
of all semaphoric methods." 2
1 Die Anwendung des Electromagnetismus, 1873, p. 172. "We now
have these means in "the electric eye"of Hertz ! See pp. 181,256m/ra.
2 Sturgeon's Annals of Electricity, March 1839. Acting on this
suggestion, in June 1880 the present writer, while stationed at
FIRST PERIOD THE POSSIBLE.
EDWARD DAVY 1838.
While arranging, in 1883, the Edward Davy MSS., now
in the library of the Institution of Electrical Engineers,
the present writer discovered two passages which he at first
took to have reference to some kind of telephonic relay;
but on closer consideration it would appear that Davy had
in view some contrivance based on the conjoint use of
sound and electricity, much as Steinheil suggested the joint
use of electricity and heat. The following are the passages
to which I refer :
At the end of a long critical examination of Cooke and
Wheatstone's first patent of June 12, 1837, he says: "I
have lately found that there is a peculiar way of propagat-
ing signals between the most distant places by self-acting
means, and without the employment of any conducting
wires at all. It is to be done partly by electricity, but
combined with another principle, of the correctness of
which there can be no doubt. But until I know what
encouragement the other 1 will meet with I shall take no
Teheran, Persia, and while yet ignorant of Professor Bell's method,
worked out for himself a photophone, or rather a tele-photophone,
which will be found described in the 'Electrician,' February 26, 1881.
On my temporary return to England in 1882, I found that as early
as 1878 Mr A. C. Brown, of the Eastern Telegraph Company, was
working at the photophone. In September of that year he sub-
mitted his plans to Prof. Bell, who afterwards said of them : " To
Mr Brown is undoubtedly due the honour of having distinctly and
independently formulated the conception of using an undulatory
beam of light, in contradistinction to a merely intermittent one, in
connection with selenium and a telephone, and of having devised
apparatus, though of a crude nature, for carrying it into execution "
('Jour. Inst. Elec. Engs.,' vol. ix. p. 404). Indeed the photophone is
as much the invention of Mr Brown as of Prof. Bell, who, however,
has all the credit for it in popular estimation.
1 That is, his chemical recording telegraph. See my ' History of
Electric Telegraphy,' London, 1884, p. 379.
EDWARD DAVY. 7
steps in this, as it may happen there will be other rivals.
To give you a general idea of it, a bell may be rung at
the first station, and then in the next instant a bell will
ring at the next station a mile off, and so on for an
unlimited series, though there is nothing between them
but the plain earth and air ! At the termination of the
series, the signals may be given in letters, as in the present
contrivance."
Again, in a paper of numbered miscellaneous memor-
anda, ^o. 20 reads as follows : " 20. The plan proposed
(101) of propagating communications by the conjoint
agency of sound and electricity the original sound pro-
ducing vibrations which cause sympathetic vibrations in a
unison -sounding apparatus at a distance, this last vibra-
tion causing a renewing wire to dip 1 and magnetise soft
iron so as to repeat the sound, and so on in unlimited
succession."
It is not easy to say from these passages (which are all
we could find on the subject) what plan Davy had in
contemplation. In the first quotation he speaks of bells,
for which we may read a powerful trumpet at one end,
and a concave reflector to focus the sound at the other
end; or some arrangement like the compressed-air tele-
phone, proposed by Captain Taylor, R.N., in 1844 ; or
the modern siren; or, in short, any means of producing
sharp concussions of the air, such as were known in his
day. Let us suppose he used any of these methods for
projecting sound waves, then, at the focus of the distant
reflector he may have designed a "renewing wire," so
delicately poised as to respond to the vibration, and so
1 I.e., causing a relay to close a local circuit containing an electro-
magnet. Davy always spoke of the relay as the " renewer " or the
" renewing wire " ; and by dip he meant to dip into mercury, or, as
we say nowadays, to close the circuit.
8 FIRST PERIOD THE POSSIBLE.
close a local circuit in which was included the electro-
magnetic apparatus for recording the sound, or for renewing
it as required.
In- the second passage he speaks. of something on the
principle of the tuning-fork. Now, tuning-forks in com-
bination with reflectors may be practicable for short dis-
tances, but it is difficult to see how their vibrations could
be utilised, at the distance of a mile, for "causing a
renewing wire to dip."
However this may be, Davy's idea deserves at least
this short notice in a history of early attempts at wireless
telegraphy ; for, although hardly possible of realisation
with the apparatus at his command, it is perfectly feasible
in these days of megaphones and microphones. As regards
its practical utility, that is a question for the future, as
to which we prefer not to prophesy. 1
Davy's idea was probably the result of an incautious
dose of the Auticatelephor of Edwards, which made a
great stir a few years previously, and which, at first sight,
might be taken to be a telegraph without apparently any
connecting medium. We take the following announcement
from the ' Kaleidoscope ' of June 30, 1829 (p. 430) :
U THE AUTICATELEPHOR.
" We have received several papers descriptive of a new
and curious engine, with the above name, invented by Mr
T. W. C. Edwards, Lecturer on Experimental Philosophy
1 Such a plan as Davy's was again suggested, in 1881, by Signer
Senlicq d' Andres (' Telegraphic Journal,' vol. ix. p. 126), who, however,
proposed to use, instead of a renewing wire or relay, the mouthpiece
of a microphonic speaker, rendered more sensitive by a contact lever
with unequal arms. Mr A. R. Senuett has also worked at the idea
in more recent years. His method is very clearly described in the
'Jour. Inst. Elec. Engs.,' No. 137, p. 908.
EDWARD DAVY. 9
and Chemistry, and designed for the instantaneous convey-
ance of intelligence to any distance. After noticing some
of the greatest inventions of preceding times, Mr Edwards
undertakes to demonstrate clearly and briefly, in the work
which he has now in the press, 1 the practicability and
facility of transmitting from London, instantaneously, to an
agent at Edinburgh, Dublin, Paris, Vienna, St Petersburg,
Constantinople, the Cape of Good Hope, Madras, Calcutta,
&c., any question or message whatever, and of receiving
back again at London, within the short space of one minute,
an acknowledgment of the arrival of such question or
message at the place intended, and a distinct answer to it in
a few minutes. In principle this engine is altogether
different from every kind of telegraph or semaphore, and
requires neither intermediate station nor repetition. In its
action it is totally unconnected with electricity, magnetism,
galvanism, or any other subtle species of matter; .and
although the communication from place to place is instan-
taneous, and capable of ringing a bell, firing a gun, or
hoisting a flag if required, yet this is not effected by the
transit of anything whatever to and fro ; nor in the opera-
tion is aught either audible or visible, except to the persons
communicating. It may be proper, however, to state that a
channel or way must previously be prepared, by sinking a
series of rods of a peculiar description in the ground, or
dropping them in the sea ; but these, after the first cost,
will remain good for ages to come, if substantial when laid
down." 2
1 In 1883 we searched for this book in vain. Under the name T.
W. C. Edwards we found in the British Museum Catalogue no less
than twenty entries of translations from Greek authors, and of Greek
and Latin grammars, &c. ; but nothing to show that the writer was
either a natural philosopher or a chemist.
2 See also the 'Mechanics' Magazine,' vol. xiii., First Series,
p. 182.
.10 FIRST PERIOD THE POSSIBLE.
From the concluding words of this paragraph it would
seem that the Auticatelephor was simply an application to
telegraphy of pneumatic or hydraulic pressure in pipes
cautiously styled " rods of a peculiar description." On this
supposition the last sentence may be paraphrased thus :
" It may be proper, however, to state that a channel or way
must previously be prepared, by laying down a continuous
series of hollow rods or tubes under the ground or along the
sea-bottom." If our supposition be correct, and if Edwards
contemplated the use of compressed air, his proposal was
certainly novel ; but if he designed the use of compressed
water, the idea was by no means new. Without going
back to the old Roman plan of ^Eneas Tacticus, we have
its revival by Brent and others towards the close of the
last century, and the still more practical arrangements of
Joseph Eramah in 1796, of Vallance in 1825, and of
Jobard in 1827.
PROFESSOR MORSE 1842.
The idea of a wireless telegraph next appears to have
presented itself to Professor Morse. In a letter to the
Secretary of the Treasury, which was laid before the
House of Representatives on December 23, 1844, he
says :
"In the autumn of 1842, at the request of the American
Institute, I undertook to give to the public in New York
a demonstration of the practicability of my telegraph, by
connecting Governor's Island with Castle Garden, a dis-
tance of a mile ; and for this purpose I laid my wires
properly insulated beneath the water. I had scarcely
begun to operate, and had received but two or three
characters, when my intentions were frustrated by the
PROFESSOR MORSE.
11
accidental destruction of a part of my conductors by a
vessel, which drew them up on her anchor, and cut them
off. In the moments of mortification I immediately de-
vised a plan for avoiding such an accident in future, by
so arranging my wires along the banks of the river as to
cause the water itself to conduct the electricity across.
The experiment, however, was deferred till I arrived in
Washington; and on December 16, 1842, I tested my
arrangement across the canal, and with success. The
simple fact was then ascertained that electricity could be
made to cross a river without other conductors than the
water itself; but it was not until the last autumn that
I had the leisure to make a series of experiments to ascer-
tain the law of its passage. The following diagram will
serve to explain the experiment :
"A, B, c, D, are the banks of the river; N, p, is the
battery ; G is the galvanometer ; w w, are the wires along
the banks, connected with copper plates,/, g, h, i, which
are placed in the water. When this arrangement is com-
plete, the electricity, generated by the battery, passes from
the positive pole, p, to the plate ^, across the river through
the water to plate i, and thence around the coil of the
galvanometer to plate /, across the river again to plate g,
and thence to the other pole of the battery, N.
12
FIRST PERIOD THE POSSIBLE.
"The distance across the canal is 80 feet; on August
24 the following were the results of the experiment :
No. of the experiment.
1st,
2nd.
3rd.
4th.
5th.
6th.
No. of cups in battery
14
14
14
7
,
7
Length of conductors, w, w
Degrees of motion of gal-
vanometer
400
32&24
400
131 & 41
400
l&l
400
24&13
SCO
29&21
200
211 & 15
Size of the copper plates, )
/, <7, ft, i f
5 by
21ft.
1(5 by
13 in.
6 by
5 in.
5 by
21ft.
5 by
21 ft.
5 by
21 ft.
" Showing that electricity crosses the river, and in quan-
tity in proportion to the size of the plates in the water. The
distance of the plates on the same side of the river from
each other also affects the result. Having ascertained the
general fact, I was desirous of discovering the best practical
distance at which to place my copper plates, and not having
the leisure myself, I requested my friend Professor Gale to
make the experiments for me. I subjoin his letter and the
results. 1
'"NEW YORK, Nov. 5th, 1844.
" ' MY DEAR SIR, I send you herewith a copy of a
series of results, obtained with four different-sized plates,
as conductors to be used in crossing rivers. The batteries
used were six cups of your smallest size, and one liquid
used for the same throughout. I made several other series
of experiments, but these I most rely on for uniformity and
accuracy. You will see, from inspecting the table, that the
distance along the shores should be three times greater than
that from shore to shore across the stream ; at least, that
four times the distance does not give any increase of
power. I intend to repeat all these experiments under
1 We omit the tables of results, as of no present value. They can
be seen in Vail's book, quoted infra.
JAMES BOWMAN LINDSAY. 13
more favourable circumstances, and will communicate to
you the results. Very respectfully, L. D. GALE.
" < Professor S. F. B. MORSE,
Superintendent of Telegraphs'
" As the results of these experiments, it would seem that
there may be situations in which the arrangements I have
made for passing electricity across rivers may be useful,
although experience alone can determine whether lofty
spars, on which the wires may be suspended, erected in the
rivers, may not be deemed the most practical. The experi-
ments made were but for a short distance ; in which, how-
ever, the principle was fully proved to be correct. It has
been applied under the direction of my able assistants,
Messrs Vail and Eogers, across the Susquehanna river, at
Havre-de-Grace, with complete success, a distance of nearly
a mile." l
JAMES BOWMAN LINDSAY 1843.
The next to pursue the subject was J. B. Lindsay of
Dundee, whose extensive labours in this, as well as in the
department of electric lighting, have hitherto been little
appreciated by the scientific world. Through the kind
assistance of Dr Robert Sinclair of Dundee, I have lately
collected a number of facts relating to this extraordinary
man, and as I believe they will be new to most of my
readers, I will draw largely from them in what follows. 2
James Bowman Lindsay was born at Carmyllie, near
Arbroath, on September 8, 1799, and but for the delicacy
1 Tail's American Electro-Magnetic Telegraph, Philadelphia, 1845.
2 Extracts from the writer's articles in the * Electrical Engineer,'
vol. xxiii. pp. 21, 51.
14 FIRST PERIOD THE POSSIBLE.
of his constitution would have been bred a farmer. At an
early age he evinced a great taste for reading, and every
moment that he could spare from his work as a linen-
weaver was devoted to his favourite books. Often, indeed,
he would be seen on his way to Arbroath with a web of
cloth tied on his back and an open book in his hands ; and,
after delivering the cloth and obtaining fresh materials for
weaving, he would return to Carmyllie in the same fashion.
Encouraged by these studious habits, Lindsay's parents
wisely arranged that he should go to St Andrews Uni-
versity. Accordingly, in 1821 he entered on his studies,
and, self-taught though he had hitherto been, he soon made
for himself a distinguished place among his fellow-students,
particularly in the mathematical and physical sciences, in
which departments, indeed, he became the first student of
his time. Having completed the ordinary four years'
course, Lindsay entered as a student of theology, and duly
completed his studies in the Divinity Hall ; but he never
presented himself for a licence, his habits of thought in-
clining more to scientific than to theological pursuits. In
the long summer vacations he generally returned to his
occupation of weaving, though latterly he took up teaching,
and thus enjoyed more time for the prosecution of his own
studies.
Coming to Dundee in 1829, he was appointed Science
and Mathematical Lecturer at the Watt Institution, then
conducted by a Mr M'Intosh. Soon after, Alexander
Maxwell, the historian of Dundee, became a pupil, and this
is the picture he has left us of Lindsay :
" When I was with Mr M'Intosh, I attended classes that
were taught by Mr Lindsay, a man of profound learning
and untiring scientific research, who, had he been more
practical, less diffident, and possessed of greater worldly
wisdom, would have gained for himself a good place
JAMES BOWMAN LINDSAY. 15
amongst distinguished men. As it was, he remained
little more than a mere abstraction, a cyclopaedia out of
order, and went through life a poor and modest school-
master.
" By the time I knew him he was devoting much of his
attention to electricity, to the celerity with which it was
transmitted to any distance, and to the readiness with
which its alternating effects may be translated into speech
and I have no doubt he held in his hand the modern
system of the telegraph, but it needed a wiser man than
he to turn it to practical use. He also produced from gal-
vanic cells a light which burned steadily for a lengthened
period.
" His acquaintance with languages was extraordinary,
and almost equalled that of his famous contemporary, the
Cardinal Mezzofanti. In 1828 he began the compilation of
a dictionary in fifty languages, the object of which was to
discover, if possible, by language the place where, and the
time when, man originated. This stupendous undertaking,
which occupied the main part of his life's work, he left
behind in a vast mass of undigested manuscript, consist-
ing of dissertations on language and cogitations on social
science a monument of unpractical and inconclusive in-
dustry. In 1845 he published *A Pantecontaglossal
Paternoster,' intended to serve as a specimen of his fifty-
tongued lexicon.
"In 1858 he published 'The Chrono - Astrolabe,' for
determining with certainty ancient chronology a work on
which he had been engaged for many years; and in 1861
; A Treatise on Baptism,' which is a curious record of his
philosophical knowledge. . . .
"In 1832 he obtained a situation as travelling tutor,
which was to take him abroad for some time. We loved
him as much as consists with a boy's nature to love his
16 FIRST PERIOD THE POSSIBLE.
teacher, and subscribed for a silver snuff-box as a slight
mark of our regard. 1 . . .
" I am afraid that the situation of travelling tutor did
not turn out well, for within two years Lindsay was back
again in Dundee, and resumed his position of assistant
teacher, arduously following at the same time his favourite
studies." 2
The scope of his teaching at this time is shown by the
following notice which appeared in the ' Dundee Advertiser '
of April 11, 1834:
" J. B. Lindsay resumes classes for cultivating the intel-
lectual and historical portions of knowledge and instruction
on April 14, 1834, in South Tay Street, Dundee.
" In a few weeks hence a course of lectures will be formed
on frictional, galvanic, and voltaic electricity ; magnetism ;
and electro-magnetism. The battery, already powerful, is
undergoing daily augmentation. The light obtained from
it is intensely bright, and the number of lights may be
increased without limit.
"A great number of wheels may be turned [by electricity],
and small weights raised over pulleys.
"Houses and towns will in a short time be lighted by
electricity instead of gas, and heated by it instead of coal ;
and machinery will be worked by it instead of steam all
at a trifling expense.
" A miniature view of all these effects will be exhibited,
besides a number of subordinate experiments, including the
discoveries of Sir Humphry Davy."
In March 1841, Lindsay was appointed teacher in the
1 On a previous occasion (July 1829) he was presented with a new
hat (!) by the pupils "for the attention he had bestowed in facili-
tating their studies."
2 Alex. Maxwell's (unpublished) Autobiographical Notes and
Keminiscenees.
JAMES BOWMAN LINDSAY. 17
Dundee Prison on a salary of 50 a-year, a post which he
held for upwards of seventeen years, till October 1858.
It is stated that shortly after taking up this office he could
have obtained an appointment in the British Museum, a
situation which would have been most congenial to his
tastes, and which would certainly have led to a lasting
recognition of his great abilities ; but, being unwilling to
leave his aged mother, he declined the offer a rare example
of devotion and self-denial. . . .
Lindsay was a bachelor, and lived alone, buried, it might
be said, in his books, collections of which, in history and
philosophy, science and languages, were heaped in every
corner of his dwelling a small house of three apartments
(11 South Union Street). The kitchen was filled with
electrical apparatus, mostly the work of his own hands ; and
his little parlour was so crowded with books, philosophical
apparatus, and other instruments of his labour, that it was
difficult to move in it. To provide these things, he denied
himself through life the ordinary comforts and conveniences,
bread and coffee, and other simple articles, forming the
principal part of his diet. His house in time acquired a
celebrity as one of the curiosities of Dundee, and men of
learning from distant parts, not only of the kingdom but of
the world, often came to pay him a visit.
In July 1858, on the recommendation of Lord Derby,
then Prime Minister, her Majesty granted Lindsay an
annual pension of 100 a-year, "in recognition of his
great learning and extraordinary attainments." This well-
deserved bounty relieved him from the drudgery of a prison
teacher, and henceforth to the close of his life he devoted
himself entirely to literary and scientific pursuits.
Although never robust, Lindsay on the whole enjoyed
tolerably good health through life, but trouble came at last.
B
18 FIRST PERIOD THE POSSIBLE.
On June 24, 1862, he was seized with diarrhoea, which
carried him off on June 29, 1862, in the sixty -third year of
his age. 1
Although languages and chronology took up much (I am
inclined to think too much) of Lindsay's time, still electricity
and its applications were his first, as they were always his
favourite, study. Amongst some notes and memoranda,
bound up with his manuscripts in the Albert Institute,
Dundee, he says :
"Previous to the discovery of Oersted, I had made many
experiments on magnetism, with the view of obtaining from
it a motive power. No sooner, however, was I aware of the
deflection of the needle and the multiplication of the power
by coils of wire than the possibility of power appeared
certain, and I commenced a series of experiments in 1832.
The power on a small scale was easily obtained, and during
these experiments I had a clear view of the application of
electricity to telegraphic communication. The light also
drew my attention, and I was in a trilemma whether to fix
upon the power, the light, or the telegraph. After reflection
I fixed upon the light as the first investigation, and had
many contrivances for augmenting it and rendering it
constant. Several years were spent in experiments, and I
obtained a constant stream of light on July 25, 1835.
Having satisfied myself on this subject, I returned to some
glossological investigations that had been left unfinished,
and was engaged with these till 1843. In that year I pro-
proposed a submarine telegraph across the Atlantic, after
having proved the possibility by a series of experiments.
Inquiries on other subjects have since that time engaged
my attention, but I eagerly desire to return, to electricity."
The first public announcement of Lindsay's success in
1 Norrie's Dundee Celebrities of the Nineteenth Century, Dundee,
1873.
JAMES BOWMAN LINDSAY. 19
electric lighting was contained in a short paragraph in the
'Dundee Advertiser' of July 31, 1835 ; and on October 30
following the same paper published a letter on the subject
from Lindsay himself :
"ELECTRIC LIGHT.
" SIR, As a notice of my electric light has been exten-
sively circulated, some persons may be anxious to know its
present state, and my views respecting it.
" The apparatus that I have at present is merely a small
model. It has already cost a great deal of labour, and will
yet cost a good deal more before my room is sufficiently
lighted. Had circumstances permitted, it would have been
perfected two years ago, as my plans were formed then. I
am writing this letter by means of it, at 6 inches or 8 inches
distant ; and, at the present moment, can read a book at
the distance of 1 J foot. From the same apparatus I can get
two or three lights, each of which is fit for reading with. I
can make it burn in the open air, or in a glass tube without
air, and neither wind nor water is capable of extinguishing
it. It does not inflame paper nor any other combustible.
These are facts.
" As I intend in a short time to give a lecture on the
subject, my views on the further progress will be unfolded
then. A few of these, however, may be mentioned just
now.
" Brilliant illumination will be obtained by a light incap-
able of combustion ; and, on its introduction to spinning
mills, conflagrations there will be unheard of. Its beauty
will recommend it to the fashionable ; and the producing
apparatus, framed, may stand side by side with the piano in
the drawing-room. Requiring no air for combustion, and
emitting no offensive smell, it will not deteriorate the
20 FIRST PERIOD THE POSSIBLE.
atmosphere in the thronged hall. Exposed to the open
day, it will blaze with undiminished lustre amidst tempests
of wind and rain ; and, being capable of surpassing all lights
in splendour, it will be used in lighthouses and for telegraphs.
The present generation may yet have it burning in their
houses and enlightening their streets. Nor are these pre-
dictions the offshoots of an exuberant fancy or disordered
imagination. They are the anticipated results of laborious
research and of countless experiments. Electricity, moreover,
is destined for mightier feats than even universal illumina-
tion. J. B. LINDSAY.
"DUNDEE, Oct. 28, 1835."
Lindsay's connection with electric telegraphy forms a
very interesting episode. We have seen that from about
the year 1830 he was familiar with telegraphic projects,
and that he made them the subject of illustration in his
classes. At this date electric telegraphs were distinctly
in the air, but, like electric lighting, they had hardly
advanced beyond the laboratory stage. 1 Lindsay does
not appear to have carried them much further for several
years, for it was not until 1843 that he conceived the bold
idea of a submarine telegraph to America by means of a
naked wire and earth-batteries, "after having proved the
possibility by a series of experiments."
It is true that at this time the earth-battery was known.
It was first proposed by Kemp, of Edinburgh, in 1828;
Prof. Gauss in 1838 suggested its employment for tele-
graphic purposes, and Steinheil, acting on the suggestion,
actually used it with some success on the Munich-Nanhofen
1 From the public exhibition of Baron Schilling's needle instru-
ment in Germany in 1835-36 dates the first real start of electric
telegraphy. See my 'History of Electric Telegraphy to 1837,'
chap. ix.
JAMES BOWMAN LINDSAY. 21
Railway, twenty-two miles long ; and Bain in October 1842
employed it for Avorking clocks. Similarly, the idea of
signalling with uninsulated wire and without any wire at
all was not new, for, as we have seen, the possibility of
doing so was in a manner forced on the notice of Steinheil
in 1838 and on Morse in 1842, but Lindsay was certainly
the first to combine the two principles in his daring pro-
posal of an Atlantic telegraph ; and this, be it remembered,
at a time when electric telegraphy was still a young and
struggling industry, and when submarine telegraphy was
yet a dream.
On June 19, 1845, a short paragraph appeared in the
'Northern Warder,' Dundee, referring to a New York
project of communicating between England and America
by means of a submerged copper wire "properly covered
and of sufficient size." This called forth the following
letter from Lindsay, which was published in the same
paper on June 26 following :
"ELECTRIC TELEGRAPH TO AMERICA.
" SIR, The few lines I now send you have been occa-
sioned by a notice in your last in reference to an electric
telegraph to America. Should the plan be carried into
effect the following hints should be attended to : The wire
should be of pure copper, as otherwise it would be injured
by the electro-chemical action of the water. The wire
must not be composed of parts joined by soldering, but
welded together ; this welding can be performed by elec-
tricity. In order to prevent the action of water on the
wire, a button of a more oxidable metal should be welded
to it at short distances; the best metal for this purpose
would be lead. If soldered to the wire, it must be soldered
by lead alone. No third metal must be used. If welded,
22 FIRST PERIOD THE POSSIBLE.
it may be done by electricity. In this way the wire resting
on the bottom of the sea might last a long time. The one
end of the wire is then to be soldered or welded to a plate
of zinc immersed in the ocean on the coast of Britain, and
the other end similarly joined to a plate of copper deposited
in the same ocean on the coast of America. In reference
to the expense, suppose the wire to be a ninth or tenth of
an inch diameter, then the length of 100 inches would con-
tain a cubic inch of copper, and three miles of wire would
contain a cubic foot, weighing 9000 ounces, of the value
of about 36 sterling. Owing to the inequalities in the
bottom of the ocean, the distance to America might be
3000 miles, and the expense 36,000 sterling a trifle
when compared with the resulting benefit. The only
injury that the wire is likely to undergo is from sub-
marine eruptions. It may be broken by these. The two
ends, however, being accessible, the greater part of the
wire may be drawn up, and the necessary length of wire
welded to it. It should be remembered that this welding
must be done by electricity. To Calcutta, by the Cape of
Good Hope, the expense would be 200,000. The wire
from Calcutta to Canton would cost 70,000, to New
Zealand 120,000, to Tahiti nearly 200,000. A wire
might be placed round the coast of Britain, and another
along the coast of America. There might be stations at
different towns and electric clocks agreeing with each other
to a second of time. Each town might have a specific time
for intelligence. Suppose Dundee to have the hour from
nine to ten. From nine to ten minutes past nine, mes-
sages are sent and answers received between Dundee and
New York. From ten minutes to twenty minutes past
nine communication is made between Dundee and Quebec.
The rest of the hour is for intercourse between Dundee
and other towns. The same is done with Edinburgh,
JAMES BOWMAN LINDSAY. 23
Glasgow, Liverpool, &c., each town having an hour for
itself. L.
"DUNDEE, June 21, 1845. "^
From this letter it is clear that Lindsay then contem-
plated an uninsulated wire across the Atlantic in connection
with what have come to be known as earth -batteries at
the stations along the coasts. His plan of protecting the
wire from the corrosive action of the sea-water was evidently
borrowed from Sir Humphry Davy's proposal of 1824 for
the protection of the copper sheathing of ships by strips of
zinc ; while the further suggestion, on which he insists so
much, of welding the various lengths of wire by electricity,
if not original with him, was at all events a very early
recognition of a process which has cropped up again in
recent years, and which is now largely employed. 1
Between 1845 and 1853 Lindsay does not appear to have
done anything in furtherance of his Atlantic project, being
probably wholly absorbed in his linguistic and chronological
studies. At all events, we hear nothing from him until
March 11, 1853, when a notice appeared in the 'Dundee
Advertiser ' of a lecture which he proposed to give on the
ensuing Tuesday at the Thistle Hall.
In the same paper a week later a report of the lecture is
given as follows :
" TELEGRAPHIC COMMUNICATION.
" On Tuesday evening our learned and ingenious towns-
man, Mr J. B. Lindsay, delivered a lecture on the above
subject, one with which he has an acquaintance second to
1 Electric welding was proposed by Joule in 1856 ; by Wilde in
1865 ; and by Prof. Elihu Thomson (America) and Dr Benardos
(Russia) in 1887.
24 FIRST PERIOD THE POSSIBLE.
no man in the kingdom. It would be impossible, in the
limited space at our disposal, to give any vidimus of the
lecture j we can only indicate the outline of a recent dis-
covery made by Mr Lindsay, involving a principle which, if
capable of acting irrespective of distance (and we see no
reason to doubt that it is), must by-and-by revolutionise
all our ideas of time and space. Mr Lindsay stated the
principle to be that submerged wires, such as those now
used for telegraphic intelligence between this country and
Ireland and France, were no longer necessary. By a
peculiar arrangement of the wires at the sides of rivers or
seas, the electric influence can be made to pass on through
the water itself. This proposition was certainly startling,
but he illustrated it on a small scale by means of a water-
trough, and, so far as the experiment went, it faithfully
developed the principle. Mr Lindsay, after concluding
these experiments, proceeded to point out the lines which
appeared to him most eligible for transmitting telegraphic
intelligence throughout the world ; and, having done so, he
wound up with a peroration of great beauty, in which the
wonders to be achieved by electric influence in the days to
come were eloquently set forth. It is a fine sight to see
this learned and philosophic man pursuing the studies of
science and literature, not for the sake of any empty
applause, but for those pure pleasures they are in themselves
so well fitted to bestow. At the same time it is gratifying
to know that there are many people capable of appreciating
the modest and retiring character of Mr Lindsay, a fact
which was clearly evidenced on Tuesday evening by the
numerous and most respectable meeting which then
assembled to hear his scientific lecture."
In the following August Lindsay delivered another
lecture (probably the same) in Glasgow, and so sanguine
JAMES BOWMAN LINDSAY. 25
was lie at this time of the practicability of his method that
he actually patented it on June 5, 1854. The following
account, which I have condensed from the specification of
his patent, explains the modus operandi, and also shows
how well he understood the conditions of the problem :
" My invention consists of a mode of transmitting tele-
graphic messages by means of electricity or magnetism
through and across water without submerged wires, the
water being made available as the connecting and conduct-
ing medium by the following means :
"On the land, on the side from which the message is to
be sent, I place a battery and telegraph instrument, to
which are attached two wires terminating in metal balls,
tubes, or plates placed in the water or in moist ground
adjacent to the water at a certain distance apart, according
to the width of the water to be crossed (the distance
between the two balls, plates, or tubes to be greater than
across the water when practicable). On the land which is
situated on the opposite side of the water, and to which
the message is to be conveyed, I place two similar metal
balls, plates, or tubes, immersed as above stated, and
having wires attached to them which lead to, and are in
connection with, another battery and needle indicator, or
other suitable telegraphic instrument. A, A in the diagram
(fig. 2) show the position of the battery and instru-
ment on one side of the water, z ; B, B, the battery and
instrument on the opposite side ; c, D, E, F, metallic or
charcoal terminators; G, H, i, K, wires insulated in the usual
way, and connecting the terminators, batteries, and instru-
ments, as shown.
"As regards the power or primary agent, it may be
either voltaic, galvanic, or magnetic electricity, and the
apparatus for evolving the same, such as is used for ordi-
nary telegraphic purposes.
26
FIRST PERIOD THE POSSIBLE.
"As regards the indicating apparatus, I propose to
employ any of the instruments in known use which are
most efficient for my purpose, observing that the needle
indicator may be arranged either in a vertical or in a hori-
zontal position, and that the coil of wire which actuates
Water
Z
the needle may be increased or diminished according to
circumstances.
" Suppose it is required to transmit a message from A,
the operator completes the circuit of the electric current as
ordinarily practised. 1 It will be evident that the current
1 That is, by a key, which is not shown in the diagram. The
absence of keys, no doubt, led a writer to say that Lindsay's method
consisted ' ' in providing strong enough batteries, one to send the
current half the distance and the other to attract it the other half " !
JAMES BOWMAN LINDSAY. 27
will have two courses open to it, the one being directly
back through the water from c to D, and the other across the
water from c to E, along the wires I K, through the instru-
ment B, and back from F to D. Kow, I have found that if
each of the two distances c D and E F be greater than c E
and D F, the resistances through c E and D F will be so
much less than that through the water between c and D,
that more of the current will pass across the water, through
the opposite wires, and recross at F, than take the direct course
CD; or, more correctly speaking, the current will divide
itself between the two courses in inverse ratio to their
resistances. As cases may arise, from local or other causes,
such as not to admit of the distance between the immersed
plates being greater than the distance across the water,
I propose, then, to augment the force of the batteries,
and to increase the size of the plates, so as to compel a
sufficient portion of the current to cross. I prefer, how-
ever, when circumstances admit of it, employing the first
method."
Lindsay's first public trials were across the Earl Grey
Docks at Dundee, and then across the Tay at Glencarse,
where the river is nearly three-quarters of a mile wide.
Of the few friends who assisted at these experiments
Mr London of Dundee is, I believe, the only one now
left. He tells us that Lindsay would station them on
one side of the Tay, enjoining them to watch the gal-
vanometer and note down how the needle moved. He
would then insert his plates in the water on their side
of the river, and, crossing over to the opposite side,
would complete his arrangements. With a battery of
twenty-four Bunsen cells he would make a few momen-
tary contacts, reversing the connections a few times so
as to produce right and left deflections of the galvano-
meter needle. Then he would return and compare the
28 FIRST PERIOD THE POSSIBLE.
deflections of the needle which they had noted with
the order in which he had himself made the battery
contacts, and on finding them to correspond he would
be supremely happy. 1
In 1854 Lindsay was in London, and brought his plans
to the notice of the Electric Telegraph Company. It is
now curious to remark that Mr "W. H. Preece, who, as
we shall see later on, became himself in after years an
eminent wireless -telegraph inventor, was the officer who
was deputed to assist him and report on his method. Mr
Preece tells us that these were almost the first electrical
experiments of any importance in which he ever took part,
and in a letter to the writer, dated October 15, 1898, he
adds : "I remember Lindsay very well. He came up
to London with his 'great invention,' and I assisted him
in making his experiments in our gutta-percha testing tank
at Percy Wharf on the Thames. We used the old sand
battery and galvanometers ohms and volts were not in-
vented then and showed that by varying the distance
apart of the plates on each side of the tank we varied
the strength of the signals. I have no record of the
results, but they showed the feasibility of the plan. I
had, however, to crush poor Lindsay by telling him that it
was not new. Morse in 1842 had done the same thing,
and Alexander Bain had also tried about the same time
a similar experiment on the Serpentine, but I have not
found any published record of it." 2
In August 1854 Lindsay carried out a series of experi-
ments at Portsmouth, in w r hich, according to a notice in
the 'Morning Post' (August 28), he completely succeeded
1 Kerr, Wireless Telegraphy, 1898, p. 40.
2 In this, I think Mr Preece's memory betrays him. Bain's ex-
periments had to do with an insulated wire in connection with earth-
batteries. See 'The Artisan,' June 30, 1843, p. 147.
JAMES BOWMAN LINDSAY. 29
in transmitting signals across the mill dam, where it is
about 500 yards wide. 1
Lindsay repeated these experiments at intervals and at
various places, indeed whenever and wherever he had the
chance, his greatest performance being across the Tay, from
Dundee to Woodhaven, where the river is nearly two miles
broad. On one of these occasions, and when an Atlantic
telegraph began to be seriously debated, the difficulty of
finding a steamer large enough to carry the cable was
discussed, when Lindsay quietly remarked, "If it were
possible to provide stations at not more than twenty miles
distant all the way across the Atlantic, I would save them
the trouble of laying any cable."
In September 1859 Lindsay read a paper before the
British Association at Aberdeen " On Telegraphing without
Wires," which drew from Lord Eosse, the president of the
section, special commendation. Prof. Faraday and (Sir)
G. B. Airy, then Astronomer - Royal, also added their
approval of the views enunciated. Prof. Thomson (now
Lord Kelvin) was also present, and, as is well known,
was then deeply engaged with Atlantic cable projects.
History does not say what he thought of the poor Dundee
1 These experiments were also noticed in ' Charabers's Journal ' for
September 1854, as follows: "Again has an attempt been made to
send a signal through water without a wire this time at Ports-
mouth, where it was attended with partial success. The thing has
often been tried : a few years ago, a couple of savants might have
been seen sending their messages across those minor lakes known to
Londoners as the Hampstead Ponds ! " Can any reader tell me who
these savants were ?
About this time experiments in wireless telegraphy were evidently
popular. Van Reese at Portsmouth ; Gintl, the first inventor of a
duplex telegraph, in Austria ; Bouelli in Italy, and Bouchotte and
Douat in France (and doubtless others), all were engaged on the
problem, but with what results I do not know, as I have not met
with any detailed accounts of their experiments.
30 FIRST PERIOD THE POSSIBLE.
lecturer, but, with the experience of forty years, we can
easily guess.
A brief abstract of the paper was published in the
Annual Eeport of the Association for 1859, but a fuller
account appeared in the ' Dundee Advertiser,' from which
I take the following interesting details :
" The author has been engaged in experimenting on the
subject, and in lecturing on it in Dundee, Glasgow, and
other places since 1831. Eecently he had made addi-
tional experiments, and succeeded in crossing the Tay
where it was three-quarters of a mile broad. His method
had always been to immerse two plates or sheets of metal
on the one side, and connect them by a wire passing
through > a coil to move a needle, and to have on the
other side two sheets similarly connected, and nearly
opposite the two former. Experiments had shown that
only a fractional part of the electricity generated goes
across, and that the quantity that thus goes across can
be increased in four ways : (1) by an increased battery
power; (2) by increasing the surface of the immersed
sheets ; (3) by increasing the coil that moves the receiving
needle ; and (4) by increasing the lateral distance of the
sheets. In cases where lateral distance could be got he
recommended increasing it, as then a smaller battery power
would suffice. In telegraphing by this method to Ireland
or France abundance of lateral distance could be got, but
for America the lateral distance in Britain was much less
than the distance across. In the greater part of his experi-
ments the distance at the sides had been double the dis-
tance across ; but in those on the Tay the lateral distance
was the smaller, being only half a mile, while the distance
across was three-quarters of a mile.
" Of the four elements above mentioned, he thought
that if any one were doubled the portion of electricity
JAMES BOWMAN LINDSAY. 31
that crossed would also be doubled, and if all the elements
were doubled the quantity transmitted would be eight
times as great. In the experiments across the Tay the
battery was of 4 square feet of zinc, the immersed sheets
contained about 90 square feet of metal, the weight of the
copper coil was about 6 lb., and the lateral distance was,
as just stated, less than the transverse ; but if it had been
a mile, and the distance across also a mile, the signals
would, no doubt, have been equally distinct. Should this
law (when the lateral distance is equal to the transverse)
be found correct, the following table might then be
formed :
Zinc for battery. Immersed sheets. Weight of coil. Distance crossed,
sq. ft. sq. ft. lb. miles.
4 90 6 1
8 180 12 8
16 360 24 64
32 720 48 512
64 1440 96 4096
128 2880 192 l 32,768
" But supposing the lateral distance to be only half the
transverse, then the space crossed might be 16,000 miles;
and if it was only a fourth, then there would be 8000
miles a much greater distance than the breadth of the
Atlantic. Further experiments were, however, necessary
1 My readers will smile at the suggestion of such galvanometer
coils, but they should remember that forty years ago matters electri-
cal were largely ordered by the rule of thumb. The electro-magnet
first used by Morse on the Washington-Baltimore line (1844), and
exhibited in Europe, weighed 185 lb. The arms were 3^ inches
long and 18 inches diameter, the wire (copper) .being that known as
No. 16 the same size as the line wire, it being then supposed that
the wire of the coils and of the line should be of the same size
throughout. Down to 1860 not a few practical telegraphists held
this view. See D. G. FitzGerald in the London ' Electrical Keview,'
August 9, 1895, p. 157,
32 FIRST PERIOD THE POSSIBLE.
to determine this law, but, according to his calculations,
he thought that a battery of 130 square feet, immersed
sheets of 3000 square feet, and a coil of 200 lb., would
be sufficient to cross the Atlantic with the lateral distance
that could be obtained in Great Britain."
After the reading of the paper Lindsay carried out some
very successful experiments across the river Dee, in the
presence of Lord Rosse, Prof. Jacobi of St Petersburg, and
other members of the Association. In February 1860 he
made Liverpool the scene of his operations, but there,
strange to say, he had not the success which hitherto
attended him. The experiments failed, being "counter-
acted by some unaccountable influence which he had not
before met with." However, in the following July he
was again successful at Dundee in his experiments across
the Tay, below the Earn, where the river is more than
a mile wide. In communicating these results to the
'Dundee Advertiser' (July 10, 1860), he says: "The
experiment was successful, and the needle was strongly
moved ; but as I had no person with me capable of sending
or reading a message, it [regular telegraphic signalling] was
not attempted."
This was Lindsay's last public connection with the tele-
graph, but to the end of his life (June 29, 1862) he re-
mained perfectly convinced of the soundness of his views
and of their ultimate success.
J. W. WILKINS 1845.
In the New York 'Electrical Engineer' of May 29, 1895,
it was claimed for Prof. Trowbridge (of whom we shall
have more to say later on) that he was the first to telegraph
without wires in 1880,
J. W. WILKINS. 33
The paragraph in which this claim, unfounded as we
already see, was advanced, besides drawing renewed atten-
tion to Prof. Trowbridge's experiments, had the merit of
calling forth an interesting communication from our own
Mr J. "W. Wilkins, one of the very few telegraph officers of
Cooke & Wheatstone's days still with us, and whose early
and interesting reminiscences I hope we may yet see. 1
Writing in 'The Electrician/ July 19, 1895, Mr Wilkins
says :
"Nearly fifty years ago, and thirty years before Prof.
Trowbridge ' made original researches between the Observa-
tory at Cambridge and the City of Boston,' the writer of
these lines had also researched on the same subject, and a
year or two later published the results of his investigations
in an English periodical the ' Mining Journal ' of March
31, 1849 under the heading 'Telegraph communication
between England and France.' In that letter, after going
into the subject very much like the American Professor in
1880, there will be found my explanation also not differing
much from the Professor's as to how the thing was to be
done ; except that, in my case, I proposed a new and delicate
form of galvanometer or telegraph instrument for the pur-
pose, while he made use of the well-known telephone. I
suggested the erection of lengths of telegraph wires on the
English and French coasts, with terminals dipping into the
earth or sea, and as near parallel as possible to one another ;
and I suggested a form of telegraph consisting of ' coils of
finest wire, of best conductibility,' with magnets to deflect
them, on the passage of a current of electricity through them,
which I expected would take place on the discharge of elec-
tricity through the circuits on either side of the water;
1 Mr Wilkins is the author of two English patents : (1) Improve-
ments in Electric Telegraphs, January 13, 1853 ; and (2) Improve-
ments in obtaining power by Electro-Magnetism, October 28, 1853.
C
34 FIRST PERIOD THE POSSIBLE.
anticipating, of course, that a portion of the current would
flow from the one pair of earth-plates terminals of one
circuit to the other pair of terminals on the opposite shore.
" It may be interesting to relate how I came to think
that telegraphy without wires was a possibility, and that it
should have appeared to me to have some value, at a time
when gutta-percha as an insulator was not imagined,
or the ghost of a proposition for a submarine wire
existed. At that time, too, it was with the utmost diffi-
culty that efficient insulation could be maintained in
elevated wires if they happened to be subject to a damp
atmosphere.
"It was in the year 1845, and while engaged on the
only long line of telegraph then existing in England
London to Gosport that my observations led me to
question the accepted theory that currents of electricity,
discharged into the earth at each end of a line of telegraph,
sped in a direct course instinctively, so to say through
the intervening mass of ground to meet a current or find a
corresponding earth-plate at the other end of it to complete
the circuit. I could only bring myself to think that the
earth acted as a reservoir or condenser in fact, receiving
and distributing electricity almost superficially for some
certain or uncertain distance around the terminal earths,
and that according to circumstances only. A year later,
while occupied with the installation of telegraphs for
Messrs Cooke & Wheatstone (afterwards the Electric Tele-
graph Company), a good opportunity offered of testing this
matter practically upon lengths of wire erected on both
sides of a railway. To succeed in my experiment, and
detect the very small amount of electricity likely to be
available in such a case, I evidently required the aid of a
very sensitive galvanometer, much more so indeed than the
J. W. WILKINS. 35
long pair of astatic needles and coil of the Cooke & Wheat-
stone telegraph, which was then in universal use as a
detector. The influence of magnetism upon a wire con-
veying an electric current at once suggested itself to me,
and I constructed a most sensitive instrument on this
principle, by which I succeeded in obtaining actual signals
between lengths of elevated wires about 120 ft. apart.
This, however, suggested nothing more at the moment than
that the current discharged from the earth-plates of one
line found its way into the earth-plates of another and
adjacent circuit, through the earth. Later on, I had other
opportunities of verifying this matter with greater distances
between the lines of wire, and ultimately an instance in
which the wires were a considerable distance apart, and
with no very near approach to parallelism in their situa-
tion. Then it was that it entered my head that telegraph-
ing without wires might be a possibility."
The following extracts from the letter in the 'Mining
Journal,' above referred to, may now be reproduced with
interest. I have slightly altered the phraseology with a
view of making the writer's meaning more clear and
connected : l
"Allow me, through the medium of your valuable
journal, to draw attention to a principle upon which a
telegraphic communication may be made between England
and France without wires. I take for certain (as experi-
ments I have made have shown me) that when the poles
of a battery are connected with any extended conducting
medium, the electricity diffuses itself in radial lines between
1 Mr C. Bright has recently reprinted this letter verbatim in ' Jour.
Inst. Elec. Engs.,' vol. xxvii. p. 958, as containing " the first really prac-
tical suggestion in the direction of inductive telegraphy " ; but, as we
now see, it is not the first suggestion, and it is certainly not inductive.
36 FIRST PERIOD THE POSSIBLE.
the poles. The first and larger portion will pass in a
straight line, as offering the least resistance ; the rays will
then form a series of curves, growing larger and larger,
until, by reason of increasing distance, the electricity
following the outer curves is so infinitesimal as to be no
longer perceptible.
" These rays of electricity may be collected within a
certain distance focussed as it were by the interposition
of a metallic medium that shall offer less resistance than
the water or earth ; and, obviously, the nearer the battery,
the greater the possibility of collecting them. I do not
apprehend the distance of twenty miles being at all too
much to collect a sufficient quantity of electricity to be
useful for telegraphic purposes. If, then, it is possible, as
I believe, to collect in France some portion of the elec-
tricity which has been discharged from a battery in
England, all that is required is to know how to deal with
it so that it shall indicate its presence.
"The most delicate of the present telegraph apparatus,
the detector, being entirely unsuited for the purpose, I pro-
pose the following arrangement : Upon one shore I propose
to have a battery that shall discharge its electricity into the
earth or sea, with a distance between its poles of five, ten,
or twenty miles, as the case may be. Let a similar length
of wire be erected on the opposite coast, as near to, and
parallel with, it as possible, with its ends also dipping into
the earth or sea. In this circuit place an instrument con-
sisting of ten, twenty, or more round or square coils of the
finest wire of best conductibility, suspended on points or
otherwise between, or in front of, the poles of an electro-,
or permanent, magnet or magnets. Any current passing
through the coil would be indicated by its moving or shift-
ing its position with reference to the poles of the magnet.
This would constitute a receiving apparatus of the most
J. W. WILKINS. 37
delicate character, for its efficiency would depend not so
much on the strength of the current passing as on the
power of the magnet, which may be increased at pleasure.
" I hope some one will take up this suggestion and carry
it out practically to a greater extent than my limited experi-
ments have enabled me to do. Of its truth for long as well
as for short distances I am satisfied, and only want of
means and opportunity prevent me carrying it out myself."
In a recent letter to the writer apropos of this early pro-
posal, Mr Wilkins says :
" I will just say that all thought of induction was absent
in my first experiments. I modified my views in this
respect a year or two later, but I did not attach sufficient
importance to the matter to follow up my communication to
the ' Mining Journal,' especially as at that time a cable was
actually laid across the Channel, which I could not doubt
would be a success, and a permanent one too. I rather
courted forgetfulness of the proposition. Whatever my
opinion at the time was as to the source of the electricity
that I discovered in the far removed and disconnected
circuit, the result was the same, and the means I used to
obtain it the same in principle as those which make the
matter an accomplished fact to-day viz., elevated lengths of
wire, and the discharge of electricity from the one on to a
delicate receiving apparatus in the circuit of the other.
"As regards the form of receiving apparatus which I
suggested for indicating the signals, I did then, and do now,
attach great importance to the happy idea. It happens to
be the most delicate form of detector or galvanometer, and
is identical in principle with Lord Kelvin's apparatus for
long cable working, which, in his Siphon Recorder Patent,
he says is as sensitive as his Mirror Galvanometer."
This principle, as the practical reader knows, has been
largely used in telegraphy. Besides Lord Kelvin's appli-
38 FIRST PERIOD THE POSSIBLE.
cation of it, we have the Brown and Allan Eelay, the
Weston Kelay, and Voltmeter, and other contrivances of a
similar nature; 1 but Mr Wilkins was himself the first to
put it in practice, and under the following interesting cir-
cumstances : In 1851 he went to America to assist Henry
O'Reilly of New York, a well-known journalist, who had a
concession from the patentees of the Morse system for the
erection of telegraph lines, at a royalty per mile. Disputes
soon arose, and the Morse Syndicate sought to prevent
O'Reilly from using their relay, without which the Morse
instruments would be useless for long distances. In this
difficulty O'Reilly adopted Bain's electro-chemical apparatus,
and employed it for a time on the People's Telegraph from
New York to Boston, via Albany. But finding that it was
impossible to use this instrument in connection with inter-
mediate stations, O'Reilly was again in a difficulty, when Mr
Wilkins came to the rescue by saying he could devise a
relay which did not require an iron armature, or electro-
magnet of the ordinary form, and which would therefore be
independent of the Morse patent. Very soon relays con-
sisting of movable coils of wire, suspended between the
poles of a magnet, were constructed in the workshop of
John Gavitt, a friend of O'Reilly's, and then famous as a
bank-note engraver. The instruments were placed in the
circuit of the People's Telegraph, and O'Reilly was saved
but only for a time, as in the end he was beaten by his
powerful opponents. The Wilkins relay was put aside and
soon forgotten, but forty-three years later it was brought
forward again by Mr Weston as an original invention. 2
1 The germ of all these instruments, as well as the Axial Magnets
of Prof. Page and Royal E. House, was sown by Edward Davy in
England in 1837. See my 'History of Electric Telegraphy,' 1884,
pp. 356, 357.
2 See the New York ' Electrical Engineer,' February 21, 1894.
DR O'SHAUGHNESSY. 39
DR O'SHAUGHNESSY (AFTERWARDS SIR WILLIAM
O'SHAUGHNESSY BROOKE) 1849.
One of the first difficulties encountered in the early days
of the telegraph in India was the crossing of the great
water-ways that abound in that country ; and it was this
difficulty which first directed the attention of Dr O'Shaugh-
nessy, the introducer of the system in India, to the subject
of subaqueous telegraphy.
In 1849 he laid a bare iron rod under the waters of the
river Huldee, 4200 feet wide, with batteries and delicate
needle instruments in connection on each bank. Signals
were passed, but " it was found that the instruments
required the attention of skilful operators, and that in
practice such derangements occurred as caused very frequent
interruptions."
He next tried the experiment without any metallic con-
ductor, using the water alone as the sole vehicle of the
electric impulses, but, though he again succeeded in passing
intelligible signals, he found that the battery power for
practical purposes would be enormous (he used up to 250
cells of the nitric acid and platinum form), and therefore
prohibitively expensive.
Although for practical purposes he soon abandoned the
idea of signalling across rivers with naked wires, and with-
out any wires at all, O'Shaughnessy for many years took
great interest in the subject. Thus as late as 1858 we find
him performing some careful experiments in the lake at
Ootacamund, and in his Administration Report of the Tele-
graph Department for that year he says : " I have long since
ascertained that two naked uncoated wires, kept a moderate
distance say 50 or 100 yards apart, will transmit electric
currents to considerable distances (two to three miles) suf-
ficiently powerful for signalling with needle instruments."
40 FIRST PERIOD THE POSSIBLE.
E. AND H. HIGHTON 1852-72.
The brothers Edward and Henry Highton, who were
well-known inventors in the early years of electric teleg-
raphy, took up the problem of transaqueous communica-
tion about 1852. In Edward Highton's excellent little book,
* The Electric Telegraph : Its History and Progress/ pub-
lished in that year, he says : " The author and his brother
have tried many experiments on this subject. Naked
wires have been sunk in canals, for the purpose of ascer-
taining the mathematical law which governs the loss of
power when no insulation was used. Communications
were made with ease over a distance of about a quarter
of a mile. The result, however, has been to prove that
telegraphic communications could not be sent to any con-
siderable distance without the employment of an insulated
medium."
On the other hand, Henry Highton long continued to
believe in its practicability, and made many further experi-
ments to that end. These were embodied in a paper read
before the Society of Arts on May 1, 1872 (Telegraphy
without Insulation), from which I condense the following
account :
" I have for many years been convinced of the possibility
of telegraphing for long distances without insulation, or
with wires very imperfectly insulated ; but till lately I had
not the leisure or opportunity of trying sufficient experi-
ments bearing on the subject. I need hardly say that
the idea has been pronounced on all hands to be entirely
visionary and impossible, and I have been warned of the
folly of incurring any outlay in a matter where every
attempt had hitherto failed. But I was so thoroughly
E. AND H. HIGHTON. 41
convinced of the soundness of my views, and of the
certainty of being able to go a considerable distance with-
out any insulation, and any distance with very imperfect
insulation, that I commenced, some three or four months
since, a systematic series of experiments with a view to
test my ideas practically.
" I began by trying various lengths of wire, dropped in
the Thames from boats, and found that I could, without
the slightest difficulty, exceed the limits allowed hitherto
as practicable. This method, however, was attended with
much difficulty and inconvenience, owing to the rapidity of
the tides and the motion of the boats. I next tried wires
across the Thames, but had them broken five or six times
by the strength of the current and by barges dragging their
anchors across them.
"1 then put the instrument in my own room, on the
banks of the river, and sent a boat down stream with a
reel of wire and a battery to signal to me at different dis-
tances. The success was so much beyond my expectations,
that I next obtained leave to lay down wires in Wimbledon
Lake. As the result of all these experiments I found that
water is so perfect an insulator for electricity of low tension
that wires charged with it retained the charge with the
utmost obstinacy; and, whether from the effect of polar-
isation (so-called), or, as I am inclined to suppose, from
electrisation of the successive strata of water surrounding
the wire, a long wire, brought to a state of low electrical
tension, will retain that tension for minutes, or even hours.
Xotwithstanding attempts to discharge the wire every five
seconds, I have found that a copper surface of 10 or 12
square feet in fresh water will retain a very appreciable
charge for a quarter of an hour ; and even when we attempt
to discharge it continuously through a resistance of about
42 FIEST PERIOD THE POSSIBLE.
thirty units [ohms], it will retain an appreciable though
gradually decreasing charge for five or six minutes. 1
" Since that time I have constructed an artificial line,
consisting of resistance coils, condensers, and plates of
.copper in liquids, acting at once as faults and as condensers,
so that I might learn as far as possible to what extent the
principle of non- insulation can be carried, and I have
satisfied myself that, though there are difficulties in very
long lengths absolutely uninsulated, yet it is quite feasible
to telegraph, even across the Atlantic, with an insulation of
a single unit instead of the 170,000 units [absolute] of the
present cables.
" The instrument with which I propose to work is the
gold-leaf instrument, constructed by me for telegraphic
purposes twenty-six years ago, 2 acted upon by a powerful
electro-magnet, and with its motions optically enlarged.
The exclusive use of this instrument in England was
purchased by the Electric and International Telegraph
Company, but it was never practically used, except in
Baden, where a Government commission recommended it
as the best. One of its chief merits is its extreme light-
ness and delicacy. Judging by the resistance it presents
to the electric current, it would appear that the piece of
gold-leaf in the instrument now before us does not weigh
more than 2-oVo"th P ar t f a grain ; let us even say that it
weighs four times more, or Tw tn P art 'f a grain. I n
order, then, to make a visible signal we only have to move
a very, very small fraction of a grain through a very, very
small fraction of an inch. You may judge of its delicacy
1 It does not appear to have struck our author that these effects
would militate against the practical application of his method.
2 A special arrangement of this instrument, adapting it for long
and naked (or badly insulated) lines, was patented February 13,
1873. For reports of its great delicacy see 'Telegraphic Journal,'
February 15, 1874.
E. AND H. HIGHTON. 43
when I show you that the warmth of the hand, or even a
look, by means of the warmth of the face turned towards
a thermopile, can transmit an appreciable signal through a
resistance equal to that of the Atlantic cable (experiment
performed). Another great merit of this instrument is its
ready adaptability to the circumstances in which it may be
placed, as it is easy to increase or diminish the length, or
breadth, or tension of the gold-leaf. Thus, increase of
length or diminution of breadth increases the resistance,
but also increases the sensitiveness ; and again, par-
taking as it does partly of the character of a pen-
dulum and partly of a musical string, the rapidity of
vibration is increased by giving it greater tension and
greater shortness, though by doing so the sensitiveness is
diminished ; so that you can adjust it to the peculiar cir-
cumstances of any circuit. Again, you notice the deadness
of the movements and the total absence of swing, which,
whenever a needle is used, always more or less tends to
confuse the signals. The greatest advantage of all is that
we can increase the sensitiveness without increasing the re-
sistance, simply by increasing the power of the electro-magnet
" Having now explained the construction of the instru-
ment, and pointed out its merits, I proceed to show by
experiment how tenaciously a piece of copper in water will
retain a state of electrical tension. Here is a tub of fresh
water, with copper plates presenting to each other about
14 square feet of surface. I charge these plates with a
Daniell cell, and you see how they retain the charge ; in fact,
they will go on gradually discharging for several minutes
through the small resistance of the gold-leaf instrument. I
now do the same with a tub of salt water, and the result
is still the same, though less marked. In fact, these
plates, with the water between, represent the two metallic
surfaces of a Leyden jar, and the water retains the elec-
44 FIRST PERIOD THE POSSIBLE.
tricity of this small tension with much more obstinacy than
the glass of a Leyden jar does the electricity of a higher
tension. 1
" Indeed, it is a fact of the highest importance in teleg-
raphy that when there is a fault, electricity of a high
tension, say of twenty or thirty Daniell cells, will almost
wholly escape by it, and leave nothing for the instrument ;
whereas electricity of a small tension, as from a single cell
of large surface, will pass through the instrument with very
little loss of power. This is strikingly shown by the use
of an ordinary tangent galvanometer. I cannot well show
it to a large audience like the present, therefore I will
only inform you that when I have taken two currents,
each marking 30 on the galvanometer, the one of high
tension from thirty Daniell cells, and the other of low
tension from a single cell of small internal resistance, a
fault equivalent to the exposure of a mile of No. 16 wire
in sea-water will annihilate all appreciable effects on the
galvanometer when using the current of high tension,
whereas the current of low tension will still show as much
as 20. You see, then, the importance of using currents
of low tension from a battery of large surface, and how a
faulty cable can be worked with such currents when it is
absolutely useless with currents of high tension.
" There are three ways of signalling without insulation :
one, only feasible for short distances ; a second, which I
think will be found the most practicable ; and a third, in
the practical working of which for very long distances
several difficulties (though by no means insuperable) pre-
sent themselves.
1 These experiments are not clearly described in the report from
which we are quoting. If we understand them aright, they are
rather electrolytic than Leydeu-jar effects. In any case, as the tubs
were presumably fairly well insulated, they have no bearing ad rem.
AND H. HIGHTON.
45
"To explain the first plan, we will take the case of a
river, and in the water near one bank place the copper
plates A B, and connect them with a wire, including the
battery P. Near the opposite bank submerge similar plates,
c D, connected by a wire, in the circuit of which is placed
the galvanometer G. Between A and B the current will
pass by every possible route, in quantities inversely pro-
portional to their resistances ; parts will pass direct by A B ;
and other portions by A, c, D, B, and by A, c, G, D, B.
Now, if the plates be large, and A c and B D respectively
Fig. 3.
comparatively near to each other, an appreciable current
will pass from A to c, through G, and back from D to B ;
but if the plates be small, the battery power small, and
the distance from A to B and from c to D comparatively
short, no appreciable amount will pass through the galvan-
ometer circuit. I do not hesitate to say that it is possible,
by erecting a very thick line wire from the Hebrides to
Cornwall, by the use of enormous plates at each extremity,
and by an enormous amount of battery power i.e., as
regards quantity to transmit a current which would be
sensibly perceived in a similar line of very thick wire, with
46 FIRST PERIOD THE POSSIBLE.
very large plates, on the other side of the Atlantic. But
the trouble and expense would probably be much greater
than that of laying a wire across the ocean.
"The second is the simplest and most feasible plan
namely, laying across the sea two wires kept from metallic
contact with each other, and working with that portion of
the current which prefers to pass through this metallic
circuit instead of passing across the liquid conductor, using
currents of low tension from batteries of large surface.
"The third method is to lay a single wire imperfectly
insulated, and to place at the opposite end beyond the
instrument a very large earth-plate. Any electrical tension
thrown on this wire transmits itself more or less to the
opposite end, and will be shown on any instrument of
small resistance and sufficient delicacy. There are certain
difficulties in this way of working, such as the effects of
earth-currents and currents of polarisation which keep the
needle or gold-leaf permanently deflected from zero, neces-
sitating special means of counteraction. I have no doubt,
from my experiments, that these difficulties may be over-
come ; but still I think the simplest and most feasible, and
not more expensive, plan will be to work with two naked
wires kept apart from metallic contact, using electricity of
a very low tension." l
Soon after this Mr Highton turned a complete volte
face, and went back to wires perfectly insulated, but at a
1 The following cutting from 'Once a- Week' (February 26, 1876)
is given here in the hope that some American reader will kindly sup-
ply details, if any are procurable : " The ' New York Tribune ' gives
an account of what appears to be a very remarkable discovery in
electrical science and telegraphy. It is claimed that a new kind of
electricity has been obtained, differing from the old in several partic-
ulars, and notably in not requiring for transmission that the conduct-
ing wires shaU be insulated. The difference is scarcely greater in kind
than between polarised and non-polarised light, or between ordinary
E. AND H. HIGHTON. 47
ri'Uculously small cost! On April 20, 1873, "he sent the
following letter to the ' Times ' :
"CHEAP TELEGRAPHY.
" SIR, Some months ago I read a paper to the Society
of Arts on the possibility of telegraphing for great distances
without insulation, for which they were good enough to
vote me a medal. I now find, however, that by the dis-
covery of a new insulating material perfect insulation can
be provided at a ridiculously small cost.
" I find by the addition of this material, which is simply
tar chymically modified, nearly 200,000 per cent is added
to the insulating power of a thin coating of gutta-percha, I
hope the result will shortly be found in the great cheapening
of telegraphy. Yours, &c., H. HIGHTON."
The new material here referred to was a preparation of
vegetable tar and oxide of lead, which almost instantly
solidified on application. In some experiments at the
Silvertown Works, it was found that No. 18 copper wire,
covered with gutta-percha weighing only 21 Ib. to the mile,
had its insulation increased nearly 200,000 per cent,
representing an insulation per mile of nearly three billion
ohms ! enough, as the inventor needlessly remarked, for
any lengths possible on the surface of the earth. 1
iron and that which has been so changed by contact with platinum
that the strongest nitric acid fails to attack it. A genuine discovery
of the sort would be of inestimable service in cheapening the tele-
graph, cable rates would soon be permanently reduced, and the un-
sightly poles that now disfigure our cities would quickly disappear. "
1 For reports on this cable see 'Telegraphic Journal,' vol. ii. pp.
104, 129.
48 FIRST PERIOD THE POSSIBLE.
G. E. DERING 1853.
The problem of wireless telegraphy was taken up about
this time by Mr George Dering of Lockleys, Herts, who
was, like his old Rugby tutor, Henry Highton, a prolific
inventor of electrical and telegraphic appliances, patents for
which he took out on eleven separate occasions between
1850 and 1858, and many of which came into practical
use in the early Fifties. His needle telegraph, patented
December 27, 1850, was in use in the Bank of England
early in 1852, connecting the governor's room with the
offices of the chief accountant, chief cashier, secretary,
engineer, and other officials. About the same time it
was partially used on the Great Northern Railway, and
exclusively so on the first Dover-Calais cable (1851), where
it did excellent service, working direct between London
and Paris for a long time (including the busy period of the
Crimean war), until supplanted by the Morse recording
instrument.
In the same specification of 1850, Dering patented three
methods of carrying off atmospheric electricity from the line-
wires : (a) " Two roughened or grooved metallic surfaces
separated by fine linen, one of which is included in the
line-wire circuit, and the other is in connection with the
earth." This was afterwards (in 1854) repatented by (Sir)
William Siemens, and is now known as Siemens' Serrated-
Plate Lightning-Guard, (b) " The attraction or repulsion
occurring between dissimilarly or similarly electrified bodies
respectively. Thus metal balls may be suspended from the
line-wire by wires, which on separating under the influ-
ence of the lightning-discharge make contact with plates
connected with the earth ; or the separation may simply
break connection between the line-wire and the instrument."
G. E. BERING. 49
(c) "Introducing a strip of metallic leaf into the circuit, this
being fused by the passage of the atmospheric electricity."
This very effective method has also been reintroduced in
later years, and always as a novelty, by various telegraph
engineers.
Bering's telegraphic appliances made a goodly show at
the Great Exhibition of 1851, side by side with Henley's
colossal magnets, and received " honourable mention."
They were again on view at the Paris International Exhi-
bition of 1855, where they were awarded a medal for
general excellence.
Bering's proposals for a transmarine telegraph are con-
tained in his patent specification of August 15, 1853, from
P~vhich we condense the following account :
" The present invention is applicable to submarine tele-
graphs, and also to the means of communication by under-
ground or over-ground wires. Heretofore, in constructing
electric telegraphs where the whole circuit has been made
of metal, and also where the conducting property of the
earth has been employed as a part of the circuit, it has
been usual, and it has been considered absolutely necessary,
to cause the wires to be thoroughly insulated, the con-
sequence of which has been that the expense of laying
down electric circuits has been very great, particularly
where the same have crossed the sea or other waters, where
not only have the wires been insulated, but in order to
protect the insulating matter from injury further great cost
, has been caused by the use of wire rope, or other means of
protection.
"Xow, I have discovered that a metallic circuit formed
of wires, either wholly uninsulated or partially so, may be
employed for an electric telegraph, provided that the two
1 parts of the circuit are at such a distance apart that the
1 electric current will not all pass direct from one wire to the
D
50 FIRST PERIOD THE POSSIBLE.
other by the water or earth, but that a portion will follow
the wire to the distant end.
" To -carry out my invention, I cause two uninsulated or
partially insulated wires to be placed in the water or in the
earth, at a distance apart proportionate to the total length
of the circuit, the said wires being insulated where they
approach one another to communicate with the instruments,
in order to prevent the current passing through the dimin-
ished water or earth space between them. The batteries
(or other suitable source of electricity) employed are to be
constructed in the proportion of their parts in conformity
with the well-known laws which regulate the transmission
of electric currents through multiple circuits that is, they
should possess the properties generally understood by the
term quantity in a considerably greater degree than is usual
for telegraphing through insulated wires, which may be
effected (in the case of galvanic batteries) by using plates
of larger dimensions, or by other alterations in the exciting
liquids or plates. The proper distance at which to place
the conductors from one another is also determined by the
same laws, all of which will be readily understood by per-
sons conversant with the principles of electrical science. In
practice I find that from one -twentieth to one -tenth the
length of the line-wires is a sufficient distance.
" Another method of carrying out my invention consists
in establishing circuits composed in part of the uninsulated
or partially insulated conductors, and in part of the con-
ducting property of the sea, across which the communication
is to be made, or of the earth or the moisture contained
therein in the case of land telegraphs. For this purpose
the connections are effected at such a distance in a lateral
direction that a sufficient portion of the current will pass
across the water or earth space and enter the corresponding
wire connection at the other extremity. The connecting
G. E. BERING. 51
wires at the termini must be effectually insulated as in the
first method.
" A third method consists in placing in the sea or earth
two wires of dissimilar metal having the quality of generat-
ing electricity by the action of the water or moisture with
which they are in contact. If at one extremity the wires
be attached respectively to the two ends of the coil of an
electro -magnet or other telegraphic apparatus, it will be
found that the instrument is acted on by the current
generated by the wires. If now at the other extremity the
wires be connected, a portion of the current will complete
its circuit through this connection, instead of all passing
through the electro-magnet, where consequently the effect
will be diminished; and if means be adopted to indicate
this greater or less power, signals may be indicated at one
end by making and breaking contact at the other. If de-
sirable, currents derived from galvanic batteries, or other
source, may be employed as auxiliary to those generated in
the outstretched wires.
" In the different means of communication which I have
described, if strong conductors are required, as in submarine
lines, wire rope may be employed, either alone or attached
to chains for greater strength and protection, or the con-
ducting wires may be attached to hempen ropes, or envel-
oped within them. The metal composing the wires may be
iron or copper or any other suitable kind, and it may be
coated with varnish, by which means the amount of exposed
surface will be diminished, and the metal preserved from
corrosion.
" I will now suppose the case of a line to be carried out
upon the principle which I have described, say from Holy-
head to Dublin, a distance of about sixty miles. It would
be necessary, first, to select two points on each coast from
three to six miles apart, and to connect these points on each
52 FIRST PERIOD THE POSSIBLE.
coast by insulated wires. Next, the two northern points
are to be connected by a submerged uninsulated conduc-
tor, and the two southern points by a similar conductor,
unless the water be employed as a substitute in the manner
before described. Thus an oblong parallelogram of con-
tinuous conductors is formed, having for its longer sides
the uninsulated conductors, and for its shorter sides the
insulated wires along the coasts. If now these latter wires
be cut at any parts, and instruments and batteries be con-
nected in circuit, signals may be transmitted by any of the
means ordinarily employed with insulated wires.
" Or, to take the case of a longer line, say from England
to America, I should select two points, as the Land's End
in Cornwall and the Giant's Causeway in Ireland or some
suitable place on the west coast of Scotland, and corre-
sponding points on the American shore. Next, I should
unite the two points in each country by insulated wires,
and, finally, submerge two uninsulated conductors across
the Atlantic, or one if the water be employed to complete
the circuit. Then by introducing, as before, suitable tele-
graphic instruments and batteries the communication will
be established.
" From the foregoing description it will be seen that the
cost of laying down electric telegraphs, whether submarine
or otherwise, is, by this invention of employing distance
between the conductors as a means of insulation, reduced
to little more than the mere cost of the wires, together
with that of an insulated wire at each end; while the
numerous difficulties which attend the insulation of long
lengths of wire are avoided, as also the chances of the
communication being interrupted by accidents to the
insulation."
At the time of this patent, and for many years after, the
difficulties just referred to were only too real. Many of
G. E. BERING. 53
the cables laid between 1850 and 1860 failed after a longer
or shorter period, and chiefly through defective insulation.
Hence, no doubt, the persistency with which telegraph
engineers in the Fifties sought in telegraphy without in-
sulation, and telegraphy without wires, other and more
economical ways of solving the great problem of trans-
marine communication.
Bering's experiments were performed across the river
Mimram at Lockleys, Herts, with bare parallel wires of
No. 8 galvanised iron, laid at a distance apart of about
30 feet, or one-tenth of the space to be traversed. With
a small battery power of only two or three Smee cells the
signals were easily readable.
At one of these performances on August 12, 1853, the
chairman and directors of The Electric Telegraph Com-
pany of Ireland (one of several mushroom companies then
started) were present, and so impressed were they with
the results obtained that they there and then decided to
adopt the system for their intended line between Port-
patrick and Donaghadee. This is a fact not generally
known in the history of early submarine telegraph enter-
prises, and what is still less known, for there is no record
of it, is that the project was actually attempted. In a
recent letter, Mr Bering, who I am glad to say is still
with us, has given me some interesting details of the
attempt which I now publish, feeling sure that they will
be new to the reader.
On September 23, 1853, the necessary wire in bundles
was shipped to Belfast, which, "for the sake of ultra
economy," consisted of single Xo. 1 galvanised iron instead
of twisted strand wire as Dering had recommended. On
examination the wire proved to be so unreliable, with
numerous weak and brittle places chiefly at the factory
welds that Dering urged delay and the substitution of
54 FIRST PERIOD THE POSSIBLE.
stranded wire. " Had we been wise," writes Mr Dering,
"we should have abandoned the attempt with this un-
suitable material, but it was resolved to go on and risk it
testing the wire as far as might be beforehand and removing
the weak parts. I, however, addressed a formal letter to the
board of directors in London, stating that the wire was so
unreliable I must decline all responsibility as to the laying
it down, but that I would do the best I could."
After carefully testing the various lengths, removing all
weak parts and bad welds as far as they could be discovered,
and jointing and tarring the whole into one long length, the
wire was paid into the hold of the Albert. On November
21 a start was made, a shore-end wire was laid from Milisle,
carried out to sea, and buoyed. Next morning the Albert, 1
piloted by H.M.S. Asp (Lieut. Aldridge), picked up the
buoyed end, joined it to the wire on board, and paid out
successfully for about 3J miles, when the wire broke at a
factory weld, and the ship returned to Donaghadee " in a
gale of wind."
The next few days were occupied in some alterations to
the paying-out machinery, found by experience to be de-
sirable, and on the 26th another start was made. The
wire on board was joined to the buoyed end at 4 miles
from shore, and paying-out proceeded successfully as far as
mid-channel (about 12 miles) when the wire broke, again
at a factory weld, and the end was lost in 82 fathoms of
water. The ship then returned to the buoy and tried to
underrun the wire, but it soon broke again, and for the
moment further attempts were abandoned.
Previous to this two unsuccessful attempts had already
been made to connect Great Britain and Ireland by cables
made on the lines of the Dover-Calais cable of 1851, one,
1 With Dr Hamel on board, the famous Russian scientist of Alpine
celebrity, as the representative of his Government.
JOHN HAWOETH. 55
undertaken by Messrs Newall & Co., between Holyhead
and Howth, June 1, 1852, which failed three days after;
and the other, a heavy six-wired cable, undertaken by the
same firm, between Portpatrick and Donaghadee, October 9,
1852, which broke in a gale after sixteen miles had been
paid out.
In June 1854 Messrs Newall recovered the whole of this
sixteen miles of cable, and completed the laying to Port-
patrick, thus rendering another attempt at a bare wire cable
unnecessary, if, indeed, it was still thought desirable.
Mr Bering's faith in the soundness of his views is still
unshaken, for he goes on to say : " Instead of a single
wire, as in 1853, I should now advocate the use of a bare
strand of wires for each of the conductors. And I must
add, considering the craving there is at present for Wireless
Telegraphs, that it seems to me not altogether improbable
that the less ambitious but (for, at all events, long dis-
tances) far more feasible plan of using bare wires will yet
have its innings." And who, in these days of electrical
marvels, will dare to say him nay? I, for my part, will
not, for I have seen more unlikely things come to pass.
The dream of to-day, " idle and ridiculous " as it may seem,
has been so often realised on the morrow, that the cautious
historian of science must not look for finality in any of
its applications. 1
JOHN HAWORTH 1862.
On March 27, 1862, Mr Haworth patented "An im-
proved method of conveying electric signals without the
intervention of any continuous artificial conductor," in
1 For recent applications of the bare-wire principle, see Melhuish,
p. 114, infra.
56 FIRST PERIOD THE POSSIBLE.
reference to which a lecturer of the period said : l "I have
not met one single gentleman connected with the science of
telegraphy who could understand his process, or its proba-
bility of success. I applied to him for some information,
but he is unwilling to communicate any particulars until
experiment has sufficiently demonstrated the practicability
of his plans."
In the discussion which followed, Mr Cromwell Varley,
electrician of the old Electric and International Telegraph,
and the old Atlantic Telegraph, Companies, said : " Being
informed that Sir Fitzroy Kelly and the learned chairman
(Mr Grove) had seen Haworth's system in operation, and
that the latter gentleman was a believer in it, he had tried
the experiment upon a very small scale in his own garden,
with apparatus constructed according to the instructions of
Mr Haworth. His two stations were only 8 yards apart,
and, although he used a very sensitive reflecting galvano-
meter, and twelve cells of Grove's nitric acid battery, he
could not get any signals, although the experiments were
varied in every conceivable way."
Under these circumstances it will not be surprising if I,
too, after a careful study of the specification, and with the
light thrown upon it by a further patent of October 30,
1863, have failed to understand the author's method. In-
deed, I feel in much the same mental condition towards it
as Tristram Shandy's connoisseurs, who, " by long friction,
incumbition, and electrical assimilation, have the happiness,
at length, to get all be-virtu'd, be-pictured, be-butterflied,
and be-fuddled." However, I will do my best to translate
the terrible phraseology of the letters patent into plain
English ; and if after this my readers cannot divine the
mode of action I will not blame them nor must they
blame me ! My description of the apparatus is based on
1 T. A. Masey, Society of Arts, January 28, 1863.
58
FIRST PERIOD THE POSSIBLE.
the complete specification and drawings of the second patent,
which were lodged in the Patent Office on April 30, 1864,
and which must therefore be supposed to contain the in-
ventor's last word on the subject.
A, z (fig. 4) are copper and zinc plates respectively,
curved as shown, and buried in the earth about 3 feet
apart. The superficies varies according to distance and
other circumstances : thus, for distances up to 75 miles
plates 1 foot square suffice ; over 75 and up to 440 miles,
plates 24 by 16 inches are required. G, F are copper
cylinders, 24 by 4 inches, buried in earth, which is
always moist. At a point distant about 3 feet from the
Fig. 5.
centres of A and z a wooden box 3 is buried, containing a
coil of insulated copper wire, No. 1 6 gauge, wound upon a
wooden reel. The ends of the coil are attached to binding
screws shown on top of the box. B is a wooden box con-
taining a wooden reel divided into three compartments, x,
y, z (fig. 5). x is filled with fine covered-copper wire, the
ends of which are brought together and secured on the out-
side of the reel, y is filled with thicker covered-copper
wire, wound in the same direction as x, and the ends are
severally connected to binding-screws, shown on the out-
side, z is half filled with insulated iron wire, wound in the
same direction as x and y ; the ends are fastened together
JOHN HAWORTH.
59
on the outside of the reel as with coil x. The compartment
is then filled with more of the same iron wire, wound
double, and in the reverse direction to the coil below it.
These double wires are not twisted, nor bound together, nor
allowed to cross one another, but are wound evenly in
layers side by side ; and the ends of each coil are secured
together on the outside of the reel as in the case of the
lower coil, and adjacent thereto. Usually the wire of coil
x is No. 32 gauge ; ?/, No. 16 ; andz, No. 20 ; but the sizes
Fig. 6.
and quantities required must vary according to distance and
other circumstances.
c is any suitable telegraph instrument of the needle
pattern.
D is a condenser of a kind which an electrical Dominie
Sampson would call prodigious ! A wooden box divided
lengthwise into two compartments well coated with shellac.
In each compartment is placed a band of stout gold-foil
both w r ell insulated, and connected at their ends to the
binding-screws a, #, and 6, h, respectively (fig. 6). Each
compartment is filled with sixty rectangular plates of gutta-
60 FIRST PERIOD THE POSSIBLE.
percha, on which insulated copper wire, No. 32 gauge, is
wound in one continuous length from the first plate to the
last, and the ends are attached to the binding-screws a, g,
and b, h, respectively. " I fix binding-screws c, d, e, f, k,
and I in the positions shown, and connect them with the
wire upon the plates in its passage through the box. I
then pass from end to end of each compartment over the
plates, and lying on them, but well insulated from them,
another band of stout gold-foil, and connect each end of it
with the screws a, g, and &, h, respectively."
E is another wooden box, containing a reel similar to B,
but divided into only two compartments, each of which is
filled with two copper wires, one covered and the other
uncovered, wound side by side, and all four of different
gauges from No. 18 to 30. The ends of one of the covered
coils are brought to the screws p, p, shown on top of
the box ; the ends of the other covered coil are fastened
on the outside of the reel ; and the ends of the two
uncovered coils are likewise fastened on the outside
of the reel, "but in such a position that they can
never come in contact with any uncovered part of the
coated wire. Between each of the layers of wire I place a
strip of non-metallic paper to insulate it from the layers
above and below, and when in winding I arrive within an
inch of the circumference of the reel I employ gutta-percha
tissue in addition to the non-metallic paper."
H is a Smee's battery, the size and power of which will
depend on circumstances, such as the distance to which it
is intended to convey the message ; the strength and
direction of earth -currents; and even the state of the
weather more power being required in dry than in damp
weather. " For a distance of ten miles, from dotting Hill
to Croydon, I have found a Smee's battery of two cells
at each end, containing plates 3 by 5 inches, to suffice.
JOHN HAWORTH. 61
For about fifty miles, from Nbtting Hill to Brighton, I
have used with success a battery of three cells at each
end ; and from dotting Hill to Bangor, in Wales, I have
required six cells at each end. Generally speaking, I have
found that less power is required to convey a message from
north to south and from south to north than from east
to west, or from west to east."
The connections of the various instruments are shown by
lines, and an exactly similar set of instruments is arranged
at the place with which it is desired to correspond.
And now as to the modus operandi: when the handle
of the needle instrument, c, is worked in the act of signal-
ling, what happens 1 ? Here the trouble comes in. The
author, I regret to say, is silent as to what happens, and
I won't be so rash as to make a guess ; but I would suggest
the question as a safe prize-puzzle for the Questions and
Answers column of some technical journal ! Seriously, it
seems to me that the results, if any, must be a perfect
chaos of battery currents, earth -battery currents, earth-
currents, induction currents, and currents of polarisation
all fighting in a feeble way for the mastery ; and yet
some men, besides the author, believed these effects to
be intelligible signals !
The remarks of Mr Varley, quoted above, drew that
gentleman into an angry correspondence in the pages of
the old 'Electrician' journal, from which I give a few
extracts. In the number for February 20, 1863, a student
wrote :
"It is evident that Mr Varley must be imperfectly
acquainted with the electric laws relating to earth con-
duction, or, by simply replacing his delicate galvanometer
by a few turns of stout wire, he might certainly have
obtained the signals. What is obviously required in an
experiment of this kind is to oppose as little resistance
62 FIRST PERIOD THE POSSIBLE.
as possible to the current of derivation by which the signal
is produced. The resistance of a galvanometer 'of the
most sensitive kind' must clearly be enormous in com-
parison with that of the other paths through which the
electricity is free to pass.
"Since the question of signalling without wires was
first referred to in 'The Electrician,' I have myself, with
a less power than twelve Grove cells, obtained signals
through more than 8 yards of garden -ground ; but it is
well known that signals have been transmitted without
wires through a much greater distance, both in England
and America."
This is followed by a short letter from Mr Haworth,
which we need not quote, as it contains nothing in the
way of explanation.
Mr Varley replied as follows in the next number of
'The Electrician' (February 27, 1863):
" I make it a rule never to pay any attention to anony-
mous correspondents. As Mr Haworth, however, has com-
mented upon the remarks I made a short time since at the
Society of Arts, allow me to draw attention to the fact
that, the discussion having been prolonged beyond the time
allotted for that purpose, the detail of the experiments
could not then be fully entered into.
"Mr Haworth paid me 'one' visit a short time ago,
when I asked him if he had any objection to his invention
being tested by actual experiment : he said he had not, and
pointed out to me how to arrange the various parts of the
apparatus. I have preserved the pencil sketch made at the
time, as indicated and approved by him. This was strictly
followed in the experiments.
" The apparatus used was constructed especially for this
purpose. The primary coils were thoroughly insulated with
gutta-percha, the secondary coils by means of a resinous
JOHN HA WORTH. 63
compound and india-rubber. The plates of copper and zinc
at each station were but an inch and a half from each
other ; they were each 6 inches square. Th two stations
were only 8 yards apart.
"The apparatus at each station consisted of a plate of
copper and a plate of zinc, connected to a flat secondary
coil containing nearly a mile of No. 35 copper wire. The
secondary coil was placed immediately behind the plates,
and behind this was placed a flat primary coil.
"At the sending station the primary coil was connected
with six cells of Grove's battery, and contact intermitted.
At the receiving station the primary coil was connected
with one of Thomson's reflecting galvanometers, of small
resistance, no more than that of an ordinary telegraph
instrument.
"With this disposition of apparatus no current could be
obtained.
"Crossing a river without wires is an old experiment.
In March 1847 I tried experiments in my own garden,
and also across the Eegent's Canal, with a single cell of
Grove's battery. Feeble but evident currents were sent
across the canal 50 feet wide. The current received was
but a minute fraction of that leaving the battery. In this
case the distance across the canal was but one quarter of
that separating the plates on each bank. When, however,
these plates were brought near together, as in Haworth's
specification, no visible signal could be obtained.
" This experiment has been repeated by numbers in vari-
ous parts of the world, and with the same well-known
results. When tried by me in 1847, I was unaware that
the idea had occurred to Professor Morse, or any one else.
"To account for Mr Haworth's assertions that he has
worked from Ireland to London, and between other distant
places, I can only suppose that he has mistaken some
64 FIRST PERIOD THE POSSIBLE.
irregularity in the currents generated by his copper and
zinc plates for signals.
"If he can telegraph without wires, why does he not
connect England with America, when he can earn 1000
per diem forthwith, and confer upon the world a great
blessing 1
" Before speaking at the Society of Arts, I called at Mr
Haworth's house several times, and found him out on all
occasions. I wrote him more than once, giving him the
negative results of my experiments, &c. He, however,
paid no attention to any of my communications.
" I have not been able to meet with a single individual
who has seen a message transmitted by Mr Haworth ; and
every one of those who are reported to have seen it, and
with whom I have come in contact, positively deny it when
questioned.
" I have no hesitation in stating 1st, That Mr Haworth's
specification is unintelligible : it is a jumble of induction
plates, induction coils, and coils of wire connected together
in a way that can have no meaning.
" 2ndly, That he cannot send electric signals without
wires to any useful distance.
" Srdly, From my acquaintance with the laws of elec-
tricity, I cannot believe it possible that he has ever com-
municated between distant stations as stated in his speci-
fication, No. 843, 1862.
" 4thly, Supposing for a moment that he could work, as
stated, any person constructing a similar apparatus in the
neighbourhood would be able to read the communications,
and they no longer would be private."
In the number for March 6, 1863, Mr James M. Holt,
writing from Kensington Park Gardens, W., said :
"I regret that Mr Varley's experiments have proved
unsuccessful ; but this does not surprise me, as, if I read
JOHN HAWORTH. 65
his letter correctly, he did not follow Mr Haworth's specifi-
cation closely if, indeed, at all. It would seem that he
constructed only parts of the apparatus, and did not
even connect those parts in the manner prescribed in the
specification.
" I have seen Mr Haworth's apparatus at work repeatedly,
and have myself read off from the indicator the messages
which have arrived and these ' irregular currents mistaken
for signals' have consisted of words and sentences trans-
mitted as correctly as by the electric telegraph. My house
has been one station, and Brighton, or Kingstown in
Ireland, the other.
"I can certify that the delay in bringing out this
discovery arises from causes over which Mr Ha worth has no
control. Accident has injured his apparatus. He will be
delighted to transmit signals across the Atlantic as soon as
the necessary machinery is ready, but he considers not
unwisely that it is most important to make success doubly
sure by previous repeated tests and experiments."
This is followed by two letters from other eyewitnesses,
vouching for the success of Haworth's experiments, and the
correspondence concludes with the following letter from Mr
Haworth himself :
"SiR, Will you kindly allow me space for a line in
reply to Mr Yarley 1 I never received his letter of the 27th
of January, and am truly sorry for any apparent discourtesy
on my part. I fear other letters have shared the same fate.
"From Mr Yarley 's account of his experiments I find
several particulars in which there has been considerable
misapprehension on his part ; but I cannot spare the time
nor can I ask you for the space to give further explana-
tions. It certainly is a new feature in electricity, if the
earth's currents alone can register words and sentences on
E
66 FIRST PERIOD THE POSSIBLE.
the dial-plate. I hope shortly to be able to convince the
most sceptical by ocular demonstration. For the present I
am content to wait, being anxious rather to perfect my dis-
covery than to push it. I am, sir, yours truly,
"JOHN HAWORTH.
"March 3, 1863."
After this we hear nothing more of Mr Haworth, though
no doubt the publication and discussion of his views kept
the subject alive for a time. 1 Thus, in ' The Electrician '
for January 23, 1863, the editor has a long article on " The
Earth as Part of a Voltaic Circuit," in which he reviews the
problem so well that we cannot refrain from quoting him
largely. He says :
" The case, communicated by ' E. S. ' and corroborated
by Mr R S. Culley, of a telegraphic circuit being worked
through a broken wire, the ends of which were in contact
with earth, appears in some quarters to have been taken in
confirmation of the notion that electric signals may be
transmitted to any required distance without the use of
a metallic conductor. It may be necessary, therefore, to
point out that this supposed confirmation has no existence
in fact. There are no grounds whatever for supposing that
any case similar to those which have been noticed by our
correspondents is not susceptible of being readily explained
in accordance with the known laws of electrical science. It
is altogether different when we come to the practical pro-
blem of signalling by electricity without a conducting wire.
If we have hitherto been silent in regard to this question,
which seems to have latterly engaged some amount of public
attention, it is that the means proposed for its solution are,
1 In Boron's ' Me'te'orologie Simplified,' Paris, 1863, pp. 936, 937,
there is a hazy description of a wireless telegraph, apparently based
on the same lines as Haworth's.
JOHN HAWORTH. 67
to us, simply incomprehensible. We cannot dispute their
efficiency, since we are forced to admit that we cannot per-
ceive upon what principle efficiency is aimed at. While,
in such case, it would clearly be unjustifiable to deny with-
out disproving, or to use the word ' impossible ' in reference
to what has been put forward as an accomplished fact, the
only alternative is to await, ' with modest scepticism,' the
verification and elucidation of the ' fact ' thus asserted.
" To render intelligible the phenomenon observed in the
broken wire circuit, we must have recourse to the law of
derived currents. Divested of all technicality, this is
simply that, when several conducting paths are offered for
the passage of a current, the quantity of electricity travers-
ing each path respectively will be inversely proportionate
to its resistance. If, therefore, in this instance, the resist-
ance between the broken extremities of the wire, added to
the resistance of the wire from the point of rupture to the
' line ' earth - plate, plus the resistance between the two
earth-plates, be less than the resistance between the broken
portion of the wire in contact with earth and the battery
earth -plate, the quantity of electricity traversing the sig-
nalling instrument at the distant station cannot be reduced
to the extent of one - half the normal signalling power.
Under these circumstances, therefore, signals might be re-
ceived almost as usual. Provided that the earth connections
of the main circuit were very perfect, and the point of rup-
ture nearer to the receiving than to the sending station, or
that the broken ends of wire were resting upon ground
freshly moistened by rain and covering a dry substratum,
it is quite possible that the signals would not be very per-
ceptibly reduced. . . .
" We pass over some other experiments of interest in
connection with earth conduction, in order to make out the
best case possible for those who believe in the present
68
FIRST PERIOD THE POSSIBLE.
practicability of signalling by means of voltaic electricity,
without any insulation between the two halves of the cir-
cuit. Instead of placing our interposed plates in a direct
line between the earth-plates in a circuit, let us arrange
them in a path which must be traversed by an indirect or
derived current, as in the following figure, in which B is the
battery, E + and E - the two earth-plates, and e e the two
interposed plates.
Fig. 7.
" At whatever distance the two systems may be placed
apart, a current will undoubtedly traverse the galvanometer
between the plates e e', whenever the circuit of the battery
is completed. We make the admission unreservedly, from
the point of view of theory ; the practical deductions to be
drawn from it have yet to be considered. We have to cal-
culate the force of the current which may traverse from
e to e' through the galvanometer or receiving instrument, or,
in other words, the proportionate quantity of electricity
taking this path, compared with the total dynamic effect of
the battery.
JOHN HAWORTH. 69
" Now we have reason to believe that something like the
following plausible method of arriving at a conclusion upon
this point is adopted by some of the more advanced among
those who hold the untenable view above referred to :
" ' Let the wire and battery resistance in the " transmit-
ting system," E + , B, E - , equal 1000 units ;
"'The resistance of the receiving system e e', equal 100
units ;
" ' And let the resistance between the earth- plates E +
and E , and between E + and e, and E - and e', be inappre-
ciable.
" ' Then the resistance in the direct circuit completed by
the battery plates E + and E will equal 1000.
" ' And the total resistance in the indirect circuit through
e e', will equal 1100 units.
" ' And, by the law of derived currents, if the force of
the current traversing the direct circuit be represented by
1100, that of the current traversing e e' will be 1000.'
"It will be scarcely necessary for us to point out the
fallacy of this mode of reasoning. It assumes the existence
of two paths only for the return currents the path of least
resistance between E + and E , and that through e e'. But
it will readily be seen that the earth affords a multitude of
paths of conduction for the earth portion of the circuit, of
which that from e to e' is one. The latter is therefore in-
cluded in the resistance between the earth-plates E + and
E- specified as inappreciable. As this inappreciable re-
sistance is to the resistance of wire from e to e', so will be
the relative force of the currents traversing the transmitting
and receiving systems respectively. The ratio, in a circuit,
without metallic conduction of moderate length, approxi-
mates to that of infinitely great to infinitely small. Can
any practical system be based upon these data?"
70 FIRST PERIOD THE POSSIBLE.
J. H. MOWER 1868.
Of the next proposal with which we have to deal in
these pages, I find amongst my notes only a single
cutting from the New York 'Kound Table' of (August
or September) 1868. I give it, in extenso, for what
it is worth, and hope some American reader may be
able to furnish details and further developments if
any :
"Mr Mower has elaborated a discovery which, if the
description given by the 'New York Herald' is to be
relied upon, will revolutionise trans-oceanic, and generally
all subaqueous, telegraphy. For some years he had been
engrossed in electrical experiments, when the Atlantic
cable gave a special direction to his investigations into
generating and conducting substances, the decomposition
of water, the development of the electrical machine, &c., &c.
By this summer his arrangements had been so far perfected
that, a few weeks ago, he was able to demonstrate to
himself and his coadjutor the feasibility of his project,
on a scale approximate to. that which it is designed to
assume.
" Selecting the greatest clear distance on an east and
west line in Lake Ontario from a point near Toronto,
Canada West, to one on the coast of Oswego County, New
York at his first attempt he succeeded in transmitting his
message, without a wire, from the submerged machine at
one end of the route to that at the other. The messages
and replies were continued for two hours, the average time
of transmission for the 138 miles being a little less than
three-eighths of a second.
"The upshot of the discovery on what principle Mr
Mower is not yet prepared to disclose is, that electric
M. BOURBOUZE. 71
currents can be transmitted through water, salt or fresh,
without deviation vertically, or from the parallel of lati-
tude. The difficulty from the unequal level of the tidal
waves in the two hemispheres will be obviated, it is
claimed, by submerging the apparatus at sufficient depth.
The inventor, we are told, is preparing to go to Europe
to secure there the patent rights for which the caveats have
been filed here. At the inconsiderable cost of 10,000
dollars he expects within three months to establish tele-
graphic communication between Montauk Point, the eastern
extremity of Long Island, and Spain, the eastern end of
the line striking the coast of Portugal at a point near
Oporto.
" The statement of the discovery is enough to take away
one's breath ; but, with the history of the telegraph before
us, we no more venture to deny than we do to affirm
its possibility."
M. BOURBOUZE 1870.
During the' investment and siege of Paris by the German
forces in the winter of 1870-71, many suggestions were
made for the re-establishment of telegraphic communica-
tion between Paris and the provinces. Acoustic methods
were tried, based on the transmission of sound by earth
and water. A Mr Granier proposed a form of aerial line
which was thought to be feasible by the distinguished
aeronaut, Gaston Tissandier. The wire (to be paid out
from balloons) was to be enclosed in gutta-percha tubing,
inflated with hydrogen gas so as to float 1000 to 1500
metres above the earth.
Amongst other suggestions was one by M. Bourbouze,
a well-known French electrician, which only need concern
72 FIRST PERIOD THE POSSIBLE.
us in these pages. 1 His proposal was to send strong
currents into the river Seine from a battery at the nearest
approachable point outside the German lines, and to receive
in Paris through a delicate galvanometer such part of these
currents as might be picked up by a metal plate sunk in
the river. After some preliminary experiments between
the Hotel de Ville and the manufactory of M. Claparede
at St Denis, it was decided to put the plan in practice.
Accordingly, on December 17, 1870, M. d' Almeida left the
beleaguered city by balloon, descended after many perils
at Champagne outside the enemy's lines, and proceeded
via Lyons and Bordeaux to Havre. Thence the necessary
apparatus was ordered from England and conveyed to
Poissy, where M. d'Almeida regained the banks of the
Seine on January 14, 1871. Here, however, the river
was found to be completely frozen over, and the attempt
at communicating with Paris was deferred to January 24.
Meanwhile the armistice was proclaimed, and the project
was allowed to drop.
M. Bourbouze did not, however, abandon his idea, and,
thinking he found in the principle of La Cour's phonic wheel
telegraph a better means of indicating the signals than the
galvanometer, he again took up the problem. Between 1876
and 1878 an occasional notice of his experiments appeared
in the technical journals, but they are all provokingly silent
on the point of actual results over considerable distances. 2
1 On March 27, 1876, Bourbouze requested to be opened at the
Academy of Sciences a sealed packet which he had deposited on
November 28, 1870. It was found to contain a note entitled " Sur
les Communications a Distance par les Cours d'Eau." The contents
of the document, so far as I know, have not been published.
2 See, amongst other accounts, the ' English Mechanic,' September
8, 1876 ; ' Engineering,' April 13, 1878 ; and the French journal, ' La
Nature,' July 8, 1876. For Bourbouze's earlier experiments, see ' La
Lumiere Electrique,' August 19, 1879.
MAHLON LOOMIS. 73
MAHLON LOOMIS 1872.
In 1872 Mr Mahlon Loomis, an American dentist, pro-
posed to utilise the electricity of the higher atmosphere for
telegraphic purposes in a way which caused some excite-
ment in America at the time.
It had long been known that the atmosphere is always
charged with electricity, and that this charge increases
with the ascent : thus, if at the surface of the earth we
represent the electrical state or charge as 1, at an elevation
of 100 feet it may be represented as 2 ; at 200 feet as 3 ;
and so on in an ascending series of imaginary strata.
Hitherto this had been considered as a rough-and-ready
way of stating an electrical fact, just as we say that the
atmosphere itself may, for the sake of illustration, be
divided into strata of 100 or any agreed number of feet,
and that its density decreases pro rata as we ascend through
each stratum. But Mr Loomis appears to have made the
further discovery that these electrical charges are in some
way independent of each other, and that the electricity of
any one stratum can be drawn off without the balance being
immediately restored by a general redistribution of elec-
tricity from the adjacent strata. On this assumption,
which is a very large one, he thought it would be easy to
tap the electricity at any one point of a stratum, preferably
an elevated one where the atmosphere is comparatively
undisturbed, which tapping would be made manifest at
any distant point of the same stratum by a corresponding
fall or disturbance there of the electrical density ; and thus,
he argued, an aerial telegraph could be constructed.
The following is an extract from his (American) patent,
dated July 30, 1872 :
" The nature of my discovery consists in utilising natural
74 FIRST PERIOD THE POSSIBLE.
electricity, and establishing an electrical current or circuit
for telegraphic and other purposes without the aid of wires,
artificial batteries, or cables, and yet capable of communi-
cating from one continent of the globe to another.
" As it was found possible to dispense with the double
wire (which was first used in telegraphing), making use of
but one, and substituting the earth instead of a wire to
form the return half of the circuit ; so I now dispense with
both wires, using the earth as one-half the circuit and the
continuous electrical element far above the earth's surface
for the other half. I also dispense with all artificial bat-
teries, but use the free electricity of the atmosphere, co-
operating with that of the earth, to supply the current for
telegraphing and for other useful purposes, such as light,
heat, and motive power.
"As atmospheric electricity is found more and more
abundant when moisture, clouds, heated currents of air,
and other dissipating influences are left below and a greater
altitude attained, my plan is to seek as high an elevation as
practicable on the tops of high mountains, and thus establish
electrical connection with the atmospheric stratum or ocean
overlying local disturbances. Upon these mountain-tops I
erect suitable towers and apparatus to attract the electricity,
or, in other words, to disturb the electrical equilibrium, and
thus obtain a current of electricity, or shocks or pulsations,
which traverse or disturb the positive electrical body of the
atmosphere between two given points by connecting it to
the negative electrical body of the earth below."
To test this idea, he selected two lofty peaks on the
mountains of West Virginia, of the same altitude, and about
ten miles apart. From these he sent up two kites, held by
strings in which fine copper wires were enclosed. To the
ground end of the wire on one peak he connected an electrical
MAHLON LOOMIS. 75
detector presumably of the electrometer kind and on the
other peak a key for connecting the kite wire to earth when
required. With this arrangement we are told that messages
were sent and received by making and breaking the earth
connection, "the only electro-motor being the atmospheric
current between the kites, and which was always available
except when the weather was violently broken."
So well did this idea " take on " in the States that we
learn from the New York * Journal of Commerce ' (February
5, 1873) that a bill had passed Congress incorporating a
company to carry it out. The article then goes on to say :
" We will not record ourselves as disbelievers in the Aerial
Telegraph, but wait meekly and see what the Doctor will
do with his brilliant idea now that both Houses of Congress
have passed a bill incorporating a company for him. Con-
gressmen, at least, do not think him wholly visionary ; and
it is said that the President will sign the bill ; all of which
is some evidence that air telegraphy has another side than
the ridiculous one. The company receive no money from
the Government, and ask none. As we understand the
Loomis plan, it is something to this effect and readers are
cautioned not to laugh too boisterously at it, as also not to
believe in it till demonstrated. The inventor proposes to
build a very tall tower on the highest peak of the Eocky
Mountains. A mast, also very tall, will stand on this
tower, and an apparatus for ' collecting electricity ' will top
the whole. From the loftiest peak of the Alps will rise
another very tall tower and ditto mast, with its coronal
electrical affair. At these sky-piercing heights Dr Loomis
contends that he will reach a stratum of air loaded with
electricity ; and we cannot say that he will not. Then,
establishing his ground-wire connections the same as in
ordinary telegraphs, he feels confident that he can send
76 FIRST PERIOD THE POSSIBLE.
messages between the mast-tops, the electrified stratum of
air making the circuit complete. The inventor claims to
have proved the feasibility of this grand scheme on a small
scale. We are told that, from two of the spurs of the Blue
Eidge Mountains, twenty miles apart, he sent up kites,
using small copper wire instead of pack-thread, and tele-
graphed from one point to the other."
At intervals in the next few years brief notices of the
Loom is method appeared in the American journals, some
of which were copied into English papers. The last that
I have seen is contained in the 'Electrical Eeview' of
March 1, 1879, where it is stated that "with telephones in
this aerial circuit he (Loomis) can converse a distance of
twenty miles," to which the editor significantly adds a
note of interrogation.
The fact is, however much Mr Loomis and his Wall
Street friends believed that dollars were in the idea, the
technical press never took it very seriously. This is shown
by the following cutting, which we take from the New
York 'Journal of the Telegraph,' March 15, 1877:
"The never-ending procession of would-be inventors who
from day to day haunt the corridors and offices of the
Electrician's department at 195 Broadway, bringing with
them mysterious packages tied up in newspapers, was
varied the other day by the appearance of a veritable
lunatic. He announced that that much -talked -of great
discovery of a few years ago, aerial telegraphy, was in
actual operation right here in New York. A. M. Palmer,
of the Union Square Theatre, together with one of his
confederates, alone possessed the secret ! They had un-
fortunately chosen to use it for illegitimate purposes, and
our visitor, therefore, felt it to be his solemn duty to expose
them. By means of a $60,000 battery, he said, they trans-
MAHLON LOOmS. 77
mitted the subtle fluid through the aerial spaces, read
people's secret thoughts, knocked them senseless in the
street ; ay, they could even burn a man to a crisp, miles
and miles away, and he no more know what had hurt him
than if he had been struck by a flash of lightning, as indeed
he had ! J The object of our mad friend in dropping in was
merely to ascertain how he could protect himself from
Palmer's illegitimate thunderbolts. Here the legal gentle-
man, lifting his eyes from ' Curtis on Patents/ remarked :
*Xow, I'll tell you what you do. Bring a suit against
Palmer for infringement of Mahlon Loomis's patent. Here
it is ' (taking down a bound volume of the 'Official Gazette '),
1 No. 129,971. That'll fix Palmer.' But the madman pro-
tested that this would take too long, and meanwhile he was
in danger of his life every minute, and casually remarked
that it had occurred to him that by appearing on the streets
in a robe of pea-green corded silk, gutta-percha boots, and a
magenta satin hat with a blue-glass skylight in the top of it,
he would be effectually protected from injury during his
daily perambulations."
In conclusion of this period of our history, it will suffice
to say that between 1858 and 1874 many patents were
taken out in England for electric signalling on the bare
wire system of Highton and Bering, with or without the
use of the so-called " earth battery." As they are all very
much alike, and all unsupported, so far as I have seen, by
any experimental proofs, it would be a tiresome reiteration
to describe them, even in the briefest way. I therefore
content myself with giving the following list, which will
be useful to those of my readers who desire to consult
them.
1 This lunatic must be still abroad, for we occasionally hear much
the same thing of the diabolic practices of Tesla and Marconi.
78
FIRST PERIOD THE POSSIBLE.
Name of patentee.
B. Nickels . ...
A. V. Newton . .
A. Barclay . . .
Do. ...
J. Moles worth , .
H. S. Eosser . .
W. E. Newton . .
H.Wilde . . .
Lord A. S. Churchill .
H.Wilde . . .
Do. ...
T. Walker . . , .
Do.
No. and date of patent.
2317 October 16, 1858.
2514 November 9, 1858.
56 January 7, 1859.
263 January 28, 1859.
687 March 18, 1859.
2433 October 25, 1859.
1169 May 11, 1860.
2997 November 28, 1861.
458 February 20, 1862.
3006 December 1, 1863.
2762 October 26, 1865.
2870 November 6, 1866.
293 January 23, 1874.
79
SECOND PEEIOD THE PKACTICABLE.
PRELIMINARY: NOTICE OF THE TELEPHONE IN RELATION
TO WIRELESS TELEGRAPHY.
- . " Give me the ocular proof,
Make me see't ; or, at least, so prove it,
That the probation bear no hinge, nor loop,
To hang a doubt on."
WE have now arrived at a period in the history of our
subject at which experiments begin to assume a character
more hopeful of practical results. All that went before
was more or less crude and empirical, and could not be
otherwise from the very necessities of the case. The intro-
duction of the telephone in 1876 placed in the hands of the
electrician an instrument of marvellous delicacy, compared
with which the most sensitive apparatus hitherto employed
was as the eye to the eye aided by the microscope. Thus,
Prof. Pierce of Providence, Ehode Island, has found that
the Bell telephone gives audible signals with consider-
ably less than one-hundred-thousandth part of the current
of a single Leclanche cell. In testing resistances with a
Wheatstone bridge, the telephone is far more sensitive than
the mirror galvanometer ; in ascertaining the continuity of
fine wire coils it gives the readiest answers ; and for all the
different forms of atmospheric electrical discharges and
80 SECOND PERIOD THE PRACTICABLE.
they are many it has a language of its own, and opens up
to research a new field in meteorology.
The sound produced in the telephone by lightning, even
when so distant that only the flash can be seen in the hori-
zon, and no thunder can be heard, is very characteristic
something like the quenching of a drop of molten metal in
water, or the sound of a distant rocket ; but the remarkable
circumstance for us in this history is, that this sound is
always heard just before the flash is seen, showing that
there is an inductive disturbance of the electricity overhead,
due to the distant concentration preceding the disruptive
discharge. Thus, on November 18, 1877, these peculiar
sounds were heard in Providence, and the papers next
morning explained them by reporting thunderstorms in
Massachusetts. Sounds like those produced by lightning,
but fainter, are almost always heard many hours before a
thunderstorm actually breaks. 1
The Bell telephone was tried for the first time on a wire
from New York to Boston on April 2, 1877, and soon after-
wards its extraordinary sensitiveness to induction currents,
and currents through the earth (leakages) from distant
telegraph circuits, began to be observed. 2 Thus, in August
1877, Mr Charles Eathbone of Albany, KY., had been ex-
perimenting with a Bell telephone which was attached to a
private telegraph line connecting his house with the Ob-
1 'Journal of the Telegraph,' N.Y., December 1, 1877. See also
'Jour. Inst. Elec. Engs.,' vol. vi. p. 523, vol. vii. p. 329; 'The Elec-
trician,' vol. ix. p. 362.
2 The disturbing effects of induction on ordinary telegraph wires on
the same poles had long before this been noticed. See Culley's paper
and the discussion thereon in the 'Jour. lust. Elec. Engs.,' vol. iv.
p. 54. See also p. 427 for Winter's interesting observations in India
in 1873. As far back as 1868 Prof. Hughes, at the request of the
French Telegraph Administration, undertook a series of experiments
with a view of finding a remedy. The results are given in his paper
read before the Inst. Elec. Engs., March 12, 1879.
THE TELEPHONE AND WIRELESS TELEGRAPHY. 81
servatory. One evening he heard some singing which he
thought came from the Observatory, but found on inquiry
that that was not the case. He then carefully noted what
followed, and next morning sent a note to the newspapers
stating the facts and giving the names of the tunes which
he had heard. This elicited the information that the tunes
were those of an experimental concert with Edison's singing
telephone over a telegraph wire between New York and
Saratoga Springs. It was then resolved to follow up this
curious discovery, and, accordingly, when Edison's agent
gave another concert in Troy, arrangements were made to
observe the effects. A wire running from Albany to Troy
alongside the Edison wire was earthed with a Bell telephone
in circuit at each end. The concert was heard as before,
the music coming perfectly clear, and the tunes distinguish-
able without the least difficulty.
Later in the evening the instruments were put in circuit
on one of the wires running from Albany to New York.
Again the music was heard, and much louder, so that by
placing the telephone in the centre of the room persons
seated around could hear with perfect distinctness.
These observations were made on six separate occasions
between August 28 and September 11, and, strangely enough,
two other and independent observers in Providence, 200
miles away, noted the same effects on five out of the six
dates given by Mr Rathbone. 1
Dr Channing, one of the observers in Providence, has
published a very interesting account 2 of his observations,
from which I will make a few extracts. During five
1 'Journal of the Telegraph,' N.Y., October 1 and 16, and No-
vember 1, 1877. For other early observations of the same kind see
'The Telegraphic Journal,' March 1, 1878, p. 96 ; 'Journal of the
Telegraph,' March 16, 1878 ; ' The Electrician,' vol. vi. pp. 207, 303.
2 'Journal of the Telegraph,' December 1, 1877, and reproduced
in the 'Jour. Inst. Elec. Engs.,' vol. vi. p. 545.
F
82 SECOND PERIOD THE PRACTICABLE.
evenings in the latter part of August and first part of
September 1877 concerts were given in the Western Union
Office, N.Y., for the benefit of audiences in Saratoga,
Troy, and Albany respectively. The performers sang or
played into an Edison musical telephone, actuated by a
powerful battery, and connected with one or other of the
above-named places by an ordinary telegraph line, with
return through the ground.
In Providence, on the evening of the first concert, Dr
Channing and a friend were conversing through Bell tele-
phones over a shunt wire, made by grounding one of the
American District Telegraph wires at two places, a quarter
of a mile apart, through the telephones and several hun-
dred ohms resistance. At about half-past eight o'clock
they were surprised by hearing singing on the line, at first
faint, but afterwards becoming clear and distinct. After-
wards, during that and subsequent evenings, various airs
were heard, sung by a tenor or soprano voice, or played
on the cornet. On investigation, the music heard proved
to be the same as that of the Edison concerts performed
in New York.
The question how this music passed from the New York
and Albany wire to a shunt on the District wire in Provi-
dence is of scientific importance. The Edison musical
telephone consists of an instrument which converts sound
waves into galvanic waves at the transmitting station, and
another apparatus which reconverts galvanic waves into
sound waves at the receiving station. The battery used
in these concerts consisted of 125 carbon-bichromate cells
(No. 1J), with from 1000 to 3000 ohms resistance inter-
posed between the battery and the line. The line wire
extended from the Western Union office, via the Harlem
Eailway, to Albany. On the same poles with this Albany
wire, for sixteen miles, are carried four other wires, all
THE TELEPHONE AND WIRELESS TELEGRAPHY. 83
running to Providence, and also, for eight miles, a fifth
wire from Boston, via New London, to Providence. All
these lines, including the Albany wire, are understood to
have a common earth connection at New York, and to be
strung at the usual distance apart, and with the ordinary
insulation.
At Providence six New York and Boston wires run
into the Western Union office on the same poles and
brackets for the last 975 feet with an American District
wire. This wire belongs to an exclusively metallic circuit
of four and a half miles, having, therefore, no earth con-
nection. Finally, in a shunt on this wire, the telephones
were placed as before described.
It will thus be seen that the music from the Albany
wire passed first to the parallel New York -Providence
wires; secondly, from these to a parallel District wire in
Providence ; and thirdly, through a shunt on the "District
wire "to the telephones.
This transfer may have taken place by induction, by
cross-leakage, or, in the first instance, in New York by
a crowded ground connection ; but in the transfer in Provi-
dence from the New York-Boston to the District wire there
was no common ground connection, and it is difficult to
suppose that sufficient leakage took place on the three
brackets and three poles (common to the New York and
District wires) to account for it. Without wholly reject-
ing the other modes of transfer, Dr Channing ascribes to
induction the principal part in the effects.
The next question arises, What proportion of the electri-
cal force set in motion in New York could have reached the
listeners on the short shunt line in Providence 1 Whether
induction or cross-leakage or crowded ground was concerned,
who will say that the New York -Providence wires had
robbed the Albany wire of one-tenth or even one-hundredth
84 SECOND PERIOD THE PRACTICABLE.
of its electrical force 1 When this reached Providence, did
the New York wires in the course of 975 feet give up to
the District wire one-tenth or one-hundredth of their force 1
Lastly, when the District circuit had secured this minute
fraction, did the shunt, with its 500 ohms resistance as
against the few ohms of the shunted quarter-mile, divert
one-hundredth part of this minute fraction from the Dis-
trict wire ] Plainly, the music reproduced in the Providence
telephone did not require one ten - thousandth, nor one
hundred-thousandth of the force originally imparted to the
Albany wire.
In December 1877 Prof. E. Sacher of Yienna undertook
some careful investigations with a view of measuring the
inductive effect in telephone circuits. He found that
signals from three Smee cells sent through one wire, 120
metres long, could be distinctly heard in the telephone on
another and parallel wire 20 metres distant from it. 1
Early in 1879 M. Henri Dufour tried similar experi-
ments, and with the same results. Two covered copper
wires were stretched parallel over a length of 15 metres, and
at distances apart varying from 15 to 45 centimetres. In
connection with one of the wires were the battery and the
ordinary Morse apparatus, the gas -pipes being used to com-
plete the circuit. The ends of the other wire were joined
to the telephone so as to form a complete metallic circuit.
The current employed produced a deflection of 60 on the
galvanometer. Under these conditions all the motions of
the key were distinctly heard in the telephone, and the
author was satisfied that a telegraphist would have under-
stood the signals, even when the distance between the two
wires was 45 centimetres. 2
When we consider the shortness of these wires, the
effects are sufficiently striking ; but before this, equally
1 Electrician, vol. i. p. 194. 2 Ibid., vol. ii. p. 182.
PEOFESSOR JOHN TROWBRIDGE. 85
striking results had been obtained on actual telegraph lines,
where there was no battery, and where the infinitesimal
currents produced by speaking into a Bell telephone on one
wire were able to induce currents in a parallel wire sufficient
to render the words audible in another telephone in its
circuit. Dr Channing found this to be possible "under
very favourable conditions." l
Another striking illustration is furnished by Prof. Blake,
of Brown University, U.S., who talked with a friend for
some distance along a railway (using the two lines of rails
for the telephonic circuit), hearing at the same time the
Morse signals passing along the telegraph wires overhead. 2
PKOFESSOR JOHN TROWBRIDGE-1880.
Such are a few of the early instances noted of the
extreme sensitiveness of the telephone, by the aid of which
the problem of wireless telegraphy was now to be attacked
with a fair measure of success, and advanced a long way
towards a practical solution.
Mr J. Gott, then superintendent of the Anglo-American
Telegraph Company at St Pierre, was, I believe, the first to
suggest the employment of the telephone in this connection.
In a brief communication, published in the ' Jour. Inst.
Elec. Engs.' (vol. vi. p. 523), he says: "The island of
1 For a curiously similar case, the result of a wrong connection of
the line wires, see the ' Telegraphic Journal,' vol. ix. p. 68.
2 The absence of insulation in this experiment recalls the fact that
a telephone line using the earth for the return circuit often works
better when the insulation is defective, as it is then less affected by
extraneous currents. Thus, in 1882, the Evansville (Ind.) Telephone
Exchange Company worked 400 miles of line without insulators of any
kind (the wires being simply attached to the poles), and generally
with better results than when insulators were used. (' Electrician,'
vol. ix. p. 481.)
86 SECOND PERIOD THE PRACTICABLE.
St Pierre is, perhaps, better insulated than most places.
Hundreds of yards from the station, if a wire be connected
to earth, run some distance, and put to earth again, with a
telephone in circuit, the signals passing through the cables
can be heard."
There are two offices on the island, one used for
repeating the cable business on the short cables between
Sydney, C.B., and Placentia, KF., and operated by the
Morse system, with a comparatively powerful battery ; the
other is the office at which the Brest and Duxbury cables
terminate, and is furnished with very delicate instruments
the Brest cable, which is upwards of 2500 miles long,
being operated by Thomson's exceedingly sensitive dead-
beat mirror galvanometer ; whilst on the Duxbury cable the
same inventor's instrument, the siphon recorder, is used.
The Brest instrument was found seriously affected by earth-
currents, which flowed in and out of the cable, interfering
very much with the true currents or signals, and rendering
it a difficult task for the operator to decipher them ac-
curately. The phenomenon is not an uncommon one ; and
the cause being attributed to the ground used at the
office, a spare insulated wire, laid across the island, a
distance of nearly three miles, and a metal plate connected
to it and placed in the sea, was used in lieu of the office
ground. This had a good effect, but it was now found that
part of the supposed earth-currents had been due to the
signals sent by the Morse operator into his wire, for when
the recorder was put in circuit between the ground at the
cable office and the sea ground three miles distant the
messages sent by the Morse were clearly indicated, so
clearly, in fact, that they were automatically recorded on
the tape.
It must be clearly understood that the two offices were in
no way connected, nor were they within some 200 yards of
PROFESSOR JOHN TROWBRIDGE. 87
each other; and yet messages sent at one office were
distinctly read at the other, the only connection between
the two being through the earth, and it is quite evident
that they could be so read simultaneously at many offices in
the same neighbourhood. The explanation is clear enough.
The potential of the ground at the two offices is alternately
raised and lowered by the Morse battery. The potential of
the sea remains almost, if not wholly, unaffected by these,
and the island thus acts like an immense Ley den jar, con-
tinually charged by the Morse battery and discharged, in
part, through the short insulated line. Each time the
Morse operator depressed his key he not only sent a current
into his cable, but electrified the whole island, and this
electrification was detected and indicated on the recorder. 1
As the result of these experiences, Mr Gott gave it as his
opinion that "speaking through considerable distances of
earth without wires is certainly possible with Bell's tele-
phone, with a battery and Morse signals."
Professor John Trowbridge of Harvard University,
America, was, however, the first to systematically study
the problem, and to revive the daring project of an Atlantic
telegraph without connecting wires, and the less ambitious
but equally useful project of intercommunication between
ships at sea. 2 In fact, Trowbridge' s researches may truly be
1 See now Salvd's curious anticipation in 1795 of this phenomenon,
p. 1, ante. The peculiarity, due to geological formation, is not con-
fined to St Pierre ; it is often met with in practice, though usually in
lesser degrees. See some interesting cases, noted by G. K. Winter
and James Graves, ' Jour. Inst. Elec. Engs.,' vol. L p. 88, and vol.
iv. p. 34.
2 Mr H. C. Strong of Chicago, Illinois, claims to have suggested
in 1857, in a Peoria, 111., newspaper, the possibility of communication
between ships at sea by means of a wireless telegraph then recently
invented by his friend Henry Nelson of Galesburg. See Mr Strong's
letter in the New York 'Journal of the Telegraph/ August 15,
1877.
88 SECOND PERIOD THE PRACTICABLE.
said to form a new starting-point in the history of our
subject, for, as we shall see later on, it is chiefly to him
that Messrs Preece, Bell, and other experimenters in this
field owe their inspirations. His investigations, therefore,
deserve to be carefully followed. 1
The observatory at Harvard transmits time-signals from
Cambridge to Boston, a distance of about four miles, and
the regular recurrence of the beats of the clock afforded
a good means of studying the spreading of the electric
currents from the terminal of the battery which is grounded
at the observatory. In all the telephone circuits between
Boston and Cambridge, in the neighbourhood of the observ-
atory line, the ticking of the clock could be heard. This
ticking had been attributed to induction, but this, accord-
ing to Prof. Trowbridge, is an erroneous conclusion, as he
shows by a mathematical analysis into which we need not
enter. The result goes to show that, with telephones of
the resistance usually employed, no inductive effect will
be perceived by the use of even ten quart Bunsen cells
between wires running parallel, a foot apart, for a distance
of 30 or 40 feet.
For this and other reasons, he says, it is impossible to
hear telephonic messages by induction from one wire to
another, unless the two run parallel and very close to each
other for a long distance. This distance generally exceeds
the limit at which the ordinary Bell telephone ceases to
transmit articulate speech. The effects which have usually
been attributed to induction are really, he says, due to the
earth connections and to imperfect insulation.
Having determined in this manner that the echoes of the
1 They are given at length in a paper, " The Earth as a Conductor
of Electricity," read before the American Academy of Arts and
Sciences in 1880. See also * Silliman's American Journal of
Science,' August 1880, which I follow in the text.
PROFESSOR JOHN TROWBRIDGE. 89
time-signals observed on the telephone lines were not due
to induction, but to leakage from the clock circuit, Prof.
Trowbridge proceeded to study the extent of the equally
electrified or equi- potential surfaces of the ground sur-
rounding the clock battery. His method of exploration
was to run a wire 500 or 600 feet long to earth at each
end, including a telephone of 50 to 60 ohms resistance.
Evidence of a current in this exploratory circuit was plainly
shown by the ticking sound which making and breaking
the circuit caused in the telephone, and the time-signals
could be distinctly heard in a field 220 yards from the
observatory where one earth of the time-signal wire is
located. At a distance of a mile from the observatory, and
not in the direct line between that place and the Boston
telephone office, the time-signals were heard by connecting
through a telephone the gas-pipes of one building with the
water-pipes of another only 50 feet apart. In another ex-
periment at the Fresh Pond lake in Cambridge, signals
sent from Boston to Waltham (ten to twelve miles) were
heard by simply dipping the terminal wires of the telephone
in the lake, and some distance apart, where they must have
been far away (? four miles) from the battery earth.
Prof. Trowbridge performed a large number of similar
experiments, varied in every way, all going to prove (1)
that a battery terminal discharging electricity to earth is
the centre of waves of electrical energy, ever widening,
and ever decreasing in strength or potential as they widen ;
and (2) that on tapping the earth in the way described at
two points of different potentials (not very distant, if near
the central source, and more removed the farther we recede
from the source) we can obtain in the telephone evidence
of their existence. Prof. Trowbridge then goes on to
say :
" In a discussion on the earth as a conductor, Steinheil
90 SECOND PERIOD THE PRACTICABLE.
says : 1 ' We cannot conjure up gnomes at will to convey
our thoughts through the earth. Nature has prevented
this. The spreading of the galvanic effect is proportional
... to the square of the distance ; so that, at the distance
of 50 feet, only exceedingly small effects can be produced.
. . . Had we means which could stand in the same relation
to electricity that the eye stands to light, nothing would
prevent our telegraphing through the earth without con-
ducting wires.'
"The telephone of Prof. Bell, though far from fulfilling
the conditions required by Steinheil, is nevertheless our
nearest approach to the desideratum.
"The theoretical possibility of telegraphing across the
Atlantic without a cable is evident from the survey which
I have undertaken. The practical possibility is another
question. Powerful dynamo - electric machines could be
placed at some point in Nova Scotia, having one end of
their circuit grounded near them and the other end grounded
in Florida, the connecting wire being of great conductivity
and carefully insulated throughout. By exploring the coast
of France, two points on surface lines not at the same
potential could be found; and by means of a telephone
of low resistance, Morse signals sent from Nova Scotia
to Florida could be heard in France. Theoretically, this
is possible; but practically, with the light of our present
knowledge, the expenditure of energy on the dynamo-
electric machines would be enormous." 2
Professor Trowbridge has suggested the applicability of
this method to the intercommunication of ships at sea.
1 See p. 5, ante.
2 A writer in the 'Electrician' (vol. v. p. 212), commenting on
this passage, says : " Prof. Trowbridge seems to overlook the advan-
tage of employing large condensers between the dynamo machines
and the earth. They would prove of great service in exalting the
earth potentials at the terminal stations."
PROFESSOR JOHN TROWBRIDGE. 91
Let, he says, a steamer be provided with a powerful
dynamo. Connect one terminal of the dynamo with the
water at the bow of the steamer, and allow a long wire,
insulated except at its extreme end, to drag over the stern,
and be buoyed so as not to sink. The current from the
dynamo will thus pass into the water and spread out over
a large area, as before explained, saturating, so to speak,
the water with electricity. Suppose this current be inter-
rupted by any suitable means, say one hundred times a
second. Let the approaching steamer be provided with
a telephone wire, the ends of which dip into the water
at her bow and stern respectively. On entering the sat-
urated area the telephone will respond to the interruptions
of the dynamo by giving out a continuous buzzing sound.
If now in the dynamo circuit we have a manipulating
arrangement for breaking up the electric impulses into
long and short periods, corresponding to the Morse alpha-
bet, one ship can speak to the other. It is hardly neces-
sary to add that by providing each steamer with a dynamo
circuit and a telephone circuit reciprocal correspondence
could be maintained, it being only necessary for the
steamer desiring to listen to stop and disconnect the
dynamo. The success of this method of communicating
between ships in a fog depends upon the distance between
the ends of the dynamo circuit and upon the strength of
the current, or electrical impulses imparted to the water.
It is probable that a dynamo capable of maintaining
one hundred incandescent lamps could establish a sufficient
difference of potential between the water at the bow and
at the end of a trailing wire, half a mile long, to affect
a telephone on an approaching ship while yet half a mile
distant.
In a discussion on Prof. Graham Bell's paper, read before
the American Association for the Advancement of Science,
92 SECOND PERIOD THE PRACTICABLE.
1884, Prof. Trowbridge described another plan, using in-
stead of the telephone circuit a sensitive galvanometer con-
nected up to a cross-arm of wire, whose ends dip into the
water at each side of the ship. When one vessel comes
within the area electrically saturated by another, the galvan-
ometer will show how the equipotential lines are disturbed,
and if a map of these lines be carefully traced we can fix
the position of the approaching ship. He adds : " The
method could also be applied to saturating the water around
a rock, and you could take electrical soundings, so to speak,
and ascertain your position from electrical maps carefully
made out."
In a later paper published in the 'Scientific American
Supplement/ February 21, 1891, Prof. Trowbridge discusses
the phenomena of induction, electro-magnetic and static,
as distinguished from leakage or earth conduction, and with
reference to their employment in wireless telegraphy.
The hope, he says, that we shall be able to transmit
messages through the air by electricity without the use
of connecting wires is supposed by some to indicate its
realisation at a future day. Let us examine how near we
are at present to the realisation of this hope.
He supposes that the chief use of any method by which
connecting wires could be dispensed with would be at sea
in a fog. On land for considerable distances it is hardly
probable that any electrical method could be devised in
which air or the ether of space could advantageously re-
place a metallic conductor. The curvature of the earth
would probably demand a system of frequent repetition,
which is entirely obviated by the use of a wire. If, how-
ever, an electrical or magnetic system could be made to work
through the air even at the distance of a mile, it would
be of very great use at sea in averting collisions ; for any
system of signals depending upon the use of fog-horns or
PKOFESSOR JOHN TROWBRIDGE.
93
fog-whistles is apt to mislead on account of the reflection
of the sound from layers of air of different densities and
from the surface of the water. The difficulty of ascertain-
ing the direction of a fog-horn in a thick fog is well known.
The waves of sound, even if they are carefully directed by
a trumpet or by parabolic reflectors, diverge so rapidly that
there is no marked difference in the intensity between a
position in the direct line and one far to one side.
The most obvious method of signalling by electricity
through the air is by electro-magnetic induction. Suppose
Fig. 8.
we have a coil of copper wire consisting of many convolu-
tions, the ends of which are connected with a telephone
(fig. 8). If we place a similar coil, the ends of which
are connected to a battery through a key, within a few
feet of the first and parallel to it, each time the current
is made and broken in the battery coil instantaneous cur-
rents are produced by induction in the other coil, as can be
heard by the clicks in the telephone.
To illustrate induction at a distance, Prof. Joseph Henry
94 SECOND PERIOD THE PRACTICABLE.
placed a coil of wire, 5J feet in diameter, against a door,
and at a distance of 7 feet another coil of 4 feet diameter.
When contact was made and broken with a battery of
eight cells in the first coil, shocks were felt when the
terminal wires of the second were placed close together
on the tongue.
In all such methods the wires or coils which produce
an electrical disturbance in a neighbouring coil are never
more than a few feet apart. Now let us suppose that
a wire is stretched ten or twelve times, to and fro, from
yard-arm to yard-arm of a steamer's foremast, and con-
nected at the ends either with a powerful battery or
dynamo, or with a telephone, as may be required either
for signalling or for listening. Let an approaching steamer
have a similar arrangement. If now the current on one
vessel be interrupted a great number of times per second, a
musical note will be heard in the telephone of the other
vessel, and vice versa. The sound will be strongest when
the two coils are parallel to each other. If, therefore, the
coils be movable the listener can soon find the position
of greatest effect, and so fix the direction in which the
signalling steamer is approaching.
It may not even be necessary to connect the telephone
with the coil, for it has been found that if a telephone,
pure and simple, be held to the ear and pointed towards
a coil in which a current of electricity is rapidly inter-
rupted, the makes and breaks will be heard, and this even
when the wire coil of the telephone is removed, leaving
only the iron core and the diaphragm. 1
1 Mr Willoughby Smith was, I believe, the first in recent times to
observe these effects. See his paper on " Volta-Electric Induction,"
'Jour. Inst. Elec. Eugs.,' vol. xii. p. 457. But exactly similar
effects, mutatis mutandis, were described by Page in 1837, to which
he gave the name of Galvanic Music, and which he found to be due
to the fact that iron when magnetised and demagnetised gave out a
PROFESSOR JOHN TROWBRIDGE. 95
Nothing could seem simpler than this, but, unfortunately,
calculation shows that under the best conditions the size of
the coils would have to be enormous. Prof. Trowbridge
has computed that to produce an audible note in the tele-
phone at a distance of half a mile, a coil of ten turns of
800 feet radius would be necessary ; but it is evident that
a coil of this size would be out of the question. Instead,
however, of increasing the size of the coil beyond the
practical limits of the masts and yard-arms, we could in-
crease the strength of the current so as to be effective at
the distance of half a mile; but, again, calculation shows
that this strength of current would be beyond all practical
limits of dynamo construction, unless we discover some
method of tuning, so to speak, two coils so that the elec-
trical oscillations set up in one may be able to evoke in
the other sympathetic vibrations. 1
Since, then, we have little, apparently, to hope for from
electro - magnetic induction in signalling through a fog,
cannot we expect something from static induction 1 This
form of induction can be well illustrated by an early
experiment of Prof. Henry. An ordinary electrical machine
was placed in the third storey of his house, and a metal
plate 4 feet in diameter was suspended from the prime
conductor. On the first floor or basement, 30 feet below
in a direct line, was placed a similar plate, well insulated.
When the upper plate was charged by working the
machine, the lower plate showed signs of electrification,
as was evidenced by its effect on the pith-ball electroscope. 2
sound. De la Rive, in 1843, rightly traced this sound to the slight
elongation of iron under the magnetic strain a fact which, in its
turn, was first observed by Joule in 1842. For Page's discovery see
the 'Magazine of Popular Science,' 1837, p. 237.
1 Prof. Oliver Lodge is now engaged on this very problem. See
p. 235, note 2, infra.
2 See an excellent account of Henry and his work in the New
96 SECOND PERIOD THE PRACTICABLE.
The distance to which this electrical influence can be ex-
tended depends upon the charging power of the machine
and the dimensions of the plate. If we could erect an
enormous metal plate on a hill, insulated and powerfully
charged, it is probable that its electrical influence could be
felt at the distance of the horizon ; but here, again, the
question of practical limits conies in as a bar, so that, at the
present time (February 1891), this method of signalling
without wires seems as little practicable as the others.
After following me in this study of Prof. Trowbridge,
the reader may well begin to despair, for while the learned
Professor's investigations are extremely interesting, his con-
clusions are very disappointing. But the darkest hour is
just before the dawn, and so it is in this case.
PROFESSOR GRAHAM BELL 1882.
Following the lines suggested by Prof. Trowbridge, Prof.
Bell carried out some successful experiments, an account of
which is given in his paper read before the American Asso-
ciation for the Advancement of Science in 1884.
" A few years ago," he says, " I made a communication
on the use of the telephone in tracing equipotential lines
and surfaces. I will briefly give the chief points of the
experiment, which was based on experiments made by Prof.
Adams of King's College, London. Prof. Adams used a
galvanometer instead of a telephone.
" In a vessel of water I placed a sheet of paper. At two
points on that paper were fastened two ordinary sewing
York 'Electrical Engineer,' January 13, 1892, and succeeding
numbers, from the pen of his daughter, Mary A. Henry. Abstracts
of these papers are given in the ' Electrician,' vol. xxviii. pp. 327,
348, 407, 661.
PROFESSOR GRAHAM BELL. 97
needles, which were also connected with an interrupter that
interrupted the circuit about one hundred times a second.
Then I had two needles connected with a telephone : one
needle I fastened on the paper in the water, and the moment
I placed the other needle in the water I heard a musical
sound from the telephone. By moving this needle around
in the water, I would strike a place where there would be no
sound heard. This would be where the electric tension was
the same as in the needle ; and by experimenting in the
water you could trace out with perfect ease an equipotential
line around one of the poles in the water.
" It struck me afterwards that this method, which is true
on the small, is also true on the large scale, and that it
might afford a solution of a method of communicating elec-
trical signals between vessels at sea.
" I made some preliminary experiments in England, and
succeeded in sending signals across the river Thames in this
way. On one side were two metal plates placed at a dis-
tance from each other, and on the other two terminals
connected with the telephone. A current was established
in the telephone each time a current was established
through the galvanic circuit on the opposite side, and if
that current was rapidly interrupted you would get a musical
tone.
" Urged by Prof. Trowbridge, I made some experiments
which are of very great value and suggestiveness. The first
was made on the Potomac river.
"I had two boats. In one boat we had a Leclanche
battery of six elements and an interrupter for interrupting
the current very rapidly. Over the bow of the boat we made
water connection by a metallic plate, and behind the boat we
trailed an insulated wire, with a float at the end carrying a
metallic plate, so as to bring these two terminals about 100
feet apart. I then took another boat and sailed off. In
G
98 SECOND PERIOD THE PRACTICABLE.
this boat we had the same arrangement, but with a tele-
phone in the circuit. In the first boat, which was moored,
I kept a man making signals ; and when my boat was near
his I would hear those signals very well a musical tone,
something of this kind : turn, turn, turn. I then rowed my
boat down the river, and at a distance of a mile and a
quarter, which was the farthest distance I tried, I could
still distinguish those signals.
"It is therefore perfectly practicable for steam-vessels
with dynamo machines to know of each other's presence in a
fog when they come, say, within a couple of miles of one
another, or, perhaps, at a still greater distance. I tried the
experiment a short time ago in salt water of about 20 fathoms
in depth. I used then two sailing-boats, and did not get so
great a distance as on the Potomac. The distance, which
we estimated by the eye, seemed to be about half a mile ;
but on the Potomac we took the distance accurately on the
shore."
Later, in urging a practical trial of his method, Prof. Bell
further said : "Most of the passenger steamships have dynamo
engines, and are electrically lighted. Suppose, for instance,
one of them should trail a wire a mile long, or any length,
which is connected with the dynamo engine and electrically
charged. The wire would practically have a ground connec-
tion by trailing in the water. Suppose you attach a telephone
to the end "on board. Then your dynamo or telephone end
would be positive, and the other end of the wire trailing
behind would be negative. All of the water about the ship
will be positive within a circle whose radius is one-half of
the length of the wire. All of the water about the trailing
end will be negative within a circle whose radius is the
other half of the wire. If your wire is one mile long, there
is then a large area of water about the ship which is affected
either positively or negatively by the dynamo engine and the
PROFESSOR A. E. DOLBEAR. 99
electrically charged wire. It will be impossible for any ship
or object to approach within the water so charged in relation
to your ship without the telephone telling the whole story
to the listening ear. Now, if a ship coming in this area also
has a similar apparatus, the two vessels can communicate
with each other by their telephones. If they are enveloped
in a fog, they can keep out of each other's way. The ship
having the telephone can detect other ships in its track, and
keep out of the way in a fog or storm. The matter is so
simple that I hope our ocean steamships will experiment
with it." l
PROFESSOR A. E. DOLBEAR 1883.
Prof. Dolbear of Tuft's College, Boston, was also, about
the same time as Graham Bell, engaged on the problem of a
wireless telegraph, and produced a very simple and workable
(at least for short distances) apparatus, which he patented
in the United States, and of which he gave a description at
a meeting of the American Association for the Advancement
of Science in 1883. I take the following account from his
specification as published in the ' Scientific American Sup-
plement/ December 11, 1886 :
" In the diagram, A represents one place (say Tuft's College)
and B a distant place (say my residence).
" c is a wire leading into the ground at A, and D a wire
leading into the ground at B.
" G is an induction coil, having in the primary circuit a
microphone transmitter T, and a battery /', which has a
number of cells sufficient to establish in the wire c, which
is connected with one terminal of the secondary coil, an
electro-motive force of, say, 100 volts. The battery is so
1 Public Opinion, January 31, 1886.
100
SECOND PERIOD THE PRACTICABLE.
connected that it not only furnishes the current for the
primary circuit, but also charges or electrifies the secondary
coil and its terminals c and H'. 1
" Now, if words be spoken in proximity to transmitter T,
the vibration of its diaphragm will disturb the electric con-
dition of the coil G, and thereby vary the potential of the
ground at A, and the variations of the potential at A will
cause corresponding variations of the potential of the ground
at B, and the receiver R will reproduce the words spoken
in proximity to the transmitter, as if the wires c D were in
contact, or connected by a third wire.
Fig. 9.
" There are various well-known ways of electrifying the
wire c to a positive potential far in excess of 100 volts, and
the wire D to a negative potential far in excess of 100 volts.
" In the diagram, H H' H 2 represent condensers, the con-
denser H' being properly charged to give the desired effect.
The condensers H and H 2 are not essential, but are of some
benefit ; nor is the condenser H' essential when the second-
ary coil is otherwise charged. I prefer to charge all these
condensers, as it is of prime importance to' keep the grounds
of wires c and D oppositely electrified, and while, as is
1 The diagram, which we have carefully copied, does not show how
this is done, but the practical reader will easily supply the necessary
connections.
PROFESSOR A. E. DOLBEAR. 101
obvious, this may be done by either the batteries or the
condensers, I prefer to use both."
Prof. Dolbear states that communication by this method
is quite practicable at a distance of half a mile at least, but
its possible range he had not yet determined.
In the article from which I am quoting the author gives
some additional particulars which are worth repeating.
" My first results," he says, " were obtained with a large
magneto-electric machine with one terminal grounded through
a Morse key, the other terminal out in free air and only a
foot or two long ; the receiver having one terminal grounded,
the other held in the hand while the body was insulated,
the distance between grounds being about 60 feet. After-
ward, much louder and better effects were obtained by using
an induction coil having an automatic break and with a
Morse key in the primary circuit, one terminal of the
secondary grounded, the other in free air, or in a condenser
of considerable capacity, the latter having an air discharge
of fine points at its opposite terminal. At times I have
employed a gilt kite carrying a fine wire from the secondary
coil. The discharges then are apparently nearly as strong
as if there was an ordinary circuit.
" The idea is to cause a series of electrical discharges into
the earth at a given place without discharging into the earth
the other terminal of the battery or induction coil a feat
which I have been told so many, many times was impossible,
but which certainly can be done. An induction coil isn't
amenable to Ohm's law always ! Suppose that at one place
there be apparatus for discharging the positive pole of the
induction coil into the ground, say 100 times per second,
then the ground will be raised to a certain potential 100
times per second. At another point let a similar apparatus
discharge the negative pole 100 times per second ; then
between these two places there will be a greater difference
102 SECOND PERIOD THE PRACTICABLE.
of potential than in other directions, and a series of earth-
currents, 100 per second, will flow from the one to the other.
Any sensitive electrical device, a galvanometer or telephone,
will be disturbed at the latter station by these currents, and
any intermittence of them, as can be brought about by a
Morse key in the first place, will be seen or heard in the
second place. The stronger the discharges that can be thus
produced, the stronger will the earth-currents be of course,
and an insulated tin roof is an excellent terminal for such a
purpose. I have generally used my static telephone receiver
in my experiments, though the magneto will answer.
" I am still at work upon this method of communication,
to perfect it. I shall soon know better its limits on both
land and water than I do now. It is adapted to telegraphing
between vessels at sea.
"Some very interesting results were obtained when the
static receiver with one terminal was employed. A person
standing upon the ground at a distance from the discharging
point could hear nothing; but very little, standing upon
ordinary stones, as granite blocks or steps ; but standing on
asphalt concrete, the sounds were loud enough to hear with
the telephone at some distance from the ear. By grounding
the one terminal of the induction coil to the gas or water
pipes, leaving the other end free, telegraph signals can be
heard in any part of a big building and its neighbourhood
without any connection whatever, provided the person be
well insulated."
When we come to speak of the Marconi system, we shall
see how near Dolbear got to that great discovery in his
acute observation of the heightened effects obtained by pro-
jecting into free air the ungrounded terminal wires of the
sending and receiving apparatus. 1 His use of condensers
1 Compare his sending apparatus with that of Marconi, fig. 41, p.
208, infra.
T. A. EDISON. 103
and gilt kites " carrying fine wire " was another step in the
direction of Marconi ; and had he used thick instead of fine
wire he would have obtained even better results. However,
Hertz had not yet come to make clear the way which
Dolbear saw but as in a glass darkly ! l
T. A. EDISON 1885.
Electric communication with trains in motion, like com-
munication with ships at sea and with lighthouses, has
long been a favourite problem with electrical engineers :
indeed it is much the older of the two, and dates back to
the first days of electric telegraphy.
In 1838 Edward Davy, the rival of Cooke and Wheat-
stone, proposed such a system. In a lecture on " Electric
Telegraphy," delivered in London during the summer of
1838, he says:
" I have a few words to say upon another application
of electricity namely, the purposes it will answer upon a
railway, for giving notices of trains, of accidents, and stop-
pages. The numerous accidents which have occurred on
railways seem to call for some remedy of the kind ; and
when future improvements shall have augmented the speed
of travelling to a velocity which cannot at present be
deemed safe, then every aid which science can afford must
be called in to promote this object. Now, there is a con-
trivance, secured by patent, by which, at every station along
the railway line, it may be seen by mere inspection of a dial
what is the exact situation of the engines running either
towards or from the station, and at what speed they are
1 Mr C. Dolbear, a son of the Professor, is understood to be engaged
on some form of wireless telegraph which is reported to have worked
successfully over a distance of 500 yards. Details are wanting.
104 SECOND PERIOD THE PRACTICABLE.
travelling. Every time the engine passes a milestone, the
pointer on the dial moves forward to the next figure, a
sound or alarm accompanying each movement.
" Not only this, but if two engines are approaching each
other, by any casualty, on the same rails, then, at a distance
of a mile or two, a timely notice can be given in each
engine by a sound or alarm, from which the engineer
would be apprised to slacken the speed ; or, if the engineer
be asleep or intoxicated, the same action might turn off the
steam, independently of his attention, and thus prevent an
accident." 1
In 1842 William Fothergill Cooke published his 'Tele-
graphic Railways,' descriptive of a crude system of train
signals, which was tried, in 1843, in the Queen Street
tunnel, Glasgow, and in the Clay Cross tunnel, Derby ;
and, on a more extensive scale, in 1844, on the Great
Eastern Railway, between Norwich and Yarmouth.
Dujardin in 1845, Brett and Little in 1847, Edwin Clark
in 1:854, Bonelli in 1855, and many others, proposed various
systems of train signalling; but as they are all based on
ordinary telegraphic principles and require connecting wires,
they do not specially concern us in this history.
Mr A. C. Brown, an officer of the Eastern Telegraph
Company, claims to have been the first to suggest, in 1881,
the method of induction for communicating with moving
trains. In a letter published in the 'Electrician,' March
21, 1885, he says:
"My object was chiefly to provide an efficient means of
fog-signalling, by enabling the signalman to communicate
directly with the drivers or guards. I proposed to run a
1 See the writer's 'History of Electric Telegraphy,' 1884, p. 407.
The most perfect block system of the present day does not do any-
thing like this. Davy's plan was actually patented by Henry Pinkus !
See his patent specification, No. 8644, of September 24, 1840.
T. A. EDISON. 105
wire along the permanent way, parallel with the rails, and
to wind a coil of wire round the engine, or carriage to be
communicated with, in such a way as to get as long a length
of wire parallel to, and as near to, the line-wire as possible,
so as to be well exposed to the inductive action thereof. I
then proposed to place in the signal-boxes a battery, sig-
nalling key, and rapid make-and-break instrument, or buzzer,
and to thereby signal to the train, using a telephone in
circuit with the train-coil as a receiver. By using an ordin-
ary carbon transmitter in the line-wire, I also found it quite
practicable to speak verbally to the train, so as to be dis-
tinctly heard in the telephone.
" This design was embodied in a paper which, in the year
1881, I laid before the managing director of the United
Telephone Company, but want of time and opportunity
prevented its being put into practice. It was experimentally
tried at that time, using wire coils, properly proportioned
in length, resistance, and distance apart to the conditions
that would be obtained in practice. It has since been
simplified and arranged to produce both visible and audible
signals on the engine or car by induction from a No. 8 iron
line-wire across a space of 6 inches, with a current of only
one quarter ampere, or such as can easily be produced by
the ordinary Daniell batteries used in railway work." *
In 1883 Mr Willoughby Smith threw out a similar
suggestion towards the end of his paper on "Voltaic-Electric
Induction," read before the Institution of Electrical En-
gineers, November 8 of that year : 2
" Telegraph engineers," he says, " have done much
towards accomplishing the successful working of our present
railway system, but still there is much scope for improve-
1 For another proposal of Mr Brown, see p. 176, infra.
- Compare also his remarks, 'Jour. Inst. Elec. Engs.,' March 23,
1882, p. 144.
106 SECOND PERIOD THE PEACTICABLE.
ments in the signalling arrangements. In foggy weather
the system now adopted is comparatively useless, and
recourse has to be had at such times to the dangerous and
somewhat clumsy method of signalling by means of de-
tonating charges placed . upon the rails.
" Now, it has occurred to me that Yolta-Electric induction
might be employed with advantage in various ways for
signalling purposes. For example, one or more spirals
could be fixed between the rails at any convenient distance
from the signalling station, so that, when necessary, inter-
mittent currents could be sent through the spirals; and
another spiral could be fixed beneath the engine, or guard's
van, and connected to one or more telephones placed near
those in charge of the train. Then, as the train passed
over the fixed spiral, the sound given out by the transmitter
would be loudly reproduced by the telephone, and indicate
by its character the signal intended.
" One of my experiments in this direction will perhaps
better illustrate my meaning. The large spiral was con-
nected in circuit with twelve Leclanche cells and the two
make-and-break transmitters before described. They were
so connected that either transmitter could be switched into
circuit when required, and this I considered the signalling
station. The small spiral was so arranged that it passed in
front of the large one at the distance of 8 inches, and at a
speed of twenty-eight miles per hour. The terminals of the
small spiral were connected to a telephone fixed in a distant
room, the result being that the sound produced from either
transmitter could be clearly heard and recognised every time
the spirals passed each other. With a knowledge of this
fact I think it will be readily understood how a cheap and
efficient adjunct to the present system of railway signalling
could be obtained by such means as I have ventured to
bring to your notice this evening."
T. A. EDISON. 107
In 1885 Mr T. A. Edison had his attention directed to
the subject, and with his usual thoroughness he soon pro-
duced a very complete system, with the assistance of
Messrs Gilliland, Phelps, and W. Smith to the last-
named of whom the original idea is said to be due. 1
The inevitable avant-coureur appeared in the technical
journals of the period, and as it is delightfully character-
istic of the great magician of Menlo Park, we venture to
reproduce it here : " Mr Edison's latest invention, an
arrangement to telegraph from moving trains, is thus
described by a recent visitor to his laboratory : Overhead
was a board eight inches wide, suspended from the ceiling
by ropes fastened to one of its edges. One side of it was
covered with tinfoil, and was facing toward a wall 20 feet
distant. That,' said Mr Edison, ' is my railroad signal ;
I make electricity jump 35 feet, and carry a message.
This is something quite new ; no induction has ever been
known that extended over 3 or 4 or 5 feet. This inven-
tion uses what is called static electricity, and it makes
every running train of cars a telegraph station, accessible to
every other telegraph station on the road. Messages may
be sent to and from conductors, and to and from passengers.
It requires no extra wire, either under the cars or at the
side of the cars, but uses the ordinary telegraph just as it
is put up at the side of the track. This white board is a
receiver and transmitter. A board like it is to be fastened
lengthwise along the peak of each car, where it will be
out of the way and will not be a blemish. When the
train is telegraphed to, the message jumps from the wire
1 Although I have not seen any acknowledgment of their indebted-
ness, Mr Edison and his coadjutors can hardly have been ignorant of
Mr Willoughby Smith's very clear proposal, of which their contriv-
ance is but the practical realisation. Given the idea, the rest was
easy enough.
108
SECOND PERIOD THE PRACTICABLE.
on the side of the track
and alights on this board,
and is conveyed to the ap-
paratus in the train below.
It works beautifully from
those wires strung yonder.
I was as much astonished
as anybody at finding out
what could be done. It
costs very little, moreover,
as 300 miles of road can be
equipped for 1000 dols.'"
This contrivance was
patented in England on
June 22, 1885, in the
joint names of T. A. Edison
and E. T. Gilliland, and
is fully described in their
specification, No. 7583, of
which the following is an
abstract :
The object of the inven-
tion is to produce apparatus
for telegraphing between
moving trains, or between
trains and stations, by in-
duction and without the use
of connecting wires. The
accompanying drawing (fig.
10) represents a station and
portions of two trains with
the apparatus for signal-
ling. The carriage to be
used as the signal office
T. A. EDISON. 109
has placed upon its top or side, or upon each side, a
metallic condensing surface running the entire length of
the car. This consists of a strip a of metal, say a foot
wide, well insulated by blocks of glass ; or it may be thin
sheet metal or metallic foil secured to canvas, and similarly
insulated from the body of the car. To increase the total
condensing surface, all the carriages of the train are prefer-
ably provided with such strips, which are connected electri-
cally by suitable couplings c when the train is made up.
A wire 1 is connected with this condensing surface, and
extends through the apparatus to the carriage-truck so as
to form an earth connection through the wheels and the
rails upon which they travel. The apparatus just men-
tioned consists of an induction coil B, the secondary wire
of which is of extremely high resistance, and is in the
circuit of wire 1, in which is also connected a telephone
c of high resistance. This is preferably an electro-moto-
graph telephone, the chalk cylinder of which is kept in
constant rotation by a suitable motor, electrical or mechani-
cal; but a magneto-electric or other suitable form of tele-
phone may be employed.
In the primary circuit of the induction coil B are a local
battery d and a revolving circuit -breaker D. This is a
wheel having its surface broken by cross strips of insula-
tion ; upon it rests a spring, the circuit being through the
spring to the spindle of the wheel. This wheel is kept in
rapid motion by a suitable motor, electrical or mechanical,
the current vibrations produced by it being a great number
per second and audible in the telephone receiver.
The circuit -breaker is shunted by a back point key E,
which, normally, short - circuits it and prevents it from
affecting the induction coil. A switch F short-circuits the
secondary wire of the induction coil when receiving, and is
opened in transmitting.
110 SECOND PERIOD THE PRACTICABLE.
. The ordinary telegraph wires 2, 3, 4, 5, run on poles at
the side of the track, and, grounded at their ends, are util-
ised collectively for conveying the signals. They form the
other surface of the condenser (the strips on the carriages
forming one surface), while the intervening body of air is
the dielectric.
In signalling between trains, signals are transmitted by
working the key E in the office upon one train. This
causes static impulses at the condensing surface upon the
carriages which affect the telegraph wires. These in turn
affect the condensing surface upon the carriages of the other
train, and cause impulses which are audible in the tele-
phone.
At each signalling station i there is erected between the
telegraph wires a large metallic condensing surface K (fig.
11). This may be attached to a frame supported from the
telegraph poles or from separate poles. A wire 6 runs from
this condensing surface to the station, where it is connected
to ground through the same character of transmitting and
receiving apparatus already described for the carriages.
Instead of using this condensing surface outside of the
station, a separate wire (7, 8, 9, 10, fig. 10) may be at-
tached to each telegraph wire (or to each of as many as it is
desired to utilise) and run into the station, where it is con-
nected to one side of a condenser L, of ordinary form. The
other sides of the several condensers L are connected to-
gether, and by a common wire 1 1 to ground through the
transmitting and receiving apparatus.
The telegraph wires are kept constantly closed for trans-
mitting the induction impulses by shunting the regular
Morse keys M by condensers N. These condensers do not
interfere with the carrying on of the ordinary telegraphing
over such wires, at the same time that they form constantly
closed paths for the induction impulses independent of the
T. A. EDISON.
Ill
working of the ordinary Morse keys. The ordinary Morse
relay and sounder are shown at o and p respectively.
The stations being connected for railway signalling induc-
tively with the line wires the same as are the trains, signals
are received and transmitted by a station the same as by a
Fig. 11.
train. The trains and stations are connected inductively
with the line wires in multiple arc, so to speak, signals be-
ing transmitted by keys, circuit breakers, and induction
coils, and received by telephones.
The signalling is conducted by Morse characters, or
112 SECOND PERIOD THE PRACTICABLE.
by numerical signals in accordance with an established
code.
Speaking of the potentialities of his system, Edison, early
in 1886, said: "The outcome is easy to predict. Special
correspondents may, in the future, wire their despatches
straight to the offices of their journals. Eailway business
will be expedited to a degree undreamt of as things are,
and the risk of accidents will be largely diminished by
knowing the position of trains and the cause of delay or
accident, if any, at every stage, of their route. Ships at
sea, many miles apart, will be able to communicate by
means of balloon-kites, soaring several hundred feet above
their decks. Messages can be passed from ship to ship, and
a casualty like that of the Oregon telegraphed to the nearest
land. In times of war the applications of the air-telegraph
system are obvious. Kegions now remote from telegraphs
could be brought within the civilised circle by means of
mountain or forest stations equipped with the new apparatus.
Even the man of business of the future may communicate
with his employes as he journeys to and from his office, and
save time or make money while he is literally on the wing.
Not the least interesting feature of this new departure in
telegraphy is the thought that, in its turn, it may be the
harbinger of still more wondrous modifications of the
system which has girdled the earth in a space inconceivably
short when compared with that imagined by the fairy
romancer who created Puck." l
The Edison system was first put in operation at Staten
Island, U.S.; then, a few months later, on the Chicago,
Milwaukee, and St Paul line; and by October 1887 it was
established on the Lehigh Valley Eailroad, as related in the
following paragraphs :
"The success of what is called ' railway train telegraphy '
1 Weekly Irish Times, April 10, 1886,
T. A. EDISON. 113
is now assured, and October 6, 1887, will be a red-letter day
in the history of the electric telegraph. On that day a
special train left Jersey City with about 230 members of the
Electric Club and guests of the Consolidated Eailway Tele-
graph Company, in order to witness the working of the
system on the Lehigh Valley Railroad. The system is a
combination of the best features of the inventions of Edison,
Gilliland, Phelps, and Smith, and although the speed often
reached the rate of about sixty miles an hour, messages were
sent from and received on the train without difficulty,
although the current or the ' induction ' had to jump from
the train to the line wires, a distance of 25 feet. About
four hundred messages were sent as the train ran from Perth
Junction to Easton, amongst them a rather long one from
Colonel Gouraud to Mr John Fender in London." l
" One of the most interesting triumphs of invention has
been achieved on the Lehigh Valley Railroad during the
snowstorms of the past winter in the United States. This
railway for some months has been using on its trains the
system of communication known as train telegraphy. The
wire, being of steel, and stretched upon stout poles only
15 or 16 feet high, withstood the fury of the storm. The
consequence was that all snowed-up trains on the Lehigh
Valley Railroad kept up constant communication with the
terminus of the road, could define exactly their position, and,
in short, had all the advantages of perfect telegraphic com-
munication." 2
Soon after this the system fell into desuetude, and for a
very simple reason nobody wanted it. Whatever " special
correspondents " and " the man of business " in the future
may require, they, apparently, prefer nowadays to be free
from telegrams of all sorts "while on the wing."
1 Public Opinion, November 4, 1887.
2 Ibid., April 13, 1888.
H
114 SECOND PERIOD THE PRACTICABLE.
W. F. MELHUISH 1890.
We have seen (p. 39 ante) that the want of some form of
wireless telegraph was peculiarly felt at a very early date in
India, where the rivers are many and wide, and where for
various reasons cables are liable to frequent breakage, caus-
ing interruptions which are as likely as not to be of long
duration, owing to the great rush of waters and the flooding
of banks.
I have already given some account of Dr O'Shaughnessy's
experiments in this direction. It is all too short, but,
unfortunately, it is all that I have been able to gather.
About the year 1858 Mr Blissett, a superintendent in
the Indian Telegraph Department, resumed the inquiry, and
obtained a fair measure of success by employing land-lines
of considerable length on each bank of the river. In 1876
Mr Schwendler, then electrician, made some trials across the
Hooghly at Barrackpore, near Calcutta, which were continued
at intervals by his successor, the late Mr W. P. Johnston.
On September 9, 1879, this gentleman tried the following
arrangement for signalling across the water of a canal. Fig.
1 2 shows the connections :
E = 10 Bunsen's cells joined in series ;
K, a needle instrument having a resistance of 1 ohm ; also
a telephone having a resistance of 4*25 ohms ;
w = a resistance of 1"! .
, I his arrangement exactly balanced
,... > the natural current through the
e tour Mmotto cells . .
, , receiving instrument,
joined parallel J
A, B, c, D were copper plates, 8 feet 8 inches by 4 feet
4 inches by 1-1 6th inch thick, buried on the banks of the
canal. B was buried 15 yards distant from A, and D the
same distance from c. All the plates were parallel to the
W. F. MELHUISH.
115
canal. The resistance between A and B was 7*5 ohms, and
that between c and D was the same. Under these conditions
SO Z
o >
O
m
Fig. 12.
both tlie needle instrument and the telephone gave distinct
and readable signals.
After several days of experiment with another method
Bare wtr* 7 Mil* under Water
Fig. 13.
(fig. 13), using a single bare 600 Ib. per mile galvanised
wire, the following results were obtained :
E = 15 Bunsen's cells in series ;
R, a polarised Siemens relay of 21 ohms resistance;
116 SECOND PERIOD THE PRACTICABLE.
e - 4 Minottos joined parallel ) Balanced the natural
w = 10 ohms ) current.
The signals received were quite regular and safe ; the
tongue of a relay worked an ordinary sounder in local
circuit, and no difficulty was experienced in balancing the
natural current through the relay.
A trial with bare wire for a distance of one and a half
mile was not successful. Indeed, as it appeared that in
order to obtain signals the battery power must be increased
as the square of the distance, the limit of signalling through
a bare wire under water is very soon reached.
Subsequently, three miles of the same wire, but partially
insulated by being passed through a mixture of pitch and
tar, answered perfectly for the hour that the instruments
were in circuit.
At various times during the year 1888 Mr Johnston
carried out many experiments across canals and the river
Hooghly, and as the result of these and other careful in-
vestigations he was led to the following conclusions :
1. That up to one and a half mile it is perfectly easy to
signal through a bare wire under water.
2. That for greater distances, judging from experiments,
practical signalling is not possible.
Tn April 1889 Mr Johnston died, and the duties of elec-
trician were entrusted to Mr Melhuish, who immediately
took up the inquiry, and in the end produced some very
considerable results, for which, I believe, the Government
of India gave him the handsome honorarium of 5000
rupees.
The results of his investigations are embodied in a
paper which was read before the Institution of Electrical
Engineers on April 10, 1890 :
" Having studied," he says, " the recorded labours of my
predecessor, and learnt that by pursuing the same lines
W. F. MELHUISH. 117
it was hopeless to expect to be able to signal through a
bare wire across a river that had a greater breadth than
one and a half mile, I resolved to change the class of
signalling apparatus and to continue the experiment. Dis-
carding continuous steady currents and polarised receiving
relays, I adopted Cardew's vibrating sounder, and the
sequel will show how completely successful the change
of instruments proved to be. I began from the beginning,
and tried to signal across a water-way without a metallic
conductor by laying down two earth-plates on each of its
opposite banks. Readable signals having been exchanged,
the distance separating each pair of plates was varied,
with the view of ascertaining how close the plates might
be brought together, the signals remaining still readable.
Eeadable signals were exchanged when the distance separ-
ating the plates was equal to the breadth of the river,
reading becoming more difficult as the plates were made
to approach each other, and clearer and more distinct as
the distance between the plates was made to exceed the
breadth of the river. I learnt from these experiments
that in order to obtain signals of sufficient distinctness
for the practical purpose of transmitting messages, it would
be necessary to construct a line on each bank of a river
much longer than the breadth of the river; and as the
rivers along the coasts in India are extremely wide, I
became impressed with the impracticable character of such
an undertaking, and decided to strike out a new line.
" This new line was the laying of two bare uninsulated
iron wires across the water-way parallel to each other,
and separated by a certain distance, the ends on each
bank being looped together by means of an insulated
conductor. Hence, though much of the circuit was laid
under water, it was nevertheless a continuous' metallic
circuit. Beginning first with a complete square, by laying
118 SECOND PERIOD THE PRACTICABLE.
the wires as many yards apart as the river was wide,
signals were instantly exchanged that were incomparably
louder than those that were exchanged when the same
area was bounded by four earth -plates. The length of
each of the two wires under water was next gradually
increased to 740 yards, and the distance separating them
gradually diminished to 35 yards, the strength of the
signals diminishing proportionately, and ceasing to be
readable when the wires were further approached. The
conclusion arrived at from these experiments was that,
for the practical and useful purpose of signalling messages
across a broad river, in the absence of an insulated cable,
a complete metallic circuit was at least desirable. Acting
on this conclusion, it was sought to apply it practically,
and the following experiment was carried out: At a dis-
tance of fifteen miles west of Calcutta a cable is laid
across the river Hooghly, which at this point is 900 yards
wide. The iron guards of this cable were employed to
form one of the metallic conductors, and at a distance
of 450 yards down-stream a single wire, weighing 900
Ib. per mile, was laid across the river to form the second
metallic conductor, insulated land-lines having been run
up to loop the two parallel conductors together. The
experiment was quite a success, the signals being readable
without difficulty.
"An experiment was next made on a defective cable
across Channel Creek, at the mouth of the river Hooghly.
This creek is crossed by two cables laid in the same trench ;
the length of each is 3000 yards, and one of them had
been completely parted by a steamer's anchor. Several
attempts were made to signal across by using the guards
of one of the cables as a lead, and the guards of the other
as a return wire, but the efforts proved unsuccessful owing
to the too close proximity of the cables. For every crossing
W. F. MELHUISH. 119
there is a certain minimum distance apart at which the
cables must be laid, and if this minimum, which depends
on the breadth of the river, be exceeded, an absolute short-
circuit becomes established. But although it was not
possible here to signal through the iron guards, the most
perfect signals were passed through the two conductors
when they were formed into a loop, notwithstanding the
fact that the two ends of the broken conductor were ex-
posed in the sea and were lying at a considerable distance
apart. An experiment was now made in order to ascertain
what chance there might be in the future of signalling
across the two conductors, should an accident occur to the
good cable. Accordingly, the conductor of the good cable
was disconnected in the cable-house from the signalling ap-
paratus and placed upon the ground, when the signals,
though greatly diminished in volume, still continued to be
distinctly readable. It may, therefore, be reasonably in-
ferred that should the good cable suffer a similar fate to
that of the defective cable, communication can, by means of
Cardew's sounders, be kept up by looping the ruptured
conductors until arrangements can be made for laying a new
cable or repairing the defective ones.
" It will probably suffice if from the succeeding experi-
ments that were made to test the efficiency of the vibrating
sounder in the case of conductors breaking down at river
crossings I select the following three, exhibiting as they do
progressive evidence of the value of this signalling instru-
ment, and culminating in establishing it beyond dispute as
one that can be relied on for carrying on independent com-
munication through the iron guards of cables while the
insulated copper conductors form parts of other circuits.
"Experiment No. 1. The local line from the Central
Office, Calcutta, to Garden Eeach is about four miles in
length, and at about midway the wire spans a small river.
120 SECOND PERIOD THE PRACTICABLE.
Vibrating sounders having been put in circuit at each
end of this line, the wire where it crosses the river was
taken down and laid along the bed of the water-way. Sig-
nals were loud and clear at both ends.
" From the success of this experiment it may be inferred
that on any ordinary line, should the wire from accidental
causes come off the insulator and make earth by touching
the bracket, standard, or ground, or should the wire break
and both ends of it be lying on the ground or in a water-
course, communication could still be maintained by means
of the vibrating sounders.
" Experiment No. 2. The line wire which connects the
town of Chandernagore with Barrackpore is about ten and a
half miles long, 900 yards of which consist of a cable laid
across the river Hooghly. Vibrating sounders having been
joined up in the telegraph offices at Barrackpore and Chan-
dernagore, the insulated conductor of the cable was thrown
out of circuit, and the line wire on each side of the river
was joined to the iron guards of the cable. Thus for a
length of half a mile out of ten and a half miles the con-
ductor was wholly under water, yet it was found quite
feasible to transmit messages between the two offices.
" From the success of this experiment it may be reason-
ably inferred that in the case of certain cable crossings,
where the rivers are not too wide, should the copper con-
ductor of the cable make dead earth, or become insulated
by parting, communication could still be kept up between
the two offices on either side.
"Experiment No. 3. The terminus of the Northern
Bengal State Eailway at Sara is separated from that of the
Eastern Bengal State Eailway at Damukdia by the river
Ganges. The opposite banks of the river in this locality
are connected by two independent cable crossings. The
length of one of these crossings is one mile 610 yards, and
W. F. MELHUISH. 121
of the other four miles. The distance which separates the
two cable-houses on the Damukdia side is three miles 1584
yards, and on the Sara side the cable-houses are only one
mile 211 yards apart, giving a mean lateral distance in
alignment of two miles 880 yards. The two cable-houses
on each bank of the river have an insulated connecting land-
line.
" The connecting land-lines having been joined to the iron
guards of the cables, two vibrating sounders were placed in
circuit, one on each side of the river, when signals so strong
were transmitted across that it was not difficult to read
them at a distance of 6 feet away from the receiving tele-
phone.
" From the marked success of this experiment it may be
inferred that at all river cable crossings where the cables
are laid in separate alignments (and the farther apart the
better), should the cables become interrupted, communica-
tion may still be maintained from bank to bank by using
vibrating sounders, thus avoiding the delay, inconvenience,
and cost of a boat service.
" It should also be remembered in the case of such a par-
allel cable crossing that, besides the circuits afforded by the
copper conductors when these are in working order, there
is always an additional local circuit available by means of
the iron guards between the opposite cable-houses, and that
this circuit could be used by means of the vibrating sounder
as a talking circuit, in cases of necessity, without interrupt-
ing through working on either of the cables.
" It is desirable in circumstances similar to these to re-
duce all the resistance external to the actual connecting
lines to as small a quantity as possible, and therefore, when
messages are being transmitted, the telephone at the sending
end should be removed from the circuit, as also should the
vibrator from the receiving end. To effect this twofold
122
SECOND PERIOD THE PRACTICABLE.
purpose a special form of signalling key is requisite, and
should be used. The action of this key, together with the
Fig. 14.
complete set of connections for a parallel cable crossing, is
shown in fig. 14." x
C. A. STEVENSON 1892.
Early in 1892 Mr Stevenson threw out the suggestion
that telegraphic communication could be established be-
tween ship and ship by means of coils of wire. 2
In his paper read before the Royal Society of Edinburgh,
Marclvl9, 1894, he refers to this suggestion, and says that
a trial of his method on a large scale had recently been
made with a view of ultimately employing it for effecting
communication between Muckle Flugga, in the Shetlands,
and the mainland.
As regards the efficacy of the principle, the inductive
effect of one spiral on another at a distance has long been
1 Melhuish's plan is the practical realisation of the early proposals
of Highton and Bering. See pp. 40, 48, ante.
2 Engineer, March 24, 1892.
C. A. STEVENSON. 123
known ; but hitherto, even with a very strong battery, it
was impossible to bridge a greater distance than 100 yards,
which for practical purposes was, of course, useless.
It is evident that if two coils are placed so that their
axes are coincident, their planes being parallel, or if they
be placed so that their planes are in the same plane, they
will be in good positions for electric currents sent in one
to be apparent by induction in the other.
For a small diameter, and where the electrical energy is
small and the number of turns small, the first position is
best ; but where the energy is great and the number of
turns great in fact, when it is wished to carry the induction
to many times the diameter of the coils then it will be
found that it is better to let the two coils be in the same
plane, as when the axes are coincident, and the coils a
greater distance apart in comparison with the diameter, the
difference of distance from one side of the coil, say top of
primary coil to top and bottom of secondary, becomes
almost a vanishing quantity ; whereas, when the coils are
lying on their side in the same plane, the difference of
distance from back of primary to back of secondary, and
from front of primary to front of secondary, does not fall
off so fast, and consequently is more efficacious. Besides,
it becomes impracticable to erect coils of large diameter
with their planes vertical, but it is easy to lay them on
their sides.
Mr Stevenson made a large number of laboratory
experiments on the interaction of coils, with the view of
calculating the number of wires, the diameter of coils, the
number of amperes, and the resistance of the coils that
would be necessary to communicate with Muckle Flugga ;
and, after a careful investigation, it was evident the gap of
800 yards could, with certainty, be bridged by a current of
one ampere with nine turns of post-office wire in each coil,
124 SECOND PERIOD THE PRACTICABLE.
the coils being 200 yards in diameter, and with two good
telephones on the hearing coil.
Two coils, on telegraph-poles and insulators, were erected
at Murrayfield, one coil being on the farm of Damhead and
the other on the farm at Saughton, and as nearly as was
possible on a similar scale, and the coils of similar shape to
what was wished at Muckle Flugga. On erecting the coils,
communication was found impossible, owing to the induc-
tion currents from the lines from Edinburgh to Glasgow, the
messages in those lines being quite easily read, although the
coils were entirely insulated and were not earthed. The
phonophore which the North British Railway Company have
on their lines kept up nearly a constant musical sound,
which entirely prevented observations. On getting the
phonophore stopped, it was found that 100 dry cells, with 1*2
ohms resistance each and 1*4 volts, gave good results, the
observations being read with great ease in the secondary by
means of two telephones. The cells were reduced in
number down to fifteen, and messages could still easily be
sent, the resistance of the primary being 24 ohms and the
secondary no less than 260 ohms. If the circuit had been
of good iron, with soldered joints and well earthed, the
resistance would have been only 60 ohms. The induced
current generated in the secondary would therefore be in the
ratio of 480 p 520] to 210, or, allowing for the resistance
in the two telephones, we get practically only half the
current we would have got if the line had been a permanent
in place of a temporary one.
A trial was made of the parallel-wire system : l with 20
cells the sound was not heard, and with 100 cells it was
heard as a mere scratch in comparison with the sound with
the coil system with only 15 cells. A trial was made with
f l I.e., Mr Preece's method, to be presently described. See p. 154
et seq., infra.
C. A. STEVENSON. 125
the phonophore : the coils worked with 10 cells with perfect
ease, and a message was received with only 5 cells. Speech
by means of Deckert's transmitter was just possible, but it
is believed that if the hearing circuit had been of less resist-
ance it would have been easy to hear.
" It is difficult," says Mr Stevenson, " to understand how
this system of coils, in opposition to the parallel-wire system,
has not been recognised as the best ; for assume that, with
the arrangement we had, we heard equally with 100 cells by
both systems, both having the same base (200 yards), then,
by simply doubling the number of turns of wire on the
primary and using thick wire, the effect would have been
practically doubled, whereas by the parallel-wire system
there is nothing for it but to increase the battery power.
The difficulty of the current is thus removed by using a
number of turns of wire. It must always be borne in mind
that the effect is the result of simply increasing the diameter,
keeping current and resistance the same. The larger the
diameter the better. What is wanted is to get induction at
a great distance from a certain given base with a small
battery power, and the laboratory experiments and the trials
in the field show that the way to overcome the difficulty of
the current is by using a number of turns of wire. The
secret of success is to apportion the resistance of primary
and secondary, and the number of turns on each, to a
practical battery power."
1. Coil System. At 870 yards from centre to centre of
coils, averaging each 200 yards diameter, with nine turns of
wire, it was found that with a phonophore messages were sent
with five dry cells, the resistance in primary being 30 ohms
and the resistance of secondary 260 ohms, the current being
0*23 ampere, which, with nine turns, gives 2 ampere turns.
2. With a file as a make and break, it worked with 10
cells, giving 0*4 ampere or 3 '6 ampere turns.
126
SECOND PERIOD THE PRACTICABLE.
3. Parallel-Wire System. With a file as a make and
break, and with parallel lines earthed, it was heard with
100 cells, giving 1*1 ampere.
Mu&*lc Fluff yte.
\
Vznal*
o.
Fig. 15.
The primary coil circuit was entirely metallic in the
Murrayfield trials, as it would have to be if erected at
Muckle Flugga ; but the secondary coil was earthed.
When, however, the secondary was also made a complete
C. A. STEVENSON. 127
insulated metallic circuit, with eight turns of wire, there
seemed to be little difference in the result.
The calculation of the diameter necessary to hear at a
given distance is simple, from the fact that the hearing
distance is proportional to the square root of the diameter
of one of the coils, or directly as the diameter of the two
coils, so that with any given number of amperes and
number of turns, to hear double the distance requires
double the diameter of coils, and so on. 1
In concluding his paper, Mr Stevenson says :
" It has been attempted to be shown that the coil system
is not only theoretically but practically the best ; and I trust
that we will soon hear of the Admiralty, &c., experimenting
with it, and ultimately putting it in practice. Meantime my
brother has recommended the Commissioners of Northern
Lighthouses to erect the coil system at Muckle Flugga, and
the Commissioners have approved ; and I hope soon to hear
of the erection of this novel system of communication at the
most northern point of the British Isles, as well as on our
warships to assist in their manoeuvring, by the establish-
ment of instantaneous communication unaffected by wind
or weather.
" The application of the coil system to communication with
light vessels is obvious viz., to moor the vessel in the
ordinary way, and lay out from the shore a cable, and circle
1 Professor Lodge has recently shown that the law of distance is
not the square root of diameter, but the two-thirds power, with a
given primary current ; and so doubling the circumference of each
coil will permit signalling over more than double the distance, if other
things can be kept the same. For such magnification, however, the
thickness of the wire must be magnified likewise, or else more power
will be consumed in the enlarged coil ; and this consideration, as well
as others, would speedily make the cost prohibitive, unless some fresh
revolutionary devices are employed. For these see the ' Jour. Inst.
Elec. Engs.,' No. 137, p. 803.
128 SECOND PERIOD THE PRACTICABLE.
the area over which the lightship moorings will permit her
to travel by a coil of the cable of the required diameter,
which will be twice the length of her chain cable. On
board the vessel there will be another coil of a number of
turns of thick wire. Ten cells on the lightship and ten on
the shore will be sufficient for the installation." l
In a recent communication 2 Mr Stevenson gives some
additional particulars. Referring to his proposed installa-
tion at the North Unst lighthouse, on Muckle Flugga, he
tells us a gap of half a mile had to be bridged. The Com-
missioners of Northern Lighthouses being impressed with
the experiments shown them on a small scale even through
stone and mortar decided on the larger experiment, but
financial difficulties intervened, and the project was allowed
to drop.
" It is well to remember," he says, " that in the Murray-
field trials a small number of cells was purposely used.
Theory and formulae give one the impression at first sight
that a single outstretched wire is always best the simple
fact of getting a greater effect at a distance as a coiled wire
is uncoiled and made straight supporting this impression ;
but formulae, if they are to be practical, ought to take into
account a limited area and workable amounts of resistance,
current, &c., and then the fact is disclosed that the coiling
of wires (whether condensers be used with them or not) be-
comes an advantage for most work which the engineer will
be called upon to deal with.
1 Probably acting on Mr Stevenson's suggestion in the ' Engineer ' of
Marcli 24, 1892, Mr Sydney Evershed devised a plan of communicat-
ing with lightships, for which he applied for a patent on May 28, 1892.
The method was actually tried in August 1896 on the North Sand
Head (Goodwin) lightship, but failed utterly. See his patent speci-
fication, No. 10,161 ; also his paper on Telegraphy by Magnetic
Induction, 'Jour. Inst. Elec. Engs.,' No. 137, p. 852.
2 ' Jour. Inst. Elec. Engs.,' No, 137, p, 951.
C. A. STEVENSON. 129
"It is not necessary, as has been stated, that the coils
should be identical in size and shape. Far from it; each
case must be treated for size and configuration by itself.
For instance, in the case of Muckle Flugga, my design was
for a line two miles in length on the mainland, with a coil
at the end enclosing a larger area than the one on the rock,
which latter was opened out to the maximum possible.
Again, in the case of Sule Skerry and the Flannan Islands,
on the north-west of Scotland, where telegraphy by induc-
tion would be of great value, it would be impossible to
make the coils of large diameter, but the coil on the main-
land should be of large dimensions ; indeed a single long
wire with the ends earthed would be, perhaps, the best
arrangement.
" For guarding a dangerous coast, a similar wire of many
miles in length would be suitable for communicating warning
signals to vessels on board of which were detectors, with
coils necessarily of small dimensions. There are two ways
of doing this, both of which I have tried. First, by means
of a submarine cable along the line of coast. In this case
the currents set up in the cable have to bridge only the
sheet of water to the vessel, say twenty fathoms ; or, if an
electro-magnet be let down from the ship, only four or five
fathoms. But here the cost and maintenance of a cable
would be a weighty objection. The other way is to erect a
pole line on shore, either along the coast or in the form of
a coil on a peninsula. The main difference from the first
plan is that the currents would have to be stronger to bridge
the distance of several miles instead of a few fathoms ; but
the cost in comparison with a cable would be very small.
I have tried this system with two miles of pole line and a
coil about a quarter of a mile distant with perfect and
never-failing success.
" I have made numerous trials of the coil versus parallel-
i
130 SECOND PERIOD THE PRACTICABLE.
wire system since 1891, and I have found and other
observers seem also to have found that it is not prac-
tical to work the latter more than three or four times
the length of base ; whereas by coils I have found it possible
to work many times their diameter. Thus in 1892, at the
Isle of May lighthouse, I signalled to a distance 360 times
the diameter of an electro-magnet coil with currents from a
de Meritens' magneto-electric machine. Again, at Murray-
field, I signalled four times the base with five dry cells ;
and I have in Edinburgh a coil with iron core 17 inches
diameter, which with one cell can easily signal through a
space twenty -five times its diameter." 1
PROFESSOR ERICH RATH EN AU 1894.
The last example of a wireless telegraph with which we
have to deal in this part of our history is an arrangement
devised by Prof. Rathenau of Berlin, with the assistance
of Drs Rubens and W. Rathenau, and which was found
to be practicable up to a distance of three miles in water.
Reports of the experiments of Messrs Preece, Stevenson,
and others in England having appeared in the technical
journals on the Continent, Prof. Rathenau, at the request of
the Berlin Electrical Society, undertook to make a thorough
investigation of the subject de novo.
After a careful study of the work of these electricians he
felt convinced that the favourable results obtained in Eng-
land, especially by Mr Preece, were largely due to conduc-
1 Though never tried practically in England, Mr C. Bright points
out that this system has been experimented on by the Lighthouse
Board in America under the direction of Prof. Lucien Blake, and was
favourably spoken of in their report for 1895 : ' Submarine Tele-
graphs,' London, 1898. See also some recent remarks of Mr Steven-
son, 'Jour. Inst. Elec. Engs.,' No. 139, p. 307.
PROFESSOR ERICH RATHENAU.
131
tion. To verify this opinion he commenced a course of
rigorous experimentation ; and to prevent inductive effects
entering into the calculation he decided to use ordinary
battery currents, and in one direction only.
The outcome of the inquiry was published in an article
which he contributed to the Berlin ' Elektrotechnische
Zeitschrift,' x from which I make a few extracts. When a
current is sent through two electrodes immersed in a con-
ducting liquid, the electrical equilibrium between these
electrodes is not effected in a straight line, but in lines
which spread out in the manner shown in fig. 16. Now, if
we place in the liquid medium an independent conductor of
electricity, it will attract or condense upon its surface a
certain number of these lines, which can be utilised for the
excitation of a properly constructed receiving apparatus.
The distance at which these electrical effects can be produced
is found to depend upon two factors the available current
strength and the distance between the electrodes.
It was thought best to conduct the experiments on the
1 Abstract in ' Scientific American Supplement,' 'January 26, 1895,
which I follow in the text.
132 SECOND PERIOD THE PRACTICABLE.
lake Wannsee, near Potsdam, on account of the facilities in
the way of apparatus afforded by the proximity of an electric-
light station. The arrangement is shown in fig. 16. AB is
a battery of 25 cells, w a set of resistance coils (0 to 24
ohms), su an interrupter driven by a motor, AM an ampere-
meter, VM a voltmeter, T a Morse key, EP EP two zinc plates
immersed in the water, 500 yards apart, and connected by
cable as shown. The receiving circuit comprises two zinc
plates, EP I and EP I , suspended by cable x from two boats, from
50 to 100 yards apart, and nearly three miles from the
sending station ; N N are telephones included in the circuit
of x. For the purpose of transmitting signals, intermittent
currents were sent from the battery, which, by depressing
the key for long and short intervals, could be heard in the
telephones as dashes and dots of the Morse code.
The object was to establish experimentally the best
relation between the various factors i.e., the relation
between the current strength in the primary circuit and
the hearing distance for the telephones in the secondary
circuit ; the effect of various distances between the elec-
trodes EP EP upon the clearness of the signals ; the dis-
tance between EP X EP I which gave the most audible effect ;
and, finally, the effect of altering the shape and size of
the plates.
On account of the non-arrival of some apparatus specially
designed for these tests, the average current strength sent
through the water did not exceed three amperes with 150
intermissions or current impulses per second. Again, the
water of the Wannsee containing but a very small ad-
mixture of mineral salts offered a high resistance, so that
it was found necessary to use large plates of 15 square
yards surface.
With this arrangement no difficulty was encountered
in the transmission of signals from the electric-light station
PROFESSOR ERICH RATHENAU. 133
to the boats anchored off the village of New Cladow a
distance, as has been said, of nearly three miles ; and
Prof. Rathenau was satisfied that, by a slight change in
the construction of the ordinary telephone, signals could
be sent over much greater distances.
"Lord Eayleigh," he says, "has stated that the sensi-
tiveness of the telephone for currents with 600 reversals
per second is about 600 times greater than for currents
having but 130 reversals per second, but in my experi-
ments the number of impulses did not exceed 150 per
second. To get the best possible result in this system of
transmission, a telephone should be used having a carefully
tuned metallic tongue in place of the ordinary iron disc.
Then, knowing the number of current-breaks in the primary
circuit, the tongue should be so tuned as to vibrate in
unison with that number, thereby producing much more
distinct signals.
" I may point out that the resistance of the receiving
circuit should be as small as possible. At first I found
it difficult to produce a call in the distant receivers, but
this apparently knotty problem may be solved by attaching
a microphone to the membrane of the receiver, which,
acting upon a relay in a local circuit, produces the call.
"It does not seem necessary to point out that by the
use of several current generators, each one producing a
definite number of current impulses, a number of non
interfering messages may be sent through the water to
distant telephones, each being constructed to respond to
but one definite rate of vibration; or by means of one
current generator a message may be sent (simultaneously)
to several distant telephone receivers.
"The usefulness of this method of transmission would
be much increased if means can be found to produce a
written message. On the suggestion of Dr Rubens an
134
SECOND PERIOD THE PRACTICABLE.
apparatus is now being constructed, generally on the plan
of Dr Wien's optical telephone. It is expected that the
use of this apparatus will enable us to transform the
acoustical into optical signals, and to register these photo-
graphically."
Fig. 17 shows the locality of these experiments. It will
Fig. 17.
be noticed that a large sandbank intervenes between the
stations, but without any appreciable effect on the results.
Prof. Rathenau concludes a very interesting paper with
the enumeration of the chief points to be observed for in-
creasing the effective signalling distance :
" 1. Great current strength in the primary circuit.
"2. Increasing the distance between the primary
electrodes.
PROFESSOR ERICH RATHENAU. 135
"3. Increasing the distance between the receiving
electrodes.
" 4. Replacing the metallic diaphragm of the telephone
receiver by a light tongue.
" 5. Which should be tuned to respond to a definite rate
of vibration. 1
1 Experiments, based on the same conductive principle, were
tried in Austria about the same time, but with what success I
cannot say, as the results, for military reasons, have not been
published.
136
TRIED PERIOD THE PRACTICAL.
SYSTEMS IN ACTUAL USE.
" The invention all admired ; and each how he
To be the inventor missed so easy seemed
Once found, which yet unfound most would have thought
Impossible."
W. H. PREECE'S METHOD.
MR PREECE, lately the distinguished engineer-in-chief of
our postal telegraphs, has made the subject of wireless teleg-
raphy a special study for many years, his first experiment
dating back to 1882. 1 From that year up to the present he
has experimented largely in all parts of the country, and
has given us the results in numerous papers so numerous,
in fact, that they offer a veritable enibarras des richesses to
the historian. In what follows I can only attempt a resume,
and that a condensed one ; but to the reader greatly
interested in the subject I would advise a careful study of
all the papers, a list of which I append :
1. Recent Progress in Telephony : British Association
Report, 1882.
1 Indeed, it so happens that one of the first experiments he ever
made in electricity was on this very subject in 1854. See p. 28,
ante.
w. H. PREECE'S METHOD. 137
2. On Electric Induction between Wires and Wires : British
Association Report, 1886.
3. On Induction between Wires and Wires : British Associa-
tion Report, 1887.
4. On the Transmission of Electric Signals through Space :
Chicago Electrical Congress, 1893.
5. Electric Signalling without Wires : Journal of the Society
of Arts, February 23, 1894.
6. Signalling through Space : British Association Report,
1894.
7. Telegraphy without Wires : Toynbee Hall, December 12,
1896.
8. Signalling through Space without Wires : Royal Institu-
tion, June 4, 1897.
9. ^theric Telegraphy : Institution of Electrical Engineers,
December 22, 1898. 1
In his first-quoted paper of 1882, speaking of disturb-
ances on telephone lines, Mr Preece says : " The discovery
of the telephone has made us acquainted with many strange
phenomena. It has enabled us, amongst other things, to
establish beyond a doubt the fact that electric currents
actually traverse the earth's crust. The theory that the
earth acts as a great reservoir for electricity may be placed
in the physicist's waste-paper basket, with phlogiston, the
materiality of light, and other old-time hypotheses. Tele-
phones have been fixed upon a wire passing from the ground
floor to the top of a large building (the gas-pipes being used
in place of a return wire), and Morse signals, sent from a
telegraph office 250 yards distant, have been distinctly read.
There are several cases on record of telephone circuits miles
away from any telegraph wires, but in a line with the earth
terminals, picking up telegraphic signals ; and when an
electric-light system uses the earth, it is stoppage to all
telephonic communication in its neighbourhood. Thus,
1 This list does not pretend to be complete. Doubtless there are
other papers, which have escaped my notice.
138 THIRD PERIOD THE PRACTICAL.
communication on the Manchester telephones was not long
ago broken down from this cause ; while in London the
effect was at one time so strong as not only to destroy all
correspondence, but to ring the telephone - call bells. A
telephone system, using the earth in place of return wires,
acts, in fact, as a shunt to the earth, picking up the currents
that are passing in proportion to the relative resistances of
the earth and the wire." J
Mr Preece then describes the experiment which he had
recently (March 1882) made of telegraphing across the
Solent, from Southampton to Newport in the Isle of Wight,
without connecting wires. " The Isle of Wight," he says,
"is a busy and important place, and the cable across at
Hurst Castle is of consequence. For some cause the cable
broke down, and it became of great importance to know if
by any means we could communicate across, so I thought it
a timely opportunity to test the ideas that had been promul-
gated by Prof. Trowbridge. I put a plate of copper, about
6 feet square, in the sea at the end of the pier at Hyde (fig.
18). A wire (overhead) passed from there to Newport, and
thence to the sea at Sconce Point, where I placed another
copper plate. Opposite, at Hurst Castle, was a similar
plate, connected with a wire which ran through Southamp-
ton to Portsmouth, and terminated in another plate in the
sea at Southsea Pier. We have here a complete circuit, if
we include the water, starting from Southampton to South-
sea Pier, 28 miles ; across the sea, 6 miles ; Eyde through
Newport to Sconce Point, 20 miles ; across the water again,
1J mile; and Hurst Castle back to Southampton, 24 miles.
" We first connected Gower-Bell loud-speaking telephones
in the circuit, but we found conversation was impossible.
Then we tried, at Southampton and Newport, what are
called buzzers (Theiler's Sounders) little instruments that
1 For early notices of the same kind, see pp. 79-85, ante.
w. H. PREECE'S METHOD.
139
make and break the current very rapidly with a buzzing
sound, and for every vibration send a current into the
circuit. With a buzzer, a Morse key, and 30 Leclanche
cells at Southampton, it was quite possible to hear the
Morse signals in a telephone at Newport, and vice versa.
Fig. 18.
Next day the cable was repaired, so that further experi-
ment was unnecessary." 1
Mr Preece, however, kept the subject in view, and in
1884 he began a systematic investigation, theoretically and
experimentally, of the laws and principles involved an
1 Captain Hippisley, R.E., who conducted these trials, thought
that the presence of the broken cable across the Solent somewhat
vitiated the results, as its heavy iron sheathing may have aided in
conducting the current.
140 THIRD PERIOD THE PRACTICAL.
investigation which he has hardly yet completed. In his
papers read at the International Electrical Congress,
Chicago, August 23, 1893, and at the Society of Arts,
London, February 23, 1894, he gives a resume of his
experiments from 1884 to date.
He begins the latter paper by asking the same momen-
tous question which a lady once put to Faraday, What
is electricity? Faraday, with true philosophic caution,
replied (I quote from memory) : " Had you asked me forty
years ago, I think I would have answered the question ;
but now, the more I know about electricity, the less pre-
pared am I to tell you what it is." Mr Preece is not
quite so epigrammatic, nor nearly so cautious; but, then,
we have learned a great deal since Faraday's time. " Few,"
he says, "venture to reply boldly to this question first,
because they do not know ; secondly, because they do
not agree with their neighbours, even if they think they
know ; thirdly, because their neighbours do not agree
among themselves, even as to what to apply the term.
The physicist applies it to one thing, the engineer to
another. The former regards his electricity as a form
of ether, the latter as a form of energy. I cannot grasp
the concept of the physicist, but electricity as a form of
energy is to me a concrete fact. The electricity of the
engineer is something that is generated and supplied,
transformed and utilised, economised and wasted, meted
out and paid for. It produces motion of matter, heat,
light, chemical decomposition, and sound; while these
effects are reversible, and sound, chemical decomposition,
light, heat, and motion reproduce those effects which are
called electricity." 1
1 " Substantialists " call it a kind of matter. Others view it as a
form of energy. Others, again, reject both these views. Prof.
Lodge considers it a form, or rather a mode of manifestation, of the
w. H. PHEECE'S METHOD. 141
In experiments of this kind it is necessary to point out
that if we have two parallel conductors, separated from
each other by a finite space, and each forming part of
a separate and distinct circuit, either wholly metallic or
partly completed by the earth, and called respectively the
primary and the secondary circuits, we may obtain currents
in the latter either by conduction or by induction ; and we
may classify them into those due to
1. Earth-currents or leakages.
2. Electro-static induction currents.
3. Electro-magnetic induction currents.
It is very important to eliminate (1), which is a case of
conduction, from (2) and (3), which are cases of induction,
pure and simple.
1. Earth-cuirents or Leakages.
When a linear conductor dips at each end into the earth,
and voltage is impressed upon it by any means, the result-
ing return current would probably flow through the earth
in a straight line between these two points if the conducti-
bility of the earth were perfect ; but as the earth, per se,
is a very poor conductor (and probably is so only because
it is moist), lines of current-flow spread out symmetrically
in a way that recalls the figure of a magnetic field. These
diffused currents are evident at great distances, and can
be easily traced by means of exploring earth -plates or
rods. The primary current is best produced by alternating
currents of such a frequency as to excite a distinct musical
ether. Prof. Nikola Tesla demurs to this view, but sees no objection
to calling electricity ether associated with matter, or bound ether.
High authorities cannot even yet agree whether we have one elec-
tricity or two opposite electricities.
142 THIRD PERIOD THE PRACTICAL.
note in a telephone, and if these currents rise and fall
periodically and automatically, they produce an unmistak-
able wail, which, if made and broken by a Morse key into
short and long periods, can be made to represent the dots
and dashes of the Morse alphabet. The secondary circuit,
which contains the receiving telephone, is completed in the
case of an earth area by driving two rods into the ground,
and in the case of water by dipping plates therein, 5 to 10
yards apart.
It is therefore necessary to be able to distinguish these
earth-currents from those due to induction, as they are apt
to give false effects, and to lead to erroneous conclusions.
This is easily done, if the instrument be sensitive enough,
by making the primary current continuous when the earth-
current also becomes continuous, whereas the induction
currents will be momentary, and will only be observed
at the beginning and end of the primary or inducing
current.
2. Electro-static Induction Currents.
When a body, A, is electrified by any means and isolated
in a dielectric, as air, it establishes an electric field about
it ; and if in this field a similar body, B, be placed, it also
is electrified by induction. If B be placed in connection
with the earth, or with a condenser, or with any very large
body, a charge of the same sign as A is conveyed away, and
it (B) remains electrified in the opposite sense to A. A and
B are now seats of electric force or stress. The dielectric
between them is displaced or, as we say, polarised that
is, it is in a state of electric strain, and remains so as long
as A remains charged ; but if A be discharged, or have its
charge reversed or varied, then similar changes occur in B,
and in the dielectric separating them. A may be an ex-
tended wire forming part of a, complete primary circuit,
w. H. PKEECE'S METHOD. 143
and its charge may be due to a battery or other source of
electricity; then, in the equally extended secondary wire
B (fig, 19), the displaced charge in flowing to earth estab-
lishes a momentary current whose direction and duration
depend on the current in A, and on its rate of variation.
Fig. 19.
The strained (polarised) state of the dielectric, and the
charges on A and B, remain quiescent so long as the current
flows steadily ; but when it ceases we have again, and in
loth circuits, momentary currents, as shown by the arrows
(fig. 20), which flow until equilibrium is restored.
Fig. 20.
The secondary currents due to discharge, like those due
to charge, flow in opposite directions at each end, and there
is always some intermediate zero point.
It is thus easy in long circuits, by observing their direc-
tion, to differentiate currents of induction due to electro-
static displacement from those due to electro - magnetic
disturbance.
The effects of electro-static induction do not play an
important part in the inquiry immediately before us, but
they are of great consequence in questions of speed of sig-
144 THIRD PERIOD THE PRACTICAL.
nailing in submarine cables and long, well-insulated land-
lines, and in clearness of speech in long-distance telephony. 1
3. Electro-magnetic Induction Currents.
Magnetic force is that which produces, or tends to pro-
duce, polarisation in inagnetisable matter (as iron, nickel,
cobalt), and electro-magnetic disturbance or stress in non-
magnetisable matter and the ether. An electric current in
a conductor is a seat of magnetic force, and establishes in
its neighbourhood a magnetic field. The lines of force in
this field are equivalent to circles in a plane perpendicular
to the direction of the current, which circles, during the rise
of the current, flow outwards or expand, and, during the
fall of the current, flow inwards or contract, much like the
waves on the surface of smooth water when a pebble is
thrown in, but moving with the speed of light. Thus any
linear conductor placed in the field of another parallel con-
ductor carrying a current is cut at right angles to itself by
these lines of force in one direction as the current rises,
and in the opposite direction as the current falls. This out-
ward and inward projection of magnetic force through such
linear conductor excites electric force in that conductor, and
if it form part of a circuit an electric current is set up in
that circuit.
So far for the theory of the subject. Now for its experi-
mental elucidation. Besides those cases of interference
mentioned on page 137, others were of frequent occurrence
in the experience of the postal-telegraph officials, the most
striking being that known as the Gray's Inn Road case. In
1884 it was there noticed that messages sent in the ordinary
1 For an interesting investigation of electro -static phenomena on
telephone circuits, see Mr Carty's papers in the ' Electrician,' Decem*
ber 6, 1889, and April 10, 1891.
w. H. PEEECE'S METHOD. 145
way through insulated wires, buried in iron pipes along the
road, could be read upon telephone circuits erected on poles
on the house-tops 80 feet high. To cure the evil the tele-
graph wires had to be taken up and removed to a more
distant route. 1
In 1885 Mr Preece arranged an exhaustive series of ex-
periments in the neighbourhood of Newcastle, which were
ably carried out by Mr A. "W. Heaviside, to determine
whether these disturbances were due to electro-magnetic in-
duction, and were independent of earth conduction ; and
also to find out how far the distance between the wires
could be extended before this influence ceased to be evi-
dent. Insulated squares of wire, each side being 440 yards
long, were laid out horizontally on the ground one quarter
of a mile apart, and distinct speech by telephones was
carried on between them ; while when removed 1000 yards
apart inductive effects were still appreciable.
With the parallel lines of telegraph, ten and a quarter
miles apart, between Durham and Darlington, the ordinary
working currents in the one were clearly perceptible in a
telephone on the other. Even indications were obtained in
this way between Newcastle and Gretna, on the east and
west coasts, forty miles apart ; but here the observations
were doubtless vitiated by conduction or leakage through
1 The following are more recent cases of the same kind. Currents
working the City and South London Electric Railway affect recording
galvanometers at the Greenwich Observatory, four and a half miles
distant ; and even a diagram of the train service could be made out
by tapping any part of the metropolitan area.
Some ten years ago one of the dynamos at the Ferranti electric-
light station at Deptford by some accident got connected to earth,
with the result that the whole of the railway telegraphs in the signal-
boxes of the railways in South London were temporarily put out of
order and rendered inoperative, while the currents flowing in the
earth were perceived in the telegraph instruments so far northwards
as Leicester and so far south as Paris.
146 THIRD PERIOD THE PRACTICAL.
the large network of telegraph wires between those two
places. 1
The district between Gloucester and Bristol, along the
banks of the Severn, was next (1886) selected, where for a
length of fourteen miles, and an average distance apart of
four and a half miles, no intermediate disturbing lines
existed. Complete metallic circuits were employed, the
return wires passing far inland, in the one case through
Monmouth, and in the other through Stroud. In one wire
currents of about *5 ampere were rapidly made and broken
by mechanical means, producing on a telephone a continuous
note which could be broken up by a Morse key into dots
and dashes, as in Cardew's vibrator. Weak disturbances
were detected in the secondary circuit, showing that -here
the range of audibility with the apparatus in use was just
overstepped. The unexpected fact was also shown in these
experiments that, whether the circuits were entirely metallic
or earthed at the ends, the results were the same. 2
Similar trials were made on lines along the valley of the
Mersey. A new trunk line of copper wires that was being
erected between London and the coast of North Wales was
then experimented upon, and some interesting results were
obtained in the district between Shrewsbury and Much
Wenlock, and between Worcester and Bewdley.
In the autumn of the same year (1886) some admirable
results were obtained by Mr Gavey, another of Mr Preece's
able assistants, near Porthcawl, in South Wales a wide
expanse of sand well covered by the tide, thus giving the
opportunity of observing the effects in water as well as in
air. Two horizontal squares of insulated wire, 300 yards
each side, were laid side by side at various distances apart
1 British Association Report, 1886.
3 These experiments were repeated with more experience and
greater success in 1889.
w. H. PREECE'S METHOD. 147
up to 300 yards, and the inductive effects of one on the
other noted. Then one coil was suspended on poles. 15 feet
above the other, which was covered with water at high tide.
JS"o difference was observable in the strength of the induced
signals, whether the intervening space was air or water or a
combination of both, although subsequent experience (1893)
showed that with a space of 15 feet the effect in air was
distinctly better than through water.
The conclusion drawn from all these, experiments was
that the magnetic field extends uninterruptedly through the
earth, as it does through the air ; and that if the secondary-
circuit had been in a coal-pit the effect would be the same.
In fact, Mr Arthur Heaviside succeeded in 1887 in com-
municating between the surface and the galleries of Broom-
hill Colliery, 350 feet deep. He arranged a circuit in a
triangular form along the galleries about two and a quarter
miles in total length, and at the surface a similar circuit of
equal size over and parallel to the underground line. Tele-
phonic speech was easily carried on by induction from circuit
to circuit. 1
As the result of all these experiments and innumerable
laboratory investigations, Mr Preece deduced the following
formula. The first shows the strength of current C 2 in-
duced in the secondary circuit by a given current C x in the
primary circuit
1 Subsequent experiments showed that the conclusion arrived at
for earth and air was only partially true for water. Telephonic
speech was carried on in Dover Harbour through 36 feet of water,
but no practical signals could be obtained through 400 feet at North
Sand Head, Goodwin Sands, showing that the effect must diminish
in water with some high power of the distance.
2 This formula does not allow for the reverse effect of the return
current through the earth, as to which no data exist at present.
148 THIRD PERIOD THE PRACTICAL.
where R equals the resistance of the secondary circuit, D the
distance apart of the two circuits, L the length of the in-
ductive system, and I the inductance of the system. The
value of I, obtained by experiment on two parallel squares
of wire, 1200 yards round and 5 yards apart, was found to
be -003.
The second equation gives approximately the maximum
distance X which should separate any two wires of length
L, C x being the primary current and R the resistance of the
secondary circuit.
X = 1.9016-
The constant 1*9016 was obtained by experimenting on two
parallel wires, each one mile long, when the primary circuit,
being excited by one ampere, the limit of audibility in the
secondary was reached at 1 '9016 miles. This formula shows
the desirability of using copper wires of the largest size
practicable, so as to reduce the value of R. Other very
important elements of success are (1) the rate at which the
primary currents rise and fall, the faster the better, and (2)
the reduction to a minimum of such retarding causes as
capacity and self-induction.
Having thus threshed out the laws and conditions of
electro-magnetic disturbances, and determined the distance
at which they could be usefully applied, it only remained
for Mr Preece to put his conclusions to a practical test.
Accordingly, when the Royal Commission on electric com-
munication between the shore and lighthouses and light-
ships was appointed in June 1892, he made his proposals to
the Government, arid on receiving sanction forthwith pro-
ceeded to carry them out.
The Bristol Channel proved a very convenient locality to
test the practicability of communicating across distances of
W. H. PREECE S METHOD.
149
three and five miles without any intermediate conductors.
Two islands, the Flat Holm and the Steep Holm, lie off
Penarth and Lavernock Point, near Cardiff, the former
having a lighthouse upon it (fig. 21). On the shore two
thick copper wires combined in one circuit were suspended
on poles for a distance of 1267 yards, the circuit being
PENARTH fa
THOLM
STEEPHOLM
BRLAN DOWN
Fig. 21.
completed by the earth. On the sands at low-water mark,
600 yards from this primary circuit and parallel to it, two
gutta-percha covered copper wires and one bare copper wire
were laid down, their ends being buried in the ground by
means of bars driven in the sand.
One of the gutta-percha wires was lashed to an iron wire
to represent a cable. These wires were periodically covered
150 THIRD PERIOD THE PRACTICAL.
by the tide, which rises here at spring to 33 feet. On the
Flat Holm, 3 '3 miles away, another gutta-percha covered
copper wire was laid for a length of 600 yards.
There was also a small steam launch having on board
several lengths of gutta-percha covered wire. One end
of such a wire, half a mile long, was attached to a small
buoy, which acted as a kind of float to the end, keeping
the wire suspended near the surface of the water as it
was paid out while the launch slowly steamed ahead
against the tide. Such a wire was paid out and picked
up in several positions between the primary circuit and the
islands.
The apparatus used on shore was a 2-h.p. portable
Marshall's engine, working a Pyke and Harris's alternator,
sending 192 complete alternations per second of any desir-
able strength up to a maximum of 15 amperes. These
alternating currents were broken up into Morse signals by a
suitable key. The signals received on the secondary circuits
were read on a pair of telephones the same instruments
being used for all the experiments.
The object of the experiments was not only to test the
practicability of signalling between the shore and the light-
house, but to differentiate the effects due to earth conduction
from those due to electro-magnetic induction, and to deter-
mine the effects in water. It was possible to trace without
any difficulty the region where they ceased to be perceptible
as earth-currents and where they commenced to be solely
due to electro-magnetic waves. This was found by allowing
the paid-out cable, suspended near the surface of the water,
to sink. Near the shore no difference was perceptible,
whether the cable was near the surface or lying on the
bottom, but a point was reached, just over a mile away,
where all sounds ceased as the cable sank, but were received
again when the cable came to the surface. The total
w. H. PKEECE'S METHOD. 151
absence of sound in the submerged cable was rather sur-
prising, and led to the conclusion either that the electro-
magnetic waves of energy are dissipated in the sea-water,
which is a conductor, or else that they are reflected away
from the surface of the water, like rays of light.
Experiments on the Con way Estuary, showing the relative
transparency of air and water to these electro-magnetic
waves, tend to support the latter deduction ; for if much
waste of energy took place in the water, the difference
would be more marked. As it is, there seems to be ample
evidence that the electro-magnetic waves are transmitted to
considerable distances through water, though how far remains
to be found. 1
There was no difficulty in communicating between the
shore and Flat Holm, 3 '3 miles. The attempt to speak
between Lavernock and Steep Holm, 5 -35 miles, was not
so successful : though signals were perceptible, conversation
was impossible. There was distinct evidence of sound, but
it was impossible to differentiate the sounds into Morse
signals. If either line had been longer, or the primary
currents stronger, signalling would probably have been
possible.
In 1894 Mr Preece carried out some satisfactory experi-
ments near Frodsham, on the estuary of the Dee, which
was found to be a more convenient locality than the
Conway sands. Here, as at Conway and other places,
squares and rectangles were formed of insulated wires,
and numerous measurements were made (with reflecting
galvanometers and telephones) of the effects due to vary-
ing currents in the primaries, and at varying distances
between them and the secondaries.
In Scotland also some very successful trials were made.
There happens to be a very convenient and accessible loch
1 See note, p. 147, ante.
152 THIRD PERIOD THE PRACTICAL.
in the Highlands Loch Ness forming part of the route
of the Caledonian Canal between Inverness and Banavie,
having a line of telegraph on each side of it. Five miles
on each side of this loch were taken, and so arranged that
any fractional length of telegraph wire on either side could
be taken for trial. Ordinary, and not special, apparatus
was employed. Sending messages, as before, by Morse
signals and speaking by telephone across a space of one
and a quarter miles was found practical, and, in fact, easy ;
indeed, the sounds were so loud that they were found
sufficient to form a call for attention.
The following apparatus was in use on each side of
the loch : A set of batteries consisting of 100 dry cells,
giving a maximum voltage of 140 ; a rapidly revolving
rheotome, which broke up the current into a musical
note; a Morse key, by which these musical notes could
be transformed into Morse signals ; resistance coils and
ampere - meters to vary the primary current ; two Bell
telephones joined in multiple arc to act as receivers.
For the transmission of actual speech simple granular
carbon microphones, known as Deckert's, were used as
transmitters, and a current of two amperes was main-
tained through these and two Bell telephones in circuit
with the line wire.
Any lingering fear that earth conduction had principally
to do with these results was removed by making the earth's
terminals on the primary circuit at one end at Inverness
nine miles away, and at the other end in two directions
in a parallel glen about six miles away.
One very interesting fact observed at Loch Ness was
that there was one particular frequency in the primary
circuit that gave a decided maximum effect upon the
telephones in the secondary circuit. This confirms the pres-
ence of resonance, and is, of itself, a fact sufficient to prove
W. H. PREECE S METHOD.
153
the effects as being due to the transformation of electro-
magnetic waves into electric currents. 1
During the same year (1894) experiments were carried
out between the island of Arran and Kintyre across Kil-
/ ISLE
I ARRAN
Fig. 22.
brannan Sound. Two parallel lines on opposite sides, and
four miles apart, were taken (fig. 22) ; and, in addition,
two gutta-percha covered wires were laid along each coast,
at a height of 500 feet above sea-level and five miles apart
horizontally.
1 This is still a moot question, many competent authorities, as
Lodge, Rathenau, W. S. Smith, and Stevenson, being of opinion that
the effect is partly inductive and partly conductive. See Dr Lodge's
contention, 'Jour. Inst. Elec. Engs.,' No. 137, p. 814,
154 THIRD PERIOD THE PRACTICAL.
' Incidentally some extremely interesting effects of electro-
magnetic resonance were observed during the experiments
in Arran. A metallic circuit was formed partly of the
insulated wire 500 feet above the sea -level and partly
of an ordinary line wire, the rectangle being two miles
long and 500 feet high. Wires on neighbouring poles,
at right angles to the shorter side of the rectangle, cdthoucjli
disconnected at both ends, took up the vibrations, and it
was possible to read all that was signalled on a telephone
placed midway in the disconnected circuit by the surgings
thus set up.
The general conclusions arrived at as the result of these
numerous and long-continued experiments may be briefly
summed up as follows : l
The earth acts simply as a conductor, and per se it is a
very poor conductor, deriving its conducting property prin-
cipally, and often solely, from the moisture it contains. On
.the other hand, the resistance of the " earth " between the
two earth plates of a good circuit is practically nothing.
Hence it follows that the mass of earth which forms the
return portion of a circuit must be very great, for we know
by Ohm's law that the resistance of a circuit increases with
its specific resistance and length, and diminishes with its
sectional area. Now, if the material forming the " earth "
portion of the circuit were, like the sea, homogeneous, the
current-flow between the earth plates would follow innumer-
able but definite stream lines, which, if traced and plotted
out, would form a hemispheroid. These lines of current
have been traced and measured. A horizontal plan on the
surface of the earth is of the form illustrated in fig. 23,
while a vertical section through the earth is of the form
shown in fig. 24.
With earth plates 1200 yards apart these currents have
. l British Association Report, 1894, Section G.
w. H. PREECE'S METHOD. 155
been found on the surface at a distance of half a mile
behind each plate; and, in a line joining the two trans-
'-"' ---*'" - . X \
. \ ' .';''''''*-'','-- "-"_""- O\\ \ I
v\ \ t i ;'/.-'/,.'-;. -*Xcr**C\V: / *v
% * V- V^^^'::'v'.'.'.'.'"'' - - - -;;;f; : 3 rrji^^lr f f -
Fig. 23.
versely, they are evident at a. similar distance at right
angles to this line.
Now this hemispheroidal mass could be replaced electric-
ally by a resultant conductor (R, fig. 24) of a definite form
Fig. 24.
and position ; and, in considering the inductive action be-
tween two circuits having earth returns, it is necessary to
estimate the position of this imaginary conductor. This
was the object of the experiments at Frodsham.
If the material of the earth be variable and dry the he mi-
156 THIRD PERIOD THE PRACTICAL.
spheroid must become very much deformed and the section
very irregular: the lines of current-flow must spread out
farther, but the principle is the same, and there must be a
resultant return. The general result of the experiments at
Frodsham indicates that the depth of the resultant earth
was 300 feet, while those at Conway are comparable with a
depth of 350 feet. In the case of Frodsham the primary
coil had a length of 300 feet, while at Conway the length
was 1320 feet. At Loch Ness, and between Arran and
Kintyre, where the parallel lines varied from two to four
miles, the calculated depth was found to be about 900 feet.
The depth of this resultant must, therefore, increase with the
distance separating the earth plates, and this renders it pos-
sible to communicate by induction from parallel wires over
much longer distances than would otherwise be possible.
The first and obvious mode of communicating across space
is by means of coils of wire opposed to each other in the
way familiar to us through the researches of Henry and
Faraday. All the methods here described consisted in
opposing two similar coils of wire having many turns, the
one coil forming the primary circuit and the other coil the
secondary circuit.
Vibratory or alternating currents of considerable fre-
quency were sent through the primary circuit, and the
induced secondary currents were detected by the sound
or note they made on a telephone fixed in the secondary
circuit.
The distance to which the effective field formed by a coil
extends increases with the diameter of the coil more than
with the number of turns of wire upon it. A single wire
stretched across the surface of the earth, forming part of a
circuit completed by the earth, is a single coil, of which the
lower part is formed by the resultant earth return, and the
distance to which its influence extends depends upon the
w. H. PREECE'S METHOD. 157
height of the wire above the ground and the depth of this
resultant earth.
In establishing communication by means of induction,
there are three dispositions of circuit available viz., (a)
single parallel wires to earth at each extremity ; (b) parallel
coils of one or more turns ; (c) coils of one or more turns
placed horizontally and in the same plane.
The best practical results are obtained with the first
arrangement, more especially if the conformation of the
earth admits of the wires being carried to a considerable
height above the sea, whilst the earth plates are at the sea-
level. By adopting this course the size of the coil is prac-
tically enlarged, and even if it be necessary to increase the
distance between the parallel wires in order to get a larger
coil, the result is still more beneficial In a single-wire
circuit we have the full effect of electro-static and electro-
magnetic induction, as well as the benefit of any earth con-
duction, but in closed coils we have only the electro-magnetic
effects to utilise.
In one experiment two wires of a definite length were
first made up into two coils forming metallic circuits, then
uncoiled and joined up as straight lines opposed to each
other, with the circuit completed by earth. The effects,
and the distance between which they were observable, were
very many times greater with the latter than with the former
arrangement.
The general law regulating the distance to which we can
speak by induction has not been rigorously determined, and
it is hardly possible that it can be done, owing to the many
disturbing elements, geological as well as electrical. In
practice we have to deal with two complete circuits of un-
known shape, and in different planes. We have obtained
some remarkably concordant and accurate results in one
place ; but, on the other hand, we have met with equally
158 THIRD PERIOD THE PRACTICAL.
discordant results in another place. Still, from the ap-
proximate formula before given, we deduce the important
fact that for parallel lines the limiting distance increases
directly as the square of the length, which shows that if we
can make the length of the two lines long enough it would
be easy to communicate across a river or a channel. Of
course, as previously pointed out, the formula does not take
into account the effects of the reverse magnetic waves gener-
ated by the return current through the earth, and at present
no data exist on which a satisfactory calculation can be
based ; but, for example, there is little doubt that two wires,
ten miles long, would signal through a distance of ten miles
with ease.
" Although," says Mr Preece in conclusion, " communi-
cation across space has thus been proved to be practical
in certain conditions, those conditions do not exist in the
cases of isolated lighthouses and light-ships, cases which
it was specially desired to provide for. The length of
the secondary must be considerable, and, for good effects,
at least equal to the distance separating the two conductors.
Moreover, the apparatus to be used on each circuit is
cumbrous and costly, and it may be more economical to
lay an ordinary submarine cable.
" Still, communication is possible even between England
and France, across the Channel, and it may happen that
between islands where the channels are rough and rugged,
the bottom rocky, and the tides fierce, the system may be
financially possible. It is, however, in time of war that it
may become useful. It is possible to communicate with a
beleaguered city either from the sea or on the land, or
between armies separated by rivers, or even by enemies.
"As these waves are transmitted by the ether, they are
independent of day or night, of fog, or snow, or rain, and
therefore, if by any means a lighthouse can flash its indicat-
AY. H. PREECE'S METHOD. 159
ing signals by electro-magnetic disturbances through space,
ships could find out their positions in spite of darkness and
of weather. Fog would lose one of its terrors, and elec-
tricity become a great life-saving agency."
At the Society of Arts (February 23, 1894), Mr Preece
gave rein to his imagination, and, looking beyond these
mundane utilities, concluded his address with the following
magnificent peroration :
" Although this short paper is confined to a description of
a simple practical system of communicating across terrestrial
space, one cannot help speculating as to what may occur
through planetary space. Strange mysterious sounds are
heard on all long telephone lines when the earth is used as
a return, especially in the calm stillness of night. Earth-
currents are found in telegraph circuits and the aurora
borealis lights up our northern sky when the sun's photo-
sphere is disturbed by spots. The sun's surface must at
such times be violently disturbed by electrical storms, and
if oscillations are set up and radiated through space, in
sympathy with those required to affect telephones, it is not
a wild dream to say that we may hear on this earth 'a
thunderstorm in the sun.
" If any of the planets be populated with beings like our-
selves, having the gift of language and the knowledge to
adapt the great forces of nature to their wants, then, if they
could oscillate immense stores of electrical energy to and fro
in telegraphic order, it would be possible for us to hold
commune by telephone with the people of Mars."
The first application of Mr Preece's system to the ordinary
needs of the postal-telegraph service was made on March 30,
1895, when the cable between the Isle of Mull and Oban,
in Scotland, broke down. As there was no ship available
at the moment for effecting repairs, communication was
established by laying a gutta-percha-covered copper wire,
160
THIRD PERIOD THE PRACTICAL.
one and a half mile long, along the ground from Morven,
on the Argyllshire coast, while on Mull the ordinary tele-
graph (iron) wire connecting Craignure with Aros was used,
the mean distance separating the two base lines being about
two miles. No difficulty was experienced in keeping up
communication, and many public messages were transmitted
for a week until the cable was repaired. In all about 160
messages were thus exchanged, including a press telegram
of 120 words.
CURRENT^BREAKtR
a
Fig. 25.
The diagram (fig. 25) shows the apparatus and connec-
tions, as regards which it is only necessary to say that a is
a rheotome, or make-and-break wheel, driven so as to pro-
duce about 260 interruptions of the current per second,
which give a pleasant note in the telephone, and are easily
read when broken up by the key into Morse dots and
dashes; & is a battery of 100 Leclanche cells, of the so-
called dry and portable type ; c is a switch to start and stop
w. H. PREECE'S METHOD. 161
the rheotome as required ; and d is a telephone to act as
receiver.
Since March of last year (1898) this system has been
permanently established for signalling between Lavernock
Point and the Flat Holm, and has been handed over to the
"War Office. Permanent lines of heavy copper wire have
been erected parallel to each other, one being on the Flat
Holm and the other on the mainland.
The heavy and cumbrous Pyke and Harris alternator of
the earlier experiment over the same line (p. 150, ante) has
been replaced by 50 Leclanche cells. The frequency has
been raised to 400 makes and breaks per second, thus greatly
increasing the strength of the induced currents. By the
use of heavy copper base lines the resistances have been
made as low as practicable. There is no measurable capac-
ity, self-induction is eliminated, and there is no impedance.
Hence the signals are perfect, and the rate of working is
only dependent on the skill of the operator. It is said that
as many as 40 words per minute have been transmitted
without the necessity for a single repetition a speed which
few telegraphists can achieve, and still fewer can keep up.
Last summer Mr Sydney Evershed's relays were added
to work a call-bell, which was the only thing wanted to
make the system complete and practical. 1
It should be added, in conclusion, that the installation
was carried out under the immediate superintendence of Mr
Preece's able assistant, Mr Gavey, who for many years has
been intimately associated with him in these researches.
1 For a description of this very sensitive instrument see Evershed's
paper, 'Jour. Inst. Elec. Engs.,' No. 137, p. 864.
162 THIRD PERIOD THE PRACTICAL.
WILLOUGHBY SMITH'S METHOD.
Mr Smith's researches in wireless telegraphy date back to
1883. His first suggestions, of the induction order, were
contained in a paper on Voltaic-Electric Induction, which
he read before the Institution of Electrical Engineers on
November 8 of that year. These have already been noticed
in our account of Edison's invention (p. 105, ante).
Somewhat later, early in 1885, Mr Smith turned his
attention to conduction methods, and worked out a plan
which, in a modified form, has been in actual operation for
the last three years.
The rationale of the system is described by Mr Smith as
follows :
" Messages have been sent and correctly received through
a submarine cable two thousand miles in length, the earth
being the return half of the circuit, by the aid of the elec-
tricity generated by means of an ordinary gun-cap containing
one drop of water ; and small though the current emanating
from such a source naturally was, yet I believe it not only
polarised the molecules of the copper conductor, but also in
the same manner affected the whole earth through which it
dispersed on its way from the outside of the gun-cap to its
return, through the cable, to the water it contained. I further
believe that the time will come, perhaps sooner than may be
expected, when it will be possible to detect even such small
currents in any part of the world in the same way that it is
now possible to do in comparatively small sections of it.
" For researches of this description it is necessary to employ
as sensitive an instrument as it is possible to obtain, to pick
up, so to speak, such minute currents. Now, there is that
wonderful instrument the telephone. I say wonderful ad-
visedly, for as far as I know it is not to be equalled for the
WILLOUGHBY SMITH'S METHOD. 163
simplicity of its mechanical construction and the ease with
which it can be manipulated, and yet is so peculiarly sensi-
tive. I have used it in most of my experiments as the
receiving instrument, although of course there are other
well-known instruments that could be employed, as all
depends upon the potential of the current to be detected.
The sending arrangement was either an ordinary Morse key
so manipulated for a short or long time as to give the neces-
sary sounds in the telephone to represent dots and dashes,
or a double key and two pieces of mechanism giving dis-
similar sounds were employed with good results. I gave
much time and thought to the subject, the results of each
experiment giving me much encouragement to proceed.
" Of the many experiments made I select the following,
as I think it will clearly illustrate my system for telegraph-
ing to a distant point not in metallic connection with the
sending station. A wooden bathing-hut on a sandy beach
made a good shore station, from which were laid two in-
sulated copper wires 115 fathoms in length. The ends of
the wires, scraped clean, were twisted round anchors, their
position being marked by buoys about 100 fathoms apart,
and in about 6 fathoms of water. Midway between the two
a boat was anchored with a copper plate hanging fore and
aft about 10 fathoms apart, and consequently about 45
fathoms from either end of the anchored shore wires. This
boat represented the sea station, and, owing to the state of
the sea, a very wet and lively one it proved ; therefore,
taking this fact into consideration, together with the crude
nature of the experiment, it was remarkable with what dis-
tinctness and ease messages were passed. The last message
sent from shore was, * Thanks : that will do ; pick up anchors
and return.' To this the reply came from the boat, ' Under-
stand,' and they then proceeded to carry out instructions.
The boat employed was a wooden one, but it would have
164 THIRD PERIOD THE PRACTICAL.
been much better for my purpose had it been of metal, for
then I should have used it instead of one of the collecting
plates, as the larger the surface of these plates the better
the results obtained." l
This method was secured by patent, June 7, 1887, from
the specification of which (No. 8159) I take the following
particulars : At the present time wherever electric telegraph
communication is established between the shore and a light-
house, either floating or on a rock, at a distance from the
shore, it is effected through an insulated conductor or cable.
Much difficulty is, however, experienced owing to the rapid
wearing of the cable, so that it is liable to break whenever a
storm comes on, and when, consequently, it is most required
to be in working order. By this invention communication
can be effected between the sending station and the distant
point without the necessity of metallic connection between
them.
A in the drawing (fig. 26) is a two-conductor cable led
from a signal-station B on shore towards the rock c. At a
distance from the rock one of the conductors is led to a
metallic plate D submerged on one side of the rock, and at
such a distance from it as to be in water deep enough for it
not to be affected by waves. The other conductor is led to
another metallic plate E similarly submerged at a distance
from the opposite side of the rock. F F are two submerged
metallic plates, each opposite to the plates D and E respec-
tively. G G are insulated conductors leading from the plates
F F to a telephone of low resistance in the lighthouse H.
To communicate from the shore, an interrupter or re-
verser I and battery K are connected to the shore ends
of the two-wire cable. The telephone in the lighthouse
circuit then responds to the rapid makes and breaks or
reversals of the current, so that signalling can readily be
1 Electrician, November 2, 1888.
WILLOUGHBY SMITH S METHOD.
165
carried on by the Morse alphabet. If a vibrating inter-
rupter or reverser be used, a short or long sound in the
telephone can be obtained by a contact key held down for
short or long intervals.
A more convenient way is to use two finger-keys, one of
which by a series of teeth on its stem produces a few breaks
or reversals of the current, whilst the other key when
depressed produces a greater number of breaks or reversals.
Fig. 26.
For communicating from the lighthouse to the shore a
battery and make-and-break apparatus are coupled to the
insulated conductors on the rock, and a telephone to the
shore ends.
In the same way communication could be carried on
from the shore to a vessel at a distance from it, if the
vessel were in the vicinity of two submerged plates or
anchors, each having an insulated conductor passing from
it to the shore, and if two metallic plates were let go from
166 THIKD PERIOD THE PEACTICAL.
the vessel so that these plates might be at a distance apart
from one another. The position of the two submerged plates
might be indicated by buoys. In this way communication
might be effected between passing vessels and the shore, or
between the shore and a moored lighthouse or signal-station.
A similar result might be obtained with a single insulated
conductor from the shore by the use of an induction appar-
atus, the ends of the secondary coil being connected by
insulated conductors to the submerged plates.
An important modification of this method was subse-
quently effected by Messrs Willoughby S. Smith & W.
P. Granville, 1 based on the following reasoning :
In fig. 27 A B represents an insulated conductor of any
desired length, with ends to earth E E as shown, c is a
Fig. 27.
rock island on which is extended another insulated wire
c D, with its ends also connected to earth. Now, if a
current is caused to flow in A B, indications of it will be
shown on a galvanometer in the circuit c D. This is Mr
Preece's arrangement at Lavernock-Flat Holm.
1 See their patent specification, No. 10,706, of June 4, 1892.
WILLOUGHBY SMITH'S METHOD.
167
Now, if we rotate the line A B round A until it assumes
the position indicated in fig. 28, we have Messrs Smith
& Granville's arrangement, where, owing to the proximity
Fig. 28.
of B to D, signalling is practicable with a small battery
power. Thus, where the distance from B to D was 60
yards, one Leclanche cell was found to be ample. As
Fig. 29.
a permanent current in A B causes a permanent deflection
on the galvanometer in c D, this deflection cannot be pro-
duced otherwise than by conduction.
Again, let A B (fig. 29) represent an insulated conductor
168 THIRD PERIOD THE PRACTICAL.
having its ends submerged in water (the distance between A
and B being immaterial). Now cause a current to flow con-
tinuously, and it will be found that the water at each end
of the conductor is charged either positively or negatively
(according to the direction of the current) in equipotential
spheroids, diminishing in intensity as the distance from
either A or B is increased. To prove this, provide a second
circuit, connected with a galvanometer, and with its two
ends dipping into the water. Now, it will be found that a
current flows in the c D circuit as long as the current in A B
is flowing ; the current in c D diminishes as c and D are
moved farther away from B, and also diminishes to zero if
the points c D are turned until they both lie in the same
equipotential curve as shown by the dotted line.
It must be well understood that although, for the sake of
clearness, the equipotential curves are shown as planes, yet
in a body of water they are more or less spheres extending
symmetrically around the submerged ends of the conductor,
and therefore it is evident from the foregoing that the
position of c D, in relation to B, must be considered not only
horizontally but vertically. 1
Early in 1892 the Trinity Board placed the Needles
Lighthouse at the disposal of the Telegraph Construction
and Maintenance Company, so that they might prove the
practicability of the method here described. The Needles
1 This fact, Mr Smith thinks, fully explains Mr Preece's launch ex-
periments (p. 150, ante). For instance, when the launch towing the
half-mile of cable parallel to the wire on the mainland was close to the
shore, the cable, although allowed to sink, could only do so to a very
limited extent, and therefore still remained in a favourable position
for picking up the earth-currents from A B (fig. 29) ; but when one
mile from the shore, and in deep water, the cable was able to assume
somewhat of a vertical position with the two ends brought more or
less into the same equipotential sphere, it naturally resulted in a
diminution or cessation of the current in the c D or launch circuit,
and hence the absence of signals.
WILLOUGHBY SMITH'S METHOD. 169
Lighthouse was chosen on account of its easy access from
London.
In May 1892 an ordinary submarine cable was laid from
Alum Bay to within 60 yards of the lighthouse rock, where
it terminated, with its conductor attached to a specially con-
structed copper mushroom anchor. An earth plate close to
the pier allowed a circuit to be formed through the water.
On the rock itself two strong copper conductors were placed,
one on either side, so that they remained immersed in the
sea at low water, thus allowing another circuit to be formed
through the water in the vicinity of the rock.
The telephone was first tried as the receiving instrument,
with a rapid vibrator and Morse key in the sending circuit.
This arrangement was afterwards abandoned, as it was not
nearly so satisfactory as a mirror-speaking galvanometer, and
the men, being accustomed to flag work, preferred to watch
a light rather than listen to a telephone. The speaking
galvanometer used is a specially constructed one, and does
not easily get out of repair, so that, everything being once
arranged, the men had only to keep the lamp in order.
Messrs Smith & Granville devised a novel and strong
form of apparatus for a " call," and by its means any number
of bells could be rung, thus securing attention. The instru-
ments both on rock and shore were identical, and, in actual
work, two to three Leclanche cells were ample.
By the means above described, communication was ob-
tained through the gap of water 60 yards in length. This by
no means is the limit, for it will be apparent that the gap
distance is determined by the volume of water in the imme-
diate neighbourhood of the rock, as well as by the sensitive-
ness of the receiving instrument and the magnitude of the
sending current.
This method is well suited for coast defences. For
instance, if a cable is laid from the shore out to sea, with its
170 THIRD PERIOD THE PRACTICAL.
end anchored in a known position, then it would be easy for
any ship, knowing the position of the submerged . end, to
communicate with shore by simply lowering (within one or
two hundred yards of the anchored end) an insulated wire
having the end of its conductor attached to a small mass of
metal to serve as "earth," the circuit being completed
through the hull of the ship and the sea. 1
As this method has been in practical use at the Fastnet
Lighthouse for the last three years, the following account of
the installation, which has been kindly supplied by Mr W.
S. Smith, will be of interest :
" The difficulty of maintaining electrical communication
with outlying rock lighthouses is so great that it has become
necessary to forego the advantages naturally attendant upon
the use of a submarine cable laid in the ordinary way con-
tinuously from the shore to the lighthouse, inasmuch as that
portion of the cable which is carried up from the sea-bed to
the rock is rapidly worn or chafed through by the combined
action of storm and tide. By the use of the Willoughby
Smith & Granville system of communication this difficulty
is avoided, for the end of the cable is not landed on the
rock at all, but terminates in close proximity thereto and
in fairly deep undisturbed water. This system, first sug-
gested in 1887 and practically demonstrated at the Needles
Lighthouse in 1892, has on the recommendation of the
Royal Commission on Lighthouse and Lightship Communi-
cation been applied to the Fastnet, one of the most
exposed and inaccessible rock lighthouses of the United
Kingdom.
" The Fastnet Rock, situated off the extreme S. W. corner
of Ireland, is 80 feet in height and 360 feet in length, with
a maximum width of 150 feet, and is by this system placed
1 ' Electrician, ' September 29, 1893. See also the ' Times,' Novem-
ber 24, 1892.
WILLOUGHBY SMITH'S METHOD. 171
in electrical communication with the town of Crookhaven,
eight miles distant.
" The shore end of the main cable, which is of ordinary
construction, is landed at a small bay called Galley Cove,
about one mile to the west of the Crookhaven Post Office,
to which it is connected by means of a subterranean cable
of similar construction having a copper conductor weighing
107 Ib. covered with 150 Ib. of gutta-percha per nautical
mile. The distant or sea end of the main cable terminates
seven miles from shore, in 1 1 fathoms of water, at a spot
about 100 feet from the Fastnet Rock ; and the end is
securely fastened to a copper mushroom-shaped anchor
weighing about 5 cwt., which has the double duty of serving
electrically as an ' earth ' for the conductor, and mechanically
as a secure anchor for the cable end.
"The iron sheathing of the last 100 feet of the main
cable is dispensed with, so as to prevent the possibility of
any electrical disturbance being caused by the iron coming
in contact with the copper of the mushroom ; and, as a sub-
stitute, the conductor has been thickly covered with india-
rubber, then sheathed with large copper wires, and again
covered with india-rubber the whole being further protected
by massive rings of toughened glass.
"To complete the main cable circuit, a short earth line,
about 200 yards in length, is laid from the post office into
the haven.
"By reference to the diagram (fig. 30) it will be seen
that if a battery be placed at the post office, or anywhere in
the main cable circuit, the sea becomes electrically charged
the charge being at a maximum in the immediate vicinity
of the mushroom, and also at the haven ' earth.' Under
these conditions, if one end of a second circuit is inserted
in the water anywhere near the submerged mushroom for
instance, on the north side of the Fastnet it partakes,
172
THIRD PERIOD THE PRACTICAL.
more or less, of the charge ; and if the other end of this
second circuit is also connected to the water, but at a point
more remote from the mushroom for instance, at the south
side of the Fastnet then a current will flow in the second
circuit, due to the difference in the degree of charge at the
two ends ; and accordingly a galvanometer or other sensitive
Fig. 30.
instrument placed in the Fastnet circuit is affected whenever
the post office battery is inserted in the main cable circuit,
or, vice versa, a battery placed in the Fastnet circuit will
affect a galvanometer at the post office.
" In practice ten large-size Leclanche cells are used on
the rock, the sending current being about 1*5 amperes, and
WILLOUGHBY SMITH'S METHOD. 173
in this case the current received on shore is equal to about
15 of a milliampere. The received current being small,
instruments of a fair degree of sensitiveness are required,
and such instruments, when used in connection with cables
having both ends direct to earth, are liable to be adversely
affected by what are known as * earth ' and ' polarisation '
currents, consequently special means have been devised to
prevent this.
" The receiving instrument is a D'Arsonval reflecting
galvanometer, which has been modified to meet the require-
ments by mounting the apparatus on a vertical pivot, so
that by means of a handle the galvanometer can be rotated
through a portion of a circle thus enabling the zero of the
instrument to be rapidly corrected. This facility of adjust-
ment is necessary on account of the varying 'earth' and
' polarisation ' currents above mentioned.
" An entirely novel and substantial ' call ' apparatus has
also been designed, which automatically adapts itself to any
variation in the earth or polarisation current. It consists
essentially of two coils moving in a magnetic field, and
these coils are mounted one at each end of a balanced arm
suspended at its centre and free to rotate horizontally within
fixed limits. The normal position of the arm is midway
between two fixed limiting stops. Any current circulating
in the coils causes the whole suspended system to rotate
until the arm is brought into contact with one or other of
the stops the direction of rotation depending upon the
direction of the current. A local circuit is thus closed,
which releases a clockwork train connected to a torsion
head carrying the suspending wire, and thus a counter-
balancing twist or torsion is put into the wire, and this
torsion slowly increases until the arm leaves the stop and
again assumes its free position. If, however, the current
is reversed within a period of say five or ten seconds, then
174 THIRD PERIOD THE PRACTICAL.
the clockwork closes a second circuit and the electric bell is
operated. By this arrangement, whilst the relay automatic-
ally adjusts itself for all variations of current, the call-bell
will only respond to definite reversals of small period and
not to the more sluggish movements of earth-currents. It
is evident that one or more bells can be placed in any part
of the building. The receiving galvanometer and the * call '
relay have worked very satisfactorily, and any man of aver-
age intelligence can readily be taught in two or three weeks
to work the whole system.
" To enable the two short cables that connect the light-
house instruments with the water to successfully withstand
the heavy seas that at times sweep entirely over the Fastnet,
it has been found necessary to cut a deep ' chase ' or groove
down the north and south faces of the rock from summit to
near the water's edge, and to bed the cables therein by
means of Portland cement. And since the conductors must
make connection with the water at all states of sea and tide,
two slanting holes 2J inches in diameter have been drilled
through the solid rock from a little above low-water mark
to over 20 feet below. Stout copper rods connected with
the short cables are fitted into these holes, and serve to
maintain connection with the water even in the roughest
weather, and yet are absolutely protected from damage."
Mr Granville supplies some interesting particulars as to
the difficulties of their installation at the Fastnet. 1 " The
rock," he says, "is always surrounded with a belt of foam,
and no landing can be made except by means of a jib 58
feet long not at all a pleasant proceeding. Now, here is a
case where the Government desired to effect communication
telegraphically, but, as had been proved by very costly ex-
periments, it was impossible to maintain a continuous cable,
the cable being repeatedly broken in the immediate vicinity
1 Jour. Inst. Elec, Engs., Ko 137, p. 941.
WILLOUGHBY SMITH'S METHOD. 175
of the rock. This, therefore, is a case where some system
of wireless telegraphy is absolutely necessary, but neither of
the systems described would answer here. 1 Dr Lodge advises
us to eschew iron, and to avoid all conducting masses. But
the tower and all the buildings are built of boiler-plate, and
that which is not of iron is of bronze. In fact, the rock
itself is the only bit of non-conducting, and therefore non-
absorbing, substance for miles around. It is very clear in a
case of this sort and this is a typical case that it is abso-
lutely impracticable to employ here Dr Lodge's method.
Now we hear in regard to the method used and success-
fully used at Lavernock, that a certain base is required, of
perhaps half a mile, a quarter of a mile, or a mile in length ;
and that base must bear some proportion to the distance to
be bridged. But where can you get any such base on the
rock 1 You could barely get a -base of 20 yards, so that
method utterly fails. Then we come to the case suggested
by Mr Evershed, of a coil which would be submerged round
the rock. Well, where Would the coil be after the first
summer's breeze, let alone after a winter gale ? Why, prob-
ably thrown up, entangled, on the rock. A few years ago,
during a severe gale, the glass of the lantern, 150 feet above
sea-level, was smashed in ; and at the top of the rock, 80
feet above the sea-level, the men dare not, during a winter's
gale, leave the shelter of the hut for a moment, for, as they
said and I can well believe it they would be swept off
like flies. This is a practical point, and therefore one I am
glad to bring to the notice of the Institution ; and, I repeat,
if wireless telegraphy is to be of use, it must be of use for
these exceptional cases."
Strange as it may seem, we have been using, on occasion,
wireless telegraphy of this form for very many years without
1 I.e., those advocated by Professor Lodge and Mr Sydney Ever-
shed. See 'Jour. Inst. Elec. Engs.,' No. 137, pp. 799, 852.
176 THIRD PERIOD THE PRACTICAL.
recognising the fact. Every time in ordinary telegraphy
that we " work through a break," as telegraphists say, we
are doing it. An early instance of the kind is described in
the old 'Electrician,' January 9 and 23, 1863. Many years
ago, in Persia, the author has often worked with the ordinary
Morse apparatus through breaks where the wire has been
broken in one or more places, with the ends lying many
yards apart on damp ground, or buried in snow-drifts. As
the result of his experiences in such cases the following
departmental order was issued by the Director, Persian
Telegraphs, as far back as November 2, 1881 : "In cases
of total interruption of all wires, it is believed that com-
munication may in most cases be kept up by means of
telephones. Please issue following instructions : Fifteen
minutes after the disappearance of the corresponding station,
join all three wires to one instrument at the commutator.
Disconnect the relay wire from the key of said instrument,
and in its stead connect one side of telephone, other side of
which is put to earth. Now call corresponding station
slowly -by key, listening at telephone for reply after each
call. Should no reply be received, or should signals be too
weak, try each wire separately, and combined with another,
until an arrangement is arrived at which will give the best
signals." The Cardew sounder or buzzer has in recent years
been added, and with very good results. It will thus be
seen that Mr Willoughby Smith's plan is really an old
friend in a new guise. 1
1 In 1896 Mr A. C. Brown, of whose work in wireless telegraphy we
have already spoken (p. 104, ante), revived the early proposals of
Gauss (p. 3), Lindsay (p. 20), Highton (p, 40), and Bering (p. 48),
re the use of bare wire or badly insulated cables in connection with
interrupters and telephones. He also applies his method to cases
where the continuity of the cable is broken. "Providing the ends
remain anywhere in proximity under the water, communication can
usually be kept up, the telephone receivers used in this way being so
G. MAKCONI'S METHOD. 177
G. MARCONI'S METHOD.
" Even the lightning-elf, who rives the oak
And barbs the tempest, shall bow to that yoke,
And be its messenger to run."
Supples Dampier's Dream.
We now come to the crowning work of Mr Marconi in
wireless telegraphy ; but before describing this method it
will be desirable to make ourselves acquainted with the
principles involved in the special apparatus which he em-
ploys, and which differentiates his system from all those
that have hitherto occupied us. For this we need only go
back a few years, and make a rapid survey of the epoch-
marking discoveries of a young German philosopher, Hein-
rich Hertz. 1
To properly appreciate the work of Hertz we must carry
our minds back two hundred years, to the time when New-
ton made known to the world the law of universal gravita-
tion. Here, in the struggle between jSTewtonianism.and the
dying Cartesian doctrine, we have the battle-royal between
the rival theories of action-at-a-distance and action-by-contact.
The victory was to the former for a time ; and in the hands
exceedingly sensitive that they will respond to the very minute traces
of current picked up by the broken end on the receiving side from
that which is spreading out through the water in all directions from
the broken end on the sending side." (See Mr Brown's patent specifi-
cation, No. 30,123, of December 31, 1896.)
Eecently he has been successful in bridging over in this way a gap
in one of the Atlantic cables ; but in this he has done nothing more
than the present writer did in 1881, and Mr Willoughby Smith in
1887.
1 Hertz was born in Hamburg. February 22, 1857, and died in
Bonn, January 1, 1894. For interesting notices of his all too brief
life, see, inter alia, the 'Electrician,' vol. xxxiii. pp. 272, 299, 332,
and 415.
178 THIRD PERIOD THE PRACTICAL.
of Bernoulli!, and, subsequently, of Boscovich, the doctrines
of Newtonianism were carried far beyond the doctrines of
the individual Newton. In fact, Newton expressed himself
as being opposed to the notion of matter acting where it is
not; though, as we see by his support of the emission
theory of light, he was not prepared to accept the notion
of a luminiferous ether. Newton, however, suggested that
gravitation might be explained as being due to a diminution
of pressure in a fluid filling space. Thus the doctrine of
an empty space, requiring the infinitely rapid propagation
of a distance-action, held the field, and was recognised by
scientists of the eighteenth century as the only plausible
hypothesis.
History repeats itself ; and again the battle-royal was
fought, this time, early in the nineteenth century, in favour
of the ether hypothesis ; and action-at-a-distance was mort-
ally wounded. Before the phenomena of interference of
light and the magnetic and electro-static researches of Fara-
day, both the idea of empty space action and that of the
emission of light failed ; and the propagation of force
through the ether, and of light by vibratory conditions of
the ether, came to be held as necessary doctrines. Later
still, 1 Maxwell assumed the existence of, and investigated
the state of, stress in a medium through which electro-
magnetic action is propagated. The mathematical theory
which he deduced gives a set of equations which are identi-
cal in form with the equations of motion of an infinite elastic
solid ; and, on this theory, the rate of propagation of a
disturbance is equal to the ratio of the electro-magnetic
1 The date usually assigned to Clerk-Maxwell's electro-magnetic
theory of light is 1864 ; but his first communication on the subject
to the Royal Society was in 1867 ; while the full development only
appeared in his great work, ' Electricity and Magnetism,' which was
published in 1873.
G. MARCONI'S METHOD. 179
and electro-static units. The experimental determination
by Maxwell and others, that this ratio is a number equal to
the velocity of light in ether in centimetres per second, is a
fact which gave immense strength to the Maxwellian hypo-
thesis of identity of the light and electro-magnetic media.
But, although this is the case, the Maxwellian hypothesis,
even when taken in conjunction with the experimental
support which he educed for it, fell far short of being a
complete demonstration of the identity of luminous and
electro-magnetic propagation. 1
To the genius of Hertz we owe this demonstration. One
of the most important consequences of Maxwell's theory
was that disturbances of electrical equilibrium produced at
any place must be propagated as waves through space, with
a velocity equal to that of light. If this propagation was
to be traced through the small space inside a laboratory, the
disturbances must be rapid, and if a definite effect was to be
observed, they must follow each other at regular intervals ;
in other words, periodical disturbances or oscillations of
extreme rapidity must be set up, so that the corresponding
wave-length, taking into account the extraordinarily high
velocity of propagation (186,000 miles per second), may be
only a few inches, or at most feet. Hertz was led to an ex-
periment which satisfied these conditions, and thus supplied
the experimental proof which Maxwell and his school knew
must come sooner or later.
The oscillatory nature of the discharge of a Leyden jar,
under certain conditions, was theoretically deduced by Von
Helmholtz in 1847 ; its mathematical demonstration was
given by Lord Kelvin in 1853; and it was experimentally
verified by Feddersen in 1859. When a Leyden jar, or a
condenser, of an inductive capacity K, is discharged through
a circuit of resistance K and self-induction L, the result is an
1 Lord Kelvin's Address, Royal Society, November 30, 1893.
180 THIRD PERIOD THE PRACTICAL.
instantaneous flow, or a series of oscillations, according as R
is greater, or less, than 2 /= ; and in the latter case the
oscillatory period or amplitude is given in the equation
where TT is the constant 3-1415 ('Phil. Trans.,' June 1853). 1
In his collected papers 2 Hertz tells us that his interest in
the study of electrical oscillations was originally awakened
by the announcement of the Berlin prize of 1879, which
was to be awarded for an experimental proof of a relation
between electro-dynamic forces and dielectric polarisation in
insulators. At the suggestion of his master and friend,
Von Helmholtz, the young philosopher took up the inquiry,
but soon discovered that the then known oscillations were too
slow to offer any promise of success, and he gave up the
immediate research ; but from that time he was always on
the look-out for phenomena in any way connected with the
subject. Consequently, he immediately recognised the im-
portance of a casual observation which in itself and at
another time might have been considered as too trivial for
further notice. In the collection of physical apparatus at
Karlsruhe he found an old pair of so-called Riess's or
Knochenhauer's spirals short flat coils of insulated wire,
with the turns all in the same plane (IProf. Henry's
spirals). While performing some experiments with them at
a lecture he was giving, he noticed that the discharge of a
very small Leyden jar, or of a small induction coil, passed
through the one was able to excite induced currents in the
1 For a concise exposition of the theory of electrical oscillations,
see Prof. Edser's paper, 'Electrical Engineer,' June 3, 1898, and fol-
lowing numbers.
2 'Electric Waves,' London, 1893. For an interesting account of
pre-Hertzian observations, see Lodge's 'The Work of Hertz,' p. 61.
Also Appendix D. of this work.
G. MARCONI'S METHOD. 181
other, provided that a small spark-gap was made in the
circuit of the first spiral. Thus was made the all-important
discovery of the " effective spark-gap " which started Hertz
on the road of his marvellous investigations.
A very little consideration of this phenomenon enabled
him, even at this early stage, to lay down the following
propositions :
1. If we allow a condenser, such as a Leyden jar, of
small capacity, to discharge through a short and simple
circuit with a spark-gap of suitable length, we obtain a
sharply denned discharge of very short duration, which is
the long-sought-for sudden disturbance of electrical equili-
brium the exciter of electrical vibrations.
2. Such vibrations are capable of exciting in another
circuit of like form resonance effects of such intensity as to
be evident even when the two circuits are separated by
considerable distances. In this second circuit Hertz had
found the long-sought-for detector of electric waves.
With the exciter to originate electric waves and the
detector to make them evident at a distance, all the pheno-
Fig. 31.
mena of light were, one after another, reproduced in cor-
responding electro-magnetic effects, and the identity of light
and electricity was completely demonstrated. 1
In his paper " On very Eapid Electric Oscillations," Hertz
1 See Appendix A for a clear exposition of the views regarding the
relation of the two before and after Hertz.
182 THIRD PERIOD THE PRACTICAL.
occupied himself with some of these phenomena. As an
exciter he used wire rectangles, or simple rods (fig. 31) to
the ends of which metallic cylinders or spheres were con-
nected, the continuity being broken in the middle where
the ends were provided with small spherical knobs between
which the sparks passed. The exciter was charged by an
ordinary Euhmkorff induction coil of small size.
The detector was mostly a simple rectangle or circle of
wire (fig. 32), also provided with a spark-gap. When
vibrations are set up in the detector
and sparks pass across the gap, the
greater length of these sparks in-
dicates the greater intensity of the
received wave impacts. When, there-
fore, the dimensions of the detector
are so adjusted as to give the maximum
sparks with a given exciter the two
circuits are said to be in resonance, or to be electrically
tuned. 1
In the course of his experiments on electric resonance,
Hertz observed a phenomenon which for a time was inex-
plicable. It was seen that the length and brightness of the
sparks at the detector were greatly modified by the sparks
given off at the exciter. If the latter were visible from the
detector spark-gap the sparks given off there were small and
hardly perceptible, but became larger and brighter as soon
1 Fortunately this condition of resonance or syntony is not essential
to the excitement of sparks, else wireless telegraphy by Hertzian waves
would not be so advanced as it is to-day. Thus, when a good exciter
is in action it will cause little sparks between any conducting body in
its vicinity and a wire held in the hand and brought near to the body,
showing that the influence of the exciter extends to all conducting
bodies, and not merely to those which are tuned to it. Of course it
still holds good that, cceteris parilus, the maximum effect is obtained
with resonance.
G. MARCONI'S METHOD. 183
as a screen was placed between the two instruments. By
carefully thought-out experiments he showed that this
singular action was due solely to the presence of ultra-violet
light, thus furnishing a proof of the connection between
light and electricity. 1
Having made himself familiar with the phenomena of
electrical resonance, Hertz went on to study the propagation
of electric vibrations through space the most difficult, as
it is probably the most important, of all his researches.
The results he gave to the world in 1888, in his paper
" On the Action of a Eectilinear Electric Oscillation on a
Neighbouring Circuit." When sparks pass rapidly at the
exciter electric surgings occur, and we have a rectilinear
oscillation which radiates out into surrounding space. The
detectors, whose spark-gaps were adjustable by means of a
micrometer screw, were brought into all kinds of positions
with respect to the exciter, and the effects were studied and
measured. These effects were very different at different
points and in the different positions of the detector. In
short, they were found to obey a law of radiation which was
none other than the corresponding law in optics.
In his paper, " On the Velocity of Propagation of Electro-
dynamic Actions," he gave experimental proof of the hitherto
theoretical fact that the velocity of electric waves in air was
the same as that of light, whereas the velocity in wires
was found to be much smaller in the ratio of 4 to 7. For
the moment he was puzzled by this result : he suspected an
error in the calculations, or in the conditions of the experi-
ment, but and here he showed himself the true philosopher
he did not hesitate to publish the actual results, trusting
1 Prof. K. Zickler has recently proposed to use this property for
telegraphy. He has succeeded on a small scale, and thinks that with
a 25-ampere lamp and suitable reflectors the effect would be possible
over several kilometres. 'Elektrische Zeitung,' July 1898.
184 THIRD PERIOD THE PRACTICAL.
to the future to correct or explain the discrepancy. The
explanation was soon forthcoming. Messrs E. Sarasin and
L. de la Rive of Geneva took up the puzzle, and ended by
showing that the deviations from theory were caused simply
by the walls of Hertz's laboratory, which reflected the
electric waves impinging on them, so causing interferences
in the observations. When these investigators repeated
the Hertzian experiment with larger apparatus, and on a
larger scale, as they were able to do in the large turbine
hall of the Geneva Waterworks, they found the rate of prop-
agation to be the same along wires as in air. 1
In his paper, " On Electro-dynamic Waves and their Re-
flection," Hertz further developed this point, and showed the
existence of these waves in free space. Opposite the exciter
a large screen of zinc plate, 8 feet square, was suspended on
the wall ; the electric waves emitted from the exciter were
reflected from the plate, and on meeting the direct waves
interference phenomena were produced, consisting of sta-
tionary waves with nodes and loops. When, therefore,
Hertz moved the circle of wire which served as a detector
to and fro between the screen and the exciter, the sparks in
the detector circuit disappeared at certain points, reappeared
at other points, disappeared again, and so on. Thus there
was found a periodically alternating effect corresponding to
nodes and loops of electric radiation, showing clearly that in
this case also the radiation was of an undulatory character,
and the velocity of its propagation finite.
In a paper, " On the Propagation of Electric Waves along
Wires," March 1889, Hertz shows that alternating currents
or oscillations of very high frequencies, as one hundred
million per second, are confined to the surface of the con-
ductor along which they are propagated, and do not penetrate
1 ' Comptes Rendus,' March 31, 1891, and December 26, 1892. See
also the 'Electrician,' vol. xxvi. p. 701, and vol. xxx. p. 270.
G. MARCONI'S METHOD. 185
the mass. 1 This is a very important experimental proof of
Poynting's theory concerning electric currents, which he had
deduced from the work of Faraday and Maxwell. Accord-
ing to this theory, the electric force which we call the
current is in nowise produced in the wire, but under all
circumstances enters from without, and spreads itself in the
metal comparatively slowly, and according to similar laws as
govern changes of temperature in a conductor of heat. If
the electric force outside the wire is very rapidly altering
in direction or oscillating, the effect will only enter to a
small depth in the wire ; the slower the alterations occur,
the deeper will the effect penetrate, until finally, when the
changes follow one another infinitely slowly, the electric
effect occupies the whole mass of the wire with uniform
density, giving us the phenomenon of the so-called current.
Reviewing his experiments on this subject, Hertz says :
" A difference will be noticed between the views here put
forward and the usual theory. According to the latter, con-
ductors are represented as those bodies which alone take
part in the propagation of electric disturbances; non-con-
ductors are the bodies which oppose this propagation. Ac-
cording to our view, on the contrary, all transmission of
electrical disturbances is brought about by non-conductors ;
conductors oppose a great resistance to any rapid changes in
this transmission. One might almost be inclined to main-
tain that conductors and non-conductors should, on this
theory, have their names interchanged. However, such a
paradox only arises because one does not specify the kind of
1 It should be stated here that long ago Prof. Henry, the Faraday
of America, held the same views, and proved them, too, by an experi-
ment which is strangely like one of Hertz's, though, of course, he did
not explain them as Hertz does. Henry's views are given clearly in
two letters addressed to Prof. Kedzie of Lansing, Michigan, in 1876.
Being of historical interest, as well as of practical value, I give them
entire in Appendix B.
186 THIRD PERIOD THE PRACTICAL.
conduction or non-conduction considered. Undoubtedly
metals are non-conductors of electric force, and just for this
reason they compel it under certain circumstances to remain
concentrated instead of becoming dissipated ; and thus they
become conductors of the apparent source of these forces,
electricity, to which the usual terminology has reference." l
In the course of his experiments Hertz had succeeded in
producing very short electric waves of 30 centimetres in
length, the oscillations corresponding to which could be
collected by a concave cylindrical mirror and concentrated
into a single beam of electric radiation. According to
Maxwell's theory of light, such a beam must behave like
a beam of light, and that this is the case Hertz abundantly
proved in his next paper, " On Electric Eadiation." He
showed how such radiation was propagated in straight lines
like light ; that it could not pass through metals, but was
reflected by them ; that, on the other hand, it was able to
penetrate wooden doors and stone walls. He also proved,
by setting up metallic screens, that a space existed behind
them in which no electric action could be detected, thus
producing electric shadows ; and, by passing the electric
rays through a wire grating, he was able to polarise them,
just as light is polarised by passage through a Nicol prism.
Perhaps the most striking experiment of all in this field was
his last one, in which he directed the ray on to a large pitch
prism weighing 12 cwts. : the ray was deflected, being, in
fact, refracted like a ray of light in a glass prism.
1 As this is a matter of some complexity to all who, like myself,
belong to the old way of thinking the ancien regime and as, more-
over, it is of great practical importance, especially as regards the
proper construction of lightning protectors, and the supply mains of
electric light and power, I have thought it useful to give in Appendix
B some extracts, which I hope will make the new views intelligible to
the ordinary reader. Lodge's ' Modern Views of Electricity ' should
also be consulted.
G. MARCONI'S METHOD. 187
Thus he gave to the experimental demonstration of Max-
well's electro-magnetic theory of light its finishing touch,
and the edifice was now complete. Hertz's marvellous
researches were presented in succession, as rapid and sur-
prising almost as the sparks with which he dealt, to the
Berlin Academy of Sciences, between November 10, 1887,
and December 13, 1889. They were collected and pub-
lished in book form, in 1893, under the title of 'Electric
Waves ' (English translation edited by Prof. D. E. Jones),
to which the reader is jeferred for further information.
Here it will suffice, in conclusion, to briefly sum up the
chief results of these epoch-making investigations. In the
first place, Hertz has freed us from the bondage of the old
theory of action-at-a-distance ; and as regards electric and
magnetic effects, he has shown that they are propagated
through the ether which fills all space with finite velocity.
The mysterious darkness which surrounded those strange
distance-actions that something can act where it is not
has now been cleared away. Further, the identity of the
form of energy in the case of two powerful agents in nature
has been conclusively established ; light and electrical radia-
tion are essentially the same, different manifestations of the
same processes, and so the old elastic-solid theory of optics
is resolved into an electro-magnetic theory. The velocity of
propagation of light is the same as that of electro-magnetic
waves, and these in turn obey all the laws of optics. The
scope of optics is thus enormously widened ; to the ultra-
violet, visible, and infra-red rays, with their wave-lengths
of thousandths of a millimetre, are now to be added, lower
down the scale, electro-magnetic waves, producible in any
length from fractions of an inch to thousands of miles.
Hertz's ordinary waves were many metres long, and he
does not appear to have ever worked with waves of less
than 30 centimetres. Righi, however, by employing ex-
188 THIRD PERIOD THE PRACTICAL.
citers with small spheres, obtained waves of 2 '5 centimetres;
while Prof. Chunder Boze of Calcutta, using little pellets of
platinum, was able to produce them of only 6 millimetres !
The smaller the pellets the shorter the electric waves, until
we come in imagination to the pellet of the ultimate atom,
whose waves should closely approximate to light.
The following table compares approximately some of the
known vibrations in ether and air :
Ether vibrations per second
billions (?) = Rontgen rays.
10,000 (?) = Actinic
8,000 it = Violet ,,
5,500 M = Green ..
4,000 u = Red
2,800 n = Infrared
1,000 to 2,000 = Radiant heat.
50 thousands to 2,000 billions = Hertzian waves.
Air vibrations per second
33,000 = Highest audible note.
4,000 = Highest musical note.
2,000 = Highest soprano.
150 to 500 = Ordinary voice.
32 = Lowest musical note.
16 = n audible u
In another direction we owe much to Hertz's investiga-
tions ; we are brought nearer to a solution of the question,
What is electricity 1 He shows us that it is not an entity
of the nature of a fluid as in the older theories ; what we
wished to explain by assuming an electricity is in reality
nothing but a condition of a medium which, although
hypothetical, manifests itself by its effects namely, the
ether which fills all space and permeates all matter. 1
1 Our account of Hertz's investigations is chiefly drawn from Prof.
Ebert's paper in the 'Electrician,' vol. xxxiii. pp. 333-335.
G. MAKCONI'S METHOD. 189
The work of Hertz was immediately taken up, and is now
being carried on (doubtless towards fresh conquests, for
there is no finality in science) by a whole army of investi-
gators, of whom we need only mention a few as Lodge,
Eighi, Branly, Sarasin, and de la Rive whose discoveries,
especially as regards the exciter and detector, more imme-
diately concern us in this history.
The exciter of Hertz, although sufficing for his special
purposes, had the disadvantage that the sparks in a short
time oxidised the little knobs and roughened their surfaces,
which made their action irregular and necessitated their
frequent polishing. Messrs Sarasin & de la Rive of Geneva
obviated this difficulty by placing the knobs in a vessel con-
taining olive-oil. The effect of this arrangement was at
once to augment the sparks at the detector, so that when it
was placed close to the exciter the sparks were a perfect
blaze ; and at 10 metres' distance, with detectors of large
diameter ('75 to 1 metre), they were still very bright and
visible from afar. It is true that here, too, the oil carbon-
ises in time and loses its transparency ; but if a considerable
quantity, as two or three litres, be employed, there is no
perceptible heating, and the intensity of the sparks is hardly
altered, even after half an hour's continuous working. Prof.
Righi substituted vaseline-oil, made suitably thick by the ad-
dition of solid vaseline. His exciter is composed of two metal
balls, each set in an ebonite frame ; a parchment envelope
connects these frames and contains the oil which thus fills
the spark-gap. Righi attributes the increased efficiency of
his exciter (1) to the heightening effect which a cushion of
(insulating) liquid seems to have on the electric potential
which gives rise to the sparks a sort of (to adopt an ex-
pressive French phrase) reculant pour mieux sauter; and
(2) to some sort of regularising effect making their produc-
tion more uniform. Like Sarasin and de la Rive, he found
190 THIRD PERIOD THE PRACTICAL.
that the use of vaseline obviated the necessity of frequent
cleaning of the knobs, for even after long usage, when the
liquid had become black and a deposit of carbon had formed
on the opposing surfaces, the apparatus continued to work
satisfactorily. Kighi also found that solid knobs gave
better results than hollow ones, the oscillations in the former
case being perceptible in the detector at nearly double the
distance attained in the latter case.
The detector usually employed by Hertz consisted of a
metal wire bent into a rectangle or a circle (see fig. 32), and
terminated by two little knobs between which the sparks
played. But this form is not obligatory : any two distinct
conducting surfaces separated by a spark-gap will serve
equally well. Many kinds of detectors have been em-
ployed, but in this place we need only concern ourselves
with those of the microphonic order, which alone enter into
the construction of the Marconi system of telegraphy. 1
Just mentioning the well-known electrical behaviour of
selenium under the action of light; the fact observed by
Prof. Minchin that his delicate "impulsion-cells" were
affected by Hertzian waves ; the Righi detector, consisting
of thin bands of quicksilver (as used for mirrors) rendered
discontinuous by cross-lines lightly traced with a diamond ;
and the original Lodge " coherer," consisting of a metallic
point lightly resting on a metal plate, 2 we come to the
special form known as Branly's detector, or, as he prefers to
call it, the radio-conductor.
1 For other forms of detectors, based on physiological, chemical,
electrical, thermal, and mechanical principles, see Lodge's ' The Work
of Hertz and his Successors,' pp. 25, 56.
2 For the first suggestions of Lodge's detector see his paper, " On
Lightning - Guards for Telegraphic Purposes," 'Jour. Inst. Elec.
Engs.,' vol. xix. pp. 352-354. Even before this the learned professor
succeeded in detecting electric waves by means of a telephone, ' Jour.
Inst. Elec. Engs.,' vol. xviii. p. 405.
G. MARCONI'S METHOD. 191
The observance of the phenomenon manifested in Branly's
detector goes back much further than is usually supposed.
Mr S. A. Varley was, I believe, the first to notice it, and as
long ago as 1866 he applied it in the construction of a
lightning protector for telegraph apparatus.
In his paper read before the British Association (Liverpool
meeting, 1870), he says:
"The author, when experimenting with electric currents of
varying degrees of tension, had observed the very great resist-
ance which a loose mass of dust composed even of conducting
matter will oppose to electric currents of moderate tension.
" With a tension of, say, fifty Daniell cells, no appreciable
quantity will pass across the dust of blacklead or fine char-
coal powder loosely arranged, even when the battery poles
are approached very near to one another.
" If the tension be increased to, say, two or three hundred
cells, the particles arrange themselves by electrical attraction
close to one another, making good electrical contact, and
forming a channel or bridge through which the electric cur-
rent freely passes.
" When the tension was still further increased to six or
seven hundred cells the author found the electricity would
pass from one pole to the other through a considerable in-
terval of the ordinary dust which we get in our rooms, and
which is chiefly composed of minute particles of silica and
alumina mixed with more or less carbonaceous and earthy
matters.
"Incandescent matter offers a very free passage to electrical
discharge, as is indicated by the following experiments. The
author placed masses of powdered blacklead and powdered
wood charcoal in two small crucibles ; no current would pass
through these masses whilst they were cold, however close
the poles were approached, without actually touching. The
battery employed in this experiment was only twelve cells.
192 THIRD PERIOD THE PRACTICAL. .
"The crucibles were then heated to a red heat, and elec-
tricity freely passed through the heated powder ; and on
testing the resistance opposed by the heated particles, placing
the poles 1 inch apart, and employing only six cells, the
average resistance opposed by the blacklead was only four
British Association units, and that opposed by the wood
charcoal five units. The average resistance of a needle
telegraph coil may be taken at 300 units, or ohms as they
are now termed.
" These observations go to show that an interval of dust
separating two metallic conductors opposes practically a de-
creasing resistance to an increasing electrical tension, and
that incandescent particles of carbon oppose about -g^th
part of the resistance opposed by a needle telegraph coil.
Eeasoning upon these data, the author was led to construct
what he terms a 'lightning-bridge,' which he constructs in
the following way :
" Two thick metal conductors terminating in points are
inserted usually in a piece of wood. These points
approach one another within
about -iV^i of an inch in a
chamber cut in the middle of
the wood.
" This bridge is placed in
the electric circuit in the most
direct course which the light-
ning can take, as shown in
the diagram (fig. 33), and the
space separating the two points
33 is filled loosely with powder,
which is placed in the chamber,
and surrounds and covers the extremities of the pointed
conductors.
" The powder employed consists of carbon (a conductor)
G. MARCONI'S METHOD. 193
and a non-conducting substance in a minute state of division.
The lightning finds in its direct path a bridge of powder,
consisting of particles of conducting matter in close proximity
to one another ; it connects these under the influence of the
discharge, and throws the particles into a highly incandescent
state. Incandescent matter, as has been already demon-
strated, offers a very free passage to electricity, and so the
lightning discharge finds an easier passage across the heated
matter than through the coils.
" The reason a powder consisting entirely or chiefly of
conducting matter cannot be safely employed is that,
although in the ordinary conditions of things it would be
found to oppose a practically infinite resistance to the
passage of electricity of the tension of ordinary working
currents, when a high tension discharge occurs the particles
under the influence of the discharge will generally be found
to arrange themselves so closely as to make a conducting
connection between the two points of the lightning-bridge.
This can be experimentally demonstrated by allowing the
secondary currents developed by a Ruhmkorff's coil to spark
through a loose mass of blacklead.
" The crucial test, however, is the behaviour of the bridge
in practice.
" These lightning-bridges have been in use since January
1866. At the present time there are upwards of one
thousand doing duty in this country alone, and not a single
case has occurred of a coil being fused when protected by
them.
" It is only right, however, to mention that three cases,
but three cases only, have occurred where connection was
made under the influence of electrical discharge between
the two metallic points in the bridge.
"The protectors in which this occurred were amongst
those first constructed, in which a larger proportion of con-
N
194 THIRD PERIOD THE PRACTICAL.
ducting matter was employed than the inventor now adopts.
The points also in those first constructed were approached
to -g^th of an inch from one another ; and the author has no
doubt, from an examination of the bridges afterwards, that
under the influence of a high tension discharge connection
was made between the two metallic points by a bridge of
conducting matter, arranged closely together, and if the
instruments had been shaken to loosen the powder, all would
have been put right. In one of these three cases and it
was the only one in which the author was supplied with
the details he ascertained that the protector was attached
to a needle telegraph, having the ordinary magnetic needles
made of tempered steel magnetised ; and on the removal of
the bridge after the discharge, so completely had the elec-
tricity been carried away by the bridge, that the magnet-
ism of the magnetic needle was found* not to. have been
affected." *
In the little-known researches of the Italian professor,
Calzecchi-Onesti, we find this curious phenomenon again
cropping up. In 1884-85 Prof. Calzecchi-Onesti found that
copper filings heaped between two plates of brass were
conductors or non-conductors of electricity according to the
degree of heaping, and that in the latter case they could be
made conductors under the influence of induction. Fig. 34
illustrates his experiment. In the circuit of a small battery
A he placed a telephone B, a galvanometer c, and two brass
plates D E, separated by the copper filings. So long as the
1 Mr Preece tells us the arrangement acted well, but was subject to
what we now call coherence, which rendered the cure more trouble-
some than the disease, and its use had to be abandoned. Mr Preece
also says that the same action is very common in granulated carbon
microphones like Runnings', and shaking has to be resorted to to de-
cohere the carbon particles to their normal state. But here the
coherence is only partially, if at all, an electrical effect, being chiefly,
if not entirely, due to mechanical pressure.
G. MARCONI'S METHOD.
195
short-circuit arrangement F (a wire dipping into mercury) was
open, the galvanometer showed traces of a very feeble current
across the filings ; but, on dipping the wire for a moment
into the mercury and then withdrawing it, a sharp click is
heard in the telephone and the galvanometer indicates the
passing of a strong current, showing that the filings must
now be conductors. This change he traced to the induced
Fig. 34.
current of the telephone coil (the extra-current direct) at the
moment of opening the short-circuit. He repeated this
experiment with various powders or filings of metal, and
ended by showing that some of them became conductors
under the influence of a very feeble spark, while others
became so only after being subjected to strong sparks as
from an electrical machine.
These important observations were published in 'II
Nuovo Cimento,' 1884, p. 58, 1 but attracted no attention ;
and it was only after Prof. E. Branly, of the Catholic Uni-
versity of Paris, had published his results in 1890 that the
earlier discoveries of Yarley and Onesti came to be remem-
bered and appreciated at their proper value.
1 See also 'Jour. Inst. Elec. Engs.,' vol. xvi. p. 156.
196 THIRD PERIOD THE PRACTICAL.
Prof. Branly's investigations are very clearly described in
'La Lumiere Electrique, May and June 1S91.' 1 As this
now classic paper deals with facts which are at the very
foundation of the Marconi system, I give some extracts
from it in Appendix C. Here, therefore, I need only say
that Branly verified and extended Calzecchi-Onesti's obser-
vations, and made the further (and for our purpose vital)
discovery that the conducting power, imparted to filings by
electric discharges in their vicinity, can at once be destroyed
by simply shaking or tapping them.
The Branly detector, as constructed by Prof. Lodge, is
shown in fig. 35. It consists of an ebonite or glass tube
Fig. 35.
about 7 inches long, half-an-inch outer diameter, and fitted
at the ends with copper pistons, which can be regulated to
press on the filings with any required degree of pressure.
To bring back the filings to their normal non-conducting
state, Lodge applied to the tube a mechanical tapper, worked
either by clockwork or by a trembling electrical mechanism. 2
These, then, the exciters and the detectors of Hertzian
waves, are the bricks and mortar, so to speak, of the Marconi
system, and it now only remains to see how they have been
shaped and put together to produce a telegraph without
connecting wires, which is the realisation of the dream of
1 See also an abstract in the ' Electrician,' vol. xxvii. pp. 221, 448.
2 Dr Rupp of Stuttgard has proposed to suppress the tapper and to
effect decoherence by making the detector revolve on its axis. See
' Elektrotechnische Zeitschrift,' April 14, 1898, or ' Electrical Review,'
April 22, 1898.
G. MARCONI'S METHOD. 197
Steinheil in 1838. And, first, we must notice two or three
applications, or suggested applications, which preceded the
announcement of Marconi's invention. We do so without
in the least meaning to detract one iota from the merit due
to the young Irish-Italian inventor, 1 for we believe the idea
was entirely original with him, and was unprompted by any
suggestions from outside. The history of the applications
of science to art shows us that these applications often occur
simultaneously to several persons, and it is, therefore, not
strange that such is the case in the present instance.
Sir William Crookes, the eminent chemist and elec-
trician, was, I believe, the first to distinctly foresee the
applicability of Hertzian waves to practical telegraphy. In
a very interesting paper on "Some Possibilities of Elec-
tricity," 2 he gives us the following marvellous forecast of
the Marconi system:
" Rays of light will not pierce through a wall, nor, as we
know only too well, through a London fog; but electrical
vibrations of a yard or more in wave-length will easily
pierce such media, which to them will be transparent. Here
is revealed the bewildering possibility of telegraphy without
wires, posts, cables, or any of our present costly appliances.
Granted a few reasonable postulates, the whole thing comes
well within the realms of possible fulfilment. At present
experimentalists are able to generate electric waves of any
desired length, and to keep up a succession of such waves
radiating into space in all directions. It is possible, too,
1 Guglielmo Marconi was born in Marzabotto, near Bologna, 25th
April 1874, and was educated at Leghorn, and at the Bologna Uni-
versity, where he was a sedulous attendant at the lectures of Prof. A.
Righi.
2 Fortnightly Review, February 1892, p. 173. Prof. Lodge has since
kindly pointed out to me that about 1890 Prof. R. Threlfall of Sydney,
N.S. Wales, threw out a suggestion of the same kind at a meeting of
the Australasian Association for the Advancement of Science.
198 THIRD PERIOD THE PRACTICAL.
with some of these rays, if not with all, to refract them
through suitably shaped bodies acting as lenses, and so to
direct a sheaf of rays in any given direction. Also an ex-
perimentalist at a distance can receive some, if not all, of
these rays on a properly constituted instrument, and by con-
certed signals messages in the Morse code can thus pass
from one operator to another.
" What remains to be discovered is firstly, simpler and
more certain means of generating electrical rays of any
desired wave-length, from the shortest, say a few feet, which
will easily pass through buildings and fogs, to those long
waves whose lengths are measured by tens, hundreds, and
thousands of miles ; secondly, more delicate receivers which
will respond to wave-lengths between certain defined limits
and be silent to all others ; and thirdly, means of darting
the sheaf of rays in any desired direction, whether by lenses
or reflectors, by the help of which the sensitiveness of the
receiver (apparently the most difficult of the problems to be
solved) would not need to be so delicate as when the rays
to be picked up are simply radiating into space, and fading
away according to the law of inverse squares. . . .
"At first sight an objection to this plan would be its
want of secrecy. Assuming that the correspondents were a
mile apart, the transmitter would send out the waves in all
directions, and it would therefore be possible for any one
living within a mile of the sender to receive the communica-
tion. This could be got over in two ways. If the exact
position of both sending and receiving instruments were
known, the rays could be concentrated with more or less
exactness on the receiver. If, however, the sender and
receiver were moving about, so that the lens device could
not be adopted, the correspondents must attune their instru-
ments to a definite wave-length, say, for example, 50 yards.
I assume here that the progress of discovery would give
G. MARCONI'S METHOD. 199
instruments capable of adjustment by turning a screw, or
altering the length of a wire, so as to become receptive of
waves of any preconcerted length. Thus, when adjusted to
50-yard waves, the transmitter might emit, and the receiver
respond to, rays varying between 45 and 55 yards, and be
silent to all others. Considering that there would be the
whole range of waves to choose from, varying from a few
feet to several thousand miles, there would be sufficient
secrecy, for the most inveterate curiosity would surely recoil
from the task of passing in review all the millions of pos-
sible wave-lengths on the remote chance of ultimately hitting
on the particular wave-length employed by those whose
correspondence it was wished to tap. By coding the
message even this remote chance of surreptitious tapping
could be rendered useless.
" This is no mere dream of a visionary philosopher. All
the requisites needed to bring it within the grasp of daily
life are well within the possibilities of discovery, and are so
reasonable and so clearly in the path of researches which
are now being actively prosecuted in every capital of Europe,
that we may any day expect to hear that they have emerged
from the realms of speculation into those of sober fact.
Even now, indeed, telegraphing without wires is possible
within a restricted radius of a few hundred yards, and some
years ago I assisted at experiments where messages were
transmitted from one part of a house to another without an
intervening wire by almost the identical means here de-
scribed." 1
In 1893 Nikola Tesla, the lightning-juggler, proposed to
1 The experiments here referred to were made in 1879 by Prof.
Hughes, who has kindly supplied the author with an account of
them. As this interesting and important document was received
too late for embodiment in the text, I must ask my readers to
refer to Appendix D.
200 THIRD PERIOD THE PRACTICAL.
transmit electrical oscillations to any distance through space,
by erecting at each end a vertical conductor, connected at
its lower end to earth and at its upper end to a conducting
body of large surface. Owing to press of other work this
experiment was never tried, and so has remained a bare
suggestion. 1
At the Eoyal Institution, June 1, 1894, and later in the
same year at the Oxford meeting of the British Association,
Prof. Lodge showed how his form of Branly detector could
be made to indicate signals at a distance of about 150 yards
from the exciter, but at this time the applicability of his
experiment to practical long-distance telegraphy was hardly
grasped by him. Referring to this in his * Work of Hertz '
(p. 67, 1897 edition), he says :
" Signalling was easily carried on from a distance through
walls and other obstacles, an emitter being outside and a
galvanometer and detector inside the room. Distance with-
out obstacle was no difficulty, only free distance is not very
easy to get in a town, and stupidly enough no attempt was
made to apply any but the feeblest power so as to test how
far the disturbance could really be detected.
"Mr Rutherford, however, with a magnetic detector of
his own invention, constructed on a totally different prin-
ciple, and probably much less sensitive than a coherer, did
make the attempt (June 1896), and succeeded in signalling
across half a mile full of intervening streets and houses at
Cambridge."
Between 1895 and 1896 Messrs Popoff, Minchin,
Rutherford, and others applied the Hertzian method to
the study of atmospheric electricity ; and their mode of
procedure, in the use of detectors in connection with vertical
exploring rods, was much the same as that of Marconi.
1 See a full account of Tesla's marvellous researches in ' Jour.
Inst. Elec. Engs.' for 1892, No. 97, p. 51.
G. MARCONIS METHOD.
201
Popoff s arrangement especially is so like Marconi's that
we are tempted to reproduce it from the ' Elektritchestvo '
of St Petersburg for July 1896. Fig. 36 shows the
apparatus, the action of which is easily understood. The
LARTH
Pile
Relay
Fig. 36.
relay actuates another circuit, not showu, containing a
Richard's register, which plots graphically the atmospheric
perturbations.
Prof. PopofFs plans were communicated to the Physico-
Chemical Society of St Petersburg in April 1895 ; and in a
further note, dated December 1895, he adds : " I entertain
the hope that when my apparatus is perfected it will be
applicable to the transmission of signals to a distance by
means of rapid electric vibrations when, in fact, a suffi-
ciently powerful generator of these vibrations is discovered."
We shall see presently that Popoff was looking in the wrong
direction. It was not so much a more powerful generator
202 THIRD PERIOD THE PRACTICAL.
(which is easily obtained) that was wanted, as a more
sensitive detector than the ordinary Branly-Lodge arrange-
ment which he used. Mr Marconi, we shall see, supplied
this, and in doing so did the main thing necessary to make
PopofFs apparatus a practical telegraph. 1
Mr Preece tells us that in December 1895 Captain
Jackson, K.N., commenced working in the same direction,
and succeeded in getting Morse signals through space before
he heard of Marconi. His experiments, however, were
treated as confidential at the time, and have not been
published.
In 1896 the Eev. F. Jervis-Smith had a detector made
of finely-powdered carbon, such as is used in incandescent
electric lamps, for observing atmospheric electricity ; and a
little later (? after Marconi's announcement) he actually
applied it to telegraphic purposes over a distance of more
than a mile. This form of detector was to a certain extent
self-adjusting in that it did not require any tapping
device. 2
I now come to Mr Marconi, whose special application of
Hertzian waves to practical telegraphy will be easily under-
stood if my readers have carefully followed me in the
preceding pages.
His apparatus for short distances, with clear open
Spaces, consists of the parts which are shown in diagram-
matic form in figs. 37, 38, 39, and 40. The apparatus at
the sending station consists of a modified Eighi exciter A
1 On hearing of Marconi's success in England, Prof. Popoff tried his
apparatus quasi telegraph (presumably using more sensitive detectors),
and in April 1897 succeeded in signalling through a space of 1 kilo-
metre, then through 1, and finally through 5 kilometres, with vertical
wires, 18 metres high.
2 Quite recently, October 1898, I have seen it stated that Signer
Rovelli has found that a detector made of iron filings acts well, and
requires no tapping.
G. MARCONI'S METHOD.
203
(fig. 37), a Euhmkorff coil B, a battery of a few cells c,
and a Morse key K.
The exciter consists of two solid brass spheres A B (fig. 38),
11 centimetres in diameter and 1 millimetre apart, yielding
with a 6 -inch spark coil
waves of about 25 centi-
metres long. The spheres
are fixed in an oil -tight
case of parchment or
ebonite, so that an out-
side hemisphere of each
is exposed, the other hemi-
spheres being immersed
in vaseline -oil thickened
by the addition of a little
vaseline. As already ex- Fig 37
plained, the use of oil
has several advantages, all of which combine to increase
the effect, and therefore the distance at which this effect
c -o[ ?
Fig. 38.
can be detected. It keeps the opposing surfaces of the
spheres clean and bright ; it gives to the electric waves a
uniform and regular (periodic) character ; and it reduces
204 THIRD PERIOD THE PRACTICAL.
the length of these waves to the small limits best adapted
for signalling. 1 Two small balls, also of solid brass, a b,
are fixed in a line with the large ones, usually about 2 '5
centimetres apart, and are capable of adjustment. The
larger the spheres and balls, and the greater the distances
separating them, the higher the potential of the spark, and
consequently the greater the distance at which the oscilla-
tions are perceptible. The balls a b are connected each to
one end of the secondary coil of the Ruhmkorff apparatus B.
The primary wire of the induction coil is excited by the
battery c, thrown in and out of circuit by the key K. The
efficiency of the sending apparatus depends greatly on the
power and constancy of the induction coil : thus a coil yield-
ing a 6-inch spark will be effective up to three or four
miles ; but for greater distances than this more powerful
coils, as one emitting 20-inch sparks, must be used. 2
The various parts of the sending apparatus are generally
so constructed and adjusted as to emit per second about 250
million waves of about 1'2 metres long.
At the receiving station N (fig. 39) is Marconi's special
form of the Branly-Lodge detector, shown full size in fig. 40.
This is the part which gave him the most trouble. While
for laboratory experiments a detector of little delicacy suf-
ficed to give indications on a sensitive mirror galvanometer
at a distance of a few yards, Mr Marconi had to seek an
1 Mr Marconi's later experience has led him to doubt these advan-
tages, and to discard the use of oil. See 'Jour. Inst. Elec. Engs.,'
No. 139, p. 311.
2 But there is a limit ; powerful induction coils of the Ruhmkorff
kind are difficult to make and keep in order, and do not by reason of
their residual magnetism admit of the very rapid make-and -break
action required. Doubtless other and more effective means of excite-
ment will soon be discovered, as Tesla's oscillators, or by the use of
Wehnelt's electrolytic contact-breaker, which can be made to inter-
rupt a current one thousand times and more per second. See 'Jour.
Inst. Elec. Engs.,' No. 131, p. 317.
G. MARCONI'S METHOD.
205
arrangement which would respond sufficiently to the very
feeble waves which are found at a great distance from the
source, so as to allow of the passage of a current strong
A A'_
L s
Fig. 39.
enough to actuate a telegraph relay. His detector consists
of a glass tube, 4 centimetres long and 2 '5 millimetres
interior diameter, into which two silver pole-pieces, 1 milli-
Fig. 40.
metre apart, are tightly fitted, so as to prevent any scattering
of the powder. The small intervening space is filled with a
mixture of 96 parts of nickel and 4 of silver, not too finely
powdered, and worked up with a trace of mercury.
By increasing the proportion of silver powder the sensi-
tiveness of the detector is increased pro rata; but it is
better for ordinary work not to have too great sensitiveness,
as the detector then too readily responds to atmospheric
electricity and other stray currents. Similarly, the smaller
the powder space the more sensitive is the instrument ; but
206 THIRD PERIOD THE PRACTICAL.
if too small, the action is capricious. The quantity of
powder required is, of course, very small, but it must be
treated with care ; it must neither be too compressed nor
too loose. If too tight the action is irregular, and often the
particles will not return to their normal condition, or " deco-
here," as Lodge expresses it ; if too loose coherence is slight,
and the instrument is not sufficiently sensitive. The best
adjustment is obtained when the detector works well under
the action of the sparks from a small electric trembler at
one metre's distance. The tube is then hermetically sealed,
having been previously exhausted of air to about TWo'th
of an atmosphere. This, though not essential, is desirable,
as it prevents the oxidation of the powder.
In its normal condition the metallic powder, as already
stated, is practically a non-conductor, offering many megohms
resistance. The particles (to use Mr Preece's expressive
words) lie higgledy-piggledy, anyhow, in disorder. They
lightly touch each other in a chaotic manner; but when
electric waves fall upon them they are polarised order is
installed they are marshalled in serried ranks and press on
each other, in a word, they cohere, electrical continuity is
established, and a current passes, the resistance falling from
practical insulation to a few ohms or a few hundred ohms
according to the energy of the received impacts. Usually it
ranges from 100 to 500 ohms.
The detector is included in the circuit of two electro-
magnetic impedance or choking coils n n', a local battery of
one or two Leclanche cells p, and a fairly sensitive polarised
relay as ordinarily used in telegraphy R. The impedance or
choking coils, consisting of a few turns of insulated copper
wire on a glass tube, containing an iron bar 5 or 6 centi-
metres long, are intended to prevent the. electric energy
escaping through the relay circuit. Prof. Silvan us Thomp-
son doubts the efficacy of this contrivance, but Mr
G. MARCONI'S METHOD. 207
Marconi's experience shows its great utility. Thus, when
the coils are removed, all other things remaining the same,
the signalling distance is reduced by nearly one-half.
A A' are resonance plates or wings (copper strips) whose
dimensions must be adjusted so as to bring the detector
into tune electrically with the exciter.
The relay actuates two local circuits on the parallel or
shunt system, one containing an ordinary Morse instrument
M, and the other the tapper s. The relay and tapper are
provided with small shunt coils ^ and s 2 to prevent sparking
at the contacts, which would otherwise impair the good
working of the detector. The Morse instrument and the
tapper may also be connected in series in one circuit, in
which case the former may be made to act as a buzzer, the
signals being read by sound. Indeed, the Morse machine
may be left out altogether and the signals be read from the
sound of the tapper alone. The printing lever of the Morse
is so adjusted an easy matter as not to follow the rapid
makes and breaks of the local current caused by the action
of the tapper. Consequently, although the current in the
coils of the Morse is rapidly discontinuous, the lever remains
down (and prints) so long as the detector is influenced by
the waves sent out by the exciter. In this way the lever
gives an exact reproduction of the movements of the distant
sending key, dots and dashes at the key coming out as dots
and dashes in the Morse. The speed at which signalling
can be carried on is but little slower than that in ordinary
(Morse) telegraphy, fifteen words a minute being easily
attained.
In practice, the sending part of the apparatus should be
screened as much as possible by interposed metal plates from
the receiving instruments, so as to prevent local inductive
interferences ; or better, the detector may be shut up in a
metal box.
208
THIRD PERIOD THE PRACTICAL.
* This arrangement is effective for short distances, up to
two miles, with clear open spaces, especially if parabolic
reflectors are erected behind the exciter and detector, and
carefully focussed so as to throw the electric rays in the
right direction. But for long distances, and where obstacles
intervene, as trees, houses, hills in fact, for practical
purposes certain modifications are necessary which are
Fig. 41.
shown in fig. 41. Reflectors are discarded which are
troublesome and expensive to make and difficult to adjust.
One knob of the exciter is connected to a stout insulated
wire, led to the top of a mast and terminating in a square
sheet or a cylinder of zinc, or a pennant-like structure of
wire netting. For still greater distances the wire may
be flown from a kite or balloon 1 covered with tinfoil.
1 In a recent popular lecture it is seriously stated that, when kites
are used to carry the conductors, " the electricity obtained from the
G. MARCONI'S METHOD. 209
The other knob of the exciter is connected to a good
earth.
At the receiving station the resonance wings of the
detector are discarded, and one side is connected to a vertical
wire and the other side to earth, as in the case of the exciter.
Of course, in practice only one vertical wire is required at
each station, as by means of a switch it can be connected
with the exciter for sending, or with the detector for re-
ceiving, as may be necessary. The parallelism of the plates
x and y should be preserved as much as possible in order to
obtain the best effects.
The raison cCetre of the earth connections is not yet
clearly understood. An earth wire on the exciter for lonsj
distances is essential, but at the detector it may apparently
be dispensed with without any (appreciable) effect. 1 Break-
ing the connection does not prove to me that earth does not
enter into the effect. It only increases the resistance of the
earth-connecting medium, which now is not wire, but consists
of the walls, floor, table, and base-board of the instrument.
Again, why suppose that sparks are emitted at the top of
the vertical wire only"? Why not also into the ground,
giving us a complete closed circuit through the ether above
and through the ground below 1 If I may hazard an opinion
I would say that the Marconi effect is but, on a large scale,
an electrical machine effect such as every schoolboy is
air, when they were flown high enough, was sufficient to enable the
operator to do away with a primary battery" ! (' Electrical Engineer,'
October 1, 1897). This is the Mahlon Loomis idea redivivus (see
p. 73 ante), and is as true as another " vulgar error " to wit, that
Marconi, and now Tesla, can explode torpedoes and powder-magazines
at their own sweet will. This, of course, might be done, if they
could plant a properly adjusted exploding apparatus near the powder ;
but if they could do this, they could, as Mr Preece says, do many
other funny things.
1 Jour. Inst, Elec. Engs., No. 137, pp. 801, 802, 900, 918, 946, 962,
210 THIRD PERIOD THE PRACTICAL.
familiar with, and that it conforms to the same laws and
conditions.
However this may be, an earth wire (and a good one too)
should be used on the detector as well as on the exciter, if
only as a protection from lightning. The vertical wire is
practically a lightning - catcher, and the detector is an
excellent lightning-guard when connected to earth. But if
disconnected from earth, and lightning strikes the wire,
then we may expect all the disastrous results which follow
from a badly constructed or defective lightning-protector.
The fear, then, that the Marconi apparatus is dangerous
may be put aside. Being excellent lightning-conductors
and lightning-guards in one, they may, in my opinion, be
safely used, even in a powder-magazine.
Delicate as the apparatus undoubtedly is, and complicated
as it may seem, its action is simplicity itself to the telegraph-
ist, differing only in the kind of electricity and the medium
of communication from that of the everyday telegraph. On
depressing the key k (fig. 41) to make, say, a dash, induced
currents are set up in the secondary coil of the Euhmkorff
machine, which pass in sparks across the spark-gaps 1, 2, and
3, and out into space at x. The sparks at x set up electric oscil-
lations in the ether, which are radiated into space in waves.
On arriving at the receiving station some of these waves
strike the wire y, are carried to the detector, which coheres,
allowing the local battery to act ; the relay closes, and the
Morse instrument sounds, or prints the signal as may be re-
quired, the tapper all the while doing its work of decohering.
Marconi's first trials on a small scale were made at
Bologna, and these proving successful he came to England
and applied for a patent, June 2, 1896. 1 Soon after, in
1 This being the first patent of the New Telegraphy order, is his-
torically interesting. I have therefore thought it convenient to
reproduce it in Appendix E, with the original rough drawings.
G. MARCONI'S METHOD. 211
July, he submitted his plans to the postal-telegraph authori-
ties, and, to his honour be it said, they were unhesitatingly
even eagerly taken up by Mr Preece, although, as we
have already seen, he was introducing a method of his own.
The first experiments in England were from a room in
the General Post Office, London, to an impromptu station
on the roof, over 100 yards distant, with several walls, &c.,
intervening. Then, a little later, trials were made over
Salisbury Plain for a clear open distance of nearly two miles.
In these experiments roughly-made copper parabolic reflec-
tors were employed, with resonance plates on each side of
the detector (see figs. 37, 39).
In May 1897 still more extensive trials were made across
the Bristol Channel between Lavernock and Flat Holm, 3 -3
miles, and between Lavernock and Brean Down, near
Weston-super-Mare, 8 '7 miles (see tig. 21, ante). Here the
reflectors and resonance plates were discarded. Earth and
vertical air wires were employed, as in fig. 41, the vertical
wires being in the first case 50 yards high, while in the
second case kites carrying the wires were had recourse to.
The receiving apparatus was set up on the cliff at Laver-
nock Point, which is about 20 yards above sea-level. Here
was erected a pole, 30 yards high, on the top of which was
a cylindrical cap of zinc, 2 yards long and 1 yard diameter.
Connected with this cap was an insulated copper wire
leading to one side of the detector, the other side of which
was connected to a wire led down the cliff and dipping into
the sea. At Flat Holm the sending apparatus was arranged,
the Ruhmkorff coil used giving 20-inch sparks with an eight-
cell battery.
On the 10th May experiments on Mr Preece's electro-
magnetic method (already fully described) were repeated,
and with perfect success.
The next few days were eventful ones in the history of
212 THIRD PERIOD THE PRACTICAL.
Mr Marconi. On the llth and 12th his experiments were
unsatisfactory worse, they were failures and the fate of
the new system trembled in the balance. An inspiration
saved it. On the 13th the receiving apparatus was carried
down to the beach at the foot of the cliff, and connected by
another 20 yards of wire to the pole above, thus making a
height of 50 yards in all. Result, magic ! The instru-
ments, which for two days failed to record anything intelli-
gible, now rang out the signals clear and unmistakable, and
all by the addition of a few yards of wire ! Thus often, as
Carlyle says, do mighty events turn on a straw.
Prof. Slaby of Charlottenberg, who assisted at these ex-
periments, has told us in a few graphic words the feelings
of those engaged. " It will be for me," he says, " an
ineffaceable recollection. Five of us stood round the ap-
paratus in a wooden shed as a shelter from the gale, with
eyes and ears directed towards the instruments with an
attention which was almost painful, and waited for the
hoisting of a flag, which was the signal that all was ready.
Instantaneously we heard the first tic tac, tic tac, and saw
the Morse instrument print the signals which came to us
silently and invisibly from the island rock, whose contour
was scarcely visible to the naked eye came to us dancing
on that unknown and mysterious agent the ether!"
After this the further experiments passed off with scarcely
a hitch, and on the following day communication was estab-
lished between Lavernock and Brean Down.
The next important trials were carried out at Spezia, by
request of the Italian Government, between July 10 and 18,
1897. The first three days were taken up with experiments
between two land stations 3 '6 kilometres apart, which were
perfectly successful. On the 14th, the sending apparatus
being at the arsenal of San Bartolomeo, the receiving instru-
ments were placed on board a tug vessel, moored at various
G. MARCONI'S METHOD. 213
distances from the shore. The shore wire was 26 metres
high, and could be increased to 34 if necessary; the tug wire
was carried to the top of the mast, and was 16 metres high.
The results were unsatisfactory : signals came, but they were
jumbled up with other weird signals, which came from the
atmosphere (the weather was stormy) in the way which
telegraph and telephone operators know so well. On the
15th and 16th (the weather having moderated) better results
were obtained, and communication was kept up at distances
up to 7*5 kilometres.
On the 17th and 18th the receiving apparatus was trans-
ferred to a warship (ironclad), and, with a shore elevation of
34 metres and a ship elevation of 22 metres, signals were
good at all distances up to 12 kilometres, and fairly so at 16
kilometres.
During these experiments it was observed that whenever
the funnels, iron masts, and wire ropes of the vessels were
in line with the shore apparatus the detector did not work
properly, which was to be expected from the screening pro-
perty of metals ; but another and more serious difficulty
was also encountered. When the vessel got behind a point
of the land which cut off the view of the shore station, the
signals came capriciously, and good working was not estab-
lished until the shore was again in full view. Here was a
difficulty which must be surmounted if the new system was
to be of any practical utility. We have seen in our account
of the work of Hertz that electric waves pass without ap-
preciable hindrance through doors and walls and, generally,
non-conducting bodies, being only arrested by metals and
other conductors; but in practice, when we come to deal
with doors and walls in large masses as trees, buildings,
hills, especially if near the vertical wires they partake of
the nature of metals, and largely absorb the waves, just as
light passes through a thin sheet of glass, but is obscured or
214
THIRD PERIOD THE PRACTICAL.
absorbed by a thick sheet. This difficulty is in the nature
of things, and must always remain. It is surmountable to
a very great extent by increasing the height of the vertical
wires, terminating with suitable capacity areas, and by in-
creasing the power of the sending and the delicacy of the
receiving apparatus ; but we speedily reach a limit in these
directions, so that as far as one can see at present the effec-
tive distance of the new system must be small compared
with the older methods.
Fig. 42, which I borrow from Mr Preece, shows how hills
are apparently bridged over.
Fig. 42.
From a long series of experiments in Italy in 1895 Mr
Marconi worked out a law of distance which all his later
experience seems to verify. " The results," he says, " showed
that the distance at which signals could be obtained varied
approximately as the square of the height of the capacity
areas from earth, or, perhaps, as the square of the length of
the vertical conductors. This law furnishes us with a safe
means of calculating what length the vertical wire should
be in order to obtain results at a given distance. The law
has never failed to give the expected results across dear
space in any installation I have carried out, although it
usually seems that the distance actually obtained is slightly
in excess. I find that, with parity of other conditions,
vertical wires 20 feet long are sufficient for communicating
G. MARCONI'S METHOD. 215
one mile, 40 feet four miles, 80 feet sixteen miles, and
so on.
" Professor Ascoli has confirmed this law, and demon-
strated mathematically, using Neumann's formula, that the
inductive action is proportional to the square of the length
of one of the two conductors if the two are vertical and
of equal length, 1 and in simple inverse proportion of the
distance between them. Therefore the intensity of the in-
duced oscillation does not diminish with the increase of
distance if the length of the vertical conductors is increased
in proportion, or as the square root of the distance. That
is, if the height of the wire is doubled, the possible distance
becomes quadrupled." 2
On his return to Germany after witnessing the Marconi
experiments in England, Prof. Slaby in September 1897
engaged in some very instructive experiments in the vicinity
of Potsdam, first between Matrosenstation and the church at
Sacrow, 1*6 kilometre, and then between the former place
and the castle of Pfaueninsel, 3'1 kilometres. I take the
following particulars from the ' Electrical Engineer,' De-
cember 3, 1897 :
Prof. Slaby recently, at a technical college in Berlin, gave
an interesting report of his experiments on telegraphy with-
out wires, or, as he wants it to be called, " spark telegraphy."
He mentioned an experiment made by himself by which he
was able to send by means of one wire two different messages
simultaneously without interfering with each other. He
1 If of unequal lengths then the action is proportional to the pro-
duct of the two lengths, which, however, must not be too dissimilar.
2 This law ia correct for clear open spaces over water ; but over
land allowance must be made for obstacles, as trees, buildings, hills,
&c., which carry off some of the passing energy. The conductors
must be parallel (' Jour. Inst. Elec. Engs.,' No. 137, p. 902), but
need not necessarily be of the same height, although it is preferable
that they should be so.
216 THIRD PERIOD THE PRACTICAL.
explained that the continuous current used in ordinary teleg-
raphy is conducted along the middle of the wire, and he
proved that electric waves on their way through the ether
are attracted by wires which come in their way, and that
they travel along the outside of those wires without in-
fluencing the interior. In making use of these observations
he succeeded in sending a wave message along the outside
of the wire while another message was proceeding through
the centre by the continuous current.
Prof. Slaby says that, in conjunction with Dr Dietz, he
made many experiments with " spark telegraphy " before
Marconi's inventions became known, but did not achieve
any important results. 1
After his return, however, from England he experi-
mented still further. The Emperor of Germany was present
at some of these experiments, and put a number of sailors
and the large royal gardens at Potsdam at his disposal.
The receiver was erected at the naval station and the
transmitter on Peacock Island. The first experiments gave
no result, because the coherers used were a great deal too
sensitive, and contained, among other things, too much
silver, and were affected by the electricity in the atmo-
1 Referring to these experiments in his book, ' Die Funkentele-
graphie,' Berlin, 1897, Prof. Slaby handsomely acknowledges Marconi's
merits in the following words : " Like many others, I also had taken
up this study, but never got beyond the limits of our High School.
Even with the aid of parabolic reflectors and great capacity of
apparatus I could not attain any further. Marconi has made a dis-
covery. He worked with means the full importance of which had not
been recognised, and which alone explain the secret of his success. I
ought to have said this at the commencement of my subject, as latterly,
especially in the English technical press, the novelty of Marconi's
process was denied. The production of the Hert/ian waves, their
radiation through space, the sensitiveness of the electric eye, all were
known. Very good ; but with these means 50 metres were attained,
but no more."
G. MARCONI'S METHOD. 217
sphere, and in consequence were constantly affected even
when no signals were sent from the sending station.
Further experiments showed that the result^ increased in
the same measure as the sensitiveness of the coherer de-
creased. Prof. Slaby uses now very rough and jagged
nickel filings which have been carefully cleaned and
dried. As the receiving station could not be seen from the
island, the sending station was removed to a church a little
farther away, and the exciter was put between the columns
of the portico, while the mast which carried the wire was
erected on the spire. The experiments then went very well.
When the sending apparatus was put back a little farther
into the church, and the wire was put for about a length of
2 yards parallel with the stone slabs of the floor and a yard
and a half above it, it ceased to work properly, because the
waves seek the earth. Hence one must not bring the wire
too near to the earth, or lay it parallel when near the earth.
When the sending apparatus was moved back to the island,
it was found that trees near the wire proved an obstacle
because they received the waves. Therefore the Professor
says that it is best to so arrange that the wires on the
receiver and on the transmitter can be seen from each
other. Even the sail of a little boat or the smoke from
a steamer cause small interruptions, which make the words
more or less indistinct. The waves get through impedi-
menta, and even through buildings, but there is always
much loss. In order to make the wire which was placed
on the island more visible from the mainland, it was
lengthened from 25 to 65 yards, and placed upon a boat
on the river. That did not remedy matters ; but when the
wire on the receiver was also lengthened to 65 yards very
good results followed, showing that the length of the wire
is of great importance.
Prof. Slaby next proceeded, early in October, to experi-
218 THIRD PERIOD THE PRACTICAL.
ment over an open stretch of country, free from all inter-
vening obstacles, between Eangsdorf (sending station) and
Schoneberg (receiving station), a distance of 21 kilometres.
Captive balloons raised to a height of 300 metres were
employed. On the first two days the results were dis-
appointing, and the fault was found to be in the vertical
conductors, which consisted of the wire cables holding the
balloons. With a double telephone wire there was a slight
improvement ; and eventually, on the 7th October, " fine
insulated copper wire of '46 millimetres diameter was sub-
stituted with excellent results." l
Correspondence was now always good, except when dis-
turbed by atmospheric discharges (the weather being-
stormy). At such times the signals were distorted and con-
fused, and often the discharges were so strong as to un-
pleasantly shock the operators, making it necessary to
handle the apparatus with the greatest care. Here is
another serious difficulty with which Mr Marconi has to
contend, and from which we see no escape short of total
suspension of operations during stormy weather namely,
the great liability to accident and derangement, not merely
from lightning flashes, to which all telegraph systems are
subject, but from all those other electrical disturbances of
the atmosphere which have hitherto been of little account.
The greater the distance worked over, the higher must be
the conductors, and, consequently, the greater must be the
danger.
The apparatus used by Prof. Slaby differed somewhat
from Marconi's, the following being the more important
points :
1. A Weston galvanometer relay, which, it is curious to
1 The statement in inverted commas needs verification, as theo-
retically one would suppose the larger wires should have given the
better result.
a MARCONI'S METHOD. 219
note, is our old friend in modern guise, the Wilkins'
relay, used by Mr Wilkins in his wireless telegraph
experiments in 1845 (see p. 38, ante).
2. An ordinary Branly- Lodge -detector with hard nickel
powder only.
3. No impedance or "choking" coils. 1
The further course of Marconi's experiments is so suc-
cinctly given by the chairman of the Wireless Telegraph
Company in a recent address, October 7, 1898, that we
cannot do better than follow him. 2
" A year ago," he says, " when this company was started
(July 1897), Mr Marconi happened to be in Italy making
experiments for the Italian Government, and for the King
and Queen at the Quirinal. On his return to this country,
the first long-distance trial was made between Bath and
Salisbury. The receiver in this case was given to a post-
office official, who went to Bath and by himself rigged up a
station, at which he received signals thirty-four miles distant
from where they were sent at Salisbury. After this we put
a permanent station at Alum Bay, Isle of Wight. This
station at first was used in connection with a small steamer
that cruised about in the neighbourhood of Bournemouth,
Boscombe, Poole Bay, and Swanage, a distance of eighteen
miles from the Needles Hotel station, with which it was in
constant telegraphic communication.
" Various exhibitions were given later one at the House
of Commons, where a station was erected, and another sta-
tion at St Thomas's Hospital opposite (May 1898). Within
1 About this time Dr Tuma of Vienna was engaged on similar ex-
periments, using, however, instead of a Ruhmkorff coil a Tesla oscillator
or exciter, with nickel powder only in the detector. I have not seen
any detailed account of these experiments.
2 I have incorporated a few passages from Mr Marconi's recent paper
(Institution of Electrical Engineers, March 2, 1899), so as to make the
account more complete. These are shown in brackets thus [ ].
220 THIRD PERIOD THE PRACTICAL.
an hour of the time our assistants arrived to put up the
installation, the system was at work. We had many
exhibitions at our offices, at which a number of people
attended; amongst others Mr Brinton, a director of the
Donald Currie .line of steamers, who asked if we could
report a ship passing our station. This was done. The
ship was the Carisbrooke Castle, on her first voyage out,
and as she passed the Needles a message reporting the
fact was wirelessly telegraphed to Bournemouth, and there
put on the ordinary telegraph wires for transmission to
Mr Brinton.
"After this Lord Kelvin visited our station at Alum Bay,
and expressed himself highly pleased with all he saw. He
sent several telegrams, via Bournemouth, to his friends, for
each of which he insisted on paying one shilling royalty,
wishing in this way to show his appreciation of the system
and to illustrate its fitness for commercial uses. The follow-
ing day the Italian Ambassador visited the station. Among
other messages, he sent a long telegram addressed to the
Aide-de-camp to the King of Italy. As it was in Italian,
and as Mr Marconi's assistant at Bournemouth had no know-
ledge of that language, it may be taken as a severe test as,
in fact, a code message. The telegram was received exactly
as it was sent. Previously, we had a display for the
' Electrical Review ' and the ' Times,' both of which papers
sent representatives. They put the system to every possible
test, and, among others, sent a long code message, which
had to be repeated back. In their reports they stated that
this was done exactly as sent,
[In May Lloyd's desired to have an illustration of the
possibility of signalling between Ballycastle and Eathlin
Island in the north of Ireland. The distance between the
two positions is seven and a half miles, of which about four
are overland and the remainder across the sea, a high cliff
G. MARCONI'S METHOD. 221
also intervening between the two positions. At Ballycastle
a pole 70 feet high was used to support the wire, and at
Eathlin a vertical conductor was supported by the light-
house 80 feet high. Signalling was found quite possible
between the two points, but it was thought desirable to
bring the height of the pole at Ballycastle to 100 feet, as
the proximity of the lighthouse to the wire at Rathlin
seemed to diminish the effectiveness of that station. At
Rathlin we found that the lighthouse-keepers were not long
in learning how to work the instruments, and after the sad
accident which happened to poor Mr Glanville, that installa-
tion was worked by them alone, there being no expert on
the island at the time. 1 ]
" Following this, in July last (1898) we were requested
by a Dublin paper, the 'Daily Express,' to report the
Kingstown regatta. In order to do this we erected a [land]
station at Kingstown, and another on board a steamer which
followed the yachts. A telephone wire connected the
Kingstown station with the ' Daily Express ' offices, and as
the messages came from the ship they were telephoned to
Dublin and published in successive editions of the evening
papers. 2
" After this, Mr Marconi was requested to put up a sta-
tion at Osborne to connect with the Prince of "Wales' yacht
Osborne. Bulletins of the Prince's health (his Royal High-
ness, as we all know, met with a lamentable accident just
before then) were reported to her Majesty : not only that,
but the royalties made great use of our system during the
Cowes week. After the regatta had concluded the Prince
1 Mr Glanville, a promising young electrician (only twenty-five
years old), was missing from Saturday to the Tuesday evening fol-
lowing, when his body, terribly mutilated, was found at the foot of
a cliff 300 feet high in Rathliu Island.
2 Very full illustrated accounts of this remarkable experiment are
given in the Dublin ' Mail,' July 20, 21, and 22, 1898.
222 THIRD PERIOD THE PRACTICAL.
wished to cruise about, and he did so as far as Bembridge
on one occasion. The next day they went over to the
Needles, at the opposite side of the Isle of Wight. The
royal yacht was kept in telegraphic communication with the
Osborne station on the first day. On the second occasion
they were able not only to communicate with Osborne, but
also with our station at the Needles Hotel. They rang up
the Needles Hotel when seven or eight miles away, and
immediately had a reply, although about the highest land
in the Isle of Wight lay between the royal yacht and the
Needles Hotel station.
" Within the last few days we have had to move our
station at Bournemouth four' miles farther west, where we
have put up the same instruments, the same pole, and
everything at the Haven Hotel, Poole, which is eighteen
miles from Alum Bay. This increase of distance has no
detrimental effect on our work ; in fact it seems rather
easier, if anything, to receive signals at the Haven Hotel
than at our former station : thus, the height of the conductor
at Bournemouth was 150 feet, but this is now reduced to
100 feet, which is a very great improvement. 1
[The vertical conductors are stranded fa copper wire in-
sulated with india-rubber and tape. A 10-inch spark induc-
tion coil is used at each station, worked by a battery of 100
Obach cells M size, the current taken by the coil being 14
volts of from 6 to 9 amperes. The sparks take place be-
tween two small spheres about 1 inch diameter, this form
of transmitter having been found more simple and more
effective than the Kighi exciter previously used. The
length of spark is adjusted to about 1 centimetre, which,
being much shorter than the coil can give, allows a large
margin for any irregularity that may occur. No care is
now taken to polish the spheres at the place where the
1 The height has since been reduced to 60 feet.
223
sparks occur, as working seems better with dull spheres
than with polished ones.]
"We have sent our assistants to various countries to
make demonstrations in connection with our patent rights ;
and lately we sent one of our staff to Malta, where some
excellent experiments were carried out for the Government
officials.
" The Marconi invention is the only (electric) telegraph
by means of which a moving object can be kept in commu-
nication with any other moving object, or a fixed station,
and therefore any one can see the great use of the invention,
not only to the Royal Naval authorities, but also to the
mercantile marine. A ship fitted with Mr Marconi's
apparatus can not only keep in telegraphic communi-
cation with the shore up to any reasonable distance it
has been thoroughly tested up to twenty -five miles off
the shore but ships can also, if properly equipped,
be warned of approaching danger or their proximity
to dangerous coasts which are fitted with the wireless
apparatus. 1
"The weather has no effect at any rate no adverse
1 I fear the apparatus is not yet adapted for this. Take the case of
an outlying rock lighthouse. As the electric waves would radiate in
all directions, a ship in darkness or a fog could not say from the
intercepted rays what her position was, whether north, south, east,
or west of the lighthouse, which may be a matter of vital importance
for her.
By reverting, however, to the original form of the apparatus (dis-
carding vertical wires), and by revolving a metallic screen about the
detector until the position of maximum effect is obtained, the ship
could possibly fix the direction whence come the rays. But this,
though important, is not enough. As the ship does not know her
distance from the rock, it does not tell her enough as to her exact
position. The distance might possibly be ascertainable if the detector
could be calibrated to varying degrees of electric energy a very
great difficulty.
224 THIRD PERIOD THE PRACTICAL.
effect. The only thing we find is that on a foggy day,
when a place is obscured, everything is made easier for us.
Our worst electrical day is a fine, bright, sunny day in July,
when everything can be seen ; but directly everything
becomes obscured the facilities of wireless telegraphy are
increased. I had a telegram handed to me just as I came
in, querying if the Government or the Post Office were not,
as has been reported, trying to stop us. So far from that
being the case, they have actually requested us to put the
system up between Guernsey and Sark, and they have
offered us a post office at each end for the instruments.
That matter is occupying our attention, and we shall go on
with it at once. Also, as we wish to work the thing in
France as well as in England, we now intend to put up a
station between Calais and Dover. There is not the least
doubt of success being achieved, because we are doing a
parallel distance to-day without the slightest difficulty. The
sea between Calais and Dover is the same sea as between
the Isle of Wight and Poole, so the things being equal in
both cases we may expect the same success between Calais
and Dover as between the other points."
[In December of last year the Company thought it desir-
able to demonstrate that the system was available for tele-
graphic communication between lightships and the shore.
This, as you are aware, is a matter of much importance, as
all other systems tried so far have failed, and the cables by
which ships are connected are exceedingly expensive, and
require special moorings and fittings, which are troublesome
to maintain and liable to break in storms. The officials of
Trinity House offered us the opportunity of demonstrating
to them the utility of the system between the South Fore-
land Lighthouse and one of the following light-vessels
viz., the Gull, the South Goodwin, and the East Goodwin.
We naturally chose the one farthest away the East Good-
G. MAKCONl'S METHOD. 225
win which is just twelve miles from the South Foreland
Lighthouse.
[The apparatus was taken on board in an open boat and
rigged up in one afternoon. The installation started working
from the very first, December 24, without the slightest
difficulty. The system has continued to work admirably
through all the storms, which during this year have been
remarkable for their continuance and severity. On one
occasion, during a big gale in January last, a very heavy sea
struck the ship, carrying part of her bulwarks away. The
report of this mishap was promptly telegraphed to the
superintendent of Trinity House, with all details of the
damage sustained.
[The height of the wire on board the ship is 80 feet, the
mast being for 60 feet of its length of iron, and the re-
mainder of wood. The aerial wire is led down among a
great number of metal stays and chains, which do not
appear to have any detrimental effect on the strength of the
signals. The instruments are placed in the aft-cabin, and
the aerial wire comes through the framework of a skylight,
from which it is insulated by means of a rubber pipe. As
usual, a 10-inch coil is used, worked by a battery of dry
cells, the current taken being about 6 to 8 amperes at 14
volts.
[Various members of the crew learned in two days how to
send and receive, and in fact how to run the station ; and
owing to the assistant on board not being as good a sailor
as the instruments have proved to be, nearly all the messages
during very bad weather are sent and received by these
men, who, previous to our visit to the ship, had probably
never heard of wireless telegraphy, and were certainly
unacquainted with even the rudiments of electricity. It is
remarkable that wireless telegraphy, which had been con-
sidered by some as rather uncertain, or that might work one
p
226 THIRD PERIOD THE PRACTICAL.
day and not the next, has proved in this case to be more
reliable, even under such unfavourable conditions, than the
ordinary land wires, very many of which were broken down
in the storms of last month. 1
[The instruments at the South Foreland Lighthouse are
similar to those used on the ship ; but as we contemplate
making some long-distance tests from the South Foreland
to the coast of France, the height of the pole is much
greater than would be necessary for the lightship installa-
tion alone. 2 ]
It has been objected to the Marconi system that, with
the removal of the reflectors and the resonance wings on
the detectors, the condition of privacy in telegrams no
longer holds good, since any one provided with the neces-
sary apparatus can receive the signals at any point within
the circle of which the sending station is the centre and the
receiving station the radius. Another, and in some cases
more serious, objection is that any one by erecting a wire or
wires in the vicinity of a Marconi station can propagate
therefrom Hertzian waves, which by interference will so
confuse the effects as to make correct signalling impractic-
able. It is not even necessary to propagate counter-waves :
a large sheet of metal (or several such sheets) erected high
in air, in line with the stations, and connected by a wire to
the earth, will intercept much of the energy, and the more
so as it is near to either of the stations, and at right angles
to the direction of the waves. Thus, if used for naval or
military purposes, an enemy could either tap the dispatches
or render them unintelligible at pleasure. The latter ob-
jection is from the nature of things unavoidable, and in
1 Pace Mr Marconi, the system is affected by stormy weather. See
p. 218 ante; also 'Jour. Inst. Elec. Engs.,' No. 137, p. 945.
2 This has since been done. See all the London papers of March 29
and 30, 1899.
G. MARCONI'S METHOD. 227
practice must limit the application of the system to lines of
communication sufficiently apart as not to interfere with one
another. The first objection, however, can be obviated by
reverting to the condition of syntony or resonance, and
it is in this direction that improvements may soon be
expected. 1
Dr Oliver Lodge, F.R.S., the distinguished Professor of
Physics, University College, Liverpool, and the great dis-
ciple and expounder of Hertz in England, has long been
engaged on this problem of a Hertzian-wave telegraph
more especially with a view of securing syntony in the
sending and receiving apparatus, and thereby limiting the
communications to similarly attuned instruments, the ab-
sence of which selective character is at present one of the
great drawbacks of the Marconi system.
We have seen (p. 200, ante) that as early as June 1, 1894,
Prof. Lodge had exhibited apparatus which was effective
for signalling on a small scale, but, as he says, "stupidly
enough no attempt was then made to apply any but the
feeblest power, so as to test how far the disturbance could
really be detected. . . . There remained, no doubt, a
number of points of detail, and considerable improvements
in construction, if the method was ever to become practic-
ally useful." ' These he has since worked out, and some of
1 Indeed we already hear of radical changes. Mr Pasqualini, who
is charged with the working of the Marconi system under the Italian
Government, is reported to have found that electrical oscillations do
not entirely explain the process, and, following out his idea, has
altered the apparatus greatly. He is able to signal with certainty
over a distance of twenty-four miles " with apparatus that requires
no attention, and is not erratic like Marconi's " (' Electrical Engineer,'
April 7, 1899). Then, news comes from Vienna that Mr Bela Schafer,
a student of the Buda-Pesth Polytechnic, has so altered the Marconi
apparatus that he is able to determine the presence and course of
a ship six to eight miles distant.
2 The Work of Hertz, pp. 67, 68.
228
THIKD PERIOD THE PRACTICAL.
them are embodied in his patent, No. 11,575, of May 10,
1897, " Improvements in Syntonised Telegraphy without
Line Wires."
As capacity areas, spheres or square plates of metal may
be employed ; but for the purpose of combining low resist-
ance with large electro-static capacity, cones or triangles are
preferred, with the vertices adjoining and their larger areas
spreading out into space. Or a single insulated surface may
H H
Fig. 43.
be used in conjunction with the earth the earth, or con-
ductors embedded in it, constituting the other capacity area.
As radiation from these surfaces is greater in the equatorial
than in the axial direction, so, when signalling in all direc-
tions is desired, the axis of the emitter should be vertical.
Moreover, radiation in a horizontal plane is less likely to
be absorbed during its passage over partially conducting
earth or water.
Fig. 43 shows the arrangement for long-distance signalling.
229
H H 1 are large triangular sheets of metal, which by means
of suitable switches (not shown) can be connected to the
sending- or the receiving apparatus as desired. Those on
the left-hand side of the figure are shown in connection
with polished knobs H 2 H 3 (protected by glass from ultra-
violet light), which form the adjustable spark-gap of the
exciter. Between each capacity area and its knob is
inserted a self -inductance coil of thick wire or metallic
ribbon (see H 4 , fig. 44) suitably insulated, the object of
which is to prolong the electrical oscillations in a succession
of waves-, and thereby obtain a definite frequency or pitch,
rendering syntony possible, since exactitude of response
depends on the fact that with the emission of a number of
successive waves the feeble impulse at the receiving station
is gradually strengthened till it causes a perceptible effect,
on the well-known principle of sympathetic resonance.
The capacity areas and inductance coils are exactly alike
at the two communicating stations, so as to have the same
frequency of electrical vibration. This frequency can be
altered either by varying the capacity of the Leyden jars
used in the exciting circuit, or by varying the number and
position of the inductance coils, or by varying both in the
proper degree, thus permitting only those stations whose
rate of oscillation is the same to correspond.
To actuate the exciter a Kuhmkorff coil may be used, or
a Tesla coil, a Wimshurst machine, or any other high
tension apparatus.
Fig. 44 shows the details of the arrangement for exciting
and detecting the electric waves. When used as a trans-
mitter the receiving circuit is disconnected from the capacity
areas by a suitable switch (not shown). Let us first con-
sider the arrangement as a transmitter. Putting the Euhm-
korff coil A in action, it charges the Leyden jars J J, whose
outer coatings are connected, first, through a self -inductance
230
THIRD PERIOD THE PRACTICAL.
coil H 5 of fairly thin wire, so as to permit of thorough
charging of the jars ; and, second, to the " supply gaps "
H 6 H 7 . When the jars are fully charged to sparking- point,
sparks occur at the " starting-gap " H 8 . These precipitate
sparks at the " supply gaps," which evoke electrical charges
in the capacity areas H H 1 . These charges surge through
the inductance coils H 4 , and spark into each other across
the " discharge gap " between the knobs H 2 H 3 . This last
Fig. 44.
discharge, according to Prof. Lodge, is the chief agent in
starting the oscillations which are the cause of the emitted
waves ; but it is permissible to close the " discharge gap,"
and so leave the oscillations to be started by the sparks at
the " supply gaps " only, whose knobs must then be polished
and protected from ultra-violet light, " so as to supply the
electric charge in as sudden a manner as possible."
When used as a receiver the " discharge-gap " is bridged
over by a suitable cut-out, and connection is made with the
G. MARCONI'S METHOD.
231
receiving circuit, as shown on the top of fig. 44. As
detector, Lodge uses
1. His own original form of coherer, fig. 45, wherein
a metallic point N rests lightly on a flat metallic surface
o (for instance, a needle point of steel or platinum making
light contact with a steel or aluminium bar like a watch
spring), fixed at one end p, and delicately adjustable by a
micrometer screw Q, so as to regulate the pressure at the
point N. Or
2. A Branly tube filled with selected iron filings of
R
Fig. 45.
uniform size, sealed up in a good vacuum, and with the
electrodes, which are of platinum, reduced to points a short
distance apart.
His latest form of the Branly coherer is shown full size in
fig. 46, and is said to be exceedingly sensitive and certain
in its action, especially in a very high vacuum. A A is a
glass tube held tightly by ebonite supports B B ; c is a
pocket or reservoir for spare filings, which can be added to,
or taken from, the effective portion as required by inverting
the tube ; D D are the silver electrodes immersed in the
filings, which are, as before, of carefully selected iron of
232
THIED PERIOD THE PRACTICAL.
uniform size as nearly as possible ; E is one of the terminals
of the silver electrodes, the other of which is hidden from
view.
The instrument is secured by the clamp screw F to any
convenient support, to
which the tapping or
decohering apparatus is
applied. 1
When an electric wave
from a distant exciter
arrives and stimulates
electric vibrations in the
syntonised capacity areas,
the electrical resistance
of the coherer suddenly
and greatly falls and per-
mits the small battery F,
fig. 44, to actuate a relay
G, or a telephone, or other
telegraphic instrument.
To break contact, or to
restore the original great
resistance of the coherer,
any form of mechanical
vibration suffices, as a
clock, or a tuning-fork,
or a cog-wheel (as in fig.
45), or other device for
causing a shake or
motion
Fig. 46.
by a spring,
tremor, and kept in
or weight, or by electrical means.
1 It appears that to Professor Blondel is due the credit of first
constructing a coherer of this kind in August 1898. See the ' Elec-
trician,' vol. xliii. p. 277.
G. MAECONl'S METHOD. 233
Indeed, the mere motion of any clockwork attached to
the coherer stand will suffice, an exceedingly slight,
almost imperceptible, tremor being all that is usually
required.
Usually the coherer is arranged in simple series with
the battery and telegraphic instrument, and is so joined to
the capacity areas as to include in its circuit the self -induct-
ance coils an arrangement which Prof. Lodge considers of
great advantage, or, as he says, "an improvement on any
mode of connection that had previously been possible with-
out these coils."
The patent specification figures and describes another
way viz., enclosing the inductance coils in an outer or
secondary coil (constituting a species of transformer), and
making this coil part of the coherer circuit. In this case
the coherer is stimulated by the waves in the secondary coil
rather than primarily by those in the inductance coils, which
with their capacity areas are thus left free to vibrate without
disturbance from attached wires.
In all cases it is permissible, and sometimes desirable, to
shunt the coils of the telegraphic instrument G by means of
a fine wire or other non-inductive resistance coil w, "in
order to connect the coherer more effectively and closely to
the capacity areas."
At the Royal Society Conversazione on May 11, 1898, a
complete set of Lodge's apparatus was shown in action, in
which certain modifications in the signalling and recording
parts were introduced at the suggestion of Dr Alexander
Muirhead. Instead of the ordinary Morse key, Muirhead's
well-known automatic transmitter with punched tape was
employed at one end of the suite of rooms, and a siphon-
recorder as the receiving instrument at the other end. The
recorder was so arranged as to print, not as usually zigzag
traces, but (the needle working between stops) a momentary
234 THIRD PERIOD THE PRACTICAL.
deflection mark for a dot and a longer continued mark for
a dash.
The siphon-recorder is so quick in its responses that it
indicates each one of the torrent of sparks emitted from the
sending apparatus : hence a dash is not merely a deflection
held over, but is made up of a series of minute vibrations ;
and even a dot is seen to consist of similar vibrations,
though of course of a lesser number. If the speed of
signalling is slow and the recorder tape moves slowly, these
vibrations appear as actual dots and dashes ; but each signal,
when examined with a microscope, is seen to consist of a
short or long series of lines representing the constituent
vibrations.
At a slow rate of working the signals can thus be got
with exceeding clearness ; but for actual signalling this is
not at all necessary, and it is possible to attain a high speed,
making such brief contacts that a single deflection of the
recorder needle indicates a dot, and three consecutive deflec-
tions a dash. The paper thus marked does not look like
the ordinary record, but more resembles the original Morse
characters as depicted on pp. 404 and 409 of Shaffner's
' Telegraph Manual ' (New York, 1859), and is easily legible
with a little practice.
An ordinary telephone was also available as a receiver,
connected through a transformer coil, in which the dots and
dashes were heard very clearly and distinctly.
The apparatus is reported to have worked well (except at
the high speeds, when it occasionally missed fire), and did
not seem to be in the least affected by any of the numerous
electrical exhibits in the neighbourhood, although some of
them must have set up considerable radiation of Hertzian
waves.
Based on the same principles viz., the emission of
electric waves at one place and their detection by some
G. MARCONI'S METHOD. 235
form of coherer at another place there is naturally a
similarity in the outlines of the Lodge system and that of
Marconi for short distances (where vertical wires are not
used), as depicted in fig. 39, ante. The differences are
differences of arrangement and detail only, but they appear
to be fraught with some important consequences.
In the first place, Prof. Lodge claims that his arrange-
ment of the sending apparatus is a more persistent exciter,
in that it emits a longer train of longer waves, 1 which by
acting cumulatively on the detector breaks down its insula-
tion, when more powerful but fewer impulses of shorter
waves might be inoperative. Then in the next place, this
element of persistency permits of the use of syntonising
contrivances, by means of which the rate of oscillation of
any desired set of instruments can be accurately attuned so
that only those instruments can correspond, without affect-
ing or being affected by other sets tuned to a different fre-
quency, thus securing the undoubted advantage of privacy
in the communications.
Lodge's arrangement has worked well in the laboratory
and lecture-room, but he does not appear to have tried it
(which is a pity) over any considerable distance, so that it
remains to be seen how far he can go without having
recourse to vertical wires, which Marconi finds so essential
for practical work over distances of more than two or three
miles. 2
A few words as to the future, by way of conclusion, and
our task is completed. On this point we find some recent
remarks of Prof. Silvanus Thompson so appropriate that we
quote them in full, as being more authoritative than anything
1 For some important observations on this point see Mr A. Camp-
bell Swinton, 'Jour. Inst. Elec. Engs.,' No. 139, p. 317.
2 For Professor Lodge's newest developments see his paper, ' Jour.
Inst. Elec. Engs.,' No. 137, p. 799, which deserves careful study.
236 THIRD PERIOD THE PRACTICAL.
we could ourselves say. Prof. Thompson has thoroughly
studied the subject, and therefore " speaks by the card."
"It has been shown," he says, "that there are three
general methods of transmitting electric signals across space.
All of them require base lines or base areas. The first
conduction requires moist earth or water as a medium, and
is for distances under three miles the most effective of the
three. The second induction is not dependent upon
earth or water, but will equally well cross air or dry rock.
The third electric wave propagation requires no medium
beyond that of the ether of space, but is interfered with by
interposed things such as masts or trees. Given proper base
lines or base areas, given adequate methods of thro wing-
electric energy into the transmitting system, and sufficiently
sensitive instruments to pick up and translate the signals, it
is possible, in my opinion, so to develop each of the three
methods that by any one of them it will be possible to
establish electric communication between England and
America across the intervening space. It is certainly pos-
sible, either by conduction or by induction; whether by
waves I am somewhat less certain. Conduction might very
seriously interfere with other electric agencies, since the
waste currents in the neighbourhood of the primary base
line would be very great. It is certainly possible either by
conduction or induction to establish direct communication
across space with either the Cape, or India, or Australia
(under the same assumptions as before), and at a far less cost
than that of a connecting submarine cable.
" Instruments which operate by means of alternating cur-
rents of high frequency, like Mr Langdon-Davies's phono-
phore, are peculiarly liable to set up disturbance in other
circuits. A single phonophore circuit can be heard in lines
a hundred miles away. When this first came to my notice
it impressed me greatly, and coupled in my mind with the
G. MAKCONl'S METHOD. 237
Ferranti incident mentioned above" (see note, p. 145, ante),
"caused me to offer to one of my financial friends in the City,
some eight years ago, to undertake seriously to establish
telegraphic communication with the Cape, provided .10,000
were forthcoming to establish the necessary basal circuits in
the two countries, and the instruments for creating the cur-
rents. My offer was deemed too visionary for acceptance.
The thing, however, is quite feasible. The one necessary
thing is the adequate base line or area. All the rest is
detail." l
En attendant, we have the Marconi system, which has been
proved to be practicable up to thirty-five miles, and within
this limit there ought to be a wide and useful field for
activity. Thus, many outlying islands are within this dis-
tance from each other and from the continents, with which
communication at all times has hitherto been practicable
only by the use of cables, which are always costly to make
and lay, and often costly to keep in repair. Here, especially
between places where the traffic is not great, is a large field
to be occupied as cables grow old and fail.
Then we have just seen from the address of the chairman
of the Wireless Telegraph Company that negotiations are
going on with Lloyd's which, if carried into practical effect,
will result in an extensive application for signalling between
Lloyd's stations and outward and inward bound vessels
passing in their vicinity. Indeed it is not rash to predict
that the lighthouses and lightships around the coasts, not
only of the British Isles but of all countries, will in time
be supplied with wireless telegraphs, keeping up constant
correspondence with all who go down to the sea in ships.
Then, again, there is the application to intercommunication
between ships at sea. Ships carrying the Marconi ap-
paratus can carry on a definite conversation with the occu-
1 Journal, Society of Arts, April 1, 1898.
238 THIRD PERIOD THE PRACTICAL.
pants of lighthouses and lightships and with each other.
It will readily be seen that this might, in many cases, be
far more serviceable than the few light signals now obtain-
able, or the signalling by flags a tedious process at best,
and one that is often full of uncertainty, if not of positive
error.
Turning from sea to land, we find, for the reasons we
have already indicated, a more circumscribed field of ap-
plicationat all events until means are devised for focus-
sing the electric rays and rendering the apparatus syntonic.
But even then, although by these means we will be able to
record messages only where intended, there still remain
cross interferences of which I fear we can never be rid,
and therefore we can never use the system in a network
of lines as now, where wires cross, recross, and overlap each
other in all ways and directions. The waves of electricity,
like waves of light and sound in similar circumstances,
would so interfere with each other that the result would be
chaos. Therefore wireless telegraphy can only be used
in lines removed from each other's disturbing influences,
as in sparsely populated countries and undeveloped regions.
However, many cases of impromptu means of communi-
cation arise where, as Prof. Lodge says, it might be advan-
tageous to "shout" the message, spreading it broadcast
to receivers in all directions, and for which the wireless
system is well adapted, seeing that it is so inexpensive and
so easily and rapidly installed, such as for army manoeu-
vres, for reporting races and other sporting events, and,
generally, for all important matters occurring beyond the
range of the permanent lines.
But for the regular daily correspondence of a nation
with its lines ramifying in all directions and carrying
enormous traffics, the Marconi system is not adapted,
no more than any other wireless method that has been
G. MAKCONl'S METHOD. 239
proposed, or is likely to be invented. So, for a long time to
come we must keep to our present telegraphic and tele-
phonic wires, using the wireless telegraph as an adjunct for
special cases and contingencies such as I have mentioned.
POSTSCRIPT.
April 17, 1899.
On the 27th of last month communication was established
by the Marconi system between England and France. As
all the London daily papers of March 29 and 30 contain full
and glowing accounts of this installation, it may not be
necessary to do more than to refer my readers to these
reports. Still I think it desirable, so as to bring my record
quite up to date, to add these few words as the book is
passing through the press.
" On this side of the Channel the operations took place, by
permission of the Trinity House, in a little room in the front
part of the engine-house from which the power is derived for
the South Foreland lighthouses. The house is on the top
of the cliffs overlooking the Channel. The demonstrations
are being conducted for the benefit of the French Govern-
ment, who have the system under observation, and besides
Signer Marconi there were present at the Foreland yesterday
Colonel Comte du Bontavice de Heussey, French Military
Attache in England ; Captain Ferrie, representing the
French Government; and Captain Fieron, French IsTaval
Attache in England. During the afternoon a great number
of messages in French and English crossed and recrossed
between the little room at the South Foreland and the Chalet
D'Artois, at Wimreux, near Boulogne.
"The whole of the apparatus stood upon a small table about
3 feet square, in the centre of the room. Underneath the
table the space was fitted with about fifty primary cells ; a
240 THIRD PERIOD THE PRACTICAL.
10 -inch induction coil occupied the centre of the table.
The spark is 1J centimetre long, or about three-quarters of
an inch ; the pole off the top of which the current went into
space is 150 feet high. The length of spark and power of
current were the same as used for communication with the
East Goodwin lightship, a fact which seems remarkable
when it is considered that the distance over which the
messages were sent yesterday was nearly three times as
great. The greater distance is compensated for by the
increased height of the pole.
" Throughout the whole of the messages sent yesterday
there was not once a fault to be detected everything was
clearly and easily recorded. The rate of transmission was
about fifteen words a minute." 1
The first international press message sent by the new
system was secured by the 'Times,' and is as follows :
" (From our Boulogne Correspondent)
"WIMKEUX, March 28.
"Communication between England and the Continent
was set up yesterday morning by the Marconi system of
wireless telegraphy. The points between which the experi-
ments are being conducted are South Foreland and
Wimreux, a village on the French coast two miles north of
Boulogne, where a vertical standard wire, 150 feet high, has
been set up. The distance is thirty-two miles. The experi-
ments are being carried on in the Morse code. Signor
Marconi is here conducting the trials, and is very well
satisfied with the results obtained.
"This message has been transmitted by the Marconi
system from Wimreux to the Foreland."
Other demonstrations (for Mr Marconi will no longer
1 The Daily Graphic, March 30, 1899.
G. MAKCONI'S METHOD. 241
permit us to call them "experiments" and rightly) are
now contemplated, as between Newhaven and Dieppe,
sixty-four miles ; between Nice and Cape Corso in Corsica,
over a hundred miles ; between the South Foreland and
the Eiffel Tower, about 230 miles; and, finally, between
England and America, which, as shown in the First Period
of this history, was the dream of the earliest experimenters
in wireless telegraphy.
A press telegram of April 12 says: "The Wireless
Telegraph Company have been approached by the repre-
sentative of a proposed syndicate which desires to acquire
the sole rights of establishing wireless telegraphic communi-
cation between England and America. The directors of
the Company will consider the matter at their first meeting,
which is fixed for an early date."
Thus I end my task as I began it, with a dream the
self-same dream ! As to its realisation in the distant future
who can say nay ?
" There are more things in heaven and earth, Horatio,
Than are dreamt of in our philosophy."
In conclusion, I give a few extracts from a letter (the
'Times,' April 3, 1899) of Prof. Fleming of the University
College, London. Prof. Fleming is an expert in electrical
science, and therefore his views may be taken as represent-
ing the last word on our subject :
To the Editor of the ' Times.'
" SIR, During the last few days I have been permitted
to make a close examination of the apparatus and methods
being employed by Signer Marconi in his remarkable tele-
graphic experiments between South Foreland and Boulogne,
and at the South Foreland lighthouse have been allowed by
Q.
242 THIRD PERIOD THE PRACTICAL.
the inventor to make experiments and transmit messages
from the station there established both to France and to the
lightship on the Goodwin Sands, which is equipped for
sending and receiving ether wave signals. Throughout the
period of my visit messages, signals, congratulations, and
jokes were freely exchanged between the operators sitting on
either side of the Channel, and automatically printed down
in telegraphic code signals on the ordinary paper slip at the
rate of twelve to eighteen words a minute. Not once was
there the slightest difficulty or delay in obtaining an instant
reply to a signal sent. No familiarity with the subject
removes the feeling of vague wonder with which one sees a
telegraphic instrument merely connected with a length of
150 feet of copper wire run up the side of a flagstaff begin
to draw its message out of space and print down in dot
and dash on the paper tape the intelligence ferried across
thirty miles of water by the mysterious ether. . . . v
"I cannot help thinking that the time has arrived for a
little more generous appreciation by his scientific contem-
poraries of the fact that Signer Marconi has by minute atten-
tion to detail, and by the important addition of the long,
vertical air wire, translated one method of space telegraphy
out of the region of uncertain delicate laboratory experiments
and placed it on the same footing as regards certainty of
action and ease of manipulation, so far as the present results
show, as any of the other methods of electric communica-
tion employing a continuous wire between the two places.
This is no small achievement. The apparatus, moreover, is
ridiculously simple and not costly. With the exception of
the flagstaff and 150 feet of vertical wire at each end, he can
place on a small kitchen table the appliances, costing not
more than .100 in all, for communicating across thirty or
even a hundred miles of channel. . . .
" In the presence of the enormous practical importance
G. MARCONI'S METHOD. 243
of this feat alone, and of the certainty with which com-
munication can now be established between ship and shore
without costly cable or wire, the scientific criticisms which
have been launched by other inventors against Signor
Marconi's methods have failed altogether in their appreci-
ation of the practical significance of the results he has
brought about.
" The public, however, are not in the least interested in
learning the exact meed of merit to be apportioned to various
investigators in the upbuilding of this result. They do,
however, want to know whether the new method of com-
munication across the Channel established by the expendi-
ture of a few hundred pounds will take the place to any
considerable extent of submarine cables which have cost
many thousands of pounds to lay and equip. They do also
desire to learn what reasons, if any, will prevent every
lighthouse and lightship round our coasts from being forth-
with furnished with the necessary apparatus for placing it
in instantaneous and secure connection with the mainland.
They also hope to hear that the methods can be applied to
enable ships to be able in addition to communicate instantly,
in case of need, with shore stations. To understand how far
these things can be done, and to appreciate the necessary or
present limitations of the method, it is requisite to explain
that each vertical wire or rod connected to a Marconi receiv-
ing or sending apparatus has a certain ' sphere of influence/
Signor Marconi has proved by experiment up to certain
limits that the distance to which effective signalling extends
varies as the square of the height of the rod. A wire 20
feet high carries the effective signal one mile, 40 feet high
four miles, 80 feet sixteen miles, and so on. Up to the
present time he has not yet discovered any method of
shielding any particular rod so as to render it responsive
only to signals coming from one station, and not from all
244 THIRD PERIOD THE PRACTICAL.
others within its sphere of influence. In spite, however, of
what has been said, there is no inherent impossibility in
attaining this desired result. At present all signals sent
from the South Foreland to France affect the receiver on
board the Goodwin lightship. But this offers no difficulty.
In an ordinary electric bell system in a hotel the servant
recognises the room from which the signal conies by means
of a simple apparatus called an indicator, and a very similar
arrangement can be applied to distinguish the origin of an
ether wave signal when several instruments are at work in a
common region. Subsequent inventions, as also, perhaps,
the promulgation of some necessary Board of Trade regula-
tions for the use of the ether, will prevent official ether
wave receivers from being disturbed by vagrant electric
waves sent out by unauthorised persons in their neighbour-
hood. The practical upshot, however, of the matter is that
at present if more than two stations are not established
within certain regions, these stations, pair and pair, can
communicate with each other freely and regularly by means
of ether wave signals sent out and received by long vertical
rods or wires. No state of the atmosphere, and neither
darkness nor storm, interrupts, so far as yet found, the
freedom of communication.
" Up to the present time none of the other systems of
wireless telegraphy employing electric or magnetic agencies
has been able to accomplish the same results over equal
distances. Without denying that much remains yet to be
attained, or that the same may be affected in other ways,
it is impossible for any one to witness the South Foreland
and Boulogne experiments without coming to the conclusion
that neither captious criticism nor official lethargy should
stand in the way of additional opportunities being afforded
for a further extension of practical experiments. Wireless
telegraphy will not take the place of telegraphy with wires
G. MARCONI'S METHOD. 245
each has a special field of operations of its own. But the
public have a right to ask that the fullest advantage shall
be taken of that particular sendee which ether wave teleg-
raphy can now render in promoting the greater safety of
those at sea ; and that, in view of our enormous maritime
interests, this country shall not permit itself to be outraced
by others in the peaceful contest to apply the outcome of
scientific investigations and discoveries in every possible
direction to the service of those who are obliged to face the
perils of the sea. If scientific research has forged a fresh
weapon with which in turn to fight Nature, ' red in tooth
and claw,' all other questions fade into insignificance in
comparison with the inquiry how we can take the utmost
advantage of this addition to our resources. I am, &c.,
"J. A. FLEMING.
"UNIVERSITY COLLEGE, LONDON."
246
APPENDIX A.
THE KELATION BETWEEN ELECTRICITY AND LIGHT
BEFORE AND AFTER HERTZ.
Before Hertz.
SUBSTANCE of a lecture by Prof. Oliver Lodge, London In-
stitution, December 16, 1880. 1
Ever since the subject on which I have to speak to-night
was arranged, I have been astonished at my own audacity
in proposing to deal, in the course of sixty minutes, with
a subject so gigantic and so profound that a course of sixty
lectures would be inadequate for its thorough and exhaustive
treatment. I must, therefore, confine myself to some few of
the most salient points in the relation between electricity and
light, and I must economise time by plunging at once into the
middle of the matter without further preliminary.
What is electricity ? We do not know. We cannot assert
that it is a form of matter ; neither can we deny it. On the
other hand, we cannot certainly assert that it is a form of
energy ; and I should be disposed to deny it. It may be
that electricity is an entity per se, just as matter is an
entity per se. Nevertheless, I can tell you what I mean
by electricity by appealing to its known behaviour.
Here is a voltaic battery. I want you to regard it, and
all electrical machines and batteries, as kinds of electricity-
pumps, which drive the electricity along through the wire
very much as a water-pump can drive water along pipes.
1 Based on a report in ' Design and Work,' February 5, 1881.
RELATION BETWEEN ELECTRICITY AND LIGHT. 247
While this is going on, the wire manifests a whole series of
properties, which are called the properties of the current.
[Here were shown an ignited platinum wire, the electric
arc between two carbons, an electric machine spark, an in-
duction coil spark, and a vacuum tube glow. Also a large
nail was magnetised by being wrapped in the current, and
two helices were suspended and seen to direct and attract
each other.]
To make a magnet, then, we only need a current of elec-
tricity flowing round and round in a whirl. A vortex or
whirlpool of electricity is in fact a magnet, and vice versd.
And these whirls have the power of directing and attracting
other previously existing whirls according to certain laws,
called the laws of magnetism. And, moreover, they have
the power of exciting fresh whirls in neighbouring con-
ductors, and of repelling them according to the laws of
diamagnetism. The theory of the actions is known, though
the nature of the whirls, as of the simple streams of elec-
tricity, is at present unknown.
[Here was shown a large electro-magnet and an induction-
coil vacuum discharge spinning round and round when placed
in its field.]
So much for what happens when electricity is made to
travel along conductors i.e., when it travels along like a
stream of water in a pipe, or spins round and round like
a whirlpool.
But there is another set of phenomena, usually regarded
as distinct and of another order, but which are not so
distinct as they appear, which manifest themselves when
you join the pump to a piece of glass or any non-conductor
and try to force the electricity through that. You succeed
in driving some through, but the flow is no longer like that
of water in an open pipe ; it is as if the pipe were com-
pletely obstructed by a number of elastic partitions or dia-
phragms. The water cannot move without straining and
bending these diaphragms, and if you allow it, these strained
partitions will recover themselves and drive the water back
again. [Here was explained the process of charging a Leyden
jar.] The essential thing to remember is that we may have
electrical energy in two forms, the static and the kinetic;
248 APPENDIX A.
and it is therefore also possible to have the rapid alternation
from one of these forms to the other, called vibration.
Now we will pass to the second question : What do you
mean by light ? And the first and obvious answer is, Every-
body knows. And everybody that is not blind does know to
a certain extent. We have a special sense-organ for appreci-
ating light, whereas we have none for electricity. Neverthe-
less, we must admit that we really know very little about the
intimate nature of light very little more than about elec-
tricity. But we do know this, that light is a form of energy ;
and, moreover, that it is energy rapidly alternating between
the static and the kinetic forms that it is, in fact, a special
kind of energy of vibration. We are absolutely certain that
light is a periodic disturbance in some medium, periodic both
in space and time that is to say, the same appearances regu-
larly recur at certain equal intervals of distance at the same
time, and also present themselves at equal intervals of time
at the same place ; that, in fact, it belongs to the class
of motions called by mathematicians undulatory or wave
motions.
Now how much connection between electricity and light
have we perceived in this glance into their natures? Not
much truly. It amounts to about this : That on the one
hand electrical energy may exist in either of two forms
the static form, when insulators are electrically strained by
having had electricity driven partially through them (as in
the Leyden jar), which strain is a form of energy, because
of the tendency to discharge and do work ; and the kinetic
form, where electricity is moving bodily along through con-
ductors, or whirling round and round inside them, which
motion of electricity is a form of energy, because the con-
ductors and whirls can attract or repel each other and thereby
do work.
On the other hand, light is the rapid alternation of energy
from one of these forms to the other the static form where
the medium is strained, to the kinetic form when it moves.
It is just conceivable then that the static form of the energy
of light is electro- static that is, that the medium is electrically
strained and that the kinetic form of the energy of light is
electro-kinetic that is, that the motion is not ordinary motion,
RELATION BETWEEN ELECTRICITY AND LIGHT. 249
but electrical motion in fact, that light is an electrical vibra-
tion, not a material one.
On November 5 last year there died at Cambridge a man in
the full vigour of his faculties such faculties as do not appear
many times in a century whose chief work had been the
establishment of this very fact, the discovery of the link con-
necting light and electricity, and the proof for I believe that it
amounts to a proof- that they are different manifestations of
one and the same class of phenomena, that light is, in fact, an
electro-magnetic disturbance. The premature death of James
Clerk Maxwell is a loss to science which appears at present
utterly irreparable, for he was engaged in researches that no
other man can hope as yet adequately to grasp and follow out ;
but fortunately it did not occur till he had published his book
on 'Electricity and Magnetism,' one of those immortal pro-
ductions which exalt one's idea of the mind of man, and which
has been mentioned by competent critics in the same breath
as the ' Principia ' itself.
The main proof of the electro-magnetic theory of light is
this : The rate at which light travels has been measured
many timer, and is pretty well known. The rate at which
an electro-magnetic wave disturbance would travel, if such
could be generated (and Mr Fitzgerald, of Dublin, thinks
he has proved that it cannot be generated directly by any
known electrical means), can be also determined by calcula-
tion from electrical measurements. The two velocities agree
exactly.
The first glimpse of this splendid generalisation was caught
in 1845, five-and-thirty years ago, by that prince of pure ex-
perimentalists, Michael Faraday. His reasons for suspecting
some connection between electricity and light are not clear to
us in fact, they could not have' been clear to him ; but he
seems to have felt a conviction that if he only tried long
enough, and sent all kinds of rays of light in all possible direc-
tions across electric and magnetic fields in all sorts of media,
he must ultimately hit upon something. Well, this is very
nearly what he did. With a sublime patience and persever-
ance which remind one of the way Kepler hunted down guess
after guess in a different field of research, Faraday combined
electricity, or magnetism, and light in all manner of ways, and
250 APPENDIX A.
at last he was rewarded with a result and a most out-of-the-
way result it seemed. First, you have to get a most powerful
magnet, and very strongly excite it ; then you have to pierce
its two poles with holes, in order that a beam of light may
travel from one to the other along the lines of force ; then, as
ordinary light is no good, you must get a beam of plane
polarised light and send it between the poles. But still no
result is obtained until, finally, you interpose a piece of a rare
and out-of-the-way material which Faraday had himself dis-
covered and made, a kind of glass which contains borate of
lead, and which is very heavy or dense, and which must be
perfectly annealed.
And now, when all these arrangements are completed, what
is seen is simply this, that if an analyser is arranged to stop
the light and make the field quite dark before the magnet is
excited, then directly the battery is connected and the magnet
called into action a faint and barely perceptible brightening
of the field occurs, which will disappear if the analyser be
slightly rotated. [The experiment was shown.] Now, no
wonder that no one understood this result. Faraday himself
did not understand it at all. He seems to have thought that
the magnetic lines of force were rendered luminous, or that the
light was magnetised ; in fact he was in a fog, and had no idea
of its real significance. Nor had any one. Continental phil-
osophers experienced some difficulty and several failures
before they were able to repeat the experiment. It was, in
fact, discovered too soon, and before the scientific world was
ready to receive it, and it was reserved for Sir William
Thomson briefly, but very clearly, to point out, and for Clerk
Maxwell more fully to develop, its most important conse-
quences.
This is the fundamental experiment on which Clerk Max-
well's theory of light is based ; but of late years many fresh
facts and relations between electricity and light have been
discovered, and at the present time they are tumbling in in
great numbers.
It was found by Faraday that many other transparent
media besides heavy glass would show the phenomenon if
placed between the poles, only in a less degree ; and the very
important observation that air itself exhibits the same phenom-
RELATION BETWEEN ELECTRICITY AND LIGHT. 251
enon, though to an exceedingly small extent, has just been
made by Kundt and Rontgen in Germany.
Dr Kerr, of Glasgow, has extended the result to opaque
bodies, and has shown that if light be passed through mag-
netised iron its plane is rotated. The film of iron must be
exceedingly thin, because of its opacity ; and hence, though
the intrinsic rotating power of iron is undoubtedly very great,
the observed rotation is exceedingly small and difficult to
observe ; and it is only by very remarkable patience and care
and ingenuity that Dr Kerr has obtained his result. Mr
Fitzgerald, of Dublin, has examined the question mathemati-
cally, and has shown that Maxwell's theory would have
enabled Dr Kerr's result to be predicted.
Another requirement of the theory is that bodies which are
transparent to light must be insulators or non-conductors of
electricity, and that conductors of electricity are necessarily
opaque to light. Simple observation amply confirms this.
Metals are the best conductors, and are the most opaque bodies
known. Insulators such as glass and crystals are transparent
whenever they are sufficiently homogeneous, and the very
remarkable researches of Professor Graham Bell in the last few
months have shown that even ebonite, one of the most opaque
insulators to ordinary vision, is certainly transparent to some
kinds of radiation, and transparent to no small degree.
[The reason why transparent bodies must insulate, and why
conductors must be opaque, was here illustrated by mechanical
models.]
A further consequence of the theory is that the velocity of
light in a transparent medium will be affected by its electrical
strain constant ; in other words, that its refractive index will
bear some close but not yet quite ascertained relation to its
specific inductive capacity. Experiment has partially con-
firmed this, but the confirmation is as yet very incomplete.
But there are a number of results not predicted by theory,
and whose connection with the theory is not clearly made out.
We have the fact that light falling on the platinum electrode
of a voltameter generates a current, first observed, I think, by
Sir W. K. Grove ; at any rate it is mentioned in his * Correla-
tion of Forces ' extended by Becquerel and Robert Sabine to
other substances, and now being extended to fluorescent and
252 APPENDIX A.
other bodies by Professor Minchin. And finally for I must
be brief we have the remarkable action of light on selenium.
This fact was discovered accidentally by an assistant in the
laboratory of Mr Willoughby Smith, who noticed that a piece
of selenium conducted electricity very much better when light
was falling upon it than when it was in the dark. The light
of a candle is sufficient, and instantaneously brings down the
resistance to something like one-fifth of its original value.
This is the phenomenon which, as you know, has been
utilised by Professor Graham Bell in that most ingenious and
striking invention, the photophone.
I have now trespassed long enough upon your patience, but
I must just allude to what may very likely be the next strik-
ing popular discovery, and that is the transmission of light by
electricity. I mean the transmission of such things as views
and pictures by means of the electric wire. It has not yet
been done, but it seems already theoretically possible, and it
may very soon be practically accomplished.
THE KELATION BETWEEN ELECTRICITY AND LIGHT.
After Hertz.
Substance of a lecture by Prof. Oliver Lodge, Ashmolean
Society, Oxford, June 3, 1889. l
For now wellnigh a century we have had a wave-theory of
light ; and a wave-theory of light is certainly ;rue. It is
directly demonstrable that light consists of waves of some
kind or other, and that these waves travel at a certain well-
known velocity, seven times the circumference of the earth
per second, taking eight minutes on the journey from the sun
to the earth. This propagation in time of an undulatory dis-
turbance necessarily involves a medium. If waves setting out
from the sun exist in space eight minutes before striking our
eyes, there must necessarily be in space some medium in which
they exist and which conveys them. Waves we cannot have
unless they be waves in something.
i Based on a report in the (London) ' Electrician/ September 6, 1889.
RELATION BETWEEN ELECTRICITY AND LIGHT. 253
No ordinary medium is competent to transmit waves at
anything like the speed of light ; hence the luminiferous
medium must be a special kind of substance, and it is called
the ether. The luminiferous ether it used to be called, because
the conveyance of light was all it was then known to be capable
of ; but now that it is known to do a variety of other things
also, the qualifying adjective may be dropped.
Wave motion in ether light certainly is ; but what does one
mean by the term wave ? The popular notion is, I suppose,
of something heaving up and down, or perhaps of something
breaking on the shore in which it is possible to bathe. But
if you ask a mathematician what he means by a wave, he will
probably reply that the simplest wave is
# = asin (pt-nx\
and he might possibly refuse to give any other answer. And
in refusing to give any other answer than this, or its equivalent
in ordinary words, he is entirely justified ; that is what is
meant by the term wave, and nothing less general wonld be
all-inclusive.
Translated into ordinary English, the phrase signifies " a dis-
turbance periodic both in space and time." Anything thus
doubly periodic is a wave ; and all waves whether in air as
sound waves, or in ether as light waves, or on the surface of
water as ocean waves are comprehended in the definition.
What properties are essential to a medium capable of trans-
mitting wave motion ? Roughly we may say two elasticity
and inertia. Elasticity in some form, or some equivalent of
it, in order to be able to store up energy and effect recoil ;
inertia, in order to enable the disturbed substance to overshoot
the mark and oscillate beyond its place of equilibrium to and
fro. Any medium possessing these two properties can transmit
waves, and unless a medium possesses these properties in some
form or other, or some equivalent for them, it may be said
with moderate security to be incompetent to transmit waves.
But if we make this latter statement one must be prepared
to extend to the terms elasticity and inertia their very largest
and broadest signification, so as to include any possible kind
of restoring force and any possible kind of persistence of
motion respectively.
These matters may be illustrated in many ways, but perhaps
254 APPENDIX A.
a simple loaded lath or spring in a vice will serve well enough.
Pull aside one end, and its elasticity tends to make it recoil ;
let it go, and its inertia causes it to overshoot its normal
position : both causes together cause it to swing to and fro
till its energy is exhausted. A regular series of such springs
at equal intervals in space, set going at regular intervals of
time one after the other, gives you at once a wave motion and
appearance which the most casual observer must recognise
as such. A series of pendulums will do just as well. Any
wave-transmitting medium must similarly possess some form
of elasticity and of inertia.
But now proceed to ask what is this ether which in the
case of light is thus vibrating? What corresponds to the
elastic displacement and recoil of the spring or pendulum?
What corresponds to the inertia whereby it overshoots its
mark? Do we know these properties in the ether in any
other way ?
The answer, given first by Clerk Maxwell, and now reiter-
ated and insisted on by experiments performed in every im-
portant laboratory in the world, is
The elastic displacement corresponds to electro -static charge
(roughly speaking, to electricity).
The inertia corresponds to magnetism.
This is the basis of the modern electro-magnetic theory of
light. Now let me illustrate electrically how this can be.
The old and familiar operation of charging a Leyden jar
the storing up of energy in a strained dielectric any electro-
static charging whatever is quite analogous to the drawing
aside of our flexible spring. It is making use of the elasticity
of the ether to produce a tendency to recoil. Letting go the
spring is analogous to permitting a discharge of the jar per-
mitting the strained dielectric to recover itself, the electro-
static disturbance to subside.
In nearly all the experiments of electro - statics ethereal
elasticity is manifest.
Next consider inertia. How would one illustrate the fact
that water, for instance, possesses inertia the power of per-
sisting in motion against obstacles the power of possessing
kinetic energy? The most direct way would be to take a
stream of water and try suddenly to stop it. Open a water-
RELATION BETWEEN ELECTRICITY AND LIGHT. 255
tap freely and then suddenly shut it. The impetus or
momentum of the stopped water makes itself manifest by a
violent shock to the pipe, with which everybody must be
familiar. The momentum of water is utilised by engineers in
the <c water-ram."
A precisely analogous experiment in electricity is what
Faraday called " the extra current." Send a current through
a coil of wire round a piece of iron, or take any other arrange-
ment for developing powerful magnetism, and then suddenly
stop the current by breaking the circuit. A violent flash
occurs if the stoppage is sudden enough, a flash which means
the bursting of the insulating air partition by the accumulated
electro-magnetic momentum.
Briefly, we may say that nearly all electro-magnetic experi-
ments illustrate the fact of ethereal inertia.
Now return to consider what happens when a charged con-
ductor (say a Leyden jar) is discharged. The recoil of the
strained dielectric causes a current, the inertia of this current
causes it to overshoot the mark, and for an instant the charge
of the jar is reversed : the current now flows backwards and
charges the jar up as at first ; again flows the current, and so
on, discharging and charging the jar with rapid oscillations
until the energy is all dissipated into heat. The operation is
precisely analogous to the release of a strained spring, or to
the plucking of a stretched string.
But the discharging body thus thrown into strong electrical
vibration is embedded in the all-pervading ether, and we have
just seen that the ether possesses the two properties requisite
for the generation and transmission of waves viz., elasticity,
and inertia or density ; hence, just as a tuning-fork vibrating
in air excites aerial waves or sound, so a discharging Leyden
jar in ether excites ethereal waves or light.
Ethereal waves can therefore be actually produced by direct
electrical means. I discharge here a jar, and the room is for
an instant filled with light. With light, I say, though you
can see nothing. You can see and hear the spark indeed,
but that is a mere secondary disturbance we can for the
present ignore I do not mean any secondary disturbance. I
mean the true ethereal waves emitted by the electric oscilla-
tion going on in the neighbourhood of this recoiling dielectric.
256 APPENDIX A.
You pull aside the prong of a tuning-fork and let it go : vibra-
tion follows and sound is produced. You charge a Leyden jar
and let it discharge : vibration follows and light is excited.
It is light just as good as any other light. It travels at the
same pace, it is reflected and refracted according to the same
laws ; every experiment known to optics can be performed
with this ethereal radiation electrically produced, and yet you
cannot see it. Why not ? For no fault of the light ; the fault
(if there be a fault) is in the eye. The retina is incompetent
to respond to these vibrations they are too slow. The vibra-
tions set up when this large jar is discharged are from a hun-
dred thousand to a million per second, but that is too slow for
the retina. It responds only to vibrations between 4000 bil-
lions and 7000 billions per second. The vibrations are too
quick for the ear, which responds only to vibrations between
40 and 40,000 per second. Between the highest audible and
the lowest visible vibrations there has been hitherto a great
gap, which these electric oscillations go far to fill up. There
has been a great gap simply because we have no intermediate
sense-organ to detect rates of vibration between 40,000 and
4,000,000,000,000,000 per second. It was, therefore, an un-
explored territory. Waves have been there all the time in
any quantity, but we have not thought about them nor at-
tended to them.
It happens that I have myself succeeded in getting electric
oscillations so slow as to be audible. The lowest I have got
at present are 125 per second, and for some way above this
the sparks emit a musical note ; but no one has yet succeeded
in directly making electric oscillations which are visible, though
indirectly every one does it by lighting a candle.
Here, however, is an electric oscillator which vibrates 300
million times a second, and emits ethereal waves a yard long.
The whole range of vibrations between musical tones and some
thousand millions per second is now filled up.
These electro-magnetic waves have long been known on the
side of theory, but interest in them has been immensely quick-
ened by the discovery of a receiver or detector for them. The
great though simple discovery by Hertz of an " electric eye,"
as Sir W. Thomson calls it, makes experiments on these waves
for the first time possible, or even easy. We have now a sort
RELATION BETWEEN ELECTRICITY AND LIGHT. 257
of artificial sense - organ for their appreciation an electric
arrangement which can virtually "see" these intermediate
rates of vibration.
The Hertz receiver is the simplest thing in the world
nothing but a bit of wire, or a pair of bits of wire, adjusted
so that when immersed in strong electric radiation they give
minute sparks across a microscopic air-gap.
The receiver I have here is adapted for the yard-long waves
emitted from this small oscillator ; but for the far longer waves
emitted by a discharging Leyden jar an excellent receiver is
a gilt wall-paper or other interrupted metallic surface. The
waves falling upon the metallic surface are reflected, and in
the act of reflection excite electric currents, which cause sparks.
Similarly, gigantic solar waves may produce aurorae ; and
minute waves from a candle do electrically disturb the retina.
The smaller waves are, however, far the most interesting
and the most tractable to ordinary optical experiments. From
a small oscillator, which may be a couple of small cylinders
kept sparking into each other end to end by an induction coil,
waves are emitted on which all manner of optical experiments
can be performed.
They can be reflected by plain sheets of metal, concentrated
by parabolic reflectors, refracted by prisms, concentrated by
lenses. I have at the College a large lens of pitch, weighing
over 3 cwt, for concentrating them to a focus. They can be
made to show the phenomenon of interference, and thus have
their wave lengths accurately measured. They are stopped by
all conductors, and transmitted by all insulators. Metals are
opaque, but even imperfect insulators, such as wood or stone,
are strikingly transparent, and waves may be received in one
room from a source in another, the door between the two being
shut.
The real nature of metallic opacity and of transparency has
long been clear in Maxwell's theory of light, and these elec-
trically produced waves only illustrate and bring home the
well-known facts. The experiments of Hertz are in fact the
apotheosis of that theory.
Thus, then, in every way Maxwell's brilliant perception of
the real nature of light is abundantly justified ; and for the
first time we have a true theory of light, no longer based upon
258 APPENDIX A.
analogy with sound, nor upon a hypothetical jelly or elastic
solid.
Light is an electro-magnetic disturbance of the ether. Optics
is a branch of electricity. Outstanding problems in optics are
being rapidly solved now that we have the means of definitely
exciting light with a full perception of what we are doing, and
of the precise mode of its vibration.
It remains to find out how to shorten down the waves to
hurry up the vibration until the light becomes visible. No-
thing is wanted but quicker modes of vibration. Smaller oscil-
lators must be used very much smaller oscillators not much
bigger than molecules. In all probability one may almost
say certainly ordinary light is the result of electric oscillation
in the molecules of hot bodies, or sometimes of bodies not hot
as in the phenomenon of phosphorescence.
The direct generation of visible light by electric means, so
soon as we have learnt how to attain the necessary frequency
of vibration, will have most important practical consequences.
For consider our present methods of making artificial light :
they are both wasteful and ineffective.
We want a certain range of oscillation, between 7000 and
4000 billion vibrations per second, no other is useful to us,
because no other has any effect upon our retina ; but we do
not know how to produce vibrations of this rate. We can
produce a definite vibration of one or two hundred or thousand
per second in other words, we can excite a pure tone of
definite pitch ; and we can command any desired range of
such tones continuously by means of bellows and a keyboard.
We can also (though the fact is less well known) excite
momentarily definite ethereal vibrations of some millions per
second, as I have explained ; but we do not at present seem to
know how to maintain this rate quite continuously. To get
much faster rates of vibration than this, we have to fall back
upon atoms. We know how to make atoms vibrate, it is
done by what we call "heating" the substance; and if we
could deal with individual atoms unhampered by others, it is
possible that we might get a pure and simple mode of vibra-
tion from them. It is possible, but unlikely ; for atoms, even
when isolated, have a multitude of modes of vibration special
to themselves, of which only a few are of practical use to us,
RELATION BETWEEN ELECTRICITY AND LIGHT. 259
and we do not know how to excite some without also the
others. However, we do not at present even deal with indi-
vidual atoms ; we treat them crowded together in a compact
mass, so that their modes of vibration are really infinite.
We take a lump of matter, say a carbon filament or a piece
of quicklime, and by raising its temperature we impress upon
its atoms higher and higher modes of vibration, not transmut-
ing the lower into the higher, but superposing the higher upon
the lower, until at length we get such rates of vibration as our
retina is constructed for, and we are satisfied. But how waste-
ful and indirect and empirical is the process ! We want a small
range of rapid vibrations, and we know no better than to make
the whole series leading up to them. It is as though, in order
to sound some little shrill octave of pipes in an organ, we are
obliged to depress every key and every pedal, and to blow a
young hurricane.
I have purposely selected as examples the more perfect
methods of obtaining artificial light, wherein the waste radia-
tion is only useless, and not noxious. But the old-fashioned
plan was cruder even than this : it consisted simply in setting
something burning, whereby not the fuel but the air was
consumed ; whereby also a most powerful radiation was pro-
duced, in the waste waves of which we were content to sit
stewing, for the sake of the minute almost infinitesimal
fraction of it which enabled us to see.
Every one knows now, however, that combustion is not a
pleasant or healthy mode of obtaining light ; but everybody
does not realise that neither is incandescence a satisfactory
and unwasteful method, which is likely to be practised for
more than a few decades, or perhaps a century.
Look at the furnaces and boilers of a great steam-engine
driving a group of dynamos, and estimate the energy ex-
pended ; and then look at the incandescent filaments of the
lamps excited by them, and estimate how much of their
radiated energy is of real service to the eye. It will be as
the energy of a pitch-pipe to an entire orchestra.
It is not too much to say that a boy turning a handle could,
if his energy were properly directed, produce quite as much
real light as is produced by all this mass of mechanism and
consumption of material. There might, perhaps, be something
260 APPENDIX A.
contrary to the laws of nature in thus hoping to get and util-
ise some specific kind of radiation without the rest ; but Lord
Eayleigh has shown in a short communication to the British
Association at York that it is not so, and that therefore we
have a right to try to do it.
We do not yet know how, it is true, but it is one of the
things we have got to learn.
Any one looking at a common glowworm must be struck
with the fact that not by ordinary combustion, nor yet on the
steam-engine and dynamo principle, is that easy light pro-
duced. Very little waste radiation is there from phosphor-
escent things in general. Light of the kind able to affect the
retina is directly emitted ; and for this, for even a large supply
of this, a modicum of energy suffices.
Solar radiation consists of waves of all sizes, it is true ; but
then solar radiation has innumerable things to do besides
making things visible. The whole of its energy is useful. In
artificial lighting nothing but light is desired ; when heat is
wanted it is best obtained separately by combustion. And so
soon as we clearly recognise that light is an electrical vibra-
tion, so soon shall we begin to beat about for some mode of
exciting and maintaining an electrical vibration of any required
degree of rapidity. When this has been accomplished, the
problem of artificial lighting will have been solved.
PROF. HENRY ON HIGH TENSION ELECTRICITY. 261
APPENDIX B.
PROF. HENRY ON HIGH TENSION ELECTRICITY BEING CONFINED
TO THE SURFACE OF CONDUCTING BODIES, WITH SPECIAL
REFERENCE TO THE PROPER CONSTRUCTION OF LlGHTNING-
EODS.
(Extracted from the l Journal of the Telegraph? Neio York,
Sept. 1, 1877.)
WASHINGTON, March 11, 1876.
DEAR SIR, In answer to your letter of the 7th inst, I have
to say that the discrepancy which exists as to the question
whether electricity passes at the surface or through the whole
capacity of the rod has arisen principally from experiments on
galvanic electricity, which, having little or no repulsive energy,
passes through the whole substance of the rod, and also from
experiments in which a very large quantity of frictional elec-
tricity is transmitted through a small wire : in this case the
metal is resolved into its elements and reduced to an
impalpable powder.
In the case, however, of the transmission of atmospheric
electricity through a rod of sufficient size to transmit the dis-
charge freely, there can be no doubt that it tends to pass at
the surface, the thickness of the stratum of electricity varying
with the diameter of the rod and the amount and the intensity
of the charge.
To test this by actual experiment I made the following ar-
rangement : through a gun-barrel about 2 feet in length a
copper wire was passed, the ends projecting. The middle of
the wire in the barrel was coiled into the form of a magnetis-
ing spiral, and the ends of the gun-barrel were closed with
plugs of tinfoil, so as to make a perfect metallic connection
between the wire and the barrel. On the outside of the barrel
another magnetising spiral was placed, the whole arrangement
being shown in the sketch.
262 APPENDIX B.
A powerful charge was now sent through the copper wire
from a Leyden jar of about two gallons' capacity. The needle
within the barrel showed not the least sign of magnetism,
while the one on the outside was strongly magnetic.
From this experiment I conclude that a gas-pipe can convey
an ordinary charge of electricity from the clouds as well as a
solid rod of the same diameter.
The repulsive energy of the electrical discharge at right
angles to the axis remains of the same intensity as in the case
of a statical charge. This I have shown to be the case by
drawing sparks of considerable intensity from a conductor, one
end of which was connected with the ground while sparks
were thrown on the other end from a large prime conductor.
This spark is of a peculiar character, for though it gives a
pungent shock and sets fire to combustible substances, such as
an electrical pistol, it does not affect a sensitive gold-leaf elec-
trometer. The fact is, it consists of two sparks, the one
negative and the other positive. The rod during the trans-
mission of the electricity through it is charged + at the upper
end, and immediately in advance of this point it is charged -
by induction, and the electricity passes through it in the dis-
charge in the form of a series of + and waves. Yours very
truly, JOSEPH HENRY, Sec. Smithsonian Inst.
Prof. E. C. KEDZIE, Lansing, Michigan.
WASHINGTON, April 15, 1876.
DEAR SIR, Your letter was received by due course of mail,
but a press of business connected with the preparation of the
Annual Keport for 1875 and the Lighthouse Board has pre-
vented an earlier reply.
I have now to say that, as far as I know, I am the only person
who has made a special study of the conduction of frictional
electricity in regard to lightning-rods. It has long been estab-
lished by Coulomb and others that the electricity of a charged
conductor exists in a thin stratum at the surface, and this is a
PROF. HENRY ON HIGH TENSION ELECTRICITY. 263
necessary consequence of the repulsion of electricity for itself,
every particle being repelled from every other as far as possible.
From this it was hastily assumed that electricity in motion
also moves at the surface ; but this was an inference without
physical proof until I commenced the investigation. I found
from a series of experiments that frictional electricity that is,
electricity of repulsive energy, such as that from the clouds
does pass at the surface, but that galvanic electricity, the kind
to which Faraday, Daniell, De La Rive, and others refer,
passes through the whole capacity of the conductor. This
latter fact, however, was previously established by others. I
further found that whenever a charge of electricity was thrown
on a rod explosively, however well connected the rod was with
the earth, it gave off sparks in the course of its length sufficient
to fire an electric pistol and light flocculent substances. I also
found that, in sending a powerful discharge from a battery of
nine jars through a wide plate, no electricity passed along the
middle of the plate, but that it was accumulated in its passage
at the edges.
From all my study of this subject I do not hesitate to say
that the plan I have given of lightning-rods is the true one,
and that a tube of a sufficient degree of thickness serves to
conduct the electricity as well as a solid mass, provided the
thickness is sufficient to give free conduction. A very heavy
charge sent through a wire frequently deflagrates it, but no
discharge from the clouds, of which I have any knowledge, has
ever sufficed to deflagrate a gas-pipe of an inch in diameter.
The plan of increasing the surface of a rod by converting the
metal into a ribbon is objectionable. It tends to increase the
power of the lateral discharge, and gives no increase of con-
ducting power.
Another fallacy is much insisted on viz., the better conduc-
tion of copper than iron. It is true that copper is a better
conductor of galvanic electricity, which pervades the whole
mass, but in regard to frictional electricity the difference in
conducting capacity is too small to be of any importance. Iron
is sufficiently good in regard to conduction, and withstands
deflagration better than copper : besides this, it is much
cheaper. Yours truly, JOSEPH HENRY.
Prof. R. C. KEDZIE.
264 APPENDIX B.
ON MODERN VIEWS WITH EESPECT TO THE NATURE OF
ELECTRIC CURRENTS.
Substance of a lecture by Prof. H. A. Eowland, American
Institute of Electrical Engineers, May 22, 1889. l
How great, then, the difference between a current of water
and a current of electricity ! The action of the former is con-
fined to the interior of the tube, while that of the latter ex-
tends to great distances on all sides, the whole of the space being
agitated by the formation of an electric current in any part.
To show this agitation, I have here two large frames with coils
of wire around them. They hang face to face about 6 feet
apart. Through one I discharge this Ley den jar, and imme-
diately you see a spark at a break in the wire of the other coil,
and yet there is no apparent connection between the two. I
can carry the coils 50 feet or more apart, and yet, by suitable
means, I can observe the disturbances due to the current in
the first coil.
The question is forced upon us as to how this action takes
place. How is it possible to transmit so much power to such a
distance across apparently unoccupied space ? According to
our modern theories of physics, there must be some medium
engaged in this transmission. We know that it is not the air,
because the same effects take place in a vacuum, and therefore
we must fall back on that medium which transmits light, and
which we have named the ether that medium which is sup-
posed to extend unaltered throughout the whole of space,
whose existence is very certain, but whose properties we have
yet but vaguely conceived.
I cannot in the course of one short hour give even an idea
of the process by which the minds of physicists have been led
to this conclusion, or the means by which we have finally
completely identified the ether which transmits light with the
medium which transmits electrical and magnetic disturbances.
The great genius who first identified the two is Maxwell,
whose electro-magnetic theory of light is the centre around
1 Based on reports in the (London) ' Electrician,' June 21 and 28,
1889.
NATURE OF ELECTRIC CURRENTS. 265
which much scientific thought is to-day revolving, and which we
regard as one of the greatest steps by which we advance nearer
to the understanding of matter and its laws. It is this great
discovery of Maxwell which allows me to attempt to explain
to you the wonderful events which happen everywhere in
space when one establishes an electric current in any other
portion.
In the first place, we discover that the disturbance does not
take place in all portions of space at once, but proceeds out-
ward from the centre of the disturbance with a velocity exactly
equal to the velocity of light ; so that when I touch these
wires together so as to complete the circuit of yonder battery,
I start a wave of ethereal disturbance which passes outward
with a velocity of 185,000 miles per second, and continues to
pass outwards for ever, or until it reaches the bounds of the
universe. And yet none of our senses informs us of what has
taken place unless sharpened by the use of suitable instru-
ments. Thus, in the case of these two coils of wire, suspended
near each other, when the wave from the primary disturbance
reaches the second coil we perceive the disturbance by means
of the spark formed at the break in the coil. Should I move
the coils farther apart, the spark in the second coil would be
somewhat delayed, but the distance of 185,000 miles would be
necessary before this delay could amount to as much as one
second. Hence the effects we observe on the earth take place
so nearly instantaneously that the interval of time is very
difficult to measure, amounting in the present case to only
T5 oo ooo oo th of a second.
It is impossible for me to prove the existence of this interval,
so infinitesimal is it, but I can at least show you that waves
have something to do with the action observed. For instance,
I have here two tuning-forks mounted on sounding-boxes and
tuned to exact unison. I sound one and then stop its vibra-
tions with my hand ; instantly you hear that the other is in
vibration, caused by the waves of sound in the air between the
two. When, however, I destroy the unison by fixing this piece
of wax on one of the forks, the action ceases.
Now, this combination of a coil of wire and a Leyden jar
forms a vibrating system of electricity, and its time of vibra-
tion is about 10,000,000 times a second. Here is another
266 APPENDIX B.
combination of coil and jar, the same as the first, and therefore
its time of vibration is the same. You see how well the
experiment works, because the two are in unison. But let me
take away this second Leyden jar, thus destroying the unison,
and you see that the sparks instantly cease. Eeplacing it, the
sparks reappear. Adding another on one side, they disappear
again, only to reappear when the system is made symmetrical
by placing two on each side.
This experiment and that of the tuning-forks have an exact
analogy to one another. In each we have two vibrating
systems connected by a medium capable of transmitting
vibrations, and they both come under the head of what we
know as sympathetic vibrations. In the one case, we have
two mechanical tuning-forks connected by the air ; in the
other, two pieces of apparatus, which we might call electrical
tuning-forks, connected by the ether. The vibrations in one
case can be seen by the eye or heard by the ear, but in the
other case they can only be perceived when we destroy them
by making them produce a spark. The fact that we are able
to increase the effect by proper tuning demonstrates that
vibrations are concerned in the phenomenon. This can, how-
ever, be separately demonstrated by examining the spark by
means of a revolving mirror, when we find that it is made up
of many successive sparks corresponding to the successive
backward and forward movements of the current.
Thus, in the case of a charged Leyden jar whose inner and
outer coatings have been suddenly joined by a wire, the elec-
tricity flows back and forth along the wire until all the energy
originally stored up in the jar has expended itself in heating
the wire or the air where the spark takes place, and in gener-
ating waves of disturbance in the ether which move outward
into space with the velocity of light. These ethereal waves we
have demonstrated by letting them fall on this coil of wire,
causing the electrical disturbance to manifest itself by electric
sparks.
I have here another more powerful arrangement for produc-
ing electro-magnetic waves of very long wave length, each one
being about 500 miles long. It consists of a coil within which
is a bundle of iron wires. On passing a powerful alternating
current through the coil the iron wires are rapidly magnetised
NATURE OF ELECTRIC CURRENTS. 267
and demagnetised, and send forth into space a system of electro-
magnetic waves at the rate of 360 in a second.
Here also I have another piece of apparatus for sending out
the same kind of electro-magnetic waves, and on applying a
match we start it also into action. But the last apparatus is
tuned to so high a pitch that the waves are only ^oooo i ncn
long, and 55,000,000,000,000 are given out in one second. These
short waves are known by the name of light and radiant heat,
though the name radiation is more exact. Placing any body
near the lamp so that the radiation can fall on it, we observe
that when the body absorbs the rays it is heated by them. Is
it not possible for us to get some substance to absorb the long
(or electro-magnetic) waves of disturbance, and so obtain a
heating effect 1 I have here such a substance in the shape of a
sheet of copper, which I fasten on the face of a thermopile,
and I hold it where these waves are strongest. As I have
anticipated, great heat is generated by their absorption, and
soon the plate of copper becomes very warm, as we see by this
thermometer, by feeling it with the hand, or even by the steam
from water thrown upon it. In this experiment the copper
had not touched the coil or the iron wire core, although if it
did they are very much cooler than itself. The heat has been
produced by the absorption of the waves in the same way as a
blackened body absorbs the rays of shorter wave length from
the lamp.
In these experiments, so far, the wave-like nature of the
disturbance has not been proved. We have caused electric
sparks, and have heated the copper plate across an interval of
space, but have not in either of these cases proved experi-
mentally the progressive nature of the disturbance.
A ready means of experimenting on the waves, obtaining
their wave length and showing their interferences, has hitherto
been wanting. This deficiency has been recently supplied by
Prof. Hertz, of Carlsruhe.
I scarcely know how to present this subject to a non- technical
audience and make it clear how a coil of wire with a break in
it can be used to measure the velocity and length of ethereal
waves. However, I can but try. If the waves moved very
slowly, we could readily measure the time the first coil took to
affect the second, and show that this time was longer as the
268 APPENDIX B.
distance was greater. But it is absolutely inappreciable by any
of our instruments, and another method must be found. To
obtain the wave length Prof. Hertz used several methods, but
that by the formation of stationary waves is the most easily
grasped. I hold in my hand one end of a spiral spring, which
makes a heavy and flexible rope. As I send a wave down it,
you see that it is reflected at the farther end, and returns again
to my hand. If, however, I send a succession of waves down
the rope, the reflected waves interfere with the direct ones, and
divide the rope into a succession of nodes and loops which you
now observe. So, a series of sound waves, striking on a wall,
forms a system of stationary waves in front of the wall.
Indeed we can use any waves for this purpose, even ethereal
waves. With this in view Prof. Hertz established his apparatus
in front of a reflecting wall, and observed the nodes and loops
by the sparks produced in a ring of wire, somewhat resembling
the coil I have been using, but much smaller. It is impossible
for me to repeat this experiment before you, as it is a very
delicate one, and the sparks produced are almost microscopic.
Indeed I should have to erect an entirely different apparatus,
as the waves from the one before me are nearly a quarter-mile
long. To produce shorter waves we must use apparatus very
much smaller tuned, as it were, to a higher pitch, so that
several stationary waves, or nodes and loops, of a few yards
long could be obtained in the space of this room.
The testing coil would then be moved to different parts of the
room, and the nodes would be indicated by the disappearance
of the sparks, and the loops by the greater brightness of them.
The presence of stationary waves would thus be proved, and
their half -wave length found from the distance from node
to node, for stationary waves can always be considered as
produced by the interference of two waves advancing in op-
posite directions.
The closing of a battery circuit, then, and the establishment
of a current of electricity in a wire, is a very different process
from the formation of a current of water in a pipe, though
after the first shock the laws of the flow of the two are very
much alike. Furthermore, the medium around the current of
electricity has very strange properties, showing that it is ac-
companied by a disturbance throughout space. The wire is
NATURE OF ELECTRIC CURRENTS. 269
but the core of the disturbance, which latter extends indefin-
itely in all directions.
One of the strangest things about it is that we can calculate
with perfect exactness the velocity of the wave propagation
and the amount of the disturbance at every point and at any
instant of time ; but as yet we cannot conceive of the details of
the mechanism which is concerned in the propagation of an
electric current. In this respect our subject resembles all
other branches of physics in the partial knowledge we have of
it. We know that light is the undulation of the luminiferous
ether, and yet the constitution of the latter is unknown. We
know that the atoms of matter can vibrate with purer tones
than the most perfect piano, and yet we cannot even conceive
of their constitution. We know that the sun attracts the
planets with a force whose law is known, and yet we fail to
picture to ourselves the process by which it takes our earth
within its grasp at the distance of many millions of miles and
prevents it from departing for ever from its life-giving rays.
Science is full of this half -knowledge.
So far we have considered the case of alternating electric
currents in a wire connecting the inner and outer coatings of a
Leyden jar. The invention of the telephone, by which sound
is carried from one point to another by means of electrical
waves, has forced into prominence the subject of these waves.
Furthermore, the use of alternating currents for electric light-
ing brings into play the same phenomenon. Here, again, the
difference between a current of water and a current of elec-
tricity is very marked. A sound wave, traversing the water
in the tube, produces a to-and-fro current of water at any
given point. So, in the electrical vibration along a wire, the
electricity moves to and fro along it in a manner somewhat
similar to the water, but with this difference : the disturbance
from the water-motion is confined to the tube, and the oscilla-
tion of the water is greatest in the centre of the tube ; while in
the case of the electric current the ether around the wire is dis-
turbed, and the oscillation of the current is greatest at the
surface of the wire and least in its centre. The oscillations in
the water take place in the tube without reference to the
matter outside the tube, whereas the electric oscillations in the
wire are entirely dependent on the surrounding space, and the
270 APPENDIX B.
velocity of the propagation is nearly independent of the nature
of the wire, provided it is a good conductor.
We have then in the case of electrical waves along a wire a
disturbance outside the wire and a current within it, and the
equations of Maxwell allow us to calculate these with perfect
accuracy and give all the laws with respect to them.
We thus find that the velocity of propagation of the waves
along a wire, hung far away from other bodies and made of
good conducting material, is that of light, or 185,000 miles per
second ; but when it is hung near any conducting matter, like
the earth, or enclosed in a cable and sunk into the sea, the
velocity becomes much less. When hung in space, away from
other bodies, it forms, as it were, the core of a system of waves
in the ether, the amplitude of the disturbance becoming less
and less as we move away from the wire. But the most
curious fact is that the electric current penetrates only a
short distance into the wire, being mostly confined to the
surface, especially where the number of oscillations per second
is very great.
The electrical waves at the surface of a conductor are thus,
in some respects, very similar to the waves on the surface of
water. The greatest motion in the latter case is at the surface,
while it diminishes as we pass downwards and soon becomes
inappreciable. Furthermore, the depth to which the disturb-
ance penetrates into the water increases with increase of the
length of the wave, being confined to very near the surface for
very short waves. So the disturbance in the copper penetrates
deeper as the waves and the time of oscillation are longer, and
the disturbance is more nearly confined to the surface as the
waves become shorter. 1
There are very many practical applications of these theor-
etical results for electric currents. The most obvious one is
to the case of conductors for the alternating currents used
1 A striking illustration of this skin-deep penetration of high-voltage
electricity was communicated by Lord Armstrong to Sir William Thom-
son (now Lord Kelvin) at the Newcastle meeting of the British Associa-
tion in 1889. A bar of steel about a foot long, which Lord Armstrong
was holding in his hand, was allowed accidentally to short circuit the
two terminals of a dynamo giving an alternate current of 85 amperes, at
a difference of potential of 103 volts. He instantly felt a sensation of
NATURE OF ELECTRIC CURRENTS. 271
in producing the electric light. We find that when these are
larger than about half an inch diameter they should be re-
placed by a number of conductors less than half an inch dia-
meter, or by strips about a quarter of an inch thick, and of
any convenient width.
Prof. Oliver Lodge has recently drawn attention to another
application of these results that is, to lightning-rods. Al-
most since the time of Franklin there have been those who
advocated the making of lightning-rods hollow in order to in-
crease the surface for a given amount of copper. We now
know that these persons had no reason for their belief, as they
simply drew the inference that electricity at rest is on the
surface. Neither were the advocates of the solid rods quite
correct, for they reasoned that electricity in a state of steady
flow occupies the whole area of the conductor equally. The
true theory, we now know, indicates that neither party was
entirely correct, and that the surface is a very important factor
in the case of a current of electricity so sudden as that from a
lightning discharge. But increase of surface can best be ob-
tained by multiplying the number of conductors, rather than
making them flat or hollow. Theory indicates that the current
penetrates only one-tenth the distance into iron that it does
into copper. As the iron has seven times the resistance of
copper, we should need seventy times the surface of iron that
we should of copper. Hence I prefer copper wire about
a quarter of an inch diameter and nailed directly to the house
without insulators, and passing down the four corners, around
the eaves, and over the roof, for giving protection from light-
ning in all cases where a metal roof and metal down-spouts do
not accomplish the same purpose.
Whether the discharge of lightning is oscillatory or not does
not enter into the question, provided it is only sufficiently
sudden. I have recently solved the mathematical problem of
the electric oscillations along a perfectly conducting wire join-
burning and dropped the bar. His fingers were badly blistered, though
on examining the bar a few seconds afterwards it was found to be quite
cold. This proved that the action lay at the surface, and had not time to
sensibly penetrate the substance of the bar. There were two little
hollows burned out of the metal at the points where it touched the
dynamo terminals. J. J. F,
272 APPENDIX B.
ing two infinite and perfectly conducting planes parallel to
each other, and find that there is no definite time of oscillation,
but that the system is capable of vibrating in any time in
which it is originally started. The case of lightning between
a cloud of limited extent and the earth along a path through
the air of great resistance is a very different problem. Both
the cloud and the path of the electricity are poor conductors,
which tends to lengthen the time. If I were called on to
estimate as nearly as possible what took place in a flash of
lightning, I would say that I did not believe that the discharge
was always oscillating, but more often consisted of one or more
streams of electricity at intervals of a small fraction of a sec-
ond, each one continuing for not less than TOSOUO second. An
oscillating current with 100,000 reversals per second would
penetrate about ^ inch into copper and g^ inch into iron.
The depth for copper would constitute a considerable propor-
tion of a wire J- inch diameter, and as there are other con-
siderations to be taken into account, I believe it is scarcely
worth while making tubes, or flat strips, for such small
sizes.
It is almost impossible to draw proper conclusions from ex-
periments on this subject in the laboratory, such as those of
Prof. Oliver Lodge. 1 The time of oscillation of the current in
most pieces of laboratory apparatus is so very small, being
often the yoooooo^o f a second, that entirely wrong inferences
may be drawn from them. As the size of the apparatus in-
creases, the time of oscillation increases in the same propor-
tion, and changes the whole aspect of the case. I have given
ro^onu ^ a second as the shortest time a lightning-flash could
probably occupy. I strongly suspect it is often much greater,
and thus departs even further from the laboratory experiments
of Prof. Lodge, who has, however, done very much towards
drawing attention to this matter and showing the importance
of surface in this case. All shapes of the rod with equal sur-
face are not, however, equally efficient. Thus, the inside
surface of a tube does not count at all. Neither do the corru-
gations on a rod count for the full value of the surface they
1 For Prof. Lodge's views see his paper, 'Jour. Inst. Elec. Engs.,'
vol. xix. p. 352, and the very interesting discussion thereupon.
J. J. F.
NATURE OF ELECTRIC CURRENTS. 273
expose, for the current is not distributed uniformly over the
surface ; but I have recently proved that rapidly alternating
currents are distributed over the surface of very good conduc-
tors in the same manner as electricity at rest would be dis-
tributed over them, so that the exterior angles and corners
possess much more than their share of the current, and corru-
gations on the wire concentrate the current on the outer
angles and diminish it in the hollows. Even a flat strip has
more current on the edges than in the centre.
For these reasons, shape, as well as extent of surface, must
be taken into account, and strips have not always an advan-
tage over wires for quick discharges.
The fact that the lightning-rod is not melted on being struck
by lightning is not now considered as any proof that it has done
its work properly. It must, as it were, seize upon the discharge,
and offer it an easier passage to the earth than any other. Such
sudden currents of electricity we have seen to obey very dif-
ferent laws from continuous ones, and their tendency to stick
to a conductor and not fly off to other objects depends not only
on having them of small resistance, but also on having what we
call the self-induction as small as possible. This latter can be
diminished by having the lightning-rod spread sideways as
much as possible, either by rolling it into strips, or better, by
making a network of rods over the roof with several connections
to the earth at the corners, as I have before described.
Thus we see that the theory of lightning-rods, which appeared
so simple in the time of Franklin, is to-day a very complicated
one, and requires for its solution a very complete knowledge of
the dynamics of electric currents. In the light of our present
knowledge the frequent failure of the old system of rods is no
mystery, for I doubt if there are a hundred buildings in the
country properly protected from lightning. With our modern
advances, perfect protection might be guaranteed in all cases,
if expense were no object.
We have now considered the case of oscillations of electricity
in a few cases, and can turn to that of steady currents. The
closing of an electric circuit sends ethereal waves throughout
space, but after the first shock the current flows steadily with-
out producing any more waves. However, the properties of
the space around the wire have been permanently altered, as
274 APPENDIX B.
we have already seen. Let us now study these properties more
in detail. I have before me a wire in which I can produce a
powerful current of electricity, and we have seen that the
space around it has been so altered that a delicately suspended
magnetic needle cannot remain quiet in all positions, but
stretches itself at right angles to the wire, the north pole
tending to revolve around it in one direction and the south
pole in the other. This is a very old experiment, but we now
regard it as evidence that the properties of the space around
the wire have been altered rather than that the wire acts on
the magnet from a distance.
Put, now, a plate of glass around the wire, the latter being
vertical and the former with its plane horizontal, and pass a
powerful current through the wire. On now sprinkling iron
filings on the plate they arrange themselves in circles around
the wire, and thus point out to us the celebrated lines of mag-
netic force of Faraday. Using two wires with currents in the
same direction we get these other curves, and, testing the forces
acting on the wire, we find that they are trying to move towards
each other.
Again, pass the currents in the opposite directions and we
get these other curves, and the currents repel each other. If
we assume that the lines of force are like rubber bands which
tend to shorten in the direction of their length and repel each
other sideways, Faraday and Maxwell have shown that all mag-
netic attractions and repulsions are explained. The property
which the presence of the electric current has conferred on the
ether is then one by which it tends to shorten in one direction
and spread out in the other two directions.
We have thus done away with action at a distance, and have
accounted for magnetic attraction by a change in the inter-
vening medium, as Faraday partly did almost fifty years ago.
For this change in the surrounding medium is as much a
part of the electric current as anything that goes on within
the wire.
To illustrate this tension along the lines of force, 1 have con-
structed this model, which represents the section of a coil of
wire with a bar of iron within it. The rubber bands represent
the lines of force which pass around the coil and through the
iron bar, as they have an easier passage through the iron than
NATURE OF ELECTRIC CURRENTS. 275
the air. As we draw the bar down and let it go, you see that
it is drawn upward and oscillates around its position of equili-
brium until friction brings it to rest. Here, again, I have a
coil of wire with an iron bar within it with one end resting on
the floor. As we pass the current, and the lines of magnetic
force form around the coil and pass through the iron, it is lifted
upwards, although it weighs 24 lb., and oscillates around its
position of equilibrium exactly the same as though it were
sustained by rubber bands as in the model. The rubber bands
in this case are invisible to our eye, but our mental vision
pictures them as lines of magnetic force in the ether drawing
the bar upward by their contractile force. This contractile
force is no small quantity, as it may amount, in some cases, to
one or even two hundred pounds to the square inch, and
thus rivals the greatest pressure which we use in our steam-
engines.
Thus the ether is, to-day, a much more important factor in
science than the air we breathe. We are constantly surrounded
by the two, and the presence of the air is manifest to us all ;
we feel it, we hear by its aid, and we even see it under favour-
able circumstances, and the velocity of its motion as well as the
amount of moisture it carries is a constant topic of conversation.
The ether, on the other hand, eludes all our senses, and it is
only with imagination, the eye of the mind, that its presence
can be perceived. By its aid in conveying the vibrations we
call light we are enabled to see the world around us ; and by its
other motions, which cause magnetism, the mariner steers his
ship through the darkest night when the heavenly bodies are
hid from view. When we speak in a telephone, the vibrations
of the voice are carried forward to the distant point by waves
in the ether, there again to be resolved into the sound waves
of the air. When we use the electric light to illuminate our
streets, it is the ether which conveys the energy along the
wires as well as transmits it to our eye after it has assumed the
form of light. We step upon an electric street-car and feel it
driven forward with the power of many horses, and again it is
the ether whose immense force we have brought under our
control and made to serve our purpose no longer a feeble, un-
certain sort of medium, but a mighty power, extending through-
out all space, and binding the whole universe together.
276 APPENDIX C.
APPENDIX C.
VARIATIONS OF CONDUCTIVITY UNDER ELECTRICAL
INFLUENCE.
Substance of a paper by Prof. E. Branly, of the Catholic
University of Paris. 1
The object of this article is to describe the first results
obtained in an investigation of the variation or resistance of a
large number of conductors under various electrical influences.
The substances which up to the present have presented the
greatest variations in conductivity are the powders or filings
of metals. The enormous resistance offered by metal in a
state of powder is well known ; indeed, if we take a somewhat
long column of very fine metallic powder, the passage of the
current is completely stopped. The increase in the electrical
conductivity by pressure of powdered conducting substances is
also well known, and has had various practical applications.
The variations of conductivity, however, which occur on sub-
jecting conducting bodies to various electrical influences have
not been previously investigated.
The Effect of Electric Sparks. Let us take a circuit compris-
ing a single cell, a galvanometer, and some powdered metal
enclosed in an ebonite tube of one square centimetre cross section
and a few centimetres long. Close the extremities of the tube
with two cylindrical copper tubes pressing against the powdered
metal and connected to the rest of the circuit. If the powder
is sufficiently fine, even a very sensitive galvanometer does
not show any evidence of a current passing. The resistance is
of the order of millions of ohms, although the same metal
melted or under pressure would only offer (the dimensions
being the same) a resistance equal to a fraction of an ohm.
There being, therefore, no current in the circuit, a Leyden
1 Based on reports in the (London) ' Electrician/ June 26 and August
21, 1891.
VAKIATIOXS OF CONDUCTIVITY. 277
jar is discharged at some little distance off, when the abrupt
and permanent deflection of the galvanometer needle shows
that an immediate and a permanent reduction of the resistance
has been caused. The resistance of the metal is no longer to
be measured in millions of ohms, but in hundreds. Its con-
ductivity increases with the number and intensity of the
Some 20 or 30 centimetres from a circuit comprising some
metallic filings contained in an ebonite cup, let us place a
hollow brass sphere, 15 to 20 centimetres in diameter, insu-
lated by a vertical glass support. The filings offer an enormous
resistance and the galvanometer needle remains at zero. But
if we bring an electrified stick of resin near the sphere, a little
spark will pass between the stick and the sphere, and imme-
diately the needle of the galvanometer is violently jerked and
then remains permanently deflected. On some fresh filings
being placed in the ebonite cup, the resistance of the circuit
will again keep the needle at zero. If now the charged brass
sphere is touched with the finger, there is a minute discharge
and the galvanometer needle is again deflected. With a few
accumulators the experiment can easily be made without a
galvanometer. The circuit consists of the battery, some
metallic powder, a platinum wire, and a mercury cup. The re-
sistance of the powder is so high that the interruption of the
circuit takes place without any sparking of the mercury cup.
If now a Leyden jar is discharged in the neighbourhood of the
circuit the powder is rendered conducting, the platinum wire
immediately becomes red hot, and a violent spark occurs on
breaking the circuit.
The influence of the spark decreases as the distance increases,
but its influence is observable several metres away from the
powder, even with a small Wimshurst machine. Repeating
the spark increases the conductivity ; in fact, with certain
substances successive sparks produce successive jerks, and a
gradually increasing and persistent deflection of the galvan-
ometer needle.
Influence of a Conductor traversed by Condenser Discharges.
While using the Wimshurst machine it was noticed that the
reduction in the resistance of the filings frequently took place
before discharge. This led me to the following experiment :
278 APPENDIX C.
Take a long brass tube, one end of which is close to the circuit
containing the metallic powder ; its other end, several metres
distant from the circuit, is fairly close to a charged Leyden
jar. A spark takes place and the conductor is charged. At
the same instant, the conductivity of the metallic powder is
greatly increased.
The following arrangement, owing to its efficacy, conven-
ience, and regularity of action, was used by me in most of
my researches, and I shall briefly call it the A arrangement
(%. 1).
The source of electricity is a two-plate Holtz machine driven
at from 100 to 400 revolutions. A sensitive substance is intro-
duced into one of the arms of a Wheatstone bridge, or into the
circuit of a single Daniell cell at a dis-
u^ 11 LIL1 j Uil tance of some 10 metres from the Holtz
I , Q Q-J I j machine. Between the discharge knobs of
the machine and the Wheatstone bridge,
and connected to the former, there are
two insulated brass tubes, A A', running
A' parallel to one another 40 centimetres
apart. The Leyden jars usually attached
to a Holtz machine may be dispensed
with, the capacity of the long brass tubes
Fig. 1. being in some measure equivalent to them.
The knobs s were 1 mm., *5 mm., or -1 mm.
apart. When the plates were rotated, sparks rapidly succeeded
each other. Experiments showed that these sparks had no di-
rect effect at a distance of 10 metres. The two tubes A A' are not
absolutely necessary ; the diminution of resistance is easily pro-
duced if only one is employed, and in some cases, indeed, a
single conductor is more efficacious. An increase in the speed
of the machine increases its action to a marked extent. The
sparks at s may be suppressed by drawing the knobs apart,
but the conductor A will still continue to exert its influence,
especially if there is a spark-gap anywhere about.
Effects of Induced Currents. The passage of induced currents
through a sensitive substance produces similar effects to those
described above. In one instance an induction coil was taken,
having two similar wires. The circuit of the secondary wire
was closed through a tube containing filings, the galvanometer
K
VARIATIONS OF CONDUCTIVITY. 279
being also in circuit. Care was taken to ascertain before intro-
ducing the filings into the circuit that the currents on make
and break gave equal and opposite deflections. Filings were
then introduced into the circuit, the primary being made and
broken at regular intervals. The following table gives the
results obtained in the case of zinc filings :
ZINC FILINGS.
Galvanometer throws. Galvanometer throws.
1st closing . . 1 1st opening . . 18
2nd . . 64 2nd . 100
3rd . . 146 3rd / 140
Effects of passing Continuous Currents of High E.M.F. If a
continuous current of high E.M.F. is employed, it renders
a sensitive substance conducting. The phenomenon may be
shown in the following manner. A circuit is made up con-
sisting of a battery, a sensitive substance, and a galvanometer.
The E.M.F. of the battery is first 1 volt, then 100 volts, then 1
volt. Below I give the galvanometer deflections obtained
with an E.M.F. of 1 volt for three different substances before
and after the application of the E.M.F. of 100 volts :
Before application After application
of current of current.
16 100
15
1 500
In the case of some measurements taken on a Wheatstone
bridge, a prism of aluminium filings interposed between two
copper electrodes offered a resistance of several million ohms
before a high E.M.F. was applied, but only offered a resistance
of 350 ohms after the application of this pressure for one
minute. The time during which the powder should be inter-
posed in the battery circuit should not be too short. Thus, in
one instance the application for 10 seconds of 75 mercury
sulphate cells produced no effect, but their application for 60
seconds resulted in the resistance being reduced from several
megohms to 2500 ohms.
It should be observed that the phenomenon of suddenly in-
creased conductivity occurs even if the sensitive substance is
280
APPENDIX C.
not in circuit with a battery at the time it is influenced.
Thus, the metallic filings, after having been placed in circuit
with a Daniell cell, and their high resistance observed, may then
be completely insulated and submitted in this condition to the
action of a distant spark, or of a charged rod, or of induced
currents. If, after this, the filings are replaced in their
original circuit, the enormous increase in their conductivity
is immediately apparent.
The conductivity produced by these various methods takes
place throughout the whole mass of the
metallic filings, and in every direction,
as the following experiment will show.
A vertical ebonite cup containing alu-
minium powder (fig. 2) is placed between
two metal plates A, B ; laterally the pow-
der is in contact with two short rods
c, D, which pass through the sides of
the ebonite cylinder. A and B can be
connected to two terminals of one of
the arms of the Wheatstone bridge,
c and D being free, and vice versa.
Whatever arrangement is adopted, if a
battery of 100 cells is joined up for a
few seconds with one or the other of
the pairs of terminals, the increase in
the conductivity is immediately visible in that direction, and
is found to exist also in the direction at right angles.
Substances in which Diminution of Resistance has been ob-
served. The substances in which the phenomenon of the sudden
increase of conductivity is most easily observed are filings of
iron, aluminium, copper, brass, antimony, tellurium, cadmium,
zinc, bismuth, &c. The size of the grains and their nature are
not the only elements to be considered, for grains of lead of
the same size, but coming from different quarters, offer at the
same temperature great differences in resistance (20,000 to
500,000 ohms). Extremely fine metallic powder, as a rule,
offers almost perfect resistance to the passage of a current.
But if we take a sufficiently short column and exert a suffi-
ciently great pressure, a point is soon reached when the elec-
trical influence will effect a sudden increase in the conductivity.
If*
Fig. 2.
VARIATIONS OF CONDUCTIVITY.
281
Thus, a layer of copper reduced by hydrogen, which does not
become conducting under the influence of the electric spark or
otherwise, will become so on being submitted to a pressure of
500 grammes to the square centimetre (7 Ib. per square inch).
Instead of using pressure, I employed as a conductor in some
experiments a very fine coating of powdered copper spread on
a sheet of unpolished glass or ebonite E (fig. 3), 7 centimetres
long and 2 centimetres
broad. A layer of this
kind, polished with a
burnisher, has a very
variable resistance.
With a little care one
can prepare sheets which
are more or less sensi-
tive to electrical action.
Metal powders or
metal filings are not
the only sensitive sub-
stances, as powdered
galena, which is slightly
conducting under pres-
sure, conducts much
better after having been submitted to electrical influence.
Powdered binoxide of manganese is not very sensitive unless
mixed with powdered antimony and compressed.
Making use of the A arrangement with very short sparks
at s (fig. 1), the phenomenon of increased conductivity can be
observed with platinised and silvered glass, also with glass
covered with gold, silver, and aluminium foil. Some of the
mixtures employed had the consistency of paste. These were
mixtures of colza oil and iron, or antimony filings, and of ether
or petroleum and aluminium, and plumbago, &c. Other mix-
tures were solid. If we make a mixture of iron filings and
Canada balsam, melted in a water bath, and pour the paste
into a little ebonite cup, the ends of which are closed by
metallic rods, a substance is obtained which solidifies on cool-
ing. The resistance of such a mixture is lowered from several
megohms to a few hundred ohms by an electric spark. Similar
results are obtained with a solid rod composed of fused flowers
Fig. 3.
282 APPENDIX C.
of sulphur and iron or aluminium filings, also by a mixture
of melted resin and aluminium filings. In the preparation
of these solid sensitive mixtures, care must be taken that the
insulating substance should only form a small percentage of
the whole.
Some interesting results are also obtained with mixtures of
sulphur and aluminium, and with resin and aluminium, when
in a state of powder. When cold these mixtures, as a rule, do
not conduct either directly or after they have been exposed to
electrical influences, but they become conducting on combining
pressure with electrical influences. Thus, a mixture of flowers-of -
sulphur and aluminium filings in equal volumes was placed in a
glass tube 24 mm. in diameter. The weight of the mixture was
20 grammes, and the height of the column 22 mm., with a pres-
sure of 186 grammes per square centimetre (2j Ib. per square
inch). The mixture is not conducting, but after exposure to
electrical influence, obtained by the A arrangement, the resist-
ance falls to 90 ohms. In a similar manner a mixture of
selenium and aluminium, placed in a tube 99 mm. long, was
not conducting until after it was exposed to the combined in-
fluence of pressure and electricity.
The following is one of the group of numerous experiments
of a slightly different character. A mixture of flowers-of -
sulphur and fine aluminium filings, containing two of sulphur
to one of aluminium, is placed in a cylindrical glass tube 35
mm. long. By means of a piston, a pressure of 20 kilogrammes
per square centimetre (284 Ib. per square inch) was applied.
It was only necessary to connect the column for 10 seconds to
the poles of a 25-cell battery, for the resistance originally in-
finite to be reduced to 4000 ohms.
The arrangement shown in fig. 4 illustrates another order of
experiment. Two rods of copper were oxidised in the flame of
a Bunsen burner, and were then arranged to lie across each
other, as shown, and were connected to the terminals of the
arm of a Wheatstone bridge, the high resistance of the circuit
being due to the layers of oxide. Amongst the many measure-
ments made, I found, in one case, a resistance of 80,000 ohms,
which, after exposure to the influence of the electric spark,
was reduced to 7 ohms. Analogous effects are obtained with
oxidised steel rods. Another pretty experiment is to place a
VARIATIONS OF CONDUCTIVITY.
283
4
cylinder of copper, with an oxidised hemispherical head, on a
sheet of oxidised copper. Before exposure to the influence of
the electric spark, the oxide offers considerable resistance.
The experiment can be
repeated several times by
merely moving the cylin-
der from one place to
another on the oxidised
sheet of copper, thus
showing that the pheno-
menon only takes place
at the point of contact of
the two layers of oxide.
It may be worth noting
that, for most of the sub-
stances enumerated, an
elevation of temperature
diminishes the resistance, but the effect of a rise of tempera-
ture is transient, and is incomparably less than the effect due
to currents of high potential. For a few substances the two
effects are opposed.
Restoration of Original Resistance. The conductivity caused
by the various electrical influences lasts sometimes for a long
period (twenty-four hours or more), but it is always possible to
make it rapidly disappear, particularly by a shock.
The majority of substances tested snowed an increase of
resistance on being shaken previous to being submitted to any
special electrical influence, but after having been influenced
the effect of shock is much more marked. The phenomenon is
best seen with the metallic filings, but it can also be observed
with metallised ebonite sheets with mixtures of liquid insulators
and metallic powders, mixtures of metallic filings and insulating
substances (compressed or not compressed), and finally with
solid bodies.
I observed the return to original resistance in the following
manner :
The sensitive substance was placed at K (fig. 1), and formed
part of a circuit which included a Daniell cell and galvanometer.
At first no current passes. Sparks are then caused at s, and
the needle of the galvanometer is permanently deflected. On
284 APPENDIX C.
smartly tapping the table supporting the ebonite cup in which
the sensitive substance is contained, the original condition is
completely restored. When the electric action has been of a
powerful character, violent blows are necessary. I employed
for the purpose of these shocks a hammer fixed on the table,
the blows of which could be regulated.
With some substances, when feebly electrified, the return
seemed to be spontaneous, although it was slower than the
return of the galvanometer needle to equilibrium. This resto-
ration of the original resistance is attributable to surrounding
trepidations, as it was only necessary to walk about the room
at a distance of a few metres, or to shake a distant wall. This
spontaneous return to original resistance after weak electrical
action was visible with a mixture of equal parts of fine selenium
and tellurium powders. The restoration of resistance by shock
was not observable so long as the electrical influence was at
work.
After having been submitted to powerful electric action,
shock does not seem to entirely restore substances to their
original state ; in fact, the substances generally show greater
sensitiveness to electric action. Thus, a mixture of colza oil
and antimony powder being exposed to the influence of arrange-
ment A, a spark of 5 mm. was at first necessary to break down
the resistance ; but after the conductivity had been made to
disappear by means of blows, a spark of only 1 mm. was suffi-
cient to again render the substance conducting. Finely
powdered aluminium has an extremely high resistance. A
vertical column of powdered aluminium 5 mm. long of 4 square
cms. cross-section, submitted to considerable pressure, com-
pletely stopped the current from a Daniell cell. The influence
of arrangement A produced no effect, but, by direct contact
with a Leyden jar, the resistance was reduced to 50 ohms. The
effect of shock was then tried, and after this the sparks pro-
duced by arrangement A were able to reduce the resistance.
The following experiment is also of the same kind : Alum-
inium filings placed in a parallelipidic trough completely stopped
the current from a Daniell cell, and the resistance offered to a
single cell remained infinite after the trough had been placed
in the circuit of 25 sulphate of mercury cells for 10 seconds.
The aluminium was next placed in circuit with a battery of 75
VARIATIONS OF CONDUCTIVITY. 285
cells ; a single Daniell cell was then able to send a current
through the substance. The original resistance was restored
by shock, but not the original condition of things, since a single
cell was able to send a current after the aluminium had been
circuited for 10 seconds with a battery of only 25 cells. I may
add that if the restoration of resistance was brought about by
a violent shock, it was necessary to place the aluminium in
circuit with 75 cells for one minute before the resistance was
again broken down.
It must be observed that electrical influence is not always
necessary to restore conductivity after an apparent return to
the original resistance, repeated feeble blows being sometimes
successful in bringing this about. Both in the case of slow
return by time and sudden return by shock, the original value
of the resistance is often increased. Eods of Carre carbon, 1
metre long and 1 mm. in diameter, were particularly noticeable
for this phenomenon.
Return to Original Resistance by Temperature Elevation. A
plate of coppered ebonite rendered conducting by electricity,
and placed close to a gas-jet, quickly regained its original
resistance. A solid rod of resin and aluminium, or of sulphur
and aluminium, rendered conducting by connection to the poles
of a small battery, will regain its original resistance by shock ;
but if the conducting state has been caused by powerful means,
such, for instance, as direct contact with a Leyden jar, shock
no longer has any effect, at least such a shock as the fragile
nature of the material can stand. A slight rise of temperature,
however, has the desired result. By suitably regulating the
electric action it is possible to get a substance into such a
condition that the warmth of the fingers suffices to annul con-
ductivity.
Influence of Surroundings. Electric action gives rise to no
alteration of resistance when the substance is entirely within a
closed metal box. The sensitive substance, in circuit with a
Daniell cell and a galvanometer, is placed inside a brass box
(fig. 5). The absence of current is ascertained, the circuit
broken, and the box closed. A Wimshurst machine is then
worked a little way off, and will be found to have had no
effect. The same result will be obtained if the circuit is kept
closed during the time the Wimshurst machine is in operation.
286
APPENDIX C.
Fig. 5.
If a wire connected at some point to the circuit is passed out
through a hole in the box to a distance of 20 to 50 cms., the
influence of the Wimshurst machine makes itself felt. On
tapping the lid to re-
store resistance, the
galvanometer needle
remains deflected so
long as the sparks
continue to pass. If,
however, the wires
are pushed in so that
they only project a
few millimetres, the
sparks still passing,
a few taps suffice to
bring back the needle
to zero. On touch-
ing the end of the
wire with the fingers or a piece of metal, conductivity is imme-
diately restored. The movements of the galvanometer needle
were rendered visible in these experiments by looking through
apiece of wide -mesh wire -gauze with a telescope. The re-
spective position of the things was reversed ; that is to say,
a Kuhmkorff coil and a periodically discharged Leyden jar
were placed inside, and the sensitive substance outside, the
box, with the same results.
In some later experiments with a larger metallic case, and
with the Daniell cell, sensitive substance, delicate galvan-
ometer, and Wheatstone bridge placed inside, I found that a
double casing was necessary in order to absolutely suppress all
effects. A glass covering afforded no protection.
Considerations on the Mechanism of the Effects produced.
What conclusions are we to draw from the experiments de-
scribed ? The substances employed in these investigations
were not conductors, since the metallic particles composing
them were separated from each other in the midst of an in-
sulating medium. It was not surprising that currents of high
potential, and especially currents induced by discharges, should
spark across the insulating intervals. But as the conductivity
persisted afterwards, even for the weakest thermo - electric
VARIATIONS OF CONDUCTIVITY. 287
currents, there is some ground for supposing that the insulating
medium is transformed by the passage of the current, and that
certain actions, such as shock and rise of temperature, bring
about a modification of this new state of the insulating body.
Actual movement of the metallic particles cannot be imagined
in experiments where the particles in a layer a few millimetres
thick were fixed in an invariable relative position by extreme
pressures, reaching at times to more than 100 kilogrammes
per square cm. (1420 Ib. to the square inch). Moreover, in the
case of solid mixtures, in which the same variations of re-
sistance were produced, displacement seems out of the question.
To explain the persistence of the conductivity after the cessation
of the electrical influence, are we to suppose in the case of
metallic filings a partial volatilisation of the particles creating
a conducting medium between the grains of metal ? In the
case of mixtures of metallic powders and insulating substances
agglomerated by fusion, are we to suppose that the thin in-
sulating layers are pierced by the passage of very small sparks,
and that the holes left behind are coated with conducting
material ? If this explication is admissible for induced cur-
rents, it must hold good for continuous currents. If so, we
must conclude that these mechanical actions may be produced
by batteries of only 10 to 20 volts electromotive force, and
which only cause an insignificant current to pass. The following
experiment is worth quoting in this connection :
A circuit was formed by a Daniell cell, a sensitive galvan-
ometer, and some aluminium filings in an ebonite cup. The
galvanometer needle remained at zero. The filings were cut
out of this circuit, and switched for one minute into circuit
with a battery of 43 sulphate of mercury cells. On being re-
placed in the first circuit, the filings exhibited high conductivity.
The result was the same when 10 or 20 cells were employed, or
when the current was diminished by interposing in the circuit
a column of distilled water, 40 cm. long and 20 mm. in diameter.
The cells used (platinum, sulphate of mercury, sulphate of zinc,
zinc) had a high internal resistance. Thus, 43 cells (60 volts),
when short circuited, only gave a current of 5 milliamperes.
The same battery, with the column of distilled water in circuit
only, caused a deflection of 100 mm. on a scale one metre off,
with an astatic galvanometer wound with 50,000 turns. We
288 APPENDIX C.
can, therefore, see how infinitesimally small the initial current
must have been when the filings were added to the circuit. The
battery acted, therefore, essentially by virtue of its electro-
motive force.
If mechanical displacement of particles or transportation of
conducting bodies seem inadmissible, it is probable that there
is a modification of the insulator itself, the modification per-
sisting for some time by virtue of a sort of "coercive force."
An electric current of high potential, which would be com-
pletely stopped by a thick insulating sheet, may be supposed to
gradually traverse the very thin dielectric layers between the
conducting particles, the passage being effected very rapidly if
the electric pressure is great, and more slowly if the pressure
is less.
Increase of Resistance. An increase of resistance was observed
in these investigations less often than a diminution ; neverthe-
less, a number of frequently repeated experiments enable me to
say that increase of resistance is not exceptional, and that the
conditions under which it takes place are well defined. Short
columns of antimony or aluminium powder, when subjected to
a pressure of about 1 kilogramme per square cm. (14'2 Ib. per
square inch), and offering but a low resistance, exhibited an
increase of resistance under the influence of a powerful electri-
fication. Peroxide of lead, a fairly good conductor, always
exhibited an increase, so also did some kinds of platinised
glass, while others showed alternate effects. For instance, a
sheet of platinised glass, which offered a resistance of 700 ohms,
became highly conducting after 150 sulphate of mercury cells
had been applied to it for 10 seconds. This condition of con-
ductivity was annulled by contact with a charged Leyden jar,
and reappeared after again applying 150 cells for 10 seconds,
and so on. Similar effects were obtained with a thin layer of a
mixture of selenium and tellurium poured, when fused, into a
groove in a sheet of mica placed between two copper plates.
These alternations were always observed several times in suc-
cession, and at intervals of several days.
These augmentations and alternations are in no way incom-
patible with the hypothesis of a physical modification of the
insulator by electrical influence.
KESEARCHES OF PROF. D. E. HUGHES. 289
APPENDIX D.
RESEARCHES OF PROF. D. E. HUGHES, F.B.S., IN ELECTRIC
WAVES AND THEIR APPLICATION TO WlRELESS TELEGRAPHY,
1879-1886.
It may be desirable to place briefly on record the circum-
stances under which the following remarkable communication
was written.
While revising the last sheets of this work, it occurred to the
author to ask Sir William Crookes for some particulars of the
experiments to which he alluded in his ' Fortnightly ' article,
some passages from which are quoted on pp. 197-199. On April
22, 1899, Sir William replied as follows :
DEAR MR FAHIE, The experiments referred to at page
176 of my 'Fortnightly' article as having taken place "some
years ago" were tried by Prof. Hughes when experimenting
with the microphone.
I have not ceased since then urging on him to publish an
account of his experiments. I do not feel justified in saying
more about them, but if you were to write to him, telling him
what I say, it might induce him to publish.
It is a pity that a" man who was so far ahead of all other
workers in the field of wireless telegraphy should lose all the
credit due to his great ingenuity and prevision. Believe me,
very truly yours, WILLIAM CROOKES.
On receipt of this letter I wrote to Prof. Hughes. In reply
he said :
" Your letter of 26th instant has brought upon me a flood
of old souvenirs in relation to my past experiments on aerial
telegraphy. They were completely unknown to the general
public, and I feared that the few distinguished men who saw
them had forgotten them, or at least had forgotten how the
results shown them were produced. . . .
"At this late date I do not wish to set up any claim to
T
290 APPENDIX D.
priority, as I have never published a word on the subject ; and
it would be unfair to later workers in the same field to spring
an unforeseen claimant to the experiments which they have
certainly made without any knowledge of my work."
On second (and my readers will say, wiser) thoughts, Prof.
Hughes sent me the following letter, in the eliciting of which
I consider myself especially fortunate and privileged :
40 LANGHAM STREET, W., April 29, 1899.
DEAR SIR, In reply to yours of the 26th inst., in which
you say that Sir William Crookes has told you that he saw
some experiments of mine on aerial telegraphy in about De-
cember 1879, of which he thinks I ought to have published an
account, and of which you ask for some information, I beg to
reply with a few leading experiments that I made on this
subject from 1879 up to 1886 :
In 1879, being engaged upon experiments with my micro-
phone, together with my induction balance, I remarked that at
some times I could not get a perfect balance in the induction
balance, through apparent want of insulation in the coils ; but
investigation showed me that the real cause was some loose
contact or microphonic joint excited in some portion of the
circuit. I then applied the microphone, and found that it gave
a current or sound in the telephone receiver, no matter if the
microphone was placed direct in the circuit or placed inde-
pendently at several feet distance from the coils, through which
an intermittent current was passing. After numerous experi-
ments, I found that the effect was entirely caused by the
extra current, produced in the primary coil of the induction
balance.
Further researches proved that an interrupted current in
any coil gave out at each interruption such intense extra cur-
rents that the whole atmosphere in the room (or in several
rooms distant) would have a momentary invisible charge,
which became evident if a microphonic joint was used as a re-
ceiver with a telephone. This led me to experiment upon the
best form of a receiver for these invisible electric waves, which
evidently permeated great distances, and through all apparent
obstacles, such as walls, &c. I found that all microphonic con-
tacts or joints were extremely sensitive. Those formed of a
RESEAKCHES OF PEOF. D. E. HUGHES. 291
hard carbon such as coke, or a combination of a piece of coke
resting upon a bright steel contact, were very sensitive and
self -restoring ; whilst a loose contact between metals was
equally sensitive, but would cohere, or remain in full contact,
after the passage of an electric wave.
The sensitiveness of these microphonic contacts in metals
has since been rediscovered by Mons. Ed. Branly of Paris,
and by Prof. Oliver Lodge, in England, by whom the name of
" coherer " has been given to this organ of reception ; but, as
we wish this organ to make a momentary contact and not
cohere permanently, the name seems to me ill-suited for the
instrument. The most sensitive and perfect receiver that I
have yet made does not cohere permanently, but recovers its
original state instantly, and therefore requires no tapping or
mechanical aid to the separation of the contacts after moment-
arily being brought into close union.
I soon found that, whilst an invisible spark would pro-
duce a thermo-electric current in the microphonic contacts
(sufficient to be heard in the telephone in its circuit), it
was far better and more powerful to use a feeble voltaic cell
in the receiving circuit, the microphonic joint then acting
as a relay by diminishing the resistance at the contact,
under the influence of the electric wave received through
the atmosphere.
I will not describe the numerous forms of the transmitter
and receiver that I made in 1879, all of which I wrote down in
several volumes of manuscripts in 1879 (but these have never
been published), and most of which can be seen here at my
residence at any time ; but I will confine myself now to a few
salient points. I found that very sudden electric impulses,
whether given out to the atmosphere through the extra current
from a coil or from a frictional electric machine, equally affected
the microphonic joint, the effect depending more on the sudden
high potential effect than on any prolonged action. Thus, a
spark obtained by rubbing a piece of sealing-wax was equally
effective as a discharge from a Leyden jar of the same poten-
tial. The rubbed sealing-wax and charged Leyden jar had no
effect until they were discharged by a spark, and it was evi-
dent that this spark, however feeble, acted upon the whole
surrounding atmosphere in the form of waves or invisible rays,
292 APPENDIX D.
the laws of which I could not at the time determine. Hertz,
however, by a series of original and masterly experiments,
proved in 1887-89 that they were real waves similar to light,
but of a lower frequency, though of the same velocity. In
1879, whilst making these experiments on aerial transmission,
I had two different problems to solve : 1st, What was the true
nature of these electrical aerial waves, which seemed, whilst
not visible, to spurn all idea of insulation, and to penetrate all
space to a distance undetermined. 2nd, To discover the best
receiver that could act upon a telephone or telegraph instru-
ment, so as to be able to utilise (when required) these waves
for the transmission of messages. The second problem came
easy to me when I found that the microphone, which I had
previously discovered in 1877-78, had alone the power of
rendering these invisible waves evident, either in a telephone
or a galvanometer, and up to the present time I do not know
of anything approaching the sensitiveness of a microphonic
joint as a receiver. Branly's tube, now used by Marconi, was
described in my first paper to the Eoyal Society (May 8, 1878)
as the microphone tube, filled with loose filings of zinc and
silver ; and Prof. Lodge's coherer is an ordinary steel micro-
phone, used for a different purpose from that in which I first
described it. 1
During the long - continued experiments on this subject,
between 1879 and 1886, many curious phenomena came out
which would be too long to describe. I found that the effect
1 Prof. Hughes is rightly regarded as the real discoverer of the elec-
trical behaviour of a bad joint or loose contact, the study of which in his
hands has given us the microphone ; but as in the case of Hertzian-wave
effects before Hertz, so, long before Hughes, " mere phenomena of loose
contact," as Sir George Stokes called them, must have often manifested
themselves in the working of electrical apparatus. For an interesting
example see Arthur Schuster's paper read before the British Association
in 1874 (or abstract, ' Telegraphic Journal,' vol. ii. p. 289), where the
effects are described as a new discovery in electricity, and disguised
under the title of the paper, "On Unilateral Conductivity." Schuster
suspected the cause "Two wires screwed together may not touch each
other, but be separated by a thin layer of air "but he missed its real
significance. The phenomenon was a kind of bye-product, cropped up
while he was engaged on other work, and so was not pursued far enough.
J. J. F.
RESEARCHES OF PROF. D. E. HUGHES. 293
of the extra current in a coil was not increased by having an
iron core as an electro-magnet the extra current was less
rapid, and therefore less effective. A similar effect of a
delay was produced by Leyden-jar discharges. The material
of the contact-breaker of the primary current had also a great
effect. Thus, if the current was broken between two or one
piece of carbon, no effect could be perceived of aerial waves,
even at short distances of a few feet. The extra current from
a small coil without iron was as powerful as an intense spark
from a secondary coil, and at that time my experiments
seemed to be confined to the use of a single coil of my in-
duction balance, charged by six Daniell cells. With higher
battery power the extra current invariably destroyed the in-
sulation of the coils.
In December 1879 I invited several persons to see the re-
sults then obtained. Amongst others who called on me and
saw my results were
Dec. 1879. Mr W. H. Preece, F.E.S. ; Sir William Crookes,
F.RS. ; Sir W. Roberts - Austen, F.RS. ; Prof. W. Grylls
Adams, F.RS. ; Mr W. Grove.
Feb. 20, 1880. Mr Spottiswoode, Pres. RS. ; Prof. Huxley,
F.RS. ; Sir George Gabriel Stokes, F.RS.
Nov. 7, 1888. Prof. Dewar, F.RS. ; Mr Lennox, Royal
Institution.
They all saw experiments upon aerial transmission, as al-
ready described, by means of the extra current produced from
a small coil and received upon a semi-metallic microphone,
the results being heard upon a telephone in connection with
the receiving microphone. The transmitter and receiver were
in different rooms, about 60 feet apart. After trying success-
fully all distances allowed in my residence in Portland Street,
my usual method was to put the transmitter in operation and
walk up and down Great Portland Street with the receiver in
my hand, with the telephone to the ear.
The sounds seemed to slightly increase for a distance of 60
yards, then gradually diminish, until at 500 yards I could
no longer with certainty hear the transmitted signals. What
struck me as remarkable was that, opposite certain houses, I
could hear better, whilst at others the signals could hardly be
perceived. Hertz's discovery of nodal points in reflected waves
294 APPENDIX D.
(in 1887-89) has explained to me what was then considered a
mystery.
At Mr A. Stroh's telegraph instrument manufactory Mr
Stroh and myself could hear perfectly the currents trans-
mitted from the third storey to the basement, but I could not
detect clear signals at my residence about a mile distant. The
innumerable gas and water pipes intervening seemed to absorb
or weaken too much the feeble transmitted extra currents from
a small coil.
The President of the Eoyal Society, Mr Spottiswoode, to-
gether with the two hon. secretaries, Prof. Huxley and Prof.
G. Stokes, called upon me on February 20, 1880, to see my
experiments upon aerial transmission of signals. The experi-
ments shown were most successful, and at first they seemed
astonished at the results ; but towards the close of three hours'
experiments Prof. Stokes said that all the results could be
explained by known electro - magnetic induction effects, and
therefore he could not accept my view of actual aerial electric
waves unknown up to that time, but thought I had quite
enough original matter to form a paper on the subject to be
read at the Eoyal Society.
I was so discouraged at being unable to convince them of the
truth of these aerial electric waves that I actually refused to
write a paper on the subject until I was better prepared to
demonstrate the existence of these waves ; and I continued my
experiments for some years, in hopes of arriving at a perfect
scientific demonstration of the existence of aerial electric waves
produced by a spark from the extra currents in coils, or from
frictional electricity, or from secondary coils. The triumphant
demonstration of these waves was reserved to Prof. Hertz, who
by his masterly researches upon the subject in 1887-89 com-
pletely demonstrated not only their existence but their identity
with ordinary light, in having the power of being reflected and
refracted, &c., with nodal points, by means of which the length
of the waves could be measured. Hertz's experiments were
far more conclusive than mine, although he used a much less
effective receiver than the microphone or coherer.
I then felt it was now too late to bring forward my previous
experiments ; and through not publishing my results and means
employed, I have been forced to see others remake the dis-
RESEARCHES OF PROF. D. E. HUGHES. 295
coveries I had previously made as to the sensitiveness of the
microphonic contact and its useful employment as a receiver
for electric aerial waves.
Amongst the earliest workers in the field of aerial trans-
mission I would draw attention to the experiments of Prof.
Henry, who describes in his work, published by the Smithsonian
Institute, Washington, B.C., U.S.A., vol. i. p. 203 (date un-
known, probably about 1850), how he magnetised a needle in
a coil at 30 feet distance, and magnetised a needle by a dis-
charge of lightning at eight miles' distance. 1
Marconi has lately demonstrated that by the use of the
Hertzian waves and Branly's coherer he has been enabled to
transmit and receive aerial electric waves to a greater distance
than previously ever dreamed of by the numerous discoverers
and inventors who have worked silently in this field. His efforts
at demonstration merit the success he has received ; and if (as
I have lately read) he has discovered the means of concentrating
these waves on a single desired point without diminishing their
power, then the world will be right in placing his name on the
highest pinnacle in relation to aerial electric telegraphy.
Sincerely yours, D. E. HUGHES.
J. J. FAHIE, Esq.,
Claremont Hill, St Heller's, Jersey.
In the fifty years (just completed) of a brilliant professorial
career at Cambridge, Sir George Stokes has given, times out of
number, sound advice and helpful suggestions to those who
have sought him ; but in this case, as events show, the great
weight of his opinion has kept back the clock for many years.
With proper encouragement in 1879-80 Prof. Hughes would
have followed up his clues, and, with his extraordinary keenness
i The ' Polytechnic Review,' March 25, 1843, says : "Professor Henry
communicated to the American Society that he had succeeded in mag-
netising needles by the secondary current in a wire more than 220 feet
distant from the wire through which the primary current, excited by a
single spark from an electrical machine, was passing." Indeed, Prof.
Henry noted many cases of what we now call Hertzian-wave effects, but
what he and every one else in those days thought were only extra-
ordinary cases of induction. Many experimenters after Henry must have
observed similar effects. See for example the 'Electrician,' vol. xliii.
p. 204. J. J. F.
296 APPENDIX E.
in research, there can be no doubt that he would have antici-
pated Hertz in the complete discovery of electric waves, and
Marconi in the application of them to wireless telegraphy, and
so have altered considerably the course of scientific history.
As a recent commentator pithily says : " Hughes's experi-
ments of 1879 were virtually a discovery of Hertzian waves
before Hertz, of the coherer before Branly, and of wireless
telegraphy before Marconi and others." The writer goes on to
say, " Prof. Hughes has a great reputation already, but these
latter experiments will add enormously to it, and place him
among the foremost electricians of all time" 1 praise which,
knowing the learned professor as I do, I consider none too
great.
APPENDIX E.
EEPRINT OF SIGNOR G. MARCONI'S PATENT.
No. 12,039, A.D. 1896.
Date of Application, 2nd June 1896. Complete Specification
Left, 2nd Mar. 1897; Accepted, 2nd July 1897.
PKOVISIONAL SPECIFICATION.
IMPROVEMENTS IN TRANSMITTING ELECTRICAL IMPULSES AND
SIGNALS, AND IN APPARATUS THEREFOR.
I, Guglielmo Marconi, of 71 Hereford Eoad, Bays water, in
the county of Middlesex, do hereby declare the nature of this
invention to be as follows :
According to this invention electrical actions or manifesta-
tions are transmitted through the air, earth, or water by means
of electric oscillations of high frequency.
At the transmitting station I employ a Euhmkorff coil
having in its primary circuit a Morse key, or other appliance
1 The < Globe,' May 12, 1899. See also an able and appreciative paper
by Mr John Munro, in the ' Electrical Review/ vol. xliv. p. 883.
EEPRINT OF SIGNOR G. MARCONI'S PATENT. 297
for starting or interrupting the current, and its pole appliances
(such as insulated balls separated by small air spaces or high
vacuum spaces, or compressed air or gas, or insulating liquids
kept in place by a suitable insulating material, or tubes separ-
ated by similar spaces and carrying sliding discs) for producing
the desired oscillations.
I find that a Kuhmkorff coil, or other similar apparatus,
works much better if one of its vibrating contacts or brakes on
its primary circuit is caused to revolve, which causes the
secondary discharge to be more powerful and more regular,
and keeps the platinum contacts of the vibrator cleaner and
preserves them in good working order for an incomparably
longer time than if they were not revolved. I cause them to
revolve by means of a small electric motor actuated by the
current which works the coil, or by another current, or in some
cases I employ a mechanical (non-electrical) motor.
The coil may, however, be replaced by any other source of
high tension electricity.
At the receiving instrument there is a local battery circuit
containing an ordinary receiving telegraphic or signalling in-
strument, or other apparatus which may be necessary to work
from a distance, and an appliance for closing the circuit, the
latter being actuated by the oscillations from the transmitting
instrument.
The appliance I employ consists of a tube containing con-
ductive powder, or grains, or conductors in imperfect contact,
each end of the column of powder or the terminals of the
imperfect contact or conductor being connected to a metallic
plate, preferably of suitable length so as to cause the system
to resonate electrically in unison with the electrical oscillations
transmitted to it. In some cases I give these plates or con-
ductors the shape of an ordinary Hertz resonator consisting of
two semicircular conductors, but with the difference that at
the spark-gap I place one of my sensitive tubes, whilst the
other ends of the conductors are connected to small con-
densers.
I have found that the best rules for making the sensitive
tubes are as follows :
1st. The column of powder ought not to be long, the effects
being better in sensitiveness and regularity with tubes contain-
298 APPENDIX E.
ing columns of powder or grains not exceeding two-thirds of
an inch in length.
2nd. The tube containing the powder ought to be sealed.
3rd. Each wire which passes through the tube, in order to
establish electrical communication, ought to terminate with
pieces of metal or small knobs of a comparatively large surface,
or preferably with pieces of thicker wire, of a diameter equal
to the internal diameter of the tube, so as to oblige the powder
or grains to be corked in between.
4th. If it is necessary to employ a local battery of higher
E.M.F. than that with which an ordinarily prepared tube will
work, the column of powder must be longer and divided into
several sections by metallic divisions, the amount of powder or
grains in each section being practically in the same condition
as in a tube containing a single section. When no oscillations
are sent from the transmitting instrument the powder or im-
perfect contact does not conduct the current, and the local
battery circuit is broken ; but when the powder or imperfect
contact is influenced by the electrical oscillations, it conducts
and closes the circuit.
I find, however, that once started, the powder or contact
continues to conduct even when the oscillations at the trans-
mitting station have ceased ; but if it be shaken or tapped,
the circuit is broken.
I do this tapping automatically, employing the current
which the sensitive tube or contact had allowed to begin to
flow under the influence of the electric oscillations from the
transmitting instrument to work a trembler (similar to that of
an electric bell), which hits the tube or imperfect contact, and
so stops the current and, consequently, its own movement, which
had been generated by the said current, which by this means
automatically and almost instantaneously interrupts itself until
another oscillation from the transmitting instrument repeats
the process. Whilst for certain purposes I prefer working the
trembler and the instruments on the same circuit which con-
tains the sensitive tube or contact, for other purposes I prefer
working the trembler and the instruments on another circuit,
which is made to work in accordance with the first by means
of a relay. It is by means of actions from the current, which
the sensitive tube or contact allows to pass when the oscilla-
REPRINT OF SIGNOR G. MARCONI'S PATENT. 299
tions influence it, that I prefer starting the apparatus that has
to interrupt automatically the same current.
In order to prevent the action of the self-induction of the
local circuits on the sensitive tube or contact, and also to de-
stroy the perturbating effect of the small spark which occurs at
the breaking of the circuit inside the tube or imperfect contact,
and also at the vibrating contact of the trembler or at the
movable contact of the relay, I put in derivation across those
parts where the circuit is periodically broken a condenser of
suitable capacity, or a coil of suitable resistance and self-in-
duction, so that its self-induction may neutralise the self-
induction of the said circuits ; or preferably I employ in
derivation on different parts of the circuit conductors or
so-called semi-conductors of high resistance and small self-
induction, such as bars of charcoal or preferably tubes contain-
ing water or other suitable liquid, in electrical communication
with those conductors of the local circuits which are liable in
course of self-induction to assume such differences of potential
as to transmit jerky currents such as would influence the
sensitive tube or contact so as to prevent its working with
regularity.
In some cases, however, I find it suitable to employ an in-
dependent trembler moved by the current from another
battery. This trembler is prevented from generating jerking
or vibrating currents by means of the appliances which I have
described. This trembler is kept going all the time during
which one expects oscillations to be transmitted, and, as
already described, the powder or imperfect contact closes the
circuit of a local battery, in which are included the instruments
which one desires to work, for the time during which the elec-
trical oscillations are transmitted, breaking the circuit in case
of the mechanical vibrations as soon as the oscillations from the
transmitting machine cease. When transmitting through the
air, and it is desired that the signal or electrical action should
only be sent in one direction, or when it is necessary to trans-
mit electrical effects to the greatest possible distance without
wires, I place the oscillation producer at the focus or focal line
of a reflector directed to the receiving station, and I place the
tube or imperfect contact at the receiving instrument in a
similar reflector directed towards the transmitting instrument.
300 APPENDIX E.
When transmitting through the earth or water I connect one
end of the tube or contact to earth and the other end to con-
ductors or plates, preferably similar to each other, in the air
and insulated from earth.
I find it also better to connect the tube or imperfect contact
to the local circuit by means of thin wires or across two small
coils of thin and insulated wire preferably containing an iron
nucleus.
Dated this second day of June 1896.
GUGLIELMO MARCONI.
COMPLETE SPECIFICATION.
IMPROVEMENTS IN TRANSMITTING ELECTRICAL IMPULSES
AND SIGNALS, AND IN APPARATUS THEREFOR.
I, Guglielmo Marconi, of 67 Talbot Road, Westbourne
Park, formerly residing at 71 Hereford Eoad, Bays water, in
the county of Middlesex, do hereby declare the nature of this
invention and in what manner the same is to be performed to
be particularly described and ascertained in and by the follow-
ing statement :
My invention relates to the transmission of signals by means
of electrical oscillations of high frequency, which are set up in
space or in conductors.
In order that my specification may be understood, and be-
fore going into details, I will describe the simplest form of my
invention by reference to figure 1.
In this diagram A is the transmitting instrument and B is
the receiving instrument, placed at say J mile apart.
In the transmitting instrument R is an ordinary induction
coil (a Ruhmkorff coil or transformer).
Its primary circuit c is connected through a key D to a battery
E, and the extremities of its secondary circuit F are connected
to two insulated spheres or conductors G H fixed at a small
distance apart.
When the current from the battery E is allowed to pass
through the primary of the induction coil, sparks will take
place between the spheres G H, and the space all around the
REPRINT OF SIGNOR G. MARCONI'S PATENT. 301
spheres suffers a perturbation in consequence of these electrical
rays or surgings.
The arrangement A is commonly called a Hertz radiator, and
the effects which propagate through space Hertzian rays.
The receiving instrument B consists of a battery circuit J,
which includes a battery or cell K, a receiving instrument L,
and a tube T containing metallic powder or filings, each end
GO
Fig. 1.
of the column of filings being also connected to plates or con-
ductors M N of suitable size, so as to be preferably tuned with
the length of wave of the radiation emitted from the trans-
mitting instruments.
The tube containing the filings may be replaced by an imper-
fect electrical contact, such as two unpolished pieces of metal
in light contact, or coherer, &c.
The powder in the tube T is, under ordinary conditions, a
non-conductor of electricity, and the current of the cell K can-
not pass through the instrument ; but when the receiver is
influenced by suitable electrical waves or radiation the powder
in the tube T becomes a conductor (and remains so until the
tube is shaken or tapped), and the current passes through the
instrument.
By these means electrical waves which are set up in the
302
APPENDIX E.
transmitting apparatus affect the receiving instrument in such
a manner that currents are caused to circulate in the circuit J,
and may be utilised for deflecting a needle, which thus re-
sponds to the impulse coming from the transmitter.
Figures 2, 3, 4, &c., show various more complete arrange-
ments of the simple form of apparatus illustrated in figure 1.
I will describe these figures generally before proceeding to
describe the improvements in detail.
Figure 2 is a diagrammatic front elevation of the instru-
ments of the receiving station, in which k Tc are the plates
corresponding to M sr in figure 1. g is the battery correspond-
Fig. 2.
ing to K, h is the reading instrument corresponding to L, n is a
relay working the reading instrument h in the ordinary
manner, p is a trembler or tapper, similar to that of an
electric bell, which is moved by the current that works the
instrument.
Figure 3 is a diagrammatic front elevation of the instru-
ments at the transmitting station, in which e e are two metallic
spheres corresponding to Q H in figure 1.
c is an induction coil corresponding to n. & is a key corres-
ponding to D, and a is a battery corresponding to E.
Figure 4 is a vertical section of the radiator or oscillation
producer mounted in the focal line of a cylindrical parabolic
REPRINT OF SIGNOR G. MARCONI'S PATENT. 303
reflector / in which a side view of the spheres e e of figure 3
is given.
Figure 5 is a full-sized view of the receiving plates Js k and
sensitive tubey.
Figure 5A is a modified form of sensitive tube.
Figure 6 is a modification of the oscillation producer in which
the spheres e e and d d are mounted in an ebonite tube d 3 .
Figure 7 is another modification of the oscillation producer
in which the spheres are substituted by hemispheres.
Figure 8 is a modified form of receiver in which the plates
k k are curved instead of being straight.
Figure 9 is another form of transmitter in which two large
metallic plates t 2 t 2 are employed.
Figure 10 shows a modification of the arrangements at the
transmitting station, and figure 11 a modification of the ar-
rangements of the receiving station, which enables one to signal
through obstacles such as hills or mountains.
Figure 12 shows a detector which is useful for determining
the proper length of the plates k k of the receivers.
Figure 13 shows an improved interrupter (make-and-break)
which is applicable to the induction coil of the transmitter.
Figure 14 shows a water resistance, the use of which shall be
explained.
My invention relates in great measure to the manner in
which the above apparatus is made and connected together.
With some of these forms I am able to obtain Morse signals,
and to work ordinary telegraphic instruments and other appar-
atus ; and with modifications of the above apparatus it is
possible to transmit signals not only through comparatively
small obstacles such as brick walls, trees, &c., but also through
or across masses of metal, or hills, or mountains, which may
intervene between the transmitting and receiving instruments.
I will first describe my improvements which are applicable
to the receiving instruments.
My first improvement consists in automatically tapping or
disturbing the powder in the sensitive tube, or in shaking the
imperfect contact, so that immediately the electrical stimulus
from the transmitter has ceased, the tube or imperfect contact
regains its ordinary non-conductive state. This part of my
invention is illustrated in figure 2, in which j represents the
304
APPENDIX E.
Fig. 5.
Fig. SA.
d 4
Fig. 6.
REPRINT OF SIGNOR G. MARCONI'S PATENT. 305
Fig. 7.
Fig. 9.
Fig. 8.
Fig. 10.
Fig. 11.
J
Fig. 12.
Fig. 13.
A
Fig. 14.
306 APPENDIX E.
sensitive tube and p the trembler or tapper. The current
which flows through the sensitive tube or contact, and which
is commenced under the influence of the electrical oscillations
from the transmitting instrument, is allowed to actuate
(directly, or indirectly by means of a relay) the trembler,
which is similar to an electric bell. This trembler must be so
arranged, as hereinafter explained, that the effect of the spark-
ing at its vibrating contacts, and the jerky currents caused by
self-induction, &c., are neutralised or removed.
The small hammer of the trembler hits the tube or imperfect
contact and so stops the current, and consequently its own
movement, which had been generated by the said current ; and
by this means the current automatically and almost instantan-
eously interrupts itself until another oscillation from the
transmitting instrument again makes the sensitive tube or
imperfect contact a conductor.
I find, however, that the current which can be started by
the sensitive tube or contact is not sufficiently strong to work
an ordinary trembler and receiving instrument.
To overcome this difficulty, instead of obliging the current of
the circuit which contains the sensitive tube or contact to work
the trembler and instrument, I use the said current for working
a sensitive relay n (figure 2), which closes and opens the circuit of
a stronger battery r, preferably of the Leclanche type. This
current, which is much stronger than the current which runs
through the sensitive tube or contact, works the trembler and
other instruments. To prevent the sparks and jerks of current
which would be caused by the self-induction of the relay from
interfering with the action of the receiver, certain means must
be taken similar to those referred to above in reference to the
trembler or tapper, which will be explained hereafter. In the
apparatus I have made I have found that the relay n should be
one possessing small self-induction, and wound to a resistance
of about 1000 ohms. It should preferably be able to work
regularly with a current of a milliampere or less. The trembler
or tapper p on the circuit of the relay n is similar in construc-
tion to that of a small electric bell, but having a shorter arm.
I have used a trembler wound to 1000 ohms resistance, having
a core of good soft iron hollow and split lengthways like most
electro-magnets used in telegraph instruments.
REPRINT OF SIGNOR G. MARCONI'S PATENT. 307
The trembler must be carefully adjusted. Preferably the
blows should be directed slightly upwards, so as to prevent the
filings from getting caked. In place of tapping the tube the
powder can be disturbed by slightly moving outwards and
inwards one or both of the stops of the sensitive tube (see
figure 5, j l j 2 \ the trembler p (figure 2) being replaced by a
small electro-magnet or magnets or vibrator whose armature
is connected to the stop.
I ordinarily work the receiving instrument A, which may be
of any description, by a derivation as shown from the circuit,
which works the trembler p. It can also, however, be worked
in series with the trembler.
It is desirable that the receiving instrument, if on a deriva-
tion of the circuit which includes the trembler or tapper, should
preferably have a resistance equal to the resistance of the
trembler p.
A further improvement consists in the mode of construction
of the sensitive tube.
I have noticed that a sensitive tube or imperfect contact,
such as is shown in figure 1 T, is not perfectly reliable.
My tube as shown in figure 5 is, if carefully constructed,
absolutely reliable, and by means of it the relay and trembler
&c., can be worked with regularity like any other ordinary
telegraphic instrument.
In figure 5,j is the sensitive tube containing two metallic
plugs j 2 connected to the battery circuit, between which is
placed powder of a conductive material j l . The two plugs
should preferably be made of silver, or may be two short pieces
of thick silver wire of the same diameter as the internal
diameter of the tube^', so as to fit tightly in it. The plugs^' 2 ^' 2
are joined to two pieces of platinum wire j 3 . The tube is
closed and sealed on to the platinum wires j 3 at both ends.
Many metals can be employed for producing the powder or
filings./ 1 , but I prefer to use a mixture of two or more different
metals. I find hard nickel to be the best metal, and I prefer
to add to the nickel filings about four per cent of hard silver
filings, which increase greatly the sensitiveness of the tube to
electric oscillations. By increasing the proportion of silver
powder or grains the sensitiveness of the tube also increases ;
but it is better for ordinary work not to use a tube of too great
308 APPENDIX E.
sensitiveness, as it might be influenced by atmospheric or other
electricity.
The sensitiveness can also be increased by adding a very
small amount of mercury to the filings and mixing up until
the mercury is absorbed. The mercury must not be in such a
quantity as to clot or cake the filings : an almost imperceptible
globule is sufficient for a tube. Instead of mixing the mercury
with the powder, one can obtain the same effects by slightly
amalgamating the inner surfaces of the plugs which are to be
in contact with the filings. Very little mercury must be used,
just sufficient to brighten the surface of the metallic plugs
without showing any free mercury or globules.
The size of the tube and the distance between the two
metallic stops or plugs may vary under certain limits : the
greater the space allowed for the powder, the larger or coarser
ought to be the filings or grains.
I prefer to make my sensitive tubes of the following size
the tube j is 1^ inch long and ^ or ^ of an inch internal
diameter. The length of the stops j* is about of an inch,
and the distance between the stops or plugs j 2 j 2 is about B a o
of an inch.
I find that the smaller or narrower the space is between the
plugs in the tube, the more sensitive it proves ; but the space
cannot under ordinary circumstances be excessively shortened
without injuring the fidelity of the transmission.
Care must be taken that the plugs J 2 j 2 fit the tube exactly,
as otherwise the filings might escape from the space between
the stops, which would soon destroy the action of the sensitive
tube.
The metallic powders ought not to be fine, but rather coarse,
as can be produced by a large and rough file.
The powder should preferably be of uniform grain or thick-
All the very fine powder or the excessively coarse powder
ought to be removed from it by blowing or sifting.
It is also desirable that the powder or grains should be dry
and free from grease or dirt, and the files used in producing the
same ought to be frequently washed and dried, and used when
warm.
The powder ought not to be compressed between the plugs,
REPRINT OF SIGNOR G. MARCONI'S PATENT. 309
but rather loose, and in such a condition that when the tube
is tapped the powder may be seen to move freely.
The tube j may be sealed, but a vacuum inside it is not
essential, except the slight vacuum which results from having
heated it while sealing it. Care should also be taken not to
heat the tube too much in the centre when sealing it, as it
would oxidise the surfaces of the silver stops, and also the
powder, which would diminish its sensitiveness. I have used,
in sealing the tubes, a hydrogen and air flame.
A vacuum is, however, desirable, and I have used one of
about T ^o of an atmosphere obtained by a mercury pump.
In this case a small glass tube must be joined to a side of the
tube,/ (6gure 5), which is put in communication with the pump
and afterwards sealed in the ordinary manner.
If the sensitive tube has been well made, it should be
sensitive to the inductive effect of an ordinary electric bell
when the same is working from one to two yards from
the tube.
A sensitive tube well prepared should also instantly in-
terrupt the current passing through it at the slightest tap or
shake, provided it is inserted in a circuit in which there is little
self-induction and small electro-motive force, such as a single
cell.
In order to keep the sensitive tube j in good working order
it is desirable, but not absolutely necessary, not to allow more
than one milliampere to flow through it when active.
If a stronger current is necessary, several tubes may be put
in parallel, provided they all get shaken by the tapper or
trembler ; but this arrangement is not always quite as satis-
factory as the single tube.
It is preferable, when using sensitive tubes of the type I
have described, not to insert in the circuit with it more than
one cell of the Leclanche type, as a higher electro-motive force
than 1'5 volts is apt to pass a current through the tube, even
when no oscillations are transmitted.
I can, however, construct sensitive tubes capable of working
with a higher electro-motive force.
Fig. 5A shows one of these tubes. In this tube, instead of
one space or gap filled with filings, there are several spaces j l j l 9
separated by plugs of tight-fitting silver wire. A tube thus
310 APPENDIX E.
constructed observing also the rules of construction of my
tubes in general will work satisfactorily if the electro-motive
force of the battery in circuit with the tube is equal to about
1*2 volts multiplied by the number of gaps.
With this tube also it is well not to allow a current of more
than one milliampere to pass through it.
Figure 5 also shows the plates Jc , which are joined to each
end of the sensitive tube, and which correspond to the plates
M N in figure 1.
The plates Tc (figure 5) are of copper or other metal, about
half an inch or more broad, and may be about ^ of an inch
thick, and preferably of such a length as to be electrically tuned
with the length of the wave of the electrical oscillations
transmitted.
The means I adopt for fixing the proper length of the plates
Tc Tc is as follows : I stick a rectangular strip of tinfoil (see
figure 12) m about 20 inches long (the length depends on the
supposed length of the wave that one is measuring), by means
of a weak solution of gum, on to a glass plate m 1 (figure 12) ;
then by means of a very sharp penknife or point and ruler I cut
across the middle of the tinfoil, leaving a mark of division m 2 .
If this glass plate is held a few feet away from the origin of the
electrical disturbances, and in such a position that the strips of
tinfoil are about parallel to the line joining the centres of the two
spheres in the transmitting apparatus, sparks will jump from
one strip to the other at m 2 . When the length of the strips of
tinfoil m has been so adjusted as to approximate to the length
of wave emitted from the oscillator, the sparking will occur at
a greater distance from the oscillation producer when the strips
are of suitable length. By shortening or lengthening the
strips, therefore, it is easy to find the length most appropriate
to the length of wave emitted by the oscillation producer.
The length so found is the proper length for the plates , or
rather these should be about half an inch shorter on account
of the length of the sensitive tube j (figure 5) connected
between them.
The plates &, tube,/, &c., are fastened to a thin glass tube 0,
preferably not longer than 12 inches, firmly fixed at one end to
a firm piece of wood o 2 , or the sensitive tube./ may be fixed
firmly at both ends i.e., preferably grasped near the ends of
REPRINT OF SIGNOR G. MARCONI'S PATENT. 311
the tube containing the powder, and not at the ends of the
tube o o, which serves as support.
By means of a tube with multiple gaps, as shown in figure
5A, it is also possible to work the trembler and also the signal-
ling or other apparatus direct on the circuit which contains the
sensitive tube, but I prefer when possible to work with the
single-gap tube and the relay as shown. With a sensitive and
specially constructed trembler it is also possible to work the
trembler with the single-gap tube in series with it without a
relay.
In order to increase the distance at which the receiver can
be actuated by the radiation from the transmitter, I place the
receiver (i.e., the sensitive tube and plates) in the focal line of
a cylindrical parabolic reflector I (figure 2), preferably of copper,
and directed towards the transmitting station.
In determining the proper length of the plates of the re-
ceiver by means of the detector shown in figure 12, it is
desirable to try the detector in the focus or focal line of the
reflector, because the length of the strips or plates which gives
the best result in a reflector differs slightly from the length
which gives the best results without reflectors.
The reflector I (figure 2) should be preferably in length and
opening not less than double the length of wave emitted from
the transmitting instrument.
It is slightly advantageous for the focal distance of the re-
flector to be equal to one-fourth or three- fourths of the wave-
length of the oscillation transmitted.
The plates Ic (figure 2) may be replaced by tubes or other
forms of conductors.
A further improvement has for its object to prevent the
electrical disturbances which are set up by the trembler and
other apparatus in proximity or in circuit with the tube from
themselves restoring the conductivity of the sensitive tube
immediately after the trembler has destroyed it, as has been
described.
This I effect by introducing into the circuits at the places
marked p l , p 2 , q, A 1 , in figure 2 high resistances having as little
self-induction as possible. The action of the high resistances is
that, while preventing any appreciable quantity of the current
from passing through them when the apparatus is working,
312 APPENDIX E.
they nevertheless afford an easy path for the currents of high
tension which would be formed at the moment when the
circuit is broken, and thus prevent sparking at contacts or
sudden jerks of currents, which would restore or maintain the
conductivity of the sensitive tube.
These coils may conveniently be made by winding the wire
(preferably of platinoid) on the bight, as it is sometimes
termed, or double wound, to prevent them producing self-
induction.
In figure 2, p 2 is one of these resistance coils which is inserted
in a circuit connecting the vibrating contacts of the trembler
p. I have used in the apparatus a coil which had a resistance
about four times the resistance of the trembler p.
p l represents a similar resistance (also of about four times
the resistance of the trembler) inserted in parallel across
the terminals of the trembler.
A similar resistance q, figure 2, is placed in parallel on the
terminals of the relay n (i.e., the terminals which are connected
to the circuit containing the sensitive tube).
The coil q should preferably have a resistance of about three
or four times the resistance of the relay.
A similar resistance h l of about four times the resistance of
the instrument is inserted in parallel across the terminals of
the instrument.
In parallel across the terminals of the relay (i.e., correspond-
ing to the circuit worked by the relay) it is well' to have a
liquid resistance s constituted of a series of tubes, one of which
is shown full size in figure 14 partially filled with water acidu-
lated with sulphuric acid. The number of these tubes in
series across the said terminals ought to be about ten for a
circuit of 15 volts, so as to prevent, in consequence of their
counter electro-motive force, the current of the local battery
from passing through them, but allowing the high tension jerk
of current generated at the opening of the circuit in the relay
to pass smoothly across them without producing perturbating
sparks at the movable contact of the relay.
A double-wound platinoid resistance may be used instead of
the water resistance, provided its resistance be about 20,000
ohms.
A resistance similar to h should be inserted in parallel on
REPRINT OF SIGNOR G. MARCONI'S PATENT. 313
the terminals of any apparatus or resistance which may be
apt to give self-induction and which is near or connected to
the receiver.
Condensers of suitable capacity may be substituted for the
above-mentioned coils, but I prefer using coils or water re-
sistances.
Another improvement has for its object to prevent the high
frequency oscillations set up across the plates of the receiver
by the transmitting instrument, which should pass through the
sensitive tube, from running round the local battery wires
and thereby weakening their effect on the sensitive tube or
contact.
This I effect by connecting the battery wires to the sensitive
tube or contact, or to the plates attached to the tube through
small coils (see k l in the figures) possessing self-induction,
which may be called choking coils, formed by winding in the
ordinary manner a short length (about a yard) of thin and
well-insulated wire round a core (preferably containing iron)
two or three inches long.
Another improvement consists in a modified form of the
plates connected to the sensitive tube, in order to make it
possible to mount the receiver in an ordinary circular parabolic
reflector. This part of my invention is illustrated in figure 8, in
which I is an ordinary concave reflector. In this case the plates
k k are curved and connected at one end to the sensitive tube^',
and at the other to a small condenser formed by two metallic
plates k* of about one inch square or more, facing each other
with a very thin piece of insulating material k? between them.
p is the trembler. The condenser may be omitted without
much altering the effects obtainable.
The connection to the local circuit is made through two
small choking coils & l k l as already described.
The adjustment of the whole is similar to that already de-
scribed for the other receivers.
The receiver should be put in such a position as to intercept
the reflected ring of radiations which exists behind or before
the focus of the reflector, and ought to be preferably tuned
with the length of wave of the oscillation transmitted, in similar
manner to that before described, except that a ring of tinfoil
with a single cut through it is employed.
314 APPENDIX E.
I will now describe my improvements which are applicable
to the transmitting instruments.
My first improvement consists in employing four spheres for
producing the electrical oscillations.
This part of my invention is illustrated in figure 3, d d, e e,
and in figure 6, d d, e e. The spheres d d, figure 3, are con-
nected to the terminals c 1 of the secondary circuit of the induc-
tion coil c. The spheres d d are carried by insulating supports
d 1 d l .
Preferably the supports d 1 consist of plates of ebonite having
holes to receive the balls, which are fixed by heating them
sufficiently to fuse the ebonite and then holding them in place
until they cool, e e are two similar balls on supports e 1 e 1 ,
whose distance apart can be adjusted by ebonite bolts and nuts
e 2 e 2 acting against other nuts e 3 . e 4 is a flexible membrane,
preferably of parchment paper, glued to the supports e 1 and
forming a vessel which is filled with dielectric liquid, prefer-
ably vaseline-oil slightly thickened with vaseline.
The oil or insulating liquid between the spheres e e increases
the power of the radiation, and also enables one to obtain con-
stant effects, which are not easily obtained if the oil is
omitted.
The balls d and e are preferably of solid brass or copper, and
the distance they should be apart depends on the quantity and
electro-motive force of the electricity employed, the effect in-
creasing with the distance (especially by increasing the dis-
tance between the spheres d and the spheres e) so long as the
discharge passes freely. With an induction coil giving an
ordinary 8-inch spark the distance between e and e should be
from Jj to ^Q of an inch, and the distance between d and e
about one inch.
When it is desired that the signal should only be sent in one
direction, I place the oscillation producer in the focus or focal
line of a reflector directed to the receiving station.
/ (figure 3) and / (figure 4) show the cylindrical parabolic
reflector made by bending a metallic sheet, preferably of brass
or copper to form, and fixing it to metallic or wooden ribs / l
(figure 3).
Other conditions being equal, the larger the balls the greater
is the distance at which it is possible to communicate. I have
REPRINT OF SIGNOR G. MARCONI'S PATENT. 315
generally used balls of solid brass of 4 inches diameter, giving
oscillations of 10 inches length of wave.
Instead of spheres, cylinders or ellipsoids, &c., may be em-
ployed.
Preferably the reflector applied to the transmitter ought to
be in length and opening the double at least of the length of
wave emitted from the oscillator.
If these conditions are satisfied, and with a suitable receiver,
a transmitter furnished with spheres of 4 inches diameter con-
nected to an induction coil giving a 10-inch spark will transmit
signals to two miles or more.
If a very powerful source of electricity giving a very long
spark be employed, it is preferable to divide the spark-gap
between the central balls of the oscillator into several smaller
gaps in series. This may be done by introducing between the
big balls smaller ones (of about half an inch diameter) held in
position by ebonite frames.
Figure 6 shows a more compact form of oscillation producer.
In this each pair of balls d and e is fixed by heat or otherwise
in the end of tubes d 2 of insulating material, such as ebonite or
vulcanite. The tubes c? 2 fit tightly in another similar tube d 3
having covers d\ through which pass the rods c? 5 connecting
the balls d to the conductors. One (or both) of the rods d 3 is
connected to the ball d by a ball-and-socket joint, and has a
screw thread upon it working in a nut in the cover d*. By
turning the rod, therefore, the distance of the balls e apart can
be adjusted, d 6 are holes in the tube c? 3 , through which the
vaseline-oil can be introduced into the space between the
balls e.
A further improvement consists in causing one of the con-
tacts of the vibrating brake applied to the induction coil to
revolve rapidly.
This improvement has for its object to maintain the plat-
inum contacts of the interrupter in good working order, and to
prevent them sticking, &c.
This part of my invention is illustrated in figure 3 (c 2 ,
c* c).
I obtain this result by having a revolvable central core e 2
(figure 3 and figure 13) in the ordinary screw c 3 , which is in
communication with the platinum contacts. I cause the said
316 APPENDIX E.
central core with one of the platinum contacts attached to it
to revolve by coupling it to a small electric motor c 4 .
This motor can be worked by the same circuit that works
the coil, or if necessary by a separate circuit the connections
are not shown in the drawing.
By this means the regularity and power of the discharge of
an ordinary induction coil with a trembler brake are greatly
improved.
The induction coil c (figure 3) may, however, be replaced by
any other source of high-tension electricity.
When working with large amounts of energy it is, however,
better to keep the coil of the transformer constantly working
for the time during which one is transmitting, and, instead of
interrupting the current of the primary, interrupting the dis-
charge of the secondary.
In this case the contacts of the key should be immersed
in oil, as otherwise, owing to the length of the spark, the
current will continue to pass after the contacts have been
separated.
A further improvement has for its object to facilitate the
focussing of the electric rays.
This part of my invention is illustrated in figure 7, in which
a view is given of the modified oscillation producer mounted in
the focus of an ordinary parabolic reflector/.
The oscillator in this case is different from the one I have
previously described, because instead of being constituted of
two spheres it is made of two hemispheres e e separated by a
small space filled with oil or other dielectric. The spark be-
tween the hemispheres takes place in the dielectric from small
projections at the centres of the hemispheres. The working
and adjusting of this oscillator are similar to that of the one
previously described.
This arrangement may be also solidly mounted in an ebonite
tube, as shown in figure 6.
A receiver which may be used with this transmitter is
shown in figure 8, and has already been described.
It is not essential to have a reflector at the transmitters and
receivers, but in their absence the distance at which one can
communicate is much smaller.
Figure 9 shows another modified form of transmitter with
REPRINT OF SIGNOR G. MARCONI'S PATENT. 317
which one can transmit signals to considerable distances with-
out using reflectors.
In figure 9, 1 1 are two poles connected by a rope t 1 , to which
are suspended by means of insulating suspenders two metallic
plates t 2 t* connected to the spheres e (in oil, or other dielectric,
as before) and to the other balls t 5 in proximity to the spheres c 1 ,
which are in communication with the coil or transformer c.
The balls t 3 are not absolutely necessary, as the plates t 2 may
be made to communicate with the coil or transformer by means
of thin insulated wires. The receiver I adopt with this trans-
mitter is similar to it, except that the spheres e are replaced
by the sensitive tube or imperfect contact j (figure 5), whilst
the spheres t 3 may be replaced by the choking coils k l in com-
munication with the local circuit. If a circular-tuned receiver
of large size be employed, the plates t 2 may be omitted from the
receiver. I have observed that, other conditions being equal,
the larger the plates at the transmitter and receiver, and the
higher they are from earth, and to a certain extent the farther
apart they are, the greater is the distance at which correspond-
ence is possible.
For permanent installations it is convenient to replace the
plates by metallic cylinders closed at one end, and put over the
pole like a hat, and resting on insulators. By this arrange-
ment no wet can come to the insulators, and the effects obtain-
able are better in wet weather.
A cone or hemisphere may be used in place of a cylinder. The
pole employed ought preferably to be dry and tarred.
Where obstacles, such as many houses or a hill or moun-
tains, intervene between the transmitter and the receiver, I
have devised and adopt the arrangement shown in figures
10 and 11.
In the transmitting instrument, figure 10, I connect one of
the spheres d to earth E preferably by a thick wire, and the
other to a plate or conductor u, which may be suspended on a
pole v and insulated from earth. Or the spheres d may be
omitted and one of the spheres e be connected to earth and
the other to the plate or conductor u.
At the receiving station, figure 11, I connect one terminal of
the sensitive tube or imperfect contact./ to earth E, preferably
also by a thick wire, and the other to a plate or conductor w.
318 APPENDIX E.
preferably similar to u. The plate w may be suspended on a
pole X) and should be insulated from earth. The larger the
plates of the receiver and transmitter, and the higher from
the earth the plates are suspended, the greater is the distance
at which it is possible to communicate at parity of other
conditions.
The figure does not show the trembler or tapping arrange-
ment. k l Jc l are the choking coils, which are connected to the
battery circuit, as has been explained with reference to the
previous figures.
At the receiver it is possible to pick up the oscillations from
the earth or water without having the plate w. This may be
done by connecting the terminals of the sensitive tube j to
two earths, preferably at a certain distance from each other and
in a line with the direction from which the oscillations are
coming. These connections must not be entirely conductive,
but must contain a condenser of suitable capacity, say of one
square yard surface (parafined paper as dielectric).
Balloons can also be used instead of plates on poles, provided
they carry up a plate or are themselves made conductive by
being covered with tinfoil. As the height to which they may
be sent is great, the distance at which communication is
possible becomes greatly multiplied. Kites may also be suc-
cessfully employed if made conductive by means of tinfoil.
When working the described apparatus, it is necessary either
that the local transmitter and receiver at each station should
be at a considerable distance from each other, or that they
should be screened from each other by metal plates. It is
sufficient to have all the telegraphic apparatus in a metal box
(except the reading instrument), and any exposed part of the
circuit of the receiver enclosed in metallic tubes which are in
electrical communication with the box (of course the part of
the apparatus which has to receive the radiation from the dis-
tant station must not be enclosed, but possibly screened
from the local transmitting instrument by means of metallic
sheets).
When the apparatus is connected to the earth or water the
receiver must be switched out of circuit when the local trans-
mitter is at work, and this may also be done when the apparatus
is not earthed.
REPRINT OF SIGNOR G. MARCONI'S PATENT. 319
Having now particularly described and ascertained the
nature of my said invention, and in what manner the same is
to be performed, I declare that what I claim is
1. The method of transmitting signals by means of electrical
impulses to a receiver having a sensitive tube or other sensitive
form of imperfect contact capable of being restored with
certainty and regularity to its normal condition substantially
as described.
2. A receiving instrument consisting of a sensitive imperfect
contact or contacts, a circuit through the contact or contacts,
and means for restoring the contact or contacts, with certainty
and regularity, to its or their normal condition after the receipt
of an impulse substantially as described.
3. A receiving instrument consisting of a sensitive imperfect
contact or contacts, a circuit through the contact or contacts,
and means actuated by the circuit for restoring with certainty
and regularity the contact or contacts to its or their normal
condition after the receipt of an impulse.
4. In a receiving instrument such as is mentioned in claims
2 and 3, the use of resistances possessing low self-induction,
or other appliances for preventing the formation of sparks at
contacts or other perturbating effects.
5. The combination with the receivers such as are mentioned
in claims 2 and 3 of resistances or other appliances for pre-
venting the self-induction of the receiver from affecting the
sensitive contact or contacts substantially as described.
6. The combination with receivers such as herein above re-
ferred to of choking coils substantially as described.
7. In receiving instruments consisting of an imperfect con-
tact or contacts sensitive to electrical impulses, the use of
automatically working devices for the purpose of restoring the
contact or contacts with certainty and regularity to their
normal condition after the receipt of an impulse substantially
as herein described.
8. Constructing a sensitive non-conductor capable of being
made a conductor by electrical impulses of two metal plugs or
theft- equivalents, and confining between them some substance
such as described.
9. A sensitive tube containing a mixture of two or more
powders, grains, or filings, substantially as described.
320 APPENDIX E.
10. The use of mercury in sensitive imperfect electrical con-
tacts substantially as described.
11. A receiving instrument having a local circuit, including
a sensitive imperfect electrical contact or contacts, and a relay
operating an instrument for producing signals, actions, or
manifestations substantially as described.
12. Sensitive contacts in which a column of powder or filings
(or their equivalent) is divided into sections by means of
metallic stops or plugs substantially as described.
13. Eeceivers substantially as described and shown in figures
5 and 8.
14. Transmitters substantially as described and shown at
figures 6 and 7.
15. A receiver consisting of a sensitive tube or other imper-
fect contact inserted in a circuit, one end of the sensitive tube
or other imperfect contact being put to earth whilst the other
end is connected to an insulated conductor.
16. The combination of a transmitter having one end of its
sparking appliance or poles connected to earth, and the other
to an insulated conductor, with a receiver as is mentioned in
claim 15.
17. A receiver consisting of a sensitive tube or other imper-
fect contact inserted in a circuit, and earth connections to each
end of the sensitive contact or tube through condensers or their
equivalent.
18. The modifications in the transmitters and receivers, in
which the suspended plates are replaced by cylinders or the
like placed hat-wise on poles, or by balloons or kites substan-
tially as described.
19. An induction coil having a revolving make and break
substantially as and for the purposes described.
Dated this 2nd day of March 1897.
GUGLIELMO MARCONI.
INDEX.
Aerial telegraph, an, 73 et seq.
Andres, Signer Senlicq d', 8 fn.
Armstrong, Lord, 270 fn.
Ascoli, Prof., 215.
Atlantic telegraph, an, Lind-
say's proposals, 21 et seq.
a telegraph without a cable,
90.
Auticatelephor of Edwards, 8
et seq.
Barclay, A., 78.
Bell, Prof. Graham, his photo-
phone, 5 and f n. experi-
ments in communicating be-
tween ships at sea, 96 et seq.
251, 252.
Beron's ' M^te"orologie Simpli-
fied ' referred to, 66 fn.
Blake, Prof. Lucien, experiment
showing sensitiveness of the
telephone, 85130 fn.
Blissett, Mr, 114.
Blondel, Prof., 232 fn.
Bonelli, 29 fn., 104.
Bouchotte, 29 fn.
Bourbouze, M., 71 et seq.
Boze, Prof. Chunder, 188.
Branly, Prof. E., 189 et seq.,
195 et seq. on variations of
conductivity, 276 et seq. 291.
Brett, 104.
Bright, Mr C., 130 fn.
Brooke, Sir William O'Shaugh-
nessy, experiments in sub-
aqueous telegraphy, 39.
Brown, Mr A. C., the inventor
of the photophone, 5 fn.
induction in train signalling,
104 et seq. 176 fn.
Call apparatus on the Fastnet
rock, 173.
Calzecchi-Onesti, Prof., 194 et
seq.
Carty, Mr, on the electro-static
phenomena on telephone cir-
cuits, 144 fn.
Charming, Dr, experiments
showing sensitiveness of the
telephone, 81 et seq.
Churchill, Lord A. S., 78.
Clark, Edwin, 104.
Coherer. See Detector.
Coils, communication between
ships, &c., by, 122 et seq.,
156.
Conduction methods of com-
munication, 130 et seq., 162
et seq. variations of con-
ductivity under electrical in-
fluence, 276 et seq.
Cooke, William Fothergill, his
system of train signals, 104.
322
INDEX.
Crookes, Sir William, 197, 289.
Davy, Edward, 6 et seq. plans
for telegraphing without
wires, ib. proposal for com-
munication with trains in
motion, 103.
Bering, G. E., his needle teleg-
raphy, 48 methods of carry-
ing off atmospheric electricity
from the line- wires, ib. pro-
posals for a transmarine tele-
graph, 49 et, seq. attempt to
apply his system, 53 et seq.
Detector, Wilkins's, 36 et seq.
Lord Kelvin's and other re-
lays, 37 et seq. Highton's
42 et seq. Hertz's, 182,
1 90 Right's, ib. Lodge's
" coherer," ib. Branly's
radio - conductor, ib., 196
- Mr Rutherford's detec-
tor, 200 Rev. F. Jervis-
Smith's, 202 Marconi's, 204
et seq.. Lodge's form of the
Branly coherer, 231 et seq.
Dietz, Dr, 216.
Dolbear, Prof. A. E., his system
of wireless telegraphy, 99 et
seq.
Dolbear, Mr C., 103 fn.
Douat, 29 fn.
Dufour, M. Henri, experiment
in inductive effect in tele-
phone circuit, 84.
Dujardin, 104.
"Earth as Part of a Voltaic
Circuit, the," extract from
'The Electrician' on, 66
et seq.
Earth, Salva's suggestion to
electrify, 2 the earth bat-
tery, 20 Steinheil's dis-
covery of the earth circuit,
3 earth- currents or leak-
ages, 141 et seq.
Edison, Mr T. A., his system
of train signals, 107 et seq.
Edser, Prof., 180.
Edwards, Mr T. W. C., the
Auticatelephor of, 8 et seq.
Electric currents, nature of,
264 et seq. electric waves
and their application to wire-
less telegraphy, 289 et seq.
Electrical oscillations, 179 et
seq. radiation, 186.
Evershed, Mr Sydney, plan for
communicating with light-
ships, 128 fn. his relays,
161175.
Exciter, Hertz's, 182, 189
Sarasin and de la Rive's, ib.
Righi's, ib. Marconi's,
203 et seq.
Fahie, J. J., reference to 'His-
tory of Electric Telegraphy
to 1837 'by, 1, 3 fn., 20 fn.,
104 fn.
Faraday, Michael, 249.
Feddersen, 179.
Fitzgerald, Mr, of Dublin, 249,
251.
Fleming, Prof., on Marconi's
system, 241 et seq.
Galvanometer. See Detector.
Gauss, 3.
Gavey, Mr, 146, 161.
Gilliland, E. T., 107 et seq.
Gintl, 29 fn.
Glanville, Mr, 221.
Gott, Mr J. , use of the telephone
in wireless telegraphy, 85 et
seq.
Granier, Mr, proposal of an
aerial line, 71.
Granville, W. P., 166.
Grove, Sir W. R., 251.
Hamel, Dr, account of Salva's
experiment, 2.
INDEX.
323
Haworth, John, unintelligibility
of his proposals, 55 et seq.
summary of his specification,
58 et seq. Mr Varley's cor-
respondence with, 61 et seq.
Mr Haworth's reply, 65.
Heaviside, Mr A. W., 145,
147.
Helmholtz, 179.
Henry, Prof. Joseph, experi-
ments in induction, 93 et seq.
185 fn. on high tension
electricity, 261 et seq. 295.
Hertz, Prof. Heinrich, 177 et
seq., 267 et seq.
Highton, Edward and Henry,
experiments in transaqueous
telegraphy, 40 et seq.
Hippisley, Capt., R.E., 139 fn.
Hughes, Prof. D. E., 199 fn.
on electric waves, 289 et
seq.
India, subaqueous telegraphy in,
39, 114 et seq.
Induction, employment in wire-
less telegraphy of, 92 et seq.
electro-static currents, 142
etseq. electro-magnetic cur-
rents, 144 et seq. com-
munication by means of in-
duction, 157 et seq.
Insulation, telegraphing with-
out, 21 et seq., 39 et seq., 49,
53, 115 et seq., 176 fn.
Jackson, Capt., R.N., 202.
Jervis-Smith, Rev. F., 202.
Johnston, Mr W. P., arrange-
ment for signalling across a
canal, 114 et seq.
Kelvin, Lord, 179, 220, 256,
270 fn.
Kerr, Dr, of Glasgow, 251.
Kerr's ' Wireless Telegraphy '
referred to, 28 fn.
Langdon-Davies, Mr, his phono-
phore, 236.
Lighthouses, telegraphic com-
munication with, 164 et seq.
Lightning, effect of, on tele-
phone, 80.
Lightships, communication with,
Evershed's plan, 128 fn.
by Marconi's system, 224 et
seq.
Lindsay, James Bowman, out-
line of his life, 13 et seq.
experiments in electric light-
ing, 18 et seq. proposals for
telegraph to America, 20 et
seq. experiments without
wires, 24 et seq. Mr Preece's
recollection of, 28.
Little, 104.
Lodge, Prof. Oliver, 95 fn. on
the law of distance, 127 fn.
his conception of electricity,
140 fn. 175, 189, 190, 196,
197 fn., 200, 227, 291 on
the relation between electric-
ity and light, 246 et seq., 271
et seq.
Loomis, Mahlon, 73 et seq.
Marconi, Guglielmo, 197 et seq.,
295 reprint of his specifi-
cation, 296 et seq.
Maxwell, James Clerk-, 178,
186, 249, 254, 257, 264 et
seq.
Melhuish, Mr W. F., experi-
ments in signalling across
rivers in India, 116 et seq.
Minchin, Prof., 190, 200, 252.
Molesworth, J., 78.
Morse, Prof., 10 et seq. experi-
ments in telegraphing through
water without wires, 11 et
seq.
Mower, J. H., 70 et seq.
Muirhead, Dr Alexander, 233.
Munro, Mr John, 296 fn.
324
INDEX.
Nelson, Henry, of Galesburg,
87 fn.
Newton, A. V., 78.
Newton, W. K, 78.
Nickels, B., 78.
Norrie's * Dundee Celebrities of
the Nineteenth Century'
quoted, 18 fn.
O'Shaughnessy, Dr. See Brooke,
Sir William O'Shaughnessy.
Page's discovery of galvanic
music, 94 fn.
Pasqualini, Mr, 227 fn.
Photophone, Steinheil's proposal,
5 the true inventor of the,
ib. fn.
Pierce, Prof., experiments show-
ing sensitiveness of the tele-
phone, 79.
Popoff, Prof., 200 et seq.
Poynting's theory concerning
electric current, 185.
Preece, W. H., papers by, 136
et seq. disturbances on tele-
phone lines, 137 et seq.
experiment in telegraphing
across the Solent without
wires, 138 et seq. definition
of electricity, 140 resume
of his experiments, 141 et
seq. 194 fn., 202, 206, 211,
214.
Radio-conductor. See Detector.
Railway: use of rails as con-
ductors, 3 railway tele-
graphs, 103 et seq.
Rathbone, Mr Charles, experi-
ments showing sensitiveness
of telephone, 80.
Rathenau, Prof. Erich, experi-
ment on the conductive prin-
ciple, 130 et seq.
Relay, Wilkins's, 38.
Righi, Prof., 189, 190.
Rive, L. de la, explanation of
"Galvanic Music," 94 fn.
184, 189.
Rosser, H. S., 78.
Rovelli, Signer, 202 fn.
Rowland, Prof. H. A., on the
nature of electric currents,
264 et seq.
Rupp, Dr, 196 fn.
Rutherford, 200.
Sacher, Prof. E., inductive ef-
fect in telephone circuits,
84.
Salva, suggestion to use the sea
as a conductor, 1 87.
Sarasin, E., 184, 189.
Schafer, Mr Bela, 227 fn.
Schilling, Baron, the needle
telegraph of, 20.
Schuster, Arthur, 292 fn.
Schwendler, Mr, 114.
Sennett, Mr A. R., 8 fn.
Shaffner's ' Telegraph Manual '
referred to, 234.
Ships, plans for intercom-
munication between, at sea,
90 et seq., 96. et seq., 102,
122 et seq.
Siemens' Serrated-Plate Light-
ning-Guard, 48.
Slaby, Prof., 212, 215 et seq.
Smith, Mr Willoughby, on
" Volta-Electric Induction,"
94 fn. induction in train
signalling, 105 et seq. his
system of wireless teleg-
raphy, 162 et seq.
Sommerring, experiment in sig-
nalling through water, 2.
Steinheil, Prof. C. A., 3 et
seq. experiments with rail-
way rails as conductors, ib.
discovery of the earth circuit,
ib. signalling without wires,
4 et seq. suggestion of the
photophone, 5 89.
INDEX.
325
Stevenson, Mr C. A., his coil
system, 122 et seq.
Stokes, Sir George, 292 fn.,
295.
Strong, Mr H. C., of Chicago,
87 fn.
Sturgeon's ' Annals of Elec-
tricity' quoted, 4, 5.
Sympathetic needle and sym-
pathetic flesh telegraphs, 1.
Taylor, Capt., R.K, the com-
pressed air telephone of, 7.
Telephone in relation to wire-
less telegraphy, 79 et seq.
Tesla, Prof. Nikola, his con-
ception of electricity, 140
fn. 199 et seq.
Thompson, Prof. Silvanus, 206,
235.
Thomson, Sir W. See Kelvin,
Lord.
Threlfall, Prof. R., 197 fn.
Trains, electric communication
with moving, 103 et seq.
Trowbridge, Prof. John, 32 et
seq. experiments with the
telephone, 87 et seq. an
Atlantic telegraph without
a cable, 90 communication
between ships at sea, ib. et
seq. induction in wireless
telegraphy, 92 et seq.
Tuma, Dr, 219 fn.
Vail's * American Electro-Mag-
netic Telegraph' quoted, 13.
Van Reese, 29 fn.
Varley, Mr S. A., 191.
Walker, T., 78.
Welding by electricity, 23.
Wilde, H., 78.
Wilkins, J. W., 32 et seq.
proposal for telegraph com-
munication without wires,
33 et seq. the Wilkins re-
lay, 36 et seq.
Zickler, Prof. K., 183 fn.
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