,transcriber's ,notes   ,all apparent   
printer's errors and variations in      
spelling have been  retained1 there are 
also some inconsistencies in the        
hyphenation of  words4 ,all these have  
been detailed at the end of the text4   
,there are a number of mathematical     
equations in the text1 these have  been 
rendered into a text representation that
 attempts to make them  as clear as     
possible while matching the text as     
closely as possible4  ,multi-line       
fractions have been rendered on one line
 with the addition  of extra brackets if
 required to ensure clarity4            
,superscripts are  denoted with         
followed by the superscripted term in 4 
,subscripts  are denoted by  with the   
subscripted term in 4 ,square roots are 
denoted by sq followed by the rooted    
term in 4 ,some equations  have         
following punctuation1 both commas or   
full stops1 in the original  text as    
though the equation is part of the      
sentence4 ,the middle dot  has been used

 in the original text1 both as a        
multiplication symbol  and as a decimal 
point4 ,these have been kept but the    
middle dot as a  multiplication symbol  
in formulae is surrounded by single     
spaces4   ,italicised text in the       
original text is represented by text1   
bold  text is represented by bold4      
99       99       99       99       99  
,,hertzian ,,wave ,,wireless            
,,telegraphy4                      ,,by 
,,dr4 ,j4 ,a4 ,,fleming1 ,f4,r4,s4      
,from the ,,popular ,,science ,,monthly1
 ,june-,december1 #aijc4                
99       99       99       99       99  
,from the ,popular ,science ,monthly1   
,june1 #aijc4                           
,,hertzian ,,wave ,,wireless            
,,telegraphy4#a                     ,,by
 ,,dr4 ,j4 ,a4 ,,fleming1 ,f4,r4,s41    
,,professor ,,of ,,electrical           
,,engineering1 ,,university ,,college1  
,,london4   ,the immense public interest
 which has been aroused of late years in
 the subject of telegraphy without      

connecting wires has undoubtedly been   
stimulated by the achievements of ,mr4  
,marconi in effecting communication over
 great distances by means of ,hertzian  
waves4 ,the periodicals and daily       
journals1 which are the chief avenues   
through which information reaches the   
public1 whilst eager to describe in a   
sensational manner these wonderful      
applications of electrical principles1  
have done little to convey an           
intelligible explanation of them4 ,hence
 it appeared probable that a service    
would be rendered by an endeavour to    
present an account of the present       
condition of electric wave telegraphy in
 a manner acceptable to those unversed  
in the advanced technicalities of the   
subject1 but acquainted at least with   
the elements of electrical science4 ,it 
is the purpose of these articles to     
attempt this task4 ,we shall1 however1  
limit the discussion to an account of   
the scientific principles underlying the
 operation of this particular form of   

wireless telegraphy1 omitting1 as far as
 possible1 references to mere questions 
of priority and development4  ,the      
practical problem of electric wave      
wireless telegraphy1 which has been     
variously called ,hertzian wave         
telegraphy1 ,marconi telegraphy1 or     
spark telegraphy 7,funkentelegraphie71  
is that of the production of an effect  
called an electric wave or train of     
electric waves1 which can be sent out   
from one place1 controlled1 detected at 
another place1 and interpreted into an  
alphabetic code4 ,up to the present     
time1 the chief part of that            
intercommunication has been effected by 
means of the ,morse code1 in which a    
group of long and short signs form the  
letter or symbol4 ,some attempts have   
been made with more or less success to  
work printing telegraphs and even       
writing or drawing telegraphs by        
,hertzian waves1 but have not passed    
beyond the experimental stage1 whilst   
wireless telephony by this means is     

still a dream of the future4  ,we shall1
 in the first place1 consider the       
transmitting arrangements and1          
incidentally1 the nature of the effect  
or wave transmitted2 in the second      
place1 the receiving appliances2 and1   
finally1 discuss the problem of the     
isolation or secrecy of the intelligence
 conveyed between any two places4  ,the 
transmitter used in ,hertzian wave      
telegraphy consists essentially of a    
device for producing electric waves of a
 type which will travel over the surface
 of the land or sea without speedy      
dissipation1 and the important element  
in this arrangement is the radiator1 by 
which these waves are sent out4 ,it will
 be an advantage to begin by explaining 
the electrical action of the radiator1  
and then proceed to discuss the details 
of the transmitting appliances4  ,it    
will probably assist the reader to      
arrive most easily at a general idea of 
the functions of the various portions of
 the transmitting arrangements1 and in  

particular of the radiator1 if we take  
as our starting point an analogy which  
exists between electric wave generation 
for telegraphic purposes and air wave   
generation for sound signal purposes4   
,most persons have visited some of the  
large lighthouses which exist around our
 coasts and have there seen a steam or  
air siren1 as used for the production of
 sound signals during fogs4 ,if they    
have examined this appliance1 they will 
know that it consists1 in the first     
place1 of a long metal tube1 generally  
with a trumpet-shaped mouthpiece4 ,at   
the bottom of this tube there is a fixed
 plate with holes in it1 against which  
revolves another similarly perforated   
plate4 ,these two plates separate a back
 chamber or wind chest from the tube1   
and the wind chest communicates with a  
reservoir of compressed air or a        
high-pressure steam boiler4 ,in the     
communication pipe there is a valve     
which can be suddenly opened for a      
longer or shorter time4 ,when the       

movable plate revolves1 the coincidence 
or non-coincidence of the holes in the  
two plates opens or shuts the air       
passage way very rapidly4 ,hence when   
the blast of air or steam is turned on1 
the flow is cut up by the revolving     
plates into a series of puffs which     
inflict blows upon the stationary air in
 the siren tube4 ,if these blows come at
 the rate1 say1 of a hundred a second1  
they give rise to aerial oscillations in
 the tube1 which impress the ear as a   
deep1 musical note or roar2 and this    
continuous sound can be cut up by       
closing the valve intermittently into   
long and short periods1 and so caused to
 signal a letter according to the ,morse
 code1 denoting the name of the         
lighthouse4 ,in this case the object is 
to produce3 first1 aerial vibrations in 
the tube1 giving rise to a train of     
powerful air waves2 secondly1 to        
intermit this wave-train so as to       
produce an intelligible signal2 and     
thirdly1 to transmit this wave as far as

 possible through space4  ,the          
production of a sound or air wave can   
only be achieved by administering a very
 sudden blow to the general mass of the 
air in the tube4 ,this impulse must be  
sufficient to call into operation the   
inertia and elastic qualities of the    
air4 ,it is found1 moreover1 that the   
amplitude of the resulting wave1 or the 
loudness of the sound1 is increased by  
suitably proportioning the length of the
 siren pipe and the frequency of the air
 puffs2 whilst the distance at which it 
is heard depends also in some degree    
upon the form of the mouthpiece4        
,inside the siren tube1 when it is in   
operation1 the air molecules are in     
rapid vibratory motion in the direction 
of the length of the tube4 ,if we could 
at any one instant examine the          
distribution and changes of air pressure
 in the tube1 we should find that at    
some places there are large1 and at     
others small1 variations in air         
pressure4 ,these latter places are      

called the nodes of pressure4 ,at the   
pressure nodes1 however1 we should find 
large variations in the velocity of the 
air particles1 and these points are     
called the antinodes of velocity4 ,in   
those places at which the pressure      
variation is greatest1 the velocity     
changes are least1 and vice versa4      
,outside the tube1 as a result of these 
air motions in it1 we have a            
hemispherical air wave produced1 which  
travels out from the mouthpiece as a    
centre2 and if we could examine the     
distribution of air pressure and        
velocity through all external space1 we 
should find a distribution which is     
periodic in space as well as time1      
constituting the familiar phenomenon of 
an air wave4  ,turning then to consider 
the production of an electric1 instead  
of an air wave1 we notice in the first  
place that the medium with which we are 
concerned is the ether filling all      
space4 ,this ether permits the          
production of physical changes in it    

which are analogous to1 but not         
identical in nature with1 the pressures 
and movements which constitute a sound  
wave4 ,the ,hertzian radiator is an     
appliance for acting on the ether as the
 siren acts on the air4 ,it produces a  
wave in it1 and it can be shown that all
 the parts of the above described siren 
apparatus have their electrical         
equivalents in the transmitter employed 
in ,hertzian wave wireless telegraphy4  
,to understand the nature of an electric
 wave we must consider1 in the first    
place1 some properties of the ether4 ,in
 this medium we can at any place produce
 a state called electric displacement or
 ether strain as we can produce         
compression or rarefaction in air2 and1 
just as the latter changes are said to  
be created by mechanical force1 so the  
former is said to be due to electric    
force4 ,we can not define more clearly  
the nature of this ether strain or      
displacement until we know much more    
about the structure of the ether than we

 do at present4 ,we can picture to      
ourselves the operation of compressing  
air as an approximation of the air      
molecules1 but the difficulty of        
comprehending the nature of an electric 
wave arises from the fact that we cannot
 yet definitely resolve the notion of   
electric strain into any simpler or more
 familiar ideas4  ,we have to be        
content1 therefore1 to disguise our     
present ignorance by the use of some    
descriptive term1 such as electric      
strain1 electrostatic strain or ether   
strain1 to describe the directed        
condition of the space around a body in 
a state of electrification which is     
produced by electric force4 ,this       
electric strain is certainly not of the 
nature of a compression in the ether1   
but much more akin to a twist or        
rotational strain in a solid body4  ,for
 our present purpose it is not so       
necessary to postulate any particular   
theory of the ether as it is to possess 
some consistent hypothesis1 in terms of 

which we can describe the phenomena     
which will concern us4 ,these effects   
are1 as we shall see1 partly states of  
electrification on the surface or       
distributions of electric current in    
wires or rods1 and partly conditions in 
the space outside them1 which we are led
 to recognise as distributions of       
electric strain and of an associated    
effect called magnetic flux4  ,we find  
such a theory at hand at the present    
time in the electronic theory of        
electricity1 which has now been         
sufficiently developed and popularised  
to make it useful as a descriptive      
hypothesis4#b ,this theory has the great
 recommendation that it offers a means  
of abolishing the perplexing dualism of 
ether and ponderable matter1 and gives a
 definite and1 in a sense1 objective    
meaning to the word electricity4 ,in    
this physical speculation1 the chief    
subject of contemplation is the         
electron1 or ultimate particle of       
negative electricity1 which1 when       

associated in greater or less number    
with a matrix of some description1 forms
 the atom of ponderable matter4 ,to     
avoid further hypothesis1 this matrix   
may be called the co-electron2 and we   
shall adopt the view that a single      
chemical atom is a union of a           
co-electron with a surrounding envelope 
or group of electrons1 one or more of   
the latter being detachable4 ,we need   
not stop to speculate on the structure  
of the atomic core or co-electron1      
whether it is composed of positive and  
negative electrons or of something      
entirely different4 ,the single electron
 is the indivisible unit or atomic      
element of so-called negative           
electricity1 and the neutral chemical   
atom deprived of one electron is the    
unit of positive electricity4 ,on this  
hypothesis1 the chemical atom is to be  
regarded as a microcosm1 a sort of a    
solar system in miniature1 the component
 electrons being capable of vibration   
relatively to the atomic centre of mass4

 ,furthermore1 from this point of view  
it is the electron which is the         
effective cause of radiation4 ,it alone 
has a grip on the ether whereby it is   
able to establish wave motion in the    
latter4  ,dr4 ,larmor has developed in  
considerable detail an hypothesis of the
 nature of an electron which makes it   
the centre or convergence-point of lines
 of a self-locked ether strain of a     
torsional type4 ,the notion of an atom  
merely as a centre of force was one     
familiar to ,faraday and much supported 
by ,boscovich and others4 ,the fatal    
objection to the validity of this notion
 as originally stated was that it offers
 no possibility of explaining the       
inertia of matter4 ,on the electronic   
hypothesis1 the source of all inertia is
 the inertia of the ether1 and until we 
are able to dissect this last quality   
into anything simpler than the          
time-element involved in the production 
of an ether strain or displacement1 we  
must accept it as an ultimate fact1 not 

more elucidated because we speak of it  
as the inductance of the electron4  ,we 
postulate1 therefore1 the following     
ideas3 ,we have to think of the ether as
 a homogeneous medium in which a strain 
of some kind1 most probably of a        
rotational type1 is possible4 ,this     
strain appears only under the influence 
of an appropriate stress called the     
electric force1 and disappears when the 
force is removed4 ,hence to create this 
strain necessitates the expenditure of  
energy4 ,an electron is a centre or     
convergence-point of lines of permanent 
ether strain of such nature that it     
cannot release itself4 ,to obtain some  
idea of the nature of such a structure1 
let us imagine a flat steel band formed 
into a ring by welding the ends         
together4 ,there is then no torsional   
strain4 ,if1 however1 we suppose the    
band cut in one place1 one end then     
given half a turn and the cut ends again
 welded1 we shall have on the band a    
self-locked twist1 which can be         

displaced on the band1 but which can not
 release itself or be released except by
 cutting the ring4 ,hence we see that to
 make an electron in an ether possessing
 torsional elasticity would require     
creative energy1 and when made1 the     
electron cannot destroy itself except by
 occupying simultaneously the same place
 as an electron of opposite type4 ,every
 electron extends1 therefore1 as        
,faraday said of the atom1 throughout   
the universe1 and the properties that we
 find in the electron are only there    
because they are first in the universal 
medium1 the ether4 ,every line of ether 
or electric strain must1 therefore1 be a
 self-closed line1 or else it must      
terminate on an electron and a          
co-electron4  ,so far we have only      
considered the electron at rest4 ,if1   
however1 it moves1 it can be            
mathematically demonstrated that it must
 give rise to a second form of ether    
strain which is related to the electric 
strain as a twist is related to a thrust

 or a vortex ring to a squirt in liquid 
or a rotation to a linear progression4  
,the ether strain which results from the
 lateral movement of lines of electric  
strain is called the magnetic flux1 and 
it can be mathematically shown that the 
movement of an electron1 consisting when
 a rest of a radial convergence of lines
 of electric strain1 must be accompanied
 by the production of self-closed lines 
of magnetic flux1 distributed in        
concentric circles or rings round it1   
the planes of these circles being       
perpendicular to the direction of motion
 of the electron4  ,this electronic     
hypothesis1 therefore1 affords a basis  
on which we can build up a theory       
affording an explanation of the nature  
of the intimate connection known to     
exist between ether1 matter and         
electricity4 ,the electron is the       
connecting link between them all1 for it
 is in itself a centre of convergent    
ether strain2 isolated1 it presents     
itself as electricity of the negative or

 resinous kind2 and1 in combination with
 co-electrons and other electrons1 it   
forms the atoms of ponderable matter4   
,at rest the electron or the co-electron
 constitutes an electric charge1 and    
when in motion it is an electric        
current4 ,a steady flux or drift of     
electrons in one direction and          
co-electrons in the opposite direction  
is a continuous electric current1 whilst
 their mere oscillation about a mean    
position is an alternating current4     
,furthermore1 the vibration of an       
electron1 if sufficiently rapid1 enables
 it to establish what are called        
electric waves in the ether1 but which  
are really detached and self-closed     
lines of ether strain distributed in a  
periodic manner through space4  ,we     
have1 therefore1 to start with1 three   
conceptions concerning the electron1    
viz43 ,its condition when at rest2 its  
state when in uniform motion2 and its   
operations when in vibration or rapid   
oscillation4 ,in the first case1 by our 

fundamental supposition1 it consists of 
lines of ether strain of a type called  
the electric strain1 radiating uniformly
 in all directions4 ,when in uniform    
motion1 it can be shown that these lines
 of electric strain tend to group       
themselves in a plane perpendicular to  
the line of motion drawn through the    
electron1 and their lateral motion      
generates another class of strain called
 the magnetic strain1 disposed in       
concentric circles described round the  
electron and lying in this equatorial   
plane4  ,the proof of the above         
propositions cannot be given verbally1  
but requires the aid of mathematical    
analysis of an advanced kind4 ,the      
reader must be referred for the complete
 demonstration to the writings of       
,professor ,j4 ,j4 ,thomson#c and ,mr4  
,oliver ,heaviside4#d  ,in the third    
case1 when the electron vibrates1 we    
have a state in which self-closed lines 
of electric strain and magnetic flux are
 thrown off and move away through the   

ether constituting electric radiation1  
,the manner in which this happens was   
first described by ,hertz in a ,paper on
 ,electric ,oscillations treated        
according to the ,method of ,maxwell4#e 
,as this phenomenon lies at the very    
root of ,hertzian wave wireless         
telegraphy1 we must spend a moment or   
two in its careful examination4  ,let us
 imagine two metal rods placed in line  
and constituting what is called a linear
 oscillator4 ,let these rods have       
adjacent ends separated by a very small 
air space1 and let one rod be charged   
with positive and the other with        
negative electricity4 ,on the electronic
 theory this is explained by stating    
that there is an accumulation of        
electrons in one and of co-electrons in 
the other4 ,these charges create a      
distribution of electric strain         
throughout their neighbourhood1 which   
follows approximately the same law of   
distribution as the lines of magnetic   
force of a bar magnet1 and may be       

roughly represented as in ,fig4 #a4     
,suppose then that the air gap is       
destroyed1 these charges move towards   
each other and disappear by uniting1 the
 lines of electric strain then collapse1
 and as they shrink in give rise to     
circular lines of magnetic flux         
embracing the rods4 ,this external      
distribution of magnetism constitutes an
 electric current in the rods produced  
by the movement of the two opposite     
electric charges4 ,at this stage it may 
be explained that the electrons or atoms
 of electricity can in some cases make  
their way freely between the atoms of   
ponderable matter4 ,the former are      
incomparably smaller than the latter1   
and in those cases in which this        
electronic movement can take place      
easily1 we call the material a good     
conductor4  ,illustration3 ,,fig4       
#a4--,,lines ,,of ,,electric ,,strain   
,,between ,a ,,positive ,,and ,,negative
 ,,electron ,,at ,,rest4  ,suppose then 
the electric charges reappear in        

reversed positions and go through an    
oscillatory motion4 ,the result in the  
external space would be the alternate   
production of lines of electric strain  
and magnetic flux1 the direction of     
these lines being reversed each half    
cycle4 ,inside the rods we have a       
movement of electrons and co-electrons  
to and fro1 electric charges at the ends
 of the rods alternating with electric  
currents in the rods1 the charges being 
at a maximum when the current is zero1  
and the current at a maximum when the   
charges have for the moment disappeared4
 ,outside the rods we have a            
corresponding set of charges1 lines of  
electric strain stretching from end to  
end of the rod1 alternating with rings  
of magnetic flux embracing the rod4 ,so 
far we have supposed the oscillation to 
be relatively a slow one4               
,illustration3 ,,fig4 #b4--,,successive 
,,stages ,,in ,,the ,,deformation ,,of  
,a ,,line ,,of ,,strain ,,between       
,,positive ,,and ,,negative ,,electrons 

,,in ,,rapid ,,oscillation1 ,,showing   
,,closed ,,loop ,,of ,,electric ,,strain
 ,,thrown ,,off4  ,imagine next that the
 to and fro movement of the electrons or
 charges is sufficiently rapid to bring 
into play the inertia quality of the    
medium4 ,we then have a different state 
of affairs4 ,the lines of strain in the 
external medium cannot contract or      
collapse quickly enough to keep up with 
the course of events1 or movements of   
the electrons in the rods1 and hence    
their regular contraction and absorption
 is changed into a process of a         
different kind4 ,as the electrons and   
co-electrons1 i4e41 the electric        
charges1 vibrate to and fro1 the lines  
of electric strain connecting them are  
nipped in and thrown off as completely  
independent and closed lines of electric
 strain1 and at each successive         
alternation1 groups or batches of these 
loops of strain are detached from the   
rod1 and1 so to speak1 take on an       
independent existence4 ,the whole       

process of the formation of these       
self-closed lines of electric strain is 
best understood by examining a series of
 diagrams which roughly represent the   
various stages of the process4 ,in ,fig4
 #b we have a diagram 7a7 the curved    
line in which delineates approximately  
the form of one line of electric strain 
round a linear oscillator1 with spark   
gap in the centre1 one half being       
charged positively and the other        
negatively4 ,let us then suppose that   
the insulation of the spark gap is      
destroyed1 so that the opposite electric
 charges rush together and oscillate to 
and fro4 ,the strain lines at each      
oscillation are then crossed or         
decussate1 and the result1 as shown in  
,fig4 #b1 d1 is that a portion of the   
energy of the field is thrown off in the
 form of self-closed lines of strain    
7see ,fig4 #b1 e74 ,at each oscillation 
of the charges the direction of the     
lines of strain springing from end to   
end of the radiator is reversed4 ,it is 

a general property of lines of strain   
whether electric or magnetic1 that there
 is a tension along the line and a      
pressure at right angles4 ,in other     
words1 these lines of electric strain   
are like elastic threads1 they tend to  
contract in the direction of their      
length and press sideways on each other 
when in the same direction4 ,hence it is
 not difficult to see that as each batch
 of self-closed lines of strain is      
thrown off1 the direction of the strain 
round each loop is alternately in one   
direction and in the other4 ,hence these
 loops of electric strain press each    
other out1 and each one that is formed  
squeezes the already formed loops       
further and further from the radiator4  
,the loops1 therefore1 march away into  
space 7see ,fig4 #b1 f74 ,if we imagine 
ourselves standing at a little distance 
at a point on the equatorial line and   
able to see these loops of strain as    
they pass1 we should recognise a        
procession of loops1 consisting of      

alternately directed strain lines       
marching past4 ,this movement through   
the ether of self-closed lines of       
electric strain constitutes what is     
called electric radiation4  ,hence along
 a line drawn perpendicular to the      
radiator through its centre1 there is a 
distribution of electric strain normal  
to that line1 which is periodic in space
 and in time4 ,moreover1 in addition to 
these lines of electric strain1 there   
are at right angles to them another set 
of self-closed lines of magnetic flux4  
,alternated between the instants when   
the electric charges at the ends of the 
radiator are at their maximum1 we have  
instants when the radiator rod is the   
seat of an electric current1 and hence  
the field round it is filled with       
circular lines of magnetic flux coaxial 
with the radiator4 ,as the current      
alternates in direction each half       
period1 these rings of magnetic flux    
alternate in direction as regards the   
flux1 and hence we must complete our    

mental picture of the space round the   
radiator rods when the charges are      
oscillating by supposing it filled with 
concentric rings of magnetic flux which 
are periodically reversed in direction1 
and have their maximum values at those  
instants and places where the lines of  
electric strain have their zero values4 
,accordingly1 along the equatorial line 
we have two sets of strains in the      
ether1 distributed periodically in space
 and in time4 ,first1 the lines of      
electric strain in the plane of the     
radiator1 and1 secondly1 the lines of   
magnetic flux at right angles to these4 
,at any one point in space these two    
changes1 the strain and the flux1       
succeed each other periodically1 being1 
however1 at right angles in direction4  
,at any one moment these two effects are
 distributed periodically or cyclically 
through space1 and these changes in time
 and space constitute an electric wave  
or electromagnetic wave4  ,we may then  
summarise the above statements by saying

 that the most recent hypothesis as to  
the nature of electrical action and of  
electricity itself is briefly comprised 
in the following statements3 ,the       
universally diffused medium called the  
ether has had created in it certain     
centres of strain or radiating points   
from which proceed lines of strain1 and 
these centres of force are called       
electrons4 ,electrons must1 therefore1  
be of two kinds1 positive and negative1 
according to the direction of the strain
 radiating from the centre4 ,these      
electrons in their free condition       
constitute what we call electricity1 and
 the electrons themselves are the atoms 
of electricity which1 in one sense1 is1 
therefore1 as much material as that     
which we call ordinary gross or         
ponderable matter4  ,collocations of    
these electrons constitute the atoms of 
gross matter1 and we must consider that 
the individuality of any atom is not    
determined merely by the identity of the
 electrons composing it1 but by the     

permanence of their arrangement or form4
 ,in any mass of material substance     
there is probably a continual exchange  
of electrons from one atom to another1  
and hence at any one given moment1      
whilst a number of the electrons are an 
association forming material atoms1     
there will be a further number of       
isolated but intermingled electrons1    
which are called the free electrons4 ,in
 substances which we call good          
conductors1 we must imagine that the    
free electrons have the power of moving 
freely through or between the material  
atoms1 and this movement of the         
electrons constitutes a current of      
electricity2 whilst a superfluity of    
electrons of either type in any one mass
 of matter constitutes what we call a   
charge of electricity4 ,hence an        
electrical oscillation1 which is merely 
a very rapid alternating current taking 
place in a conductor1 is on this        
hypothesis assumed to consist in a rapid
 movement to and fro of the free        

electrons4 ,we may picture to ourselves1
 therefore1 a rod of metal in which     
electrical oscillations are taking      
place1 as similar to an organ-pipe or   
siren tube in which movements of the air
 particles are taking place to and fro1 
the free electrons corresponding with   
the air particles4  ,owing to the nature
 of the structure of an electron1 it    
follows1 however1 that every movement of
 an electron is accompanied by changes  
in the distribution of the electric     
strain or ether strain taking place     
throughout all surrounding space1 and1  
as already explained1 certain very rapid
 movements of the electrons have the    
effect of detaching closed lines of     
strain in the ether which move off      
through space1 forming1 when cyclically 
distributed1 an electric wave4          
,illustration3 ,,fig4 #c4--,,simple     
,,marconi ,,radiator4 ,b1 battery2 ,i1  
induction coil2 ,k1 signalling key2 ,s1 
spark gap2 ,a1 aerial wire2 ,e1 earth   
plate4  ,we may next proceed to apply   

these principles to the explanation of  
the action of the simplest form of      
,hertzian wave telegraphic radiator1    
viz41 the ,marconi aerial wire4 ,in its 
original form this consists of a long   
vertical insulated wire1 ,a1 the lower  
end of which is attached to one of the  
spark balls ,s of an induction coil1 ,i1
 the other spark ball being connected to
 earth ,e1 and the two spark balls being
 placed a few millimetres apart 7see    
,fig4 #c74 ,when the coil is set in     
action oscillatory or ,hertzian sparks  
pass between the balls1 electric        
oscillations are set up in the wire and 
electric waves are radiated from it4    
,deferring for the moment a more        
detailed examination of the operations  
of the coil and at the spark gap1 we may
 here say that the action which takes   
place in the aerial wire is as follows3 
,the wire is first charged to a high    
potential1 let us suppose1 with negative
 electricity4 ,we may imagine this      
process to consist in forcing additional

 electrons into it1 the induction coil  
acting as an electron pump4 ,up to a    
certain pressure the spark gap is a     
perfect insulator1 but at a critical    
pressure1 which for spark gap lengths of
 four or five millimetres and balls     
about one centimetre in diameter        
approximates to three thousand volts per
 millmetre1 the insulation of the air   
gives way1 and the charge in the wire   
rushes into the earth4 ,in consequence1 
however1 of the inertia of the medium or
 of the electrons1 the charge1 so to    
speak1 overshoots the mark1 and the wire
 is then left with a charge of opposite 
sign4 ,this again in turn rebounds1 and 
so the wire is discharged by a series of
 electrical oscillations1 consisting of 
alternations of static charge and       
electric discharge4 ,we may fasten our  
attention either on the events taking   
place in the vertical wire or in the    
medium outside1 but the two sets of     
phenomena are inseparably connected and 
go on together4 ,when the aerial wire is

 statically charged1 we may describe it 
by saying that there is an accumulation 
of electrons or co-electrons in it4     
,outside the wire there is1 however1 a  
distribution of electric strain the     
strain lines proceeding from the wire to
 the earth 7see ,fig4 #d74              
,illustration3 ,,fig4 #d4--,,lines ,,of 
,,electric ,,strain 7,,dotted ,,lines7  
,,extending ,,between ,a ,,marconi      
,,aerial1 ,a1 ,,and ,,the ,,earth ee    
,,before ,,discharge4  ,the wire has    
capacity with respect to the earth1 and 
it acts like the inner coating of a     
,leyden jar1 of which the dielectric is 
the air and ether around it1 and the    
outer coating is the earth's surface4   
,when the discharge takes place1 we may 
consider that electrons rush out of the 
wire and then rush back again into it4  
,at the moment when the electrons rush  
out of or into the aerial wire1 we say  
there is an electric current flowing    
into or out of the wire1 and this       
electron movement1 therefore1 creates   

the magnetic flux which is distributed  
in concentric circles round the wire4   
,this current1 and1 therefore1 motion of
 electrons1 can be proved to exist by   
its heating effect upon a fine wire     
inserted in series with the aerial1 and 
in the case of large aerials it may have
 a mean value of many amperes and a     
maximum value of hundreds of amperes4   
,inside the aerial wire we have1        
therefore1 alternations of electric     
potential or charge and electric        
current1 or we may call it              
electron-pressure and electron-movement4
  ,there is1 therefore1 an oscillation  
of electrons in the aerial wire1 just as
 in the case of an organ-pipe there is  
an oscillation of air molecules in the  
pipe4 ,outside the aerial we have       
variations and distributions of electric
 strain and magnetic flux4 ,the         
resemblance between the closed          
organ-pipe and the simple ,marconi      
aerial is1 in fact1 very complete4 ,in  
the case of the closed organ-pipe1 we   

have a longitudinal oscillation of air  
molecules in the pipe4 ,at the open end 
or mouthpiece1 where we have air moving 
in and out1 the air movement is         
alternating and considerable1 but there 
is little or no variation of air        
pressure4 ,at the upper or closed end of
 the pipe we have great variation of air
 pressure1 but little or no air movement
 7see ,fig4 #e74  ,compare this now with
 the electrical phenomena of the aerial4
 ,at the spark ball or lower end we have
 little or no variation of potential or 
electron pressure1 but we have electrons
 rushing into and out of the aerial at  
each half oscillation1 forming the      
electric discharge or current4 ,at the  
upper or insulated end we have little or
 no current1 but great variations of    
potential or electron pressure4         
,supposing we could examine the wire    
inch by inch1 all the way up from the   
spark balls at the bottom to the top1 we
 should find at each stage of our       
journey that the range of variation and 

maximum value of the current in the wire
 became less and those of the potential 
became greater4 ,at the bottom we have  
nearly zero potential or no electric    
pressure1 but large current1 and at the 
top end1 no current1 but great variation
 of potential4  ,illustration3 ,,fig4   
#e4--;,,amplitude ,,of ,,pressure       
,,variation ,,in ,a ,,closed ,,organ    
,,pipe1 ,,indicated ,,by ,,the          
,,ordinates ,,of ,,the ,,dotted ,,line  
xy4  ,we can represent the amplitude of 
the current and potential values along  
the aerial by the ordinates of a dotted 
line so drawn that its distance from the
 aerial represents the potential        
oscillation or current oscillation at   
that point 7see ,fig4 #f74  ,this       
distribution of potential and current   
along the wire does not necessarily     
imply that any one electron moves far   
from its normal position4 ,the actual   
movement of any particular air molecule 
in the case of a sound wave is probably 
very small1 and reckoned in millionths  

of an inch4 ,so also we must suppose    
that any one electron may have a small  
individual amplitude of movement1 but   
the displacement is transferred from one
 to another4 ,conduction in a solid may 
be effected by the movement of free     
electrons intermingled with the chemical
 atoms1 but any one electron may be     
continually passing from a condition of 
freedom to one of combination4          
,illustration3 ,,fig4 #f4--7;a7         
,,distribution ,,of ,,electric          
,,pressure ,,in ,a ,,marconi ,,aerial1  
,a1 7b7 ,,distribution ,,of ,,electric  
,,current ,,in ,a ,,marconi ,,aerial1   
,,as ,,shown ,,by ,,the ,,ordinates ,,of
 ,,the ,,dotted ,,line xy4  ,so much for
 the events inside the wire1 but now    
outside the wire its electric charge is 
represented by lines of electric strain 
springing from the aerial to the earth4 
,it must be remembered that every line  
of strain terminates on an electron or a
 co-electron4 ,hence1 when the discharge
 or spark takes place between the spark 

balls1 the rapid movement of the        
electrons in the wire is accompanied by 
a redistribution and movement of the    
lines of strain outside4 ,as the        
negative charge flows out of the aerial 
the ends of the strain lines abutting on
 to it run down the wire and are        
transferred to the earth1 and at the    
next instant this semi-loop of electric 
or ether strain1 with its ends on the   
earth1 is pushed out sideways from the  
wire by the growth of a new set of lines
 of ether strain in an opposite         
direction4 ,the process is best         
understood by consulting a series of    
diagrams which represent the            
distribution and approximate form of a  
few of the strain lines at successive   
instants 7see ,fig4 #g74 ,in between the
 lines of formation of the successive   
strain lines between the aerial and the 
earth1 corresponding to the successive  
alternate electric charges of the aerial
 with opposite sign1 there are a set of 
concentric rings of magnetic flux formed

 round it which are alternately in      
opposite directions1 and these expand   
out1 keeping step with the progress of  
the detached strain loops and having    
their planes at right angles to the     
latter4 ,as the semi-loops of electric  
strain march outwards with their feet on
 the ground1 these strain lines must    
always be supposed to terminate on      
electrons1 but not continually on the   
same electrons4 ,since the earth is a   
conductor1 we must suppose that there is
 a continual migration of the electrons 
forming the atoms of the earth1 and that
 when one electron enters an atom1      
another leaves it4 ,hence1 corresponding
 to the electric wave in the space      
above1 there are electrical changes in  
the ground beneath4 ,this view is       
confirmed by the well-known fact that   
the achievement of ,hertzian wave       
telegraphy is much dependent on the     
nature of the surface over which it is  
conducted1 and can be carried on more   
easily over good conducting material1   

like sea water1 than over badly         
conducting dry land4  ,illustration3    
,,fig4 #g4--,,successive ,,stages ,,in  
,,the ,,production ,,of ,a ,,semi-,,loop
 ,,of ,,electric ,,strain ,,by ,a       
,,marconi ,,aerial ,,radiator4  ,the    
matter may be viewed1 however1 from     
another standpoint4 ,good conductors are
 opaque to ,hertzian waves2 in other    
words1 are non-absorptive4 ,the energy  
of the electric wave is not so rapidly  
absorbed when it glides over a sea      
surface as when it is passing over a    
surface which is an indifferent         
conductor1 like dry land4 ,in fact1 it  
is possible by the improvement of the   
signals to detect a heavy fall of rain  
in the space between two stations       
separated only by dry land4 ,it is1     
however1 clear that on the electronic   
theory the progression of the lines of  
electric strain can only take place if  
the surface over which they move is a   
fairly good conductor1 unless these     
lines of strain form completely closed  

loops4 ,hence we may sum up by saying   
that there are three set of phenomena to
 which we must pay attention in         
formulating any complete theory of the  
aerial4 ,the first is the operation     
taking place in the vertical wire1 which
 is described by saying that electrical 
oscillations or vibratory movements of  
electrons are taking place in it1 and1  
on our adopted theory1 it may be said to
 consist in a longitudinal vibration of 
electrons of such a nature that we may  
appropriately call the aerial an ether  
organ-pipe4 ,then in the next place1 we 
have the distribution and movement of   
the lines of electric strain and        
magnetic flux in the space outside the  
wire1 constituting the electric wave2   
and lastly1 there are the electrical    
changes in the conductor over which the 
wave travels1 which is the earth or     
water surrounding the aerial4 ,in       
subsequently dealing with the details of
 transmitting arrangements1 attention   
will be directed to the necessity for   

what telegraphists call a good earth in 
connection with ,hertzian wave          
telegraphy4 ,this only means that there 
must be a perfectly free egress and     
ingress for the electrons leaving or    
entering the aerial1 so that nothing    
hinders their access to the conducting  
surface over which the wave travels4    
,there must be nothing to stop or       
throttle the rush of electrons into or  
out of the aerial wire1 or else the     
lines of strain cannot be detached and  
and travel away4  ,we may next consider 
more particularly the energy which is   
available for radiation and which is    
radiated4 ,in the original form of      
simple ,marconi aerial1 the aerial      
itself when insulated forms one coating 
or surface of a condenser1 the          
dielectric being the air and ether      
around it1 and the other conductor being
 the earth4 ,the electric energy stored 
up in it just before discharge takes    
place is numerically equal to the       
product of the capacity of the aerial   

and half the square of the potential to 
which it is charged4  ,if we call ,c the
 capacity of the aerial in microfarads1 
and ,v the potential in volts to which  
it is raised before discharge1 then the 
energy storage in joules ,e is given by 
the equation1      ,e  7,,cv#b7 _/ 7#b 4
 #ajf74  ,since one joule is nearly     
equal to three-quarters of a foot-pound1
 the energy storage in foot-pounds ,f is
 roughly given by the rule ,f           
7#c_/h7;,,cv#b_/ajf4 ,for spark lengths 
of the order of five to fifteen         
millimetres1 the disruptive voltage in  
air of ordinary pressure is at the rate 
of #c1jjj volts per millimetre4 ,hence1 
if ,s stands for the spark length in    
millimetres1 and ,c for the aerial      
capacity in microfarads1 it is easy to  
see that the energy storage in          
foot-pound is      ,f  7#bg;,,cs#b7 _/  
#h4  ,if the aerial consists of a       
stranded wire formed of #g_/bb and has a
 length of #aej feet1 and is insulated  
and held vertically with its lower end  

near the earth1 it would have a capacity
 of about one three ten-thousandths of a
 microfarad or #j4jjjc mfd4#f ,hence1 if
 it is used as a ,marconi aerial and    
operated with a spark gap of one        
centimetre in length1 the energy stored 
up in the wire before each discharge    
would be only one-tenth 7#j4a7 of a     
foot-pound4  ,by no means can all of    
this energy be radiated as ,hertzian    
waves2 part of it is dissipated as heat 
and light in the spark1 and yet such an 
aerial can1 with a sensitive receiver   
such as that devised by ,mr4 ,marconi1  
make itself felt for a hundred miles    
over sea in every direction4 ,this fact 
gives us an idea of the extremely small 
energy which1 when properly imparted to 
the ether1 can effect wireless          
telegraphy over immense distances4 ,of  
course1 the minimum telegraphic signal1 
say the ,morse dot1 may involve a good  
many1 perhaps half-a-dozen1 discharges  
of the wire1 but even then the amount of
 energy concerned in affecting the      

receiver at the distant place is        
exceedingly small4  ,the problem1       
therefore1 of long-distance telegraphy  
by ,hertzian waves is largely1 though   
not entirely1 a matter of associating   
sufficient energy with the aerial wire  
or radiator4 ,there are obviously two   
things which may be done2 first1 we may 
increase the capacity of the aerial1 and
 secondly1 we may increase the charging 
voltage or1 in other words1 lengthen the
 spark gap4 ,there is1 however1 a       
well-defined limit to this last         
achievement4 ,if we lengthen the spark  
gap too much1 its resistance becomes too
 great and the spark ceases to be       
oscillatory4 ,we can make a discharge1  
but we obtain no radiation4 ,when using 
an induction coil1 about a centimetre1  
or at most a centimetre and a half1 is  
the limiting length of oscillatory      
sparks2 in other words1 our available   
potential difference is restricted to   
#cj1jjj or #dj1jjj volts4 ,by other     
appliances we can1 however1 obtain      

oscillatory sparks having a voltage of  
#ajj1jjj or #bjj1jjj volts1 and so      
obtain what ,hertz called active sparks 
five or six centimetres in length4      
,turning then to the question of        
capacity1 we may enquire in the next    
place how the capacity of an aerial wire
 can be increased4 ,this has generally  
been done by putting up two or more     
aerial wires in contiguity and joining  
them together1 and so making            
arrangements called in the admitted     
slang of the subject multiple aerials4  
,the measurement of the capacity of     
insulated wires can be easily carried   
out by means of an appliance devised by 
the author and ,mr4 ,w4 ,c4 ,clinton1   
consisting of a rotating commutator     
which alternately charges the insulated 
wire at a source of known electromotive 
force and then discharges it through a  
galvanometer4 ,if this galvanometer is  
subsequently standardised1 so that the  
ampere value of its deflection is known1
 we can determine easily the capacity ,c

 of the aerial or insulated conductor1  
reckoned in microfarads1 when it is     
charged to a potential of ,v volts1 and 
discharged n times a second through a   
galvanometer4 ,the series of discharges 
are equivalent to a current1 of which   
the value in amperes ,a is given by the 
equation      ,a  7n,v,c7 _/ 7#ajf71    
and hence1 if the value of the current  
resulting is known1 we have the capacity
 of the aerial or conductor expressed in
 microfarads1 given by the formula      
,c  7,a#ajf7 _/ 7n,v74  ,a series of    
experiments made on this plan have      
revealed the fact that if a number of   
vertical insulated wires are hung up in 
the air and rather near together1 the   
electrical capacity of the whole of the 
wires in parallel is not nearly equal to
 the sum of their individual capacities4
 ,if a number of parallel insulated     
wires are separated by a distance equal 
to about #c per cent4 of their length1  
the capacity of the whole lot together  
varies roughly as the square root of    

their number4 ,thus1 if we call the     
capacity of one vertical wire in free   
space unity1 then the capacity of four  
wires placed rather near together will  
only be about twice that of one wire1   
and that of twenty-five wires will only 
be about five times one wire4  ,this    
approximate rule has been confirmed by  
experiments made with long wires one    
hundred or two hundred feet in length in
 the open air4 ,hence it points to the  
fact that the ordinary plan of          
endeavouring to obtain a large capacity 
by putting several wires in parallel and
 not very far apart is very uneconomical
 in material4 ,the diagrams in ,fig4 #h 
show the various methods which have been
 employed by ,mr4 ,marconi and others in
 the construction of such multiple wire 
aerials4 ,if1 for instance1 we put four 
insulated stranded #g_/bb wires each    
#ajj feet long1 about six feet apart1   
all being held in a vertical position1  
the capacity of the four together is not
 much more than twice that of a single  

wire4 ,in the same manner1 if we arrange
 #aej similar wires1 each #ajj feet     
long1 in the form of a conical aerial1  
the wires being distributed at the top  
round a circle #ajj feet in diameter1   
the whole group will not have much more 
than twelve times the capacity of one   
single wire1 although it weighs #aej    
times as much4  ,illustration3 ,,fig4   
#h4--,,various ,,forms ,,of ,,aerial    
,,radiator4 a1 single wire2 b1 multiple 
wire2 c1 fan shape2 d1 cylindrical2 g1  
,conical4  ,the author has designed an  
aerial in which the wires1 all of equal 
length1 are arranged sufficiently far   
apart not to reduce each other's        
capacity4  ,as a rough guide in         
practice1 it may be borne in mind that a
 wire about one tenth of an inch in     
diameter and one hundred feet long1 held
 vertical and insulated1 with its bottom
 end about six feet from the ground1 has
 a capacity of #j4jjjb of a microfarad1 
if no other earthed vertical conductors 
are very near it4 ,the moral of all this

 is that the amount of electric energy  
which can be stored up in a simple      
,marconi aerial is very limited1 and is 
not much more than one-tenth of a joule 
or one-fourteenth of a foot-pound1 per  
hundred feet of #g_/bb wire4 ,the       
astonishing thing is that with so little
 storage of energy it should be possible
 to transmit intelligence to a distance 
of a hundred miles without connecting   
wires4  ,one consequence1 however1 of   
the small amount of energy which can be 
accumulated in a simple ,marconi aerial 
is that this energy is almost entirely  
radiated in one oscillation or wave4    
,hence1 strictly speaking1 a simple     
aerial of this type does not create a   
train of waves in the ether1 but        
probably at most a single impulse or    
two4  ,illustration3 ,,fig4             
#i4--,,marconi-,,braun ,,system ,,of    
,,inducing ,,electromotive ,,force ,,in 
,,an ,,aerial1 ,a4 ,b1 battery2 ,k1 key2
 ,i1 induction coil2 ,s1 spark gap2 ,c1 
,leyden jar2 ,e1 earth plate2 ps1       

oscillation transformer4  ,we shall     
later on consider some consequences     
which follow from this fact4 ,meanwhile1
 it may be explained that there are     
methods by which not only a much larger 
amount of energy can be accumulated in  
connection with an aerial1 but more     
sustained oscillations created than by  
the original ,marconi method4 ,one of   
these methods originated with ,professor
 ,braun1 of ,strasburg1 and a           
modification was first described by ,mr4
 ,marconi in a lecture before the       
,society of ,arts of ,london4#g ,in this
 method the charge in the aerial is not 
created by the direct application to it 
of the secondary electromotive force of 
an induction coil1 but by means of an   
induced electromotive force created in  
the aerial by an oscillation            
transformer4 ,the method due to         
,professor ,braun is as follows3 ,a     
condenser or ,leyden jar has one        
terminal1 say1 its inside1 connected to 
one spark ball of an induction coil4    

,the other spark ball is connected to   
the outside of the ,leyden jar or       
condenser through the primary coil of a 
transformer of a particular kind1 called
 an oscillation transformer 7see ,fig4  
#i74 ,the spark balls are brought within
 a few millimetres of each other4 ,when 
the coil is set in operation1 the jar is
 charged and discharged through the     
spark gap1 and electrical oscillations  
are set up in the circuit consisting of 
the dielectric of the jar1 the primary  
coil of the oscillation transformer and 
the spark gap4 ,the secondary circuit of
 this oscillation transformer is        
connected in between the earth and the  
insulated aerial wire2 hence1 when the  
oscillations take place in the primary  
circuit1 they induce other oscillations 
in the aerial circuit4 ,but the         
arrangement is not very effective       
unless1 as is shown by ,mr4 ,marconi1   
the two circuits of the oscillation     
transformer are tuned together4  ,we    
shall return presently to the           

consideration of this form of           
transmitter2 meanwhile we may notice    
that by means of such an arrangement it 
is possible to create in the aerial a   
far greater charging electromotive force
 than would be the case if the aerial   
were connected directly to one terminal 
of the secondary circuit of the         
induction coil1 the other terminal being
 to earth1 and the two terminals        
connected as usual by spark balls4 ,by  
the inductive arrangement it is possible
 to create in an aerial electromotive   
forces which are equivalent to a spark  
of a foot in length1 and when the length
 of the aerial is also properly         
proportioned the potential along it will
 increase all the way up1 until at the  
top or insulated end of the aerial it   
may reach an amount capable of giving   
sparks several feet in length4 ,from the
 remarks already made on the analogy    
between the closed organ-pipe and the   
,marconi aerial wire1 it will be seen   
that the wave which is radiated from the

 aerial must have a wave length four    
times that of the aerial if the aerial  
is vibrating in its fundamental manner4 
,it is also possible to create          
electrical oscillations in a vertical   
wire which are the harmonics of the     
fundamental4  ,all musicians are aware  
that in the case of an organ-pipe if the
 pipe is blown gently it sounds a note  
which is called the fundamental of the  
pipe4 ,the celebrated mathematician1    
,daniel ,bernouilli1 discovered that an 
organ-pipe can be made to yield a       
succession of musical notes by properly 
varying the pressure of the current of  
air blown into it4 ,if the pipe is an   
open pipe1 and if we call the frequency 
of the primary note obtained when the   
pipe is gently blown1 unity1 then when  
we blow more strongly the pipe yields   
notes which are the harmonics of the    
fundamental one2 that is to say1 notes  
which have frequencies represented by   
the numbers #b1 #c1 #d1 #e1 c4 ,if1     
however1 the pipe is closed at the top1 

then over-blowing the pipe makes it     
yield the odd harmonics or the tones    
which are related to the primary tone in
 the ratio of #c1 #e1 #g1 c41 to unity4 
,accordingly1 if a stopped pipe gives as
 its fundamental the note ,c1 its first 
overtone will be the fifth above the    
octave or ,g'4  ,illustration3 ,,fig4   
#aj4--,,seibt',s ,,apparatus ,,for      
,,showing ,,stationary ,,waves ,,in     
,,long ,,solenoid ,a4 ,i1 induction     
coil2 ,s1 spark gap2 ,l1 inductance     
coil2 ,c#a;,c#b1 ,leyden jars2 ,e1 earth
 wire4  ,as already remarked1 the aerial
 wire or radiator as used in ,marconi   
telegraphy may be looked upon as a kind 
of ether organ-pipe or siren tube1 and  
its electrical phenomena are in every   
respect similar to the acoustic         
phenomena of the ordinary closed        
organ-pipe4 ,when the aerial is sounding
 its fundamental ether note1 the        
conditions which pertain are that there 
is a current flowing into the aerial at 
the lower end1 but at that point the    

variation in potential is very small1   
whereas at the upper end there is no    
current1 but the variations of potential
 are very large4 ,accordingly1 we say   
that at the upper end of the aerial     
there is an antinode of potential and a 
node of current1 and at the bottom an   
antinode of current and a node of       
potential4 ,by altering the frequency of
 the electrical impulses we can create  
in the aerial an arrangement of nodes of
 current or potential corresponding to  
the overtones of a closed organ-pipe4   
,but whatever may be the arrangement the
 conditions must always hold that there 
is a node of current at the upper end   
and an antidote of current at the lower 
end4 ,in other words1 there are large   
variations of current at the place where
 the aerial terminates on the spark-gap 
and no current at the upper end4 ,the   
first harmonic is formed where there is 
a node of potential at one-third of the 
length of the aerial from the top4 ,in  
this case we have a node of potential   

not only at the lower end of the wire1  
but at two-thirds of the way up4 ,in the
 same way we can create in the closed   
organ-pipe1 by properly overblowing the 
pipe1 a region about two-thirds of the  
way up the pipe1 where the pressure     
changes in the air are practically no   
greater than they are at the mouthpiece4
 ,we can make evident visually in a     
beautiful manner the existence of       
similar stationary electrical waves in  
an aerial by means of an ingenious      
arrangement devised by ,dr4 ,georg      
,seibt1 of ,berlin4 ,it consists of a   
very long silk-covered copper wire1 ,a  
7see ,fig4 #aj71 wound in a close spiral
 of single layer round a wooden rod six 
feet long and about two inches in       
diameter4 ,this rod is insulated1 and at
 the lower end the wire is connected to 
a ,leyden jar circuit1 consisting of a  
,leyden jar or jars and an inductance   
coil1 ,l1 the inductance of which can be
 varied4 ,oscillations are set up in    
this jar circuit by means of an         

induction-coil discharge1 and the lower 
end of the long spiral wire is attached 
to one point on the jar circuit4 ,in    
this manner we can communicate to the   
bottom end of the long spiral wire a    
series of electric impulses1 the time   
period of which depends upon the        
capacity of the jar and the inductance  
of the discharge circuit4 ,we can1      
moreover1 vary this frequency over wide 
limits4 ,parallel to the long spiral    
wire is suspended another copper wire1  
,e 7see ,fig4 #aj71 and between this    
wire and the silk-covered copper wire   
discharges take place due to the        
potential difference between each part  
of the wire and this long aerial wire4  
,if we arrange matters so that the      
impulses communicated to the bottom end 
of the long spiral wire correspond to   
its fundamental note or periodic time1  
then in a darkened room we shall see a  
luminous glow or discharge between the  
vertical wire and the spiral wire1 which
 increases in intensity all the way up  

to the top of the spiral wire4 ,the     
luminosity of this brush discharge at   
any point is evidence of the potential  
of the spiral wire at that point1 and   
its distribution clearly demonstrates   
that the difference of potential between
 the spiral wire and the aerial         
increases all the way up from the bottom
 to the top of the spiral wire4 ,in the 
next place1 by making a little          
adjustment and by varying the inductance
 of the jar circuit1 we can increase the
 frequency of the impulses which are    
falling upon the spiral wire2 and then  
it will be noticed that the distribution
 of the brush discharge or luminosity is
 altered1 and that there is a maximum   
now at about one-third of the height of 
the spiral wire1 and a dark place at    
about two-thirds of the height1 and     
another bright place at the top1 thus   
showing that we have a node of potential
 at about two-thirds the way up the wire
 7see ,fig4 #aa71 and we have therefore 
set up in the spiral wire electrical    

oscillations corresponding to the first 
overtone4 ,it is possible to show in the
 same way the existence of the second   
harmonic in the coil1 but the luminosity
 then becomes too faint to be seen at a 
distance4  ,illustration3 ,,fig4        
#aa4--;,,harmonic ,,oscillations ,,in   
,,long ,,solenoid ,,shown ,,with        
,,seibt',s ,,apparatus4  ,an interesting
 form of aerial devised by ,professor   
,slaby1 of ,berlin1 depends for its     
action entirely on the fact that the    
electrical oscillations set up in it    
which radiate are harmonics of the      
fundamental tone4  ,illustration3 ,,fig4
 #ab4--,,non-,,radiative ,,closed ,,loop
 ,,aerial4  ,illustration3 ,,fig4       
#ac4--,,slaby',s ,,loop ,,radiator4  ,a 
closed vertical loop1 ,a#a;,a#b 7see    
,fig4 #ab71 is formed by erecting two   
parallel insulated wires vertically a   
few feet apart and joining them together
 at the top4 ,at the bottom these wires 
are connected1 with the secondary       
terminals of an induction coil1 a       

condenser1 ,c1 or ,leyden jar1 being    
bridged across the terminals and a pair 
of spark balls1 ,s1 inserted in one side
 of the loop4 ,it will readily be seen  
that on setting the coil in action1     
oscillations will take place in these   
vertical wires1 but that if the         
oscillations are simply the fundamental 
note of the system1 then at any moment  
corresponding to a current going up one 
side of the loop of wire there must be a
 current coming down the other4         
,accordingly1 an arrangement of this    
kind1 forming what is called a closed   
circuit1 will not radiate or radiates   
but very feebly4 ,professor ,slaby      
found1 however1 that it might be        
converted into a powerful radiator if we
 give the two sides of the loop unequal 
capacity or inductance and at the same  
time earth one of the lower ends of the 
loop1 as shown in ,fig4 #ac4 ,by this   
means it is possible to set up in the   
loop electrical overtones or harmonics  
of the fundamental oscillation1 and if  

we cause the system to vibrate so as to 
produce its first odd harmonic1 there is
 a potential node at the lower end of   
both vertical sides of the loop1 a      
potential node on both vertical sides at
 two-thirds of the way up1 and a        
potential antinode at the summit of the 
loop2 then1 under these circumstances1  
the closed loop of wire is in the same  
electrical condition as if two simple   
,marconi aerials1 both emitting their   
first odd harmonic oscillation1 were    
placed side by side and joined together 
at the top4  ,it is a little difficult  
without the employment of mathematical  
analysis to explain precisely the manner
 in which earthing one side of the loop 
or making the loop unsymmetrical as     
regards inductance has the effect of    
creating overtones in it4 ,the following
 rough illustration may1 however1 be of 
some assistance4 ,imagine a long spiral 
metallic spring supported horizontally  
by threads4 ,let this represent a       
conductor1 and let any movement to or   

fro of a part of the spring represent a 
current in that conductor4 ,suppose we  
take hold of the spring at one end1 we  
can move it bodily to and fro as a      
whole4 ,in this case1 every part of the 
spring is moving one way or the other in
 the same manner at the same time4 ,this
 corresponds with the case in which the 
discharge of the condenser through the  
uniform loop conductor is a flow of     
electricity1 all in one direction one   
way or the other4 ,the current is in the
 same direction in all parts of the loop
 at the same time1 and1 therefore1 if   
the current is going up one side of the 
loop it is at the same time coming down 
the other side4 ,hence the two sides of 
the loop are always in exact opposition 
as regards the effect of the current in 
them on the external space1 and the loop
 does not radiate4 ,returning again to  
the case of the spring4 ,supposing that 
we add a weight to one end of the spring
 by attaching to it a metal ball1 and   
then move the other end to and fro with 

certain periodic motion1 it will be     
found quite easy to set up in the spring
 a pulsatory motion resembling the      
movement of the air in an open          
organ-pipe4 ,under these circumstances  
both ends of the spring will be moving  
inwards or outwards at the same time1   
and the central portions of the spring1 
although being pressed and expanded     
slightly1 are moving to and fro very    
little4 ,this corresponds in the case of
 the looped aerial with a current       
flowing up or down both sides at the    
same time2 in other words1 when this    
mode of electrical oscillation is       
established in the loop1 its electrical 
condition is just that of two simple    
,marconi aerials joined together at the 
top and vibrating in their fundamental  
manner4 ,accordingly1 if one side of the
 double loop is earthed1 we then have an
 arrangement which radiates waves4      
,professor ,slaby found that by giving  
one side of the loop less inductance    
than the other1 and at the same time    

earthing the side having greater        
inductance at the bottom1 he was able to
 make an arrangement which radiated1 not
 in virtue of the normal oscillations of
 the condenser1 but in virtue of the    
harmonic oscillations set up in the     
conductor itself4 ,the mathematical     
theory of this radiator has been very   
fully developed by ,dr4 ,georg ,seibt4  
,it will be seen1 therefore1 that there 
are several ways in which we may start  
into existence oscillations in an       
aerial4 ,first1 the aerial may be       
insulated1 and we may charge it to a    
high potential and allow this charge    
suddenly to rush out4 ,although this    
process gives rise to a disturbance in  
the ether1 as already explained1 it is  
analogous to a pop or explosion in the  
air1 rather than to a sustained musical 
note4 ,the exact acoustic analogue would
 be obtained if we imagine a long pipe  
pumped full of air and then suddenly    
opened at one end4 ,the air would rush  
out1 and1 communicating a blow to the   

outer air1 would create an atmospheric  
disturbance appreciated as a noise or   
small explosion4 ,this is what happens  
when we cut the string and let the cork 
fly out from a bottle of champagne4 ,at 
the same time1 the inertia of the air   
rushing out of the tube would cause it  
to overshoot the mark1 and a short time 
after opening the valve the tube1 so far
 from containing compressed air1 would  
contain air slightly rarefied near its  
mouth1 and this rarefication would      
travel back up the tube in the form of  
wave motion1 and1 being reflected as    
condensation at the closed end1 travel  
down again2 and so after being reflected
 once or twice at the open or closed    
end1 become damped out very rapidly in  
virtue of both air friction and the     
radiation of the energy4 ,in the case1  
however1 of the ordinary organ-pipe1 we 
do not depend merely upon a store of    
compressed air put into the pipe1 but we
 have a store of energy to draw upon in 
the form of the large amount of         

compressed air contained in a wind      
chest1 which is being continually       
supplied by the bellows4 ,this store of 
compressed air is fed into the          
organ-pipe1 with the result that we     
obtain a continuous radiation of sound  
waves4 ,the first case1 in which the    
only store of energy is the compressed  
air originally contained in the pipe1   
illustrates the operation of the simple 
,marconi aerial4 ,the second case1 in   
which there is a larger store of energy 
to draw upon1 the organ-pipe being      
connected to a wind chest1 illustrates  
the ,marconi-,braun method1 in which an 
aerial is employed to radiate a store of
 electric energy contained in a         
condenser1 gradually liberated by the   
aerial in the form of a series of       
electrical oscillations and waves4 ,in  
this arrangement the condenser          
corresponds to the wind chest1 and it is
 continually kept full of electrical    
energy by means of the induction coil or
 transformer1 which answers to the      

bellows of the organ4 ,from the         
condenser1 electrical energy is         
discharged each time the spark discharge
 passes at a spark gap in the form of   
electrical oscillations set up in the   
primary circuit of an oscillation       
transformer4 ,the secondary circuit of  
this transformer is connected in between
 the earth and the aerial1 and therefore
 may be considered as part of it1 and1  
accordingly1 the energy which is        
radiated from the aerial is not simply  
that which is stored up in it in virtue 
of its own small capacity1 but that     
which is stored up in the much larger   
capacity represented by the primary     
condenser or1 as it may be called1 the  
electrical wind chest4 ,by the second   
arrangement we have therefore the means 
of radiating more or less continuous    
trains of electric waves1 corresponding 
with each spark discharge4 ,to create   
powerful oscillations in the aerial1 one
 condition of success is that there     
shall be an identity in time-period     

between the circuit of the aerial and   
that of the primary condenser4 ,the     
aerial is an open circuit which has     
capacity with respect to the earth1 and 
it has also inductance1 partly due to   
the wire of the aerial and partly due to
 the secondary circuit of the           
oscillation transformer in series with  
it4 ,the primary circuit or spark       
circuit has capacity--viz41 the capacity
 of the energy-storing condenser--and it
 has also inductance--viz41 the         
inductance of the primary circuit of the
 oscillation transformer4 ,we shall     
consider at a later stage more          
particularly the details of syntonising 
arrangements1 but meanwhile it may be   
said that one condition for setting up  
powerful waves by means of the above    
arrangement is that the electrical      
time-period of both the two circuits    
mentioned shall be the same4 ,this      
involves adjusting the inductance and   
capacity so that the product of         
conductance and capacity for each of    

these two circuits is numerically the   
same4 ,instead of employing an          
oscillation transformer between the     
condenser circuit and the aerial1 the   
aerial may be connected directly to some
 point on the condenser circuit at which
 the potential oscillations are large1  
and we have then another arrangement    
devised by ,professor ,braun 7see ,fig4 
#ad74 ,in this case1 in order to        
accumulate large potential oscillations 
at the top of the aerial1 it is1 as we  
have seen1 necessary that the length of 
the aerial shall be one quarter the     
length of the wave4 ,if1 therefore1 the 
electrical oscillations in the condenser
 circuit are at the rate of ,n per      
second1 in other words1 have a frequency
 ,n1 the wave-length correponding to    
this frequency is given by the          
expression1      #cx#ajaj_/,n cms4  ,the
 number #cx#ajaj is the value in        
centimetres per second of the velocity  
of the electromagnetic wave1 and is     
identical with that of light4 ,the      

corresponding resonant length of the    
aerial is therefore one-fourth of this  
wave-length1 or #cx#ajaj_/d,n4          
,generally speaking1 however1 it will be
 found that with any length of aerial   
which is practicable1 say1 #bjj feet or 
#f1jjj cms41 this proportion            
necessitates rather a high frequency in 
the primary oscillation circuit4 ,in the
 case considered--viz41 for an aerial   
#bjj feet in height--the oscillations in
 the primary circuit must have a        
frequency of one and a quarter million4 
,this high frequency can only be        
obtained either by greatly reducing the 
inductance of the primary discharge     
circuit1 or reducing the capacity4 ,if  
we reduce the capacity1 we thereby      
greatly reduce the storage of energy1   
and it is not practicable to reduce the 
inductance below a certain amount4      
,illustration3 ,,fig4 #ad4--;,,braun',s 
,,radiator4 ,b1 battery2 ,i1 induction  
coil2 ,k1 key2 ,s1 spark-gap2 ,l1       
inductance coil2 ,c1 condenser2 ,a1     

aerial4  ,summing up1 it may be said    
that there are three1 and1 as far as the
 writer is aware1 at present only three1
 modes of exciting the electrical       
oscillations in an aerial wire4 ,first1 
the aerial may itself be used as an     
electrical reservoir and charged to a   
high potential and suddenly discharged  
to the earth4 ,this is the original     
,marconi method4 ,the second method1 due
 to ,braun1 consist of attaching the    
aerial to some point on an oscillation  
circuit consisting of a condenser1 an   
inductance coil and a spark gap1 in     
series with one another1 and charging   
and discharging the condenser across the
 spark gap so as to create alterations  
of potential at some point on the       
oscillation circuit4 ,the length of the 
aerial must then be so proportioned as  
above described that it is resonant to  
this frequency4 ,thirdly1 we may employ 
the arrangement involving an oscillation
 transformer1 in which the oscillations 
in the primary condenser circuit are    

made to induce others in the aerial     
circuit1 the time-period of the two     
circuits being the same4 ,this method   
may be called the ,braun-,marconi       
method4 ,professor ,slaby has combined  
together in a certain way the original  
,marconi simple aerial with the resonant
 quarter-wave-length wire of ,braun4 ,he
 constructs what he calls a             
multiplicator1 which is really a wire   
wound into a loose spiral connected at  
one point to an oscillation circuit     
consisting of a condenser inductance1   
the length of this wire being           
proportioned so that there is a great   
resonance or multiplication of tension  
or potential at its free end4 ,this free
 end is then attached to the lower end  
of an ordinary ,marconi aerial1 and     
serves to charge it with a higher       
potential than could be obtained by the 
use of the induction coil directly      
attached to it4         99       99     
99       99       99  ,we have next to  
consider the appliances for creating the

 necessary charging electromotive force1
 and for storing and releasing this     
charge at pleasure1 so as to generate   
the required electrical oscillations in 
the aerial4  ,it is essential that this 
generator should be able to create not  
only large potential difference1 but    
also a certain minimum electric current4
 ,accordingly1 we are limited at the    
present moment to one of two            
appliances--viz41 the induction coil or 
the alternating current transformer4    
,it will not be necessary to enter into 
an explanation of the action of the     
induction coil4 ,the coil generally     
employed for wireless telegraphy is     
technically known as a ten-inch         
coil--i4e41 a coil which is capable of  
giving a ten-inch spark between pointed 
conductors in air at ordinary pressure4 
,the construction of a large coil of    
this description is a matter requiring  
great technical skill1 and is not to be 
attempted without considerable previous 
experience in the manufacture of smaller

 coils4 ,the secondary circuit of a     
ten-inch coil is formed of double       
silk-covered copper wire2 generally     
speaking1 the gauge called ,no4 #cf1 or 
else ,no4 #cd ,s4,w4,g4 is used1 and a  
length of ten to seventeen miles of wire
 is employed on the secondary circuit1  
according to the gauge of wire selected4
 ,for the precautions necessary in      
constructing the secondary coil1        
practical manuals must be consulted4#h  
,very great care is required in the     
insulation of the secondary circuit of  
an induction coil to be used in         
,hertzian wave telegraphy1 because the  
secondary circuit is then subjected to  
impulsive electromotive forces lasting  
for a short time1 having a much higher  
electromotive force than that which the 
coil itself normally produces4  ,the    
primary circuit of a ten-inch coil      
generally consists of a length of #cjj  
or #djj feet of thick insulated copper  
wire4 ,in such a coil the secondary     
circuit would require about ten miles of

 ,no4 #cd ,h4,c4 copper wire1 making    
#ej1jjj turns round the core4 ,it would 
have a resistance at ordinary           
temperatures of #f1fjj ohms1 and an     
inductance of #dfj henrys4 ,the primary 
circuit1 if formed of #cfj turns of ,no4
 #ab ,h4,c4 copper wire1 would have a   
resistance of #j4cf of an ohm1 and an   
inductance of #j4jb of a henry4  ,an    
important matter in connection with an  
induction coil to be used for wireless  
telegraphy is the resistance of the     
secondary circuit4 ,the purpose for     
which we employ the coil is to charge a 
condenser of some kind4 ,if a constant  
electromotive force 7,v7 is applied to  
the terminals of a condenser having a   
capacity ,c1 then the difference of     
potential 7v7 of the terminals of the   
condenser at any time that the contact  
is made is given by the expression3     
v  ,v7#a - e-t_/,,rc74  ,in the above   
equation1 the letter e stands for the   
number #b4gahbh1 the base of the        
,napierian logarithms1 and ,r is the    

resistance in series with the condenser1
 of which the capacity is ,c1 to which  
the electromotive force is applied4     
,this equation can easily be deduced    
from first principles1#i and it shows   
that the potential difference v of the  
terminals of the condenser does not     
instantly attain a value equal to the   
impressed electromotive force ,v1 but   
rises up gradually4 ,thus1 for instance1
 suppose that a condenser of one        
microfarad is being charged through a   
resistance of one megohm by an impressed
 voltage of #ajj volts1 the equation    
shows that at the end of the first      
second after contact1 the terminal      
potential difference of the condenser   
will be only #fc volts1 at the end of   
the second second1 #hf volts1 and so on4
  ,since e-#aj is an exceedingly small  
number1 it follows that in #aj seconds  
the condenser would be practically      
charged with a voltage equal to #ajj    
volts4 ,the product ,,cr in the above   
equation is called the time-constant of 

the condenser1 and we may say that the  
condenser is practically charged after  
an interval of time equal to ten times  
the time-constant1 counting from the    
moment of first contact between the     
condenser and the source of constant    
voltage4 ,the time-constant is to be    
reckoned as the product of the capacity 
7,c7 in microfarads1 by the resistance  
of the charging circuit 7,r7 in megohms4
 ,to take another illustration4         
,supposing we are charging a condenser  
having a capacity of one-hundreth of a  
microfarad1 through a resistance of ten 
thousand ohms4 ,since ten thousand ohms 
is equal to one-hundredth of a megohm1  
the time-constant would be equal to     
one-ten-thousandth of a second1 and ten 
times this time-constant would be equal 
to a thousandth of a second4 ,hence1 in 
order to charge the above capacity      
through the above resistance1 it is     
necessary that the contact between the  
source of voltage and the condenser     
should be maintained for at least       

one-thousandth part of a second4  ,in   
discussing the methods of interrupting  
the circuit1 we shall return to this    
matter1 but1 meanwhile1 it may be said  
that in order to secure a small         
time-constant for the charging circuit1 
it is desirable that the secondary      
circuit of the induction coil should    
have as low a resistance as possible4   
,this1 of course1 involves winding the  
secondary circuit with a rather thick   
wire4 ,if1 however1 we employ a wire    
larger in size than ,no4 #cd1 or at the 
most ,no4 #cb1 the bulk and the cost of 
the induction coil began to rise very   
rapidly4 ,hence1 as in all other        
departments of electrical construction1 
the details of the design are more or   
less a matter of compromise4 ,generally 
speaking1 however1 it may be said that  
the larger the capacity which is to be  
charged1 the lower should be the        
resistance of the secondary circuit of  
the induction coil4  ,in the practical  
construction of induction coils for     

wireless telegraphy1 manufacturers have 
departed from the stock designs4 ,we are
 all familiar with the appearance of the
 instrument maker's induction coil2 its 
polished mahogany base1 its lacquered   
brass fittings1 and its secondary bobbin
 constructed of and covered with        
ebonite4 ,but such a coil1 although it  
may look very pretty on the lecture     
table1 is yet very unsuited to positions
 in which it may be used in connection  
with ,hertzian wave telegraphy4  ,three 
important adjuncts of the induction coil
 are the primary condenser1 the         
interrupter and the primary key4 ,the   
interrupter is the arrangement for      
intermitting the primary current4 ,we   
have in some way or other to rapidly    
interrupt the primary current1 and the  
torrent of sparks that then appears     
between the secondary terminals of the  
coil is due to the electromotive force  
set up in the secondary circuit at each 
break or interruption of the primary    
circuit4 ,we may divide interrupters    

into five classes4  ,we have first the  
well-known hammer interrupter which     
,continental writers generally attribute
 to ,neef or ,wagner4#aj ,in this       
interrupter1 the magnetisation of the   
iron core of the coil is caused to      
attract a soft-iron block fixed at the  
top of a brass spring1 and by so doing  
to interrupt the primary circuit between
 two platinum contacts4 ,mr4 ,apps1 of  
,london1 added an arrangement for       
pressing back the spring against the    
back contact1 and the form of hammer    
that is now generally employed is       
therefore called an ,apps break4  ,as   
the ten-inch coil takes a primary       
current of ten amperes at sixteen volts 
when in operation1 it requires very     
substantial platinum contacts to        
withstand the interruption of this      
current continuously without damage4    
,the small platinum contacts that are   
generally put on these coils by         
instrument makers are very soon worn out
 in practical wireless telegraph work4  

,if a hammer break is used at all1 it is
 essential to make the contacts of very 
stout pieces of platinum1 and from time 
to time1 as they get burnt away or      
roughened1 they must be smoothed up with
 a fine file4 ,it does not require much 
skill to keep the hammer contacts in    
good order and prevent them from        
sticking together and becoming damaged  
by the break spark4  ,by regulating the 
pressure of the spring against the back 
contact1 by means of an adjusting screw1
 the rate at which the break vibrates   
can be regulated1 but as a rule it is   
not possible1 with a hammer break1 to   
obtain more than about #hjj             
interruptions per minute1 or1 say1      
twelve a second4 ,the hammer break is   
usually operated by the magnetism of the
 iron core of the coil1 but for some    
reasons it is better to separate the    
break from the coil altogether1 and to  
work it by an independent electromagnet1
 which1 however1 may be excited by a    
current from the same battery supplying 

the induction coil4 ,for coils up to the
 ten-inch size the hammer break can be  
used when very rapid interruptions are  
not required4 ,it is not in general     
practicable to work coils larger than   
the ten-inch size with a platinum       
contact hammer break1 as such a butt    
contact becomes overheated and sticks if
 more than ten amperes is passed through
 it4 ,in the case of larger coils1 we   
have to employ some form of interrupter 
in which mercury or a conducting liquid 
forms one of the contact surfaces4  ,the
 next class of interrupter is the       
vibrating or hand-worked mercury break1 
in which a platinum or steel pin is made
 to vibrate in and out of mercury4 ,this
 movement may be effected by the        
attraction of an iron armature by an    
electromagnet1 or by the varying        
magnetism of the core of the coil1 or it
 may be effected more slowly by hand4   
,the mercury surface must be covered    
with water1 alcohol1 paraffin or        
creosote oil to prevent oxidation and to

 extinguish the break spark4 ,the       
interruption of the primary current     
obtained by the mercury break is more   
sudden than that obtained by the        
platinum contact in air1 in consequence 
of the more rapid extinction of the     
spark2 hence the sparks obtained from   
coils fitted with mercury interrupters  
are generally from twenty to thirty per 
cent4 longer than those obtained from   
the same coil under the same conditions1
 with platinum contact interrupters4    
,the mercury breaks will not1 however1  
work well unless cleaned at regular     
intervals by emptying off the oil and   
rinsing well with clean water1 and hence
 they require rather more attention than
 platinum interrupters4 ,it is not      
generally possible to obtain so many    
interruptions per minute with the simple
 vibrating mercury interrupter as with  
the ordinary hammer interrupter4 ,the   
mercury interrupter has1 however1 the   
advantage that the contact time during  
which the circuit is kept closed may be 

made longer than is the case with the   
hammer break4 ,also1 if fresh water is  
allowed to flow continuously over the   
mercury surface1 it can be kept clean1  
and the break will then operate for     
considerable periods of time without    
attention4 ,the mercury interrupter may 
be worked by a separate electromagnet or
 by the magnetism of the core of the    
induction coil4  ,the third class of    
interrupter may be called the motor     
interrupter1 of which a large number    
have been invented in recent years4 ,in 
this interrupter some form of a         
continuously-rotating electromotor is   
employed to make and break a mercury or 
other liquid contact4 ,in one simple    
form the motor shaft carries an         
eccentric1 which simply dips a platinum 
point into mercury1 or else a platinum  
horseshoe into two mercury surfaces1    
making in this manner an interruption of
 the primary circuit at one or two      
places4 ,as a small motor can easily be 
run at twelve hundred revolutions per   

minute1 or twenty per second1 it is     
possible to secure easily in this manner
 a uniform rate of interruption of the  
primary current at the rate of about    
twenty per second4 ,if1 however1 much   
higher speeds are employed1 then the    
time of contact becomes abbreviated1 and
 the ability of the coil to charge a    
capacity is diminished4  ,professor ,j4 
,trowbridge has described an effective  
form of motor break for large coils1 in 
which the interruption is caused by     
withdrawing a stout platinum wire from a
 dilute solution of sulphuric acid1 and 
by this means he increased the spark    
given by a coil provided with hammer    
break and condenser from fifteen inches 
to thirty inches when using the liquid  
break and no condenser4#aa  ,a good form
 of motor-interrupter1 due to ,dr4      
,mackenzie ,davidson1 consists of a     
slate disc bearing pin contacts fixed on
 the prolonged steel axle of a motor    
placed in an inclined position2 the disc
 and the lower part of the axle lie in a

 vessel filled one-third with mercury   
and two-thirds with paraffin oil4 ,the  
circuit is made and broken by the       
revolution of the disc causing the pins 
to enter and leave the mercury4 ,the    
speed of the motor can be regulated by a
 small resistance1 and can be adapted to
 the electromotive force used in the    
primary circuit4 ,when the motor is     
running slowly the interrupter can be   
used with a low electromotive force1    
that is to say1 something between twelve
 and twenty volts1 but with a higher    
speed a large electromotive force can be
 used without danger of overheating the 
primary coil1 and with an electromotive 
force of about fifty volts1 the         
interruptions may be so rapid that an   
unbroken arc of flame1 resembling an    
alternating-current arc1 springs between
 the secondary terminals of the coil4   
,mr4 ,tesla has devised numerous forms  
of rotating mercury break4 ,in one1 a   
star-shaped metal disc revolves in a box
 so that its points dip into mercury    

covered with oil1 and make and break    
contact4 ,in another form1 a jet of     
mercury plays against a similar shaped  
rotating wheel4 ,for details1 the reader
 must consult the fuller descriptions in
 ,the ,electrical ,world of ,new ,york1 
,vol4 ,,xxxii41 p4 #aaa1 #ahih2 also    
,vol4 ,,xxxiii41 p4 #bdg2 or ,science   
,abstracts1 ,vol4 ,,ii41 pp4 #df and    
#dg1 #ahih4  ,the fourth class of       
interrupter is called a turbine         
interrupter4 ,in this appliance1 a jet  
of mercury is forced out of a small     
aperture by means of a centrifugal pump1
 and is made to squirt against a metal  
plate1 and interrupted intermittently by
 a toothed wheel made of insulating     
material rotated by the motor which     
drives the pump4 ,the current supplying 
the coil passes through or along this   
jet of mercury1 and is therefore        
rendered intermittent when the wheel    
revolves4 ,in the case of this          
interrupter1 the duration of the        
contacts1 as well as the number of      

interruptions per second1 is under      
control1 and for this reason better     
results are probably obtained with it   
than with any other form of break4  ,a  
description of a turbine mercury break  
devised by ,m4 ,max ,levy was given in  
the ,elektrotechnische ,zeitschrift1    
,vol4 ,,xx41 p4 #gag1 ,october #ab1     
#ahii 7see also ,science ,abstracts1    
,vol4 ,,iii41 p4 #fc1 abstract ,no4     
#afe7 as follows3--  ,a toothed wheel   
made of insulating material carries from
 #f to #bd teeth1 and can be made to    
rotate from #cjj to #a1jjj times per    
minute1 the interruptions being thus    
regulated between #e and #djj per       
second4 ,by raising or lowering the     
position of the jet of mercury and that 
of the plate against which it strikes1  
the duration of the contact can be      
varied1 so that it is possible to       
regulate this period without disturbing 
the number of interruptions per second4 
,the sparks obtained from a coil worked 
with a turbine interrupter have more    

quantity than the sparks obtained with  
any other interrupter under similar     
conditions1 and the coil can be worked  
with a far higher voltage than is       
possible when using the hammer break4   
,in this manner1 the appearance of the  
secondary sparks can be varied from the 
thin snappy sparks given by the hammer  
break to the thick flame-like arc sparks
 given by the electrolytic break4 ,this 
break can be adapted for any voltage    
from twelve to two hundred and fifty    
volts1 and the primary circuit cannot be
 closed before the interrupter is       
acting4 ,the mercury in the break is    
generally covered with alcohol or       
paraffin oil to reduce oxidation1 and   
the appliance is nearly noiseless when  
in operation4 ,the mercury has to be    
cleaned at intervals1 if the interrupter
 is much used4 ,if alcohol is used to   
cover the mercury1 the cleaning is very 
simple2 the break requires only to be   
rinsed under a water tap4 ,when paraffin
 oil is used1 the cleaning is generally 

effected with the help of a few ounces  
of sulphuric acid in a very few minutes4
 ,it is best1 however1 to clean the     
mercury continuously by allowing the    
water to flow over it4  ,the motor      
driving the centrifugal pump and the fan
 can be wound for any voltage1 and it is
 best to have it so arranged that this  
motor works on the same battery which   
supplies the primary circuit of the     
coil1 the two circuits working parallel 
together4 ,a rheostat can be added to   
the motor circuit to regulate the speed4
  ,the turbine break driven by an       
independent motor1 which is kept always 
running1 has another advantage over the 
hammer break in practical wireless      
telegraphy1 viz41 that a useful         
secondary spark can be secured with a   
shorter time of closure of the primary  
circuit1 since there is no inertia to   
overcome as in the case of the hammer   
break4 ,this latter form has only       
continued in use because of its         
simplicity and ease of management by    

ordinary operators4  ,the mercury       
turbine interrupter has been extensively
 adopted both in the ,german and        
,british navies in connection with      
induction coils used for wireless       
telegraphy4  ,lastly we have the        
electrolytic interrupters1 the first of 
which was introduced by ,dr4 ,wehnelt1  
of ,charlottenburg1 in the year #ahii1  
and modified by subsequent inventors4   
,in its original form1 a glass vessel   
filled with dilute sulphuric acid 7one  
of acid to five or else ten parts of    
water7 contains two electrodes of very  
different sizes2 one is a large lead    
electrode formed of a piece of sheet    
lead laid round the interior of the     
vessel1 and the other is a short piece  
of platinum wire projecting from the end
 of a glass or porcelain tube4 ,the     
smaller of these electrodes is made the 
positive1 and the large one the         
negative4 ,if this electrolytic cell is 
connected in series with the primary    
circuit of the induction coil 7the      

condenser being cut out7 and supplied   
with an electromotive force from forty  
to eighty volts1 an electrolytic action 
takes place which interrupts the current
 periodically4#ab ,an enormous number of
 interruptions can1 by suitable         
adjustment1 be produced per second1 and 
the appearance of a discharge from the  
secondary terminals of the coil1 while  
using the ,wehnelt break1 more resembles
 an alternate-current arc than the usual
 disruptive spark4  ,at the time when   
the ,wehnelt break was first introduced1
 great interest was excited in it1 and  
the technical journals in #ahii were    
full of discussions as to the theory of 
its operation4#ac ,the general facts    
concerning the ,wehnelt break are that  
the electrolyte must be dilute sulphuric
 acid in the proportion of one of acid  
to five or ten of water4 ,the large lead
 plate must be the cathode or negative  
pole1 and the anode or positive pole    
must be a platinum wire1 about a        
millimetre in diameter1 and projecting  

one or two millimetres from the pointed 
end of a porcelain1 glass or other      
acid-proof insulating tube4 ,the        
aperture through which the platinum wire
 works must be so tight that acid cannot
 enter1 yet it is desirable that the    
platinum wire should be capable of being
 projected more or less from the        
aperture by means of an adjusting screw4
 ,the glass vessel which contains these 
two electrodes should be of considerable
 size1 holding1 say1 a quart of fluid1  
and it is better to include this vessel 
in a larger one in which water can be   
placed to cool the electrolyte1 as the  
latter gets very warm when the break is 
used continuously4 ,if such an          
electrolytic cell has a continuous      
electromotive force applied to it       
tending to force a current through the  
electrolyte from the platinum wire to   
the lead plate1 we can distinguish three
 stages in its operation1 which are     
determined by the electromotive force   
and the inductance in the circuit4      

,first1 if the electromotive force is   
below sixteen or twenty volts1 then     
ordinary and silent electrolysis of the 
liquid proceeds1 bubbles of oxygen being
 liberated from the platinum wire and   
hydrogen set free against the lead      
plate4 ,if the electromotive force is   
raised above twenty-five volts1 then if 
there is no inductance in the circuit1  
the continuous flow of current proceeds1
 but if the circuit of the electrolyte  
possesses a certain minimum inductance1 
the character of the current flow       
changes1 and it becomes intermittent1   
and the cell acts as an interrupter1 the
 current being interrupted from #ajj to 
#b1jjj times per second1 according to   
the electromotive force and the         
inductance of the circuit4 ,under these 
conditions1 the cell produces a rattling
 noise and a luminous glow appears round
 the tip of the platinum wire4 ,thus1 in
 a particular case1 with an inductance  
of #j4jjd millihenry in the circuit of a
 ,wehnelt break1 no interruption of the 

circuit took place1 but with one        
millihenry of inductance in the circuit1
 and with an electromotive force of #dh 
volts1 the current became intermittent  
at the rate of #icj per second1 and by  
increasing the voltage to #abj volts1   
the intermittency rose to #a1hej a      
second4  ,the ,wehnelt break acts best  
as an interrupter with an electromotive 
force from #dj to #hj volts4 ,at higher 
voltages a third stage sets in3 the     
luminous glow round the platinum wire   
disappears1 and it becomes surrounded   
with a layer of vapour1 as observed by  
,,mm4 ,violle and ,chassagny2 the       
interruptions of current cease1 and the 
platinum wire becomes red hot4 ,if there
 is no inductance in the circuit1 the   
interrupter stage never sets in at all1 
but the first stage passes directly into
 the third stage4 ,in the first stage   
bubbles of oxygen rise steadily from the
 platinum wire1 and in the interrupted  
stage they rise at longer intervals1 but
 regularly4 ,the cell will not1 however1

 act as a break at all unless some      
inductance exists in the circuit4  ,in  
applying the ,wehnelt break to an       
induction coil1 the condenser is        
discarded and also the ordinary hammer  
break1 and the ,wehnelt break is placed 
in circuit with the primary coil4 ,in   
some cases1 the inductance of the       
primary coil alone is sufficient to     
start the break in operation1 but with  
voltages above #ej or #fj1 it is        
generally necessary to supplement the   
inductance of the primary coil by       
another inductive coil4 ,the best form  
of ,wehnelt break for operating         
induction coils is the one with multiple
 anodes 7see ,dr4 ,marchant1 ,the       
,electrician1 ,vol4 ,,xlii41 p4 #hda1   
#ahii71 and when it has to be used for  
long periods1 the cathode may           
advantageously be formed of a spiral of 
lead pipe1 through which cold water is  
made to circulate4  ,another form of    
electrolytic break was introduced by    
,mr4 ,caldwell4 ,in this1 a vessel      

containing dilute sulphuric acid is     
divided into two parts4 ,in the         
partition is a small hole1 and in the   
two compartments are electrodes of sheet
 lead4 ,the small hole causes an        
intermittency in the current which      
converts the arrangement into a break4  
,mr4 ,campbell ,swinton modified the    
above arrangement by making the         
partition to consist of a sort of       
porcelain test-tube with a hole in the  
bottom4 ,this hole can be more or less  
plugged up by a glass rod drawn out to a
 point1 and this is used to more or less
 close the hole4 ,this porcelain vessel 
contains dilute acid and stands in a    
larger vessel of acid1 and lead         
electrodes are placed in both           
compartments4 ,the current and          
intermittency can be regulated by more  
or less closing the aperture between the
 two regions4  ,when the ,wehnelt break 
is applied to an ordinary ten-inch      
induction coil1 and the inductance of   
the primary circuit and the             

electromotive force varied until the    
break interrupts the current regularly  
and with the frequency of some hundred a
 second1 the character of the secondary 
discharge is entirely different from its
 appearance with the ordinary hammer    
break4 ,the thin blue lightning-like    
sparks are then replaced by a thicker   
mobile flaming discharge1 which         
resembles an alternating-current arc1   
and1 when carefully examined or         
photographed1 is found to consist of a  
number of separate discharges           
superimposed upon one another in        
slightly different positions4  ,many    
theories have been adopted as to the    
action of the break1 but time will not  
permit us to examine these4 ,professor  
,s4 ,p4 ,thompson and ,dr4 ,marchant    
have suggested a theory of resonance4#ad
 ,one difficulty in explaining the      
action of the break is created by the   
fact that it will not work if the       
platinum wire is made a cathode4        
,although the ,wehnelt break has some   

advantages in connection with the use of
 the induction coil for ,roentgen ray   
work1 its utility as far as regards     
,hertzian wave telegraphy is not by any 
means so marked4 ,it has already been   
explained that1 in order to charge a    
condenser of a given capacity at a      
constant voltage1 the electromotive     
force must be applied for a certain     
minimum time1 which is determined by the
 value of the capacity and the          
resistance of the secondary circuit of  
the induction coil4 ,if the coil is a   
ten-inch coil and has a secondary       
resistance of1 say1 #f1jjj ohms1 and if 
the capacity to be charged has a value1 
say1 of one-thirtieth of a microfarad1  
then the time-constant of the circuit is
 #a_/e1jjj of a second4 ,therefore1 the 
contact with the condenser must be      
maintained for at least #a_/ejj of a    
second1 during the time that the        
secondary electromotive force of the    
coil is at its maximum1 so that the     
condenser may become charged to a       

voltage which the coil is then capable  
of producing4  ,in the induction coil1  
the electromotive force generated in the
 secondary coil at the break of the     
primary current is higher than that at  
the make1 and this electromotive force1 
other things being equal1 depends upon  
the rate at which the magnetism of the  
iron core dies away1 and its duration is
 shorter in proportion as the whole time
 occupied in the disappearance of the   
magnetism is less4 ,the ,wehnelt break  
does not increase the actual secondary  
electromotive force1 nor apparently its 
duration1 but it greatly increases the  
number of times per second this         
electromotive force makes it appearance4
 ,hence this break increases the        
current1 but not the electromotive force
 in the secondary coil4 ,it1 therefore1 
does not assist us in the direction     
required--viz41 in prolonging the       
duration of the secondary electromotive 
force to enable larger capacities to be 
charged4  ,the important point in       

connection with the working of a coil   
used for charging a condenser is not the
 length of spark which the coil can give
 alone1 but the length of spark which   
can be obtained between small balls     
attached to the secondary terminals1    
when these terminals are also connected 
to the two surfaces of the condenser4   
,thus1 a coil may give a ten-inch spark 
if worked alone1 but on a capacity of   
one-thirtieth of a microfarad it may not
 be able to give more than a            
five-millimetre spark4 ,hence1 in       
describing the value of a coil for      
wireless telegraph purposes1 it is not  
the least use to state the length of    
spark which the coil will give between  
the pointed conductors in air1 but we   
must know the spark length which it will
 give between brass balls1 say1 #a      
centimetre in diameter1 connected to the
 secondary terminals1 when these        
terminals are also short-circuited by a 
stated capacity1 the spark not exceeding
 that length at which it becomes        

non-oscillatory4  ,a good way of        
describing the value of an induction    
coil for wireless telegraph purposes is 
to state the length of oscillatory spark
 which can be produced between balls one
 centimetre in diameter connected to the
 secondary terminals1 when these balls  
are short-circuited by a condenser      
having a capacity1 say1 of one-hundredth
 of a microfarad1 and also one-tenth of 
a microfarad4  ,if a hammer or motor    
interrupter is employed with the coil1  
then a primary condenser must be        
connected across the points between     
which the primary circuit is broken4    
,this condenser generally consists of   
sheets of tinfoil alternated with sheets
 of paraffin paper1 and for a ten-inch  
coil may have a capacity of about #j4d  
or #j4e of a microfarad4#ae  ,lord      
,rayleigh discovered that if the        
interruption of the primary circuit is  
sufficiently sudden and complete1 as    
when the primary circuit is severed by a
 bullet from a gun1 the primary         

condenser can be removed and yet the    
sparks obtained from the secondary      
circuit are actually longer than those  
obtained with the condenser and the     
ordinary break4#af  ,in the use1        
however1 of the coil for ,hertzian wave 
telegraphy1 with all interrupters except
 the ,wehnelt break a condenser of      
suitable capacity must be joined across 
the break points4  ,turning in the next 
place to the primary key1 or signalling 
interrupter1 it is necessary to be able 
to control the torrent of sparks between
 the secondary terminals of the coil1   
and to cut them up into long and short  
periods in accordance with the letters  
of the ,morse alphabet4 ,this is done by
 means of the primary key4 ,the primary 
key generally consists of an ordinary   
massive single contact key with heavy   
platinum contacts4 ,as the current to be
 interrupted amounts to about ten       
amperes and is flowing in a highly      
inductive circuit1 the spark at break is
 considerable4 ,if the attempt is made  

to extinguish this spark by making the  
contacts move rapidly away from one     
another through a long distance1 in     
other words1 by using a key with a wide 
movement1 then the speed at which the   
signals can be set is greatly           
diminished4 ,the speed of sending       
greatly depends upon the time taken to  
move the key up and down between sending
 two dots1 and hence a short range key  
sends quicker than a long range key4 ,if
 it is desired to use a short range key1
 then some method must be employed to   
extinguish the spark at the contacts4   
,this is done in one of three ways3     
,either by using a high resistance coil 
to short-circuit these contacts1 or by a
 condenser1 or by a magnetic blow-out1  
as in the case of an electric tramcar   
circuit controller4 ,of these1 the      
magnetic blow-out is probably the best4 
,mr4 ,marconi has designed a signalling 
key which performs the function not only
 of interrupting the primary circuit1   
but at the same time breaks connection  

between the receiving appliance and the 
aerial4  ,the author has designed for   
signalling purposes a multiple contact  
key which interrupts the circuit        
simultaneously in ten or twelve         
different places4 ,the particular point 
about this break is the means which are 
taken to make the twelve interruptions  
absolutely simultaneous4 ,if these      
interruptions are not simultaneous1 the 
spark always takes place at the contact 
which is broken first1 but if the       
circuit is interrupted in a dozen places
 quite simultaneously1 then the spark is
 cut up into a dozen different portions1
 and the spark at each contact is very  
much diminished4 ,by this break1        
voltages up to two thousand volts may be
 quite easily dealt with4  ,various     
forms of break have been devised in     
which the circuit is broken under oil or
 insulating fluids1 but1 generally      
speaking1 these devices are not very    
portable1 and a dry contact between     
platinum surfaces with appropriate means

 for cutting up the spark and blowing it
 out so that the mechanical movement of 
the switch may be small is the best     
thing to use4  ,the signalling key is   
really a very important part of the     
transmitting arrangement1 because       
whatever may be the improvements in     
receiving instruments1 it is not        
possible to receive faster than we can  
send4 ,a great many statements have     
appeared in the daily papers as to the  
possibility of receiving hundreds of    
words a minute by ,hertzian wave        
telegraphy1 but the fact remains that   
whatever may be the sensibility of the  
receiving appliance1 the rate at which  
telegraphy of any kind can be conducted 
is essentially dependent upon the rate  
at which the signals can be sent1 and   
this in turn is largely dependent upon  
the mechanical movement which the key   
has to make to interrupt the primary    
circuit1 and so interrupt the secondary 
discharge4  ,in order to make the       
separation of the contact points of the 

switch as small as possible1 and yet    
prevent an arc being established1       
various blow-out devices have been      
employed4 ,the simplest arrangement for 
this purpose is a powerful permanent    
magnet so placed that its inter-polar   
field embraces the contact points and is
 at right angles to them4  ,as already  
explained1 the applicability of the     
induction coil in wireless telegraphy is
 limited by the fact of the high        
resistance of the secondary circuit and 
the small current that can be supplied  
from it4 ,data are yet wanting to show  
what is the precise efficiency of the   
induction coil1 as used in ,hertzian    
wave telegraphy1 but there are reasons  
for believing that it does not exceed   
#ej or #fj per cent4  ,where large      
condensers have to be charged--in other 
words1 where we have to deal with larger
 powers--we are obliged to discard the  
induction coil and to employ the        
alternating-current transformer4 ,but   
this introduces us to a new class of    

difficulties4 ,if an alternating-current
 transformer wound for a secondary      
voltage1 say1 of #bj1jjj or #cj1jjj     
volts1 has its primary circuit connected
 to an alternator1 then if the secondary
 terminals1 to which are connected two  
spark balls1 are gradually brought      
within striking distance of one another1
 the moment we do this an               
alternating-current arc starts between  
these balls4 ,if the transformer is a   
small one1 there is no difficulty in    
extinguishing this arc by withdrawing   
the secondary terminals1 but if the     
transformer is a large one1 say1 of ten 
or twenty kilowatts1 dangerous effects  
are apt to ensue when such an experiment
 is tried4 ,the short circuiting of the 
secondary circuit almost entirely annuls
 the inductance of the primary circuit4 
,there is1 therefore1 a rush of current 
into the transformer1 and if it is      
connected to an alternator of low       
armature resistance the fuses are       
generally blown and other damage done4  

,let us supppse1 then1 that the         
secondary terminals of the transformer  
are also connected to a condenser4 ,on  
bringing together the spark balls       
connected with the secondary terminals  
we may have one or more oscillatory     
discharges1 but the process will not be 
continuous1 because the moment that the 
alternating-current arc starts between  
the spark balls it reduces their        
difference of potential to a            
comparatively low value1 and hence the  
charge taken by the condenser is very   
small1 and1 moreover1 the circuit is not
 interrupted periodically so as to      
re-start a train of oscillations4       
,when1 therefore1 we desire to employ an
 alternating-current transformer as a   
source of electromotive force1 although 
it may have the advantage that the      
resistance of the secondary circuit of  
the transformer is generally small      
compared with that of the secondary     
circuit of an induction coil1 yet1      
nevertheless1 we are confronted with two

 practical difficulties3 7#a7 ,how to   
control the primary current flowing into
 the transformer1 and 7#b7 how to       
destroy the alternating-current arc     
between the spark balls and reduce the  
discharge entirely to the disruptive or 
oscillatory discharge of the condenser4 
,the control over the current can be    
obtained1 in accordance with a plan     
suggested by the author1 by inserting in
 the primary circuit of the transformer 
two variable choking coils4 ,the form in
 which it is preferred to construct     
these is that of a cylindrical bobbin   
standing upon a laminated cross-piece of
 iron4 ,these bobbins can have let down 
into them an ,e-shaped piece of         
laminated iron1 so as to complete the   
magnetic circuit1 and thus raise the    
inductance of the bobbin4 ,by placing   
two of these variable choking coils in  
series with the primary circuit1 the    
current is under perfect control4 ,we   
can fix a minimum value below which the 
current shall not fall1 by adjusting the

 position of the cores of these two     
choking coils1 and we can then cause    
that current to be increased up to a    
certain limit which it cannot exceed1 by
 short-circuiting one of these choking  
coils by an appropriate switch4 ,several
 ways have been suggested for           
extinguishing the alternating current   
arc which forms between the spark balls 
connected to the secondary terminals    
when these are brought within a certain 
distance of one another4 ,one of these  
is due to ,mr4 ,tesla4 ,he places a     
strong electromagnet so that its lines  
of magnetic flux pass transversely      
between the spark balls4 ,when the      
discharge takes place the electric arc  
is blown out1 but if the balls are      
short-circuited by a condenser the      
oscillatory discharge of the condenser  
still takes place across the spark gap4 
,professor ,elihu ,thomson achieves the 
same result by employing a blast of air 
thrown on the spark gap4 ,this has the  
effect of destroying the                

alternating-current arc1 but still      
leaves the oscillating discharge of the 
condenser4 ,the action is somewhat      
tedious to explain in words1 but it can 
easily be understood that the blast of  
air1 by continually breaking down the   
alternating-current arc which tends to  
form1 allows the condenser connected to 
the spark balls to become charged with  
the potential of the secondary circuit  
of the transformer1 and that this       
condenser then discharges across the    
spark gap1 producing an oscillatory     
discharge in the usual manner4 ,the     
author has found that1 without the use  
of any air blast or electromagnet1      
simple adjustment of the double choking 
coil in the primary circuit of the      
transformer1 as above described1 is     
sufficient to bring about the desired   
result1 when the capacity of the        
condenser is adjusted to be in          
resonance4  ,another method1 which has  
been adopted by ,m4 d',arsonval1 is to  
cause the spark to pass between two     

balls placed at the extremities of metal
 rods1 which are in rapid rotation like 
the spokes of a wheel4 ,in this case1   
the draught of air produced by the      
passage of the spark balls blows out the
 arc and performs the same function as  
the blast of air in ,professor ,elihu   
,thomson's method4 ,when these          
adjustments are properly made1 it is    
possible1 by means of a condenser and an
 alternating-current transformer        
supplied with current from an           
alternator1 to create a rapidly         
intermittent oscillatory discharge1 the 
sparks of which succeed one another so  
quickly that it appears almost          
continuous4 ,when using a large         
transformer and condenser1 the noise and
 brilliancy of these sparks are almost  
unbearable1 and the eyes may be injured 
by looking at this spark for more than a
 moment4 ,in the construction of        
transformers intended to be used in this
 manner1 very special precautions have  
to be taken in the insulation of the    

primary and secondary circuits1 and the 
insulation of these from the core4  ,it 
may be remarked in passing that         
experimenting with large high-tension   
transformers coupled to condensers of   
large capacity is exceedingly dangerous 
work1 and the greatest precautions are  
necessary to avoid accident4 ,in the    
light1 however1 of sufficient experience
 there is no difficulty in employing    
high-tension transformers in the        
above-described manner1 and in obtaining
 electromotive forces of upwards of a   
hundred thousand volts supplied through 
transformers capable of yielding any    
required amount of current4  ,on        
occasions where continuous current alone
 is available1 a motor generator has to 
be employed converting the continuous   
current into an alternating current4    
,this is best achieved by the employment
 of a small alternator directly coupled 
to a continuous-current motor2 or by    
providing the shaft of a                
continuous-current motor with two rings 

connected to two opposite portions of   
its armature1 so that when continuous   
current is supplied to the brushes      
pressing against the commutator1 an     
alternating current can be drawn off    
from two other brushes touching the     
above-mentioned insulated rings4  ,the  
next element of importance in the       
transmitting arrangement is the spark   
gap4 ,in the case of those transmitters 
employing an ordinary induction coil1   
the secondary spark1 or the discharge of
 any condenser connected to the         
secondary terminals can be taken between
 the brass balls about half an inch or  
one inch in diameter1 with which the    
terminals of the secondary coil are     
usually furnished2 and it is generally  
the custom to allow this spark discharge
 to take place in air at ordinary       
pressure4 ,in the very early days of his
 work ,mr4 ,marconi adopted the         
discharger devised by ,professor ,rhigi1
 in which the spark takes place between 
two brass balls placed in vaseline or   

other highly insulating oil4#ag ,but    
whatever advantage may accrue from using
 oil as the dielectric in which the     
spark discharge takes place1 when       
carrying out simple laboratory          
experiments on ,hertzian waves1 there is
 no advantage in the case of wireless   
telegraphy4 ,the ,rhigi discharger was1 
therefore1 soon discarded4 ,if          
discharges having large quantity are    
passed through oil1 it is rapidly       
decomposed or charred1 and ceases to    
retain the special insulating and       
self-restoring character which is       
necessary in the medium in which an     
oscillating spark is formed4 ,the       
conditions when the discharges of large 
condensers are passed between spark     
balls are entirely different from those 
when the quantity of the spark1 or to   
put it in more exact language1 the      
current passing1 is very small4 ,in the 
case of ,hertzian experiments it is     
necessary1 as shown by ,hertz1 to       
maintain a high state of polish on the  

spark balls when they are employed for  
the production of short waves of small  
energy1 but when we are dealing with    
large quantities of energy at each      
discharge1 those methods which succeed  
for laboratory experiments are perfectly
 impracticable4 ,the conditions         
necessary to be fulfilled by a          
discharger for use in ,hertzian wave    
telegraphy are that the surfaces shall  
maintain a constant condition and not be
 fused or eaten away by the spark1 and1 
next1 that the medium in which the      
discharge takes place shall not be      
decomposed by the passage of the spark1 
but shall maintain the property of      
giving way suddenly when a certain      
critical pressure is reached1 and       
passing instantly from a condition in   
which it is a very perfect insulator to 
one in which it is a very good          
conductor2 and1 thirdly1 that on the    
cessation of the discharge1 the medium  
shall immediately restore itself to its 
original condition4  ,when using the    

ordinary ten-inch induction coil1 and   
when the capacity charged by it does not
 exceed a small fraction of a           
microfarad1 it is quite sufficient to   
employ brass or steel balls separated by
 a certain distance in air1 at the      
ordinary pressure1 as the arrangement of
 the discharger4 ,when1 however1 we come
 to deal with the discharges of very    
large condensers1 at high electromotive 
forces1 then it is necessary to have    
special arrangements to prevent the     
destruction of the surfaces between     
which the spark passes1 or their        
continual alteration1 and many devices  
have been invented for this purpose4    
,the author has devised an arrangement  
which fulfils the above conditions very 
perfectly for use in large power        
stations1 but the details of this cannot
 be made public at the present time4    
99       99       99       99       99  
,we have to consider in connection with 
this part of the subject the dielectric 
strength of air under different         

pressures and for different thicknesses4
 ,it was shown by ,lord ,kelvin1 in     
#ahfj1 that the dielectric strength of  
very thin layers of air is greater than 
that of thick layers4#ah ,the electric  
force1 reckoned in volts per centimetre1
 required to pierce a thickness of air  
from two to ten millimetres in          
thickness1 at atmospheric pressure1 may 
be taken at #cj1jjj volts per           
centimetre4 ,the same force in          
electrostatic units is represented by   
the number #ajj1 since a gradient of    
#cjj volts per centimetre corresponds to
 a force of one electrostatic unit4 ,it 
appears also that for air and other     
gases there is a certain minimum voltage
 7approximately #djj volts7 below which 
no discharge takes place1 however near  
the conducting surfaces may be          
approximated4 ,in this particular       
practical application1 however1 we are  
only concerned with spark lengths which 
are measured in millimetres or          
centimetres1 lying1 say1 between one or 

two millimetres and five or six         
centimetres4 ,over this range of spark  
length we shall not generally be wrong  
in reckoning the voltage required to    
produce a spark between metal balls in  
air at the ordinary pressure to be given
 by the rule3      ,disruptive voltage  
#c1jjj x spark-gap length in            
millimetres4  ,if1 however1 the air     
pressure is increased above the normal  
by including the spark balls in a vessel
 in which air can be compressed1 then   
the spark length1 corresponding to a    
given potential difference1 very rapidly
 decreases4 ,mr4 ,f4 ,j4                
,jervis-,smith#ai found that by         
increasing the air pressure from one    
atmosphere to two atmospheres round a   
pair of spark balls he reduced the spark
 length given by a certain voltage from 
#b4e to #j4ge centimetre4  ,professor   
,r4 ,a4 ,fessenden has also made some   
interesting observations on the effect  
of using compressed air round spark     
gaps4 ,he found that if a certain       

voltage between metal surfaces would    
yield a spark four inches in length1 at 
the ordinary pressure of the air1 if the
 spark balls were enclosed in a         
cylinder1 the air round them compressed 
at #ejlb4 per square inch1 the spark    
length for the same potential difference
 of the balls was only one quarter of an
 inch1 or one-sixteenth of its former   
value4  ,the writer has also made       
experiments with an apparatus designed  
to study the effect of compressed air   
round the spark gap4 ,the experimental  
arrangements are as follows3 ,a ten-inch
 induction coil has one of its terminals
 connected to the internal coating of a 
battery of ,leyden jars4 ,the external  
coating is connected through the primary
 coil of an oscillation transformer with
 the other secondary terminal of the    
coil1 and these secondary terminals are 
also connected to a spark gap consisting
 of two brass balls enclosed in a glass 
vessel into which air can be forced by a
 pump1 the air pressure being measured  

by a gauge4 ,the balls in the glass     
vessel are set at a distance of about   
three millimetres apart4 ,the secondary 
circuit of the oscillation transformer  
is connected to another pair of spark   
balls1 the distance of which can be     
varied4  ,suppose we begin with the air 
in the glass vessel containing the balls
 connected to the secondary terminals of
 the induction coil1 which may be called
 the secondary balls1 at atmospheric    
pressure1 and create oscillatory        
discharges in the primary coil of the   
oscillation transformer1 we have a spark
 between the balls1 which may be called 
the tertiary balls1 connected to the    
secondary terminals of the oscillation  
transformer4 ,if the secondary balls are
 placed1 say1 three millimetres apart1  
the air in the glass vessel enclosing   
them being at the ordinary atmospheric  
pressure1 then with one particular      
arrangement of jars used1 a spark       
twenty-five or twenty-six millimetres   
long between the tertiary balls will    

take place4 ,suppose1 then1 we increase 
the pressure of the air round the       
secondary balls1 pumping it by degrees  
to #aj1 #bj1 #cj1 #dj and #ejlb4 per    
square inch above the atmospheric       
pressure4 ,we find that the spark       
between the tertiary balls will         
gradually leap a greater and greater    
distance1 and when the pressure of the  
air is #ejlb4 per square inch1 we can   
obtain a fifty-millimetre spark between 
the tertiary balls1 whereas when the air
 in the glass vessel is at atmospheric  
pressure1 we can only obtain a spark    
between the tertiary balls of half that 
length4  ,this experiment demonstrates  
that the effect of compressing the air  
round the secondary terminals of the    
induction coil is to greatly increase   
the difference of potential between     
these balls before the spark passes4 ,in
 fact1 it requires about double the     
voltage to force a spark of the same    
length through air compressed at #ejlb4 
on the square inch that it does to make 

a spark of identical length between the 
same balls in air at normal pressure4   
,this shows that there is a very great  
advantage in taking the discharge spark 
in compressed air4 ,a better effect can 
be produced by substituting dry gaseous 
hydrochloric acid for air at ordinary   
pressures4  ,one other incidental       
advantage is that the noise of the spark
 is very much reduced4 ,the continual   
crackle1 of the discharge spark of the  
induction coil in connection with       
wireless telegraphy is very annoying to 
sensitive ears1 but in this manner we   
can render it perfectly silent4         
,professor ,fessenden also states that  
when the spark balls are surrounded by  
compressed air1 and if one of the balls 
is connected with a radiator1 the       
compression of the air1 although it     
shortens the spark-gap corresponding to 
a given voltage1 does not in any way    
increase the radiation4 ,when1 however1 
the air in the spark-ball vessel is     
compressed to #fjlb4 in the square inch1

 there is a marked increase in the      
effective radiation1 and at #hjlb4 per  
square inch the energy emitted in the   
form of waves is nearly three and a-half
 times greater than at #ejlb41 the      
potential difference between the balls  
remaining the same4  ,this effect is no 
doubt connected with the fact that the  
production of a wave1 whether in ether  
or in any other material1 is not so much
 dependent upon the absolute force      
applied as upon the suddenness of its   
application4 ,to translate it into the  
language of the electronic theory1 we   
may say that the electron radiates only 
whilst it is being accelerated1 and that
 its radiating power1 therefore1 depends
 not so much upon its motion as upon the
 rate at which its motion is changing4  
,the advantage in using compressed air  
round the spark gap is that we can      
increase the effective potential        
difference between the balls without    
rendering the spark non-oscillatory4 ,in
 air of the ordinary pressure there is a

 certain well-defined limit of spark    
length for each voltage1 beyond which   
the discharge becomes non-oscillatory1  
but by the employment of spark balls in 
compressed air1 we can increase the     
potential difference between the balls  
corresponding to a given distance apart 
before a discharge takes place1 or      
employ higher potentials with the same  
length of spark gap4 ,in addition to    
this1 we have1 perhaps1 the production  
of a more effective radiation1 as       
asserted by ,fessenden1 when the air    
pressure exceeds a certain critical     
value4  ,the next element which we have 
to consider in the transmitting         
arrangements is a condenser of some kind
 for storing the energy which is        
radiated at intervals4 ,where a         
condenser other than the aerial is      
employed for storing the electric energy
 which is to be radiated by the aerial1 
some form of it must be constructed     
which will withstand high potentials4   
,as the dielectric for such a condenser1

 only two materials seem to be of any   
practical use1 viz41 glass and micanite4
 ,glass condensers in the form of       
,leyden jars have been extensively      
employed1 but they have the disadvantage
 that they are very bulky in proportion 
to their electrical capacity4 ,the      
instrument maker's quart ,leyden jar has
 a capacity of about one-five hundredth 
of a microfarad1 but it occupies about  
#aej cubic inches or more4 ,professor   
,braun has employed in his transmitting 
arrangements condensers consisting of   
small glass tubes like test tubes1 lined
 on the inside and outside with tinfoil1
 which are more economical in space4    
,the author has found that condensers   
for this purpose are best made of sheet 
glass about one-eighth or one-tenth of  
an inch in thickness1 coated to within  
one inch of their edge on both sides    
with tinfoil1 and arranged in a vessel  
containing resin or linseed oil1 like   
the plates of a storage battery4 ,m4    
d',arsonval has employed micanite1 but  

although this material has a            
considerably higher dielectric strength 
than glass1 it is much more expensive to
 obtain a given capacity by means of    
micanite than by glass1 although the    
bulk of the condenser for a given       
capacity is less4  ,to store up a       
certain amount of electric energy in a  
condenser1 we require a certain definite
 volume of dielectric1 no matter how we 
may arrange it1 and the volume required 
per unit of energy is determined by the 
dielectric strength of the material4    
,thus1 for instance1 ordinary sheet     
glass cannot be safely employed with a  
greater electric force than is          
represented by #bj1jjj volts for        
one-tenth of an inch in thickness1 or1  
say1 a potential gradient of #afj1jjj   
volts per centimetre4 ,this is          
equivalent to an electric force of about
 #ejj electrostatic units4 ,this may be 
called the safe-working force4 ,the     
electrostatic capacity of a condenser   
formed of two metal surfaces a foot     

square separated by glass three         
millimetres in thickness is between     
#a_/cfj and #a_/djj of a microfarad4 ,if
 this condenser is charged to #bj1jjj   
volts1 we have stored up in it half a   
joule of electric energy1 and the volume
 of the dielectric is #bgj cubic        
centimetres4 ,hence1 to store up in a   
glass condenser electric energy         
represented by one joule at a pressure  
of #bj1jjj volts1 we require #ejj cubic 
centimetres of glass1 and it will be    
found that if we double the pressure and
 double the thickness of the glass1 we  
still require the same volume4#bj       
,hence1 in the construction of          
high-tension condensers to store up a   
given amount of energy1 the economical  
problem is how to obtain the greatest   
energy-storing capacity for the least   
money4 ,glass fulfils this condition    
better than any other material4         
,although some materials may have very  
high dielectric strength1 such as paper 
saturated with various oils1 or resins1 

yet they cannot be used for the purpose 
of making condensers to yield           
oscillatory discharges1 because the     
oscillations are damped out of existence
 too soon by the dielectric4  ,in       
arranging condensers to attain a given  
capacity1 regard has to be taken of the 
fact that for a given potential         
difference there must be a certain total
 thickness of dielectric1 and that if   
condensers of equal size are being      
arranged in parallel it adds to their   
capacity1 whilst joining them in series 
divides their capacity4 ,if ,n equal    
condensers or ,leyden jars have each a  
capacity represented by ,c1 and if they 
are joined n in series and m in         
parallel1 the joint capacity of the     
whole number is m,c_/n1 where the       
product mn  ,n4  ,passing on next to the
 consideration of oscillation           
transformers of various kinds--these are
 appliances of the nature of induction  
coils for transforming the current or   
electromotive force of electrical       

oscillations in a required ratio4 ,these
 coils are1 however1 destitute of any   
iron core1 and they generally consist of
 coils of wire wound on a fibre1 wooden 
or ebonite frame1 and must be immersed  
in a vat of oil to preserve the         
necessary insulation4 ,no dry insulation
 of the nature of indiarubber or        
gutta-percha will withstand the high    
pressures that are brought to bear upon 
the circuits of an oscillation          
transformer4 ,in constructing these     
transformers we have to set aside all   
previous notions gathered from the      
design of low-frequency iron-core       
transformers4 ,the chief difficulty we  
have to contend against in the          
construction of an effective oscillation
 transformer is the inductance of the   
primary circuit and the magnetic leakage
 that takes place4 ,in other words1 the 
failure of the whole of the flux        
generated by the primary circuit to pass
 through or be linked with the secondary
 circuit4 ,mr4 ,marconi has employed an 

excellent form of oscillation           
transformer1 in the design of which he  
was guided by a large amount of         
experience4 ,in this transformer the two
 circuits are wound round a square      
wooden frame4 ,the primary circuit      
consists of a number of strands of thick
 insulated cable laid on in parallel1 so
 that it consists of only one turn of a 
stranded conductor4 ,the secondary      
circuit consists of a number of turns1  
say1 ten to twenty1 of thinner insulated
 wire laid over the primary circuit and 
close to it1 so that the transformer has
 the transformation ratio of one to ten 
or one to twenty4 ,in the arrangements  
devised and patented by ,mr4 ,marconi1  
these two circuits1 with their          
respective capacities in series with    
them1 are tuned to one another1 so that 
the time-period of each circuit is      
exactly the same1 and without this      
tuning the device becomes ineffective as
 a transformer4#ba ,there is no         
advantage in putting a number of turns  

on the primary circuit1 because such    
multiplication simply increases the     
inductance1 and1 therefore1 diminishes  
the primary current in the same ratio   
which it multiplies the turns1 and hence
 the magnetic field due to the primary  
circuit remains the same4 ,where it is  
desired to put a number of turns upon a 
coil1 and yet at the same time keep the 
inductance down1 the writer has adopted 
the device of winding a silk or hemp    
rope well paraffined between the turns  
of the circuit1 so as to keep them      
further apart from one another1 and as  
the inductance depends on the turns per 
centimetre1 this has the effect of      
reducing the inductance4  ,the next and 
most important element in any           
transmitting station is the aerial or   
radiator1 and it was the introduction of
 this element by ,mr4 ,marconi which    
laid the foundation for ,hertzian wave  
telegraphy as opposed to mere           
experiments with the ,hertzian waves4   
,we may consider the different varieties

 of aerial which have been evolved from 
the fundamental idea4 ,the simple single
 ,marconi aerial consists of a bare or  
insulated wire1 generally about #ajj;ft4
 or #aej;ft4 in length1 suspended from a
 sprit attached to a tall mast4 ,as     
these masts have generally to be erected
 in exposed positions1 considerable care
 has to be taken in erecting them with a
 large margin of strength4 ,to the end  
of a sprit is attached an insulator of  
some kind1 which may be a simple ebonite
 rod1 or sometimes a more elaborate     
arrangement of oil insulators1 and to   
the lower end of this insulator is      
attached the aerial wire4 ,as at the top
 of the aerial we have to deal with     
potentials capable sometimes of giving  
sparks several feet in length1 the      
insulation of the upper end of the      
aerial is an important matter4  ,in the 
original ,marconi system1 the lower end 
of the aerial was simply attached to one
 spark ball connected to one terminal of
 the induction coil1 and the other      

terminal and spark ball were connected  
to the earth4 ,in this arrangement1 the 
aerial acted not only as radiator1 but  
as energy-storing capacity1 and as      
already explained1 its radiating power  
was on that account limited4 ,the earth 
connection is an important matter4 ,for 
long distance work1 a good earth is     
essential4 ,this earth must be made by  
embedding a metal plate in the soil1 and
 many persons are under the impression  
that the efficiency of the earth plate  
depends upon its area1 but this is not  
the fact4 ,it depends much more upon its
 shape1 and principally upon the amount 
of its edge4 ,it has been shown by      
,professor ,a4 ,tanakadate1 of ,japan1  
that if a metal plate of negligible     
resistance is embedded in an infinite   
medium having a resistivity r1 the      
electrical conductance of this plate is 
equal to #dpi_/r times the electrostatic
 capacity of the same plate placed in a 
dielectric of infinite extent4 ,hence in
 designing an earth plate1 we have to   

consider not how to give it the utmost  
amount of surface1 but how to give it   
the greatest electrostatic capacity1 and
 for this purpose it is far better to   
divide a given amount of metal into long
 strips radiating out in different      
directions1 rather than to employ it in 
the form of one big square or circular  
plate4 ,the importance of the good earth
 will have been seen from our discussion
 on the mode of formation of electric   
waves4 ,there must be a perfectly free  
access for the electrons to pass into   
and out of the aerial4 ,hence1 if the   
soil is dry1 or badly conductive in the 
neighbourhood1 we have to go down to a  
level at which we get a good moist      
earth4 ,in fact1 the precautions which  
have to be taken in making a good earth 
for ,hertzian wave telegraphy are       
exactly those which should be taken in  
making a good earth for a lightning     
conductor4  ,whilst on the subject of   
aerials1 a word may be said on the      
localisation of wireless telegraph      

stations on the ,marconi system4 ,for   
reasons which were explained previously1
 the transmission of signals is effected
 more easily over water than over dry   
land1 and it is hindered if the soil in 
the neighbourhood of the sending station
 is a poor conductor4 ,hence1 all active
 ,hertzian wave telegraph stations1 like
 all active volcanoes1 are generally    
found near the sea4 ,in those cases in  
which a multiple aerial has to be put up
 consisting of many wires1 one mast may 
be insufficient to support the          
structure1 and several masts arranged in
 the form of a square or a circle have  
to be employed4 ,the illustrated papers 
have reproduced numerous pictures of the
 ,marconi power stations at ,poldhu in  
,cornwall1 ,glace ,bay in ,nova ,scotia1
 and ,cape ,cod in the ,united ,states4 
,in these stations1 after preliminary   
failures to obtain the necessary        
structural strength with ordinary masts1
 tall lattice girder wooden towers have 
been built1 about #bae feet in height1  

well stayed against wind pressure1 and  
which so far have proved themselves     
capable of withstanding any storm of    
wind which has come against them4  ,an  
important question in connection with   
the sending power of an aerial is that  
of the relation of its height to the    
distance covered4 ,some time ago ,mr4   
,marconi enunciated a law1 as the result
 of his experiments1 connecting these   
two quantities1 which may be called     
,marconi's ,law4 ,he stated that the    
height of the aerial to cover a given   
distance1 other things remaining the    
same1 varies as the square root of the  
distance4 ,let ,d be the distance and   
let ,l be the length of the aerial1 then
 if both the transmitting and receiving 
aerial are the same height1 we may say  
that ,d varies as ,l#b4 ,this relation  
may be theoretically deduced as         
follows3--,any given receiving apparatus
 for ,hertzian wave telegraphy requires 
a certain minimum energy to be imparted 
to it to make it yield a signal4 ,if the

 resistance and the capacity of the     
receiver is taken as constant1 this     
minimum working energy is proportional  
to the square of the electromotive force
 set up in the receiving aerial by the  
impact on it of the electric waves4     
,this electromotive force varies as the 
length of the receiving aerial and as   
the magnetic force due to the wave      
cutting across it1 and the magnetic     
force varies as the current in the      
transmitting aerial1 and therefore1 for 
any given voltage varies as the         
capacity1 and therefore as the length of
 the transmitting aerial4 ,if1          
therefore1 the transmitting and         
receiving aerial have the same length1  
the minimum energy varies as the square 
of the electromotive force in the       
receiving aerial1 and therefore as the  
fourth power of the length of either    
aerial1 since the electromotive force   
varies as the product of the lengths of 
the aerials4 ,hence1 when the distance  
between the aerials is constant1 the    

minimum working energy varies as the    
fourth power of the height of either    
aerial1 but when the lengths of the     
aerials are constant1 the energy caught 
up by the receiving aerial must vary    
inversely as the square of the distance 
,d between the aerials4 ,hence1 if we   
call e this minimum working energy1 e   
must vary as #a_/;,d#b when ,l is       
constant1 or as ,l#d when ,d is         
constant1 and since e is a constant     
quantity for any given arrangements of  
receiver and transmitter1 it follows    
that when the height of aerial and      
distance vary1 the ratio ,l#d_/;,d#b is 
constant1 or1 in other words1 ,d#b      
varies as ,l#d or ,d varies as          
,l#b--;i4e41 distance varies as the     
square of the height of the aerial1     
which is ,marconi's ,law4 ,the curve1   
therefore1 connecting height of aerial  
with sending distance for given         
arrangements is a portion of a parabola4
  ,otherwise1 the law may be stated in  
the form ,l  asq,d1 where a is a        

numerical coefficient4 ,if ,l and ,d are
 both measured in metres1 then1 for     
recent ,marconi apparatus as used on    
ships1 a  #j4ae roughly4 7,see a report 
on experiments made for the ,italian    
,navy1 #aijj-aija1 by ,captain ,quintino
 ,bonomo--,telegrafia senza fili1 ,rome1
 #aijb47  ,this law1 however1 must not  
be used without discretion4 ,after ,mr4 
,marconi had transmitted signals across 
the ,british ,channel1 some people1     
forgetting that a little knowledge is a 
dangerous thing1 predicted that aerials 
a thousand feet in height would be      
required to signal across the ,atlantic1
 but ,mr4 ,marconi has made such        
improvements of late years in the       
receiving arrangements that he has been 
able to receive signals over three      
thousand miles in #aijc with aerials    
only thirty-three per cent4 longer than 
those which1 in #ahii1 he employed to   
cover twenty miles across the ,english  
,channel4  ,illustration3 ,,fig4        
#ae4--;,,alternating-,,current          

,,double-,,transformation ,,power       
,,plant ,,for ,,generating ,,electric   
,,waves 7,fleming74 a1 alternator2      
,h#a;,h#b1 choking coil2 ,k1 signalling 
key2 ,t1 step-up transformer2 ,s#a,s#b  
spark-gap2 ,c#a;,c#b condensers2        
,t#a,t#b1 oscillation transformers2 ,a1 
aerial2 ,e1 earthplate4  ,we turn1 in   
the next place1 to the consideration of 
those devices for putting more power    
into the aerial than can be achieved    
when the aerial itself is simply        
employed as the reservoir of energy4    
,professor ,braun1 of ,strassburg1 in   
#ahii1 described a method for doing this
 by inducing oscillations in the aerial 
by means of an oscillation transformer1 
these oscillations being set up by the  
discharges from a ,leyden jar or battery
 of ,leyden jars1 which formed the      
reservoir of energy4 ,the induction coil
 is employed to produce a rapidly       
intermittent series of electrical       
oscillations in the primary coil of an  
oscillation transformer by the discharge

 through it of a ,leyden jar4 ,mr4      
,marconi immensely improved this        
arrangement1 as described by him in a   
lecture given before the ,society of    
,arts on ,may #ag1 #aija1 by syntonising
 the two circuits and making the        
circuit1 consisting of the capacity of  
the aerial and the inductance of the    
secondary circuit of the oscillation    
transformer1 have the same time-period  
as the circuit consisting of the ,leyden
 jars1 or energy-storing condenser1 and 
the primary circuit of the oscillation  
transformer1 and by so doing immensely  
added to the power and range of the     
apparatus4  ,starting from these        
inventions of ,braun and ,marconi1 the  
author devised a double transmission    
system in which the oscillations are    
twice transformed before being generated
 in the aerial1 each time with a        
multiplication of electromotive force   
and a multiplication of the number of   
groups of oscillations per second4 ,this
 arrangement can best be understood from

 the diagram 7see ,fig4 #ae74  ,in this 
case a transformer1 ,t1 or transformers 
receive alternating low-frequency       
current from an alternator1 a1 being    
regulated by passing through two        
variable choking coils1 ,h#a and ,h#b1  
so as to control it4 ,this alternating  
current is transformed up from a        
potential of two thousand to twenty1    
forty or a hundred thousand1 and is     
employed to charge a large condenser1   
,c#a1 which discharges across a primary 
spark-gap1 ,s#a1 through the primary    
coil of an oscillation transformer1     
,t#a4 ,the secondary circuit of the     
oscillation transformer is connected to 
a second pair of spark balls1 ,s#b1     
which in turn are connected by a        
secondary condenser1 ,c#b1 and the      
primary circuit of a third transformer1 
,t#b and the secondary circuit of this  
last transformer are inserted between a 
,marconi aerial1 ,a1 and the earth ,e4  
,when all these circuits are tuned to   
resonance by ,mr4 ,marconi's methods1 we

 have an enormously powerful arrangement
 for creating electric waves1 or rather 
trains of electric waves1 sent out from 
the aerial1 and the oscillations are    
controlled and the signals made by      
short-circuiting one of the choking     
coils4  ,another transmitting           
arrangement1 which involves a slightly  
different principle1 and employs no     
oscillation transformer1 is one due also
 to ,professor ,braun4 ,in this case1 a 
condenser and inductance are connected  
in series to the spark balls of an      
induction coil1 and oscillations are set
 up in this circuit4 ,accordingly1 there
 are rapid fluctuations of potential at 
one terminal of the condenser4 ,if to   
this we connect a long aerial1 the      
length of which has been adjusted to be 
one quarter of the length of wave       
corresponding to the frequency1 in other
 words1 to make it a quarter-wave       
resonator1 then powerful oscillations   
will be accumulated in this rod4 ,the   
relation between the height 7,h7 of the 

aerial and the frequency is given by the
 equation #c x #ajaj  #dn,h1 where n is 
the frequency of the oscillations and ,h
 the height of the aerial in            
centimetres4 ,the frequency of the      
oscillations is determined by the       
capacity 7,c7 and inductance 7,l7 of the
 condenser circuit1 and can be          
calculated from the formula      n      
7#e1jjj1jjj7 _/ 7sq,c 7in mfds47 x ,l   
7in cms4774  ,that is1 the frequency is 
obtained by dividing into the number    
#e1jjj1jjj1 the square root of the      
product of the capacity in microfarads1 
and inductance in centimetres1 of the   
condenser circuit4 ,it will be found1 on
 applying these rules1 that it is       
impossible to unite together any aerial 
of a length obtainable in practice with 
a condenser circuit of more than a very 
moderate capacity4 ,it has been shown   
that for an aerial two hundred feet in  
height the corresponding resonating     
frequency is about one and a quarter    
million4#bb ,as we are limited in the   

amount to which we can reduce the       
inductance of a discharge circuit1      
probably to something like a thousand   
centimetres1 a simple calculation shows 
that the largest capacity we can employ 
is about a sixtieth of a microfarad4    
,this capacity1 even if charged at      
#fj1jjj volts1 would only contain thirty
 joules of energy1 or about #bb4e       
foot-pounds1 which is a small storage   
compared to that which can be achieved  
when we are employing the               
above-described methods1 which involve  
the use of an oscillation transformer4  
,in such a case1 however1 it is an      
advantage to employ a spark-gap in      
compressed air1 because we can then     
raise the voltage to a much higher value
 than in air of ordinary pressure       
without lengthening the spark so much as
 to render it non-oscillatory4  ,when   
employing methods involving the use of  
an oscillation transformer1 it is       
possible to use multiple aerials having 
large capacity1 and hence to store up a 

very large amount of energy in the      
aerial1 which is liberated at each      
discharge4 ,the most effective          
arrangement is one in which the radiator
 draws off gradually a large supply of  
energy from a non-radiating circuit1 and
 so sends out a true train of waves1 and
 not mere impulses1 into the ether1 and 
as we shall see later on1 it is only    
when the radiation takes place in the   
form of true wave trains that anything  
like syntony can be obtained4  ,there   
are a number of variants of the above   
methods of arranging the radiator and   
associated energy-storing in circuit4   
,descriptions of these arrangements will
 be found in patents by ,mr4 ,marconi1  
,professor ,slaby and ,count von ,arco1 
,sir ,oliver ,lodge1 ,dr4 ,muirhead1    
,professor ,popoff1 ,professor          
,fessenden and others4 ,in all cases1   
however1 they are variations of the     
three simple forms of radiator already  
described4  ,returning to the analogy   
with the air or steam siren suggested at

 the commencement of this article1 the  
reader will see in the light of the     
explanations already given1 that all    
parts of the air-wave producing         
apparatus have their analogues in the   
electrical radiator as used in ,hertzian
 wave telegraphy4 ,the object in the one
 case is to produce rapid oscillations  
of air particles in a tube1 which result
 in the production of an air wave in    
external space2 in the other case1 the  
arrangement serves to produce           
oscillations of electrons or electrical 
particles in a wire1 the movements of   
which create a disturbance in the ether 
called an electrical wave4 ,comparing   
together1 item by item1 it will be seen1
 therefore1 that the induction coil or  
transformer used in connection with     
electric-wave apparatus is analogous to 
the air pump in the siren plant4 ,in the
 electrical apparatus1 this electron    
pump is employed to put an electrical   
charge into a condenser2 in the air wave
 apparatus1 the air pump is employed to 

charge an air vessel with high pressure 
air4 ,from the electrical condenser the 
charge is released in the form of a     
series of electrical oscillations1 and  
in the air wave producing appliance1 the
 compressed air is released in the form 
of a series of intermittent puffs or    
blasts4 ,in the electrical wave         
producing apparatus1 these electrical   
oscillations in the condenser circuit   
are finally made to produce other       
oscillations in an air wire or open     
circuit1 just as the puffs of air       
finally expend themselves in producing  
aerial oscillations in the siren tube4  
,finally1 in the one case we have a     
series of air waves and in the other    
case1 a series of electrical waves4     
,these trains of electric waves or air  
waves1 as the case may be1 are          
intermitted into long and short groups1 
in accordance with the signals of the   
,morse alphabet1 and1 therefore1 the    
,hertzian wave transmitter1 in whatever 
form it may be employed1 when operated  

by means of a ,marconi aerial1 is in    
fact an electrical siren apparatus1 the 
function of which is to create periodic 
disturbances in the universal ether of  
the same character as those which the   
siren produces in atmospheric air4      
99       99       99       99       99  
,we have to consider in the next place  
the arrangements of the receiving       
station and the various forms of        
receivers that have been devised for    
effecting telegraphy by ,hertzian waves4
 ,just as the transmitting station      
consists essentially of two parts1 viz41
 a part for creating electrical         
oscillations and a part for throwing out
 or radiating electric waves1 so the    
receiving-station appliances may be     
divided into two portions2 the function 
of one being to catch up a portion of   
the energy of the passing wave1 and that
 of the other to make a record or       
intelligible signal in some manner in   
the form of an audible or visible sign4 
,accordingly1 there must be at the      

receiving station an arrangement called 
a receiving aerial1 which in general    
takes the form of a long vertical wire  
or wires1 similar in form to the        
transmitting aerial1 ,there is1 however1
 a distinct difference in the function  
of the transmitting aerial and the      
receiving aerial4 ,the function of the  
first is effective radiation1 and for   
this purpose the aerial must have       
associated with it a store of energy to 
be released as wave energy2 but the     
function of the receiving aerial is to  
be the seat of an electromotive force   
which is created by the electric force  
and the magnetic force of the incident  
electric wave4  ,in tracing out the mode
 of operation of the transmitting       
aerial1 it was pointed out that the     
electric waves emitted consisted of     
alternations of electric force in a     
direction which is perpendicular to the 
surface of the earth1 and magnetic force
 parallel to the surface of the earth4  
,these two quantities1 the electric     

force and the magnetic force1 are called
 the wave vectors1 and they both lie in 
a plane perpendicular to the direction  
in which the wave is travelling and at  
right angles to one another1 the        
electric force being perpendicular to   
the surface of the earth4 ,in optical   
language1 the wave sent out by the      
aerial would be called a plane polarised
 wave1 the plane of polarisation being  
parallel to the magnetic force4 ,hence1 
if at any point in the path of the wave 
we erect a vertical conductor1 as the   
wave passes over it1 it is cut          
transversely by the magnetic force of   
the wave and longitudinally by the      
electric force4 ,both of these          
operations result in the creation of an 
alternating electromotive force in the  
receiving aerial wire4  ,as in all other
 cases of oscillatory motion1 the       
principle of resonance may here be      
brought into play to increase immensely 
the amplitude of the current            
oscillations thereby set up in the      

receiving aerial4 ,as already explained1
 any vertical insulated wire placed with
 its lower end near the earth has       
capacity with respect to the earth1 and 
it has also inductance1 the value of    
these factors depending on its shape and
 height4 ,accordingly1 it has a natural 
electrical time-period of its own1 and  
if the periodic electromotive impulses  
which are set up in it by the passage of
 the waves over it agree in period with 
its own natural time-period1 then the   
amplitude of the current vibrations in  
it may become enormously greater than   
when there is a disagreement between    
these two periods4 ,before concluding   
these articles we shall return to this  
subject of electric resonance and       
syntony1 and discuss it with reference  
to what is called the tuning of         
,hertzian wave stations4 ,meanwhile1 it 
may be said that for the sake of        
obtaining1 at any rate in an approximate
 degree1 this coincidence of            
time-period1 it is generally usual to   

make the receiving aerial as far as     
possible identical with the transmitting
 aerial4 ,if the receiving aerial is not
 insulated1 but is connected to the     
earth at its lower end through the      
primary coil of an oscillation          
transformer1 we can still set up in it  
electrical oscillations by the impact on
 it of an electric wave of proper       
period2 and if the oscillation          
transformer is properly constructed we  
can draw from its secondary circuit     
electric oscillations in a similar      
period4  ,one problem in connection with
 the design of a receiving aerial is    
that of increasing its effective length 
and capacity so as to increase          
correspondingly the electromotive force 
or current oscillations in it4 ,it is   
clear that if we put a number of        
receiving wires in parallel so that each
 one of them is operated upon by the    
wave separately1 although we can        
increase in this way the magnitude of   
the alternating current which can be    

drawn off from the aerial1 we cannot    
increase the electromotive force in it  
except by increasing the actual height  
of the wires4 ,unfortunately1 there is a
 limit to the height of the receiving   
aerial4 ,it has to be suspended1 like   
the transmitting aerial1 from a mast or 
tower1 and the engineering problem of   
constructing such a permanent supporting
 structure higher than1 say1 two hundred
 feet is a difficult one4  ,since any   
one station has to send as well as      
receive1 it is usual to make one and the
 same aerial wire or wires do double    
duty4 ,it is switched over from the     
transmitting to the receiving apparatus1
 as required4 ,this1 however1 is a      
concession to convenience and cost4 ,in 
some respects it would be better to have
 two separate aerials at each station1  
the one of the best form for sending1   
and the other of the best form for      
receiving4  ,in ,mr4 ,marconi's early   
arrangements1 the so-called coherer or  
sensitive wave-detecting appliance1 to  

be described more in detail presently1  
was inserted between the base of the    
insulated receiving aerial and the      
earth1 but it was subsequently found by 
him to be a great improvement to act    
upon the receiving device1 not directly 
by the electromotive force set up in the
 aerial1 but by the induced             
electromotive force of a special form of
 step-up oscillation transformer he     
calls a jigger1 the primary circuit of  
which was inserted in between the       
receiving aerial and the earth plate1   
and the secondary circuit was connected 
to the sensitive organ of the           
telegraphic receiving arrangements4#bc  
,a suggestion to employ transformed     
oscillations in affecting a coherer1 had
 also been described in a patent        
specification by ,sir ,oliver ,lodge1 in
 #ahig1 but the essence of success in   
the use of this device is not merely the
 employment of a transformer1 but of a  
transformer constructed specially to    
transform electrical oscillations4      

,turning1 then1 to the consideration of 
the relation existing between the       
transmitting and receiving aerials1 we  
note that in their simplest form these  
consist of two similar tall rods of     
metal placed upright1 with their feet in
 good connection with the earth at two  
places4 ,we may think of them as two    
identical lightning conductors1 well    
earthed at the bottom1 and supported by 
non-conducting masts or towers4 ,these  
rods must be in good connection with the
 earth1 and therefore with it form1 as  
it were1 one conductor4 ,if1 as usual1  
these aerials are separated by the sea1 
the intermediate portion of this circuit
 is an electrolyte4 ,the operations     
which take place when a signal is sent  
are as follows3--  ,at the transmitting 
station1 we set up in the transmitting  
aerial electric oscillations1 of which  
the frequency may be of the order of a  
million1 i4e41 the oscillations as long 
as they last are at the rate of a       
million a second4 ,each spark discharge 

at the transmitter results1 however1    
only in the production of a train of a  
dozen or two oscillations1 and these    
trains succeed each other at a rate     
depending upon the transmitting         
arrangements used4 ,each oscillation in 
the transmitting aerial is accompanied  
by the detachment from it of semi-loops 
of electric strain1 as already          
explained4 ,the alterations of electric 
strain directed perpendicularly to the  
earth1 and of the associated magnetic   
force parallel to the earth1 constitute 
an electric wave in the ether1 just as  
the alternations of pressure and motion 
of air molecules constitute an air wave4
 ,associated with these physical actions
 above ground1 there is a propagation   
through the earth of electric action1   
which may consist in a motion or atomic 
exchange of electrons4 ,each change or  
movement of a semi-loop of electric     
strain above ground has its equivalent  
below ground in inter-atomic exchanges  
or movements of the electrons1 on which 

the ends of these semi-loops of electric
 strain terminate4 ,the earth must play1
 therefore1 a very important part in    
so-called wireless telegraphy1 and we   
might also say the earth does as much as
 the ether in its production4  ,the     
function of the receiving aerial is to  
bring about a union between these two   
operations above and below ground4 ,when
 the electric waves fall upon it1 they  
give rise to electromotive force in the 
receiving aerial1 and1 therefore1       
produce oscillations in it which1 in    
fact1 are electric currents flowing into
 and out of the receiving aerial4 ,we   
may say that the transmitting aerial1   
the receiving aerial and the earth form 
one gigantic ,hertz oscillator4 ,in one 
part of this system1 electric           
oscillations of a certain period are set
 up by the discharge of a condenser and 
are propagated to the other part4 ,in   
the earth1 there is a propagation of    
electric oscillations2 in the space     
above and between the aerials1 there is 

a propagation of electric waves4 ,the   
receiving aerial feels1 therefore1 what 
is happening at the distant aerial and  
can be made to record it4#bd  ,we have  
next to consider the question of the    
wave-detecting devices which enable us  
to appreciate and record the impact of a
 wave or wave train against the aerial4 
,at the very outset it will be necessary
 to coin a new word to apply generally  
to these appliances4 ,most readers are  
probably familiar with the term coherer1
 which was applied by ,sir ,oliver      
,lodge1 in the first instance1 to an    
electric wave-detecting device of one   
particular kind--viz41 that in which a  
metal point was lightly pressed against 
another metal surface and caused to     
stick to it when an electric wave fell  
upon it4 ,as our knowledge increased1 it
 was found that there were many cases in
 which the effect of the electric       
radiation was to cause a severance and  
not a coherence1 and hence such clumsy  
phrases as anticoherer and              

self-decohering coherer have come into  
use4 ,moreover1 we have now many kinds  
of electric wave detectors based on     
quite different physical principles4 ,at
 the risk of incurring reprobation for  
adding to scientific nomenclature1 the  
author ventures to think that the time  
has arrived when a simple and inclusive 
term will be found useful to describe   
all the devices1 whatever their nature1 
which are employed for detecting the    
presence of an electric wave4 ,for this 
purpose the term kumascope1 from the    
,greek ,greek3 kuma 7a wave71 is        
suggested4 ,the scientific study of     
waves has already been called           
kumatology1 and in view of our          
familiarity with such terms as          
microscope1 electroscope and hygroscope1
 there does not seem to be any objection
 to enlarging our vocabulary by calling 
a wave-detecting appliance a kumascope4 
,we are then able to look at the subject
 broadly and to classify kumascopes of  
different kinds4  ,we may1 in the first 

place1 arrange them according to the    
principle on which they act4 ,thus1 we  
may have electric1 magnetic1 thermal1   
chemical and physiological operations   
involved2 and finally1 we may divide    
them into those which are               
self-restoring1 in the sense that after 
the passage or action of a wave upon    
them they return to their original      
sensitive condition2 and those which are
 non-restoring1 in that they must be    
subjected to some treatment to bring    
them back again to a condition in which 
they are fit to respond again to the    
action of a wave4  ,we have no space to 
refer to the whole of the steps of      
discovery which led up to the invention 
of all the various forms of the modern  
electric kumascope or wave detector4    
,suffice it to say that the researches  
of ,hertz in #ahhg threw a flood of     
light upon many previously obscure      
phenomena1 and enabled us to see that an
 electric spark1 and especially an      
oscillatory spark1 creates a disturbance

 in the ether1 which has a resemblance  
in ,nature to the expanding ripples     
produced by a stone hurled into water4  
,scientific investigation then returned 
with fresh interest to previously       
incomprehensible effects1 and a new     
meaning was read into many old          
observations4 ,again and again it had   
been noticed that loose metallic        
contacts1 loose aggregations of metallic
 filings or fragments1 had a mysterious 
way of altering their conductivity under
 the action of electric sparks1         
lightning discharges and high           
electromotive forces4  ,as far back as  
#aheb1 ,mr4 ,varley had noticed that    
masses of powdered metals had a very    
small conductivity1 which increased in a
 remarkable way during thunderstorms2#be
 and in #ahff1 ,c4 and ,s4 ,a4 ,varley  
patented a device for protecting        
telegraphic instruments from lightning1 
which consisted of a small box of       
powdered carbon in which were buried two
 nearly touching metal points1 and they 

stated that powdered conducting matter  
offers a great resistance to a current  
of moderate tension1 but offers but     
little resistance to currents of high   
tension4#bf  ,we then pass over a long  
interval and find that the next         
published account of similar            
observations was due to ,professor ,t4  
,calzecchi-,onesti1 who described in an 
,italian journal1 ,il ,nuovo ,cimento   
7see ,vol4 ,,xvi41 p4 #eh1 and ,vol4    
,,xvii41 p4 #ch71 in #ahhd and #ahhe his
 observations on the decrease in        
resistance of metal powders when the    
spark from an induction coil was sent   
through them4#bg ,these observations did
 not attract much attention until       
,professor ,e4 ,branly1 of ,paris1 in   
#ahij and #ahia1 repeated them on an    
extended scale and with great           
variations1 making the important        
observation that an electric spark at a 
distance had a similar effect in        
increasing the conductivity of metallic 
powders4#bh ,branly1 however1 noticed   

that in some cases of conductors in     
powder1 such as the peroxide of lead or 
antimony1 the effect of the spark was to
 cause a decrease of conductivity4  ,to 
,professor ,e4 ,branly unquestionably   
belongs the honour of giving to science 
a new weapon in the shape of a tube     
containing metallic filings or powder   
rather loosely packed between metal     
plugs1 and of showing that when the     
pressure on the powder was adjusted such
 a tube may be a conductor of very high 
resistance1 but that the electrical     
conductivity is enormously increased if 
an electric spark is made in its        
neighbourhood4 ,he also proved that the 
same effect occurred in the case of two 
slightly oxidised steel or copper wires 
laid across one another with light      
pressure1 and that this loose or        
imperfect contact was extraordinarily   
sensitive to an electric spark1 dropping
 in resistance from thousands of ohms to
 a few ohms when a spark was made many  
yards away4  ,it is curious to notice   

how long some important researches take 
to become generally known4 ,branly's    
work did not attract much attention in  
,england until #ahib1 when ,dr4 ,dawson 
,turner described his own repetition of 
,branly's experiments with the metallic 
filings tube at a meeting of the        
,british ,association in ,edinburgh4 ,in
 the discussion which followed1         
,professor ,george ,forbes made an      
important remark4 ,he asked whether it  
was possible that the decrease in       
resistance could be brought about by    
,hertz waves4#bi  ,this question shows  
that even in #ahib the idea that the    
effect of the spark on the ,branly tube 
was really due to ,hertzian waves was   
only just beginning to arise4 ,the      
following year1 however1 ,mr4 ,w4 ,b4   
,croft repeated ,branly's experiment    
with copper filings before the ,physical
 ,society of ,london1 and entitled his  
short ,paper ,electric ,radiation on    
,copper ,filings4#cj ,he exhibited a    
tube containing copper filings loosely  

held between two copper plugs and joined
 in series with a galvanometer and cell4
 ,the effect of an electric spark at a  
distance1 in causing increase of        
conductivity1 was shown1 and the return 
of the tube to its non-conducting state 
when tapped was also noticed4  ,in the  
discussion which followed the reading of
 this ,paper1 ,professor ,minchin       
described the effects of electric       
radiation on his impulsion cells4 ,he   
followed up this by reading a ,paper to 
the ,physical ,society on ,november #bd1
 #ahic1 on the action of ,hertzian      
radiation on films containing metallic  
powders1 and expressed the opinion that 
the change in resistance of the ,branly 
tube was due to electric radiation4#ca  
,thus1 at the end of #ahic1 a few       
physicists clearly recognised that a new
 means had been given to us for         
detecting those invisible ether waves1  
the chief properties of which ,hertz had
 unravelled with surpassing skill six   
years before1 by means of a detector    

consisting of a ring of wire having a   
small spark-gap in it4  ,in ,june1      
#ahid1 ,sir ,oliver ,lodge delivered a  
discourse at the ,royal ,institution1   
entitled ,the ,work of ,hertz1 and at   
this lecture use was made of the ,branly
 tube as a ,hertz wave detector4 ,the   
chief object of the lecture was to      
describe the properties of ,hertzian    
waves and their reflection1 absorption  
and transmission1 and many brilliant    
quasi-optical experiments were          
exhibited4 ,although a ,branly tube1 or 
imperfect metallic contact1 then named  
by him a coherer1 was employed by ,sir  
,oliver ,lodge to detect an electric    
wave generated in another room1 there   
was no mention in this lecture of any   
use of the instrument for telegraphic   
purposes4#cb  ,as we are here concerned 
only with the applications in           
telegraphy1 we shall not spend any more 
time discussing the purely scientific   
work done with laboratory forms of this 
wave detector4  ,without attempting to  

touch the very delicate question as to  
the precise point at which laboratory   
research passed into technical          
application1 we shall briefly describe  
the forms of kumascope which have been  
devised with special reference to       
,hertzian wave telegraphic work4 ,a very
 exact classification is at present     
impossible1 but we may say that         
telegraphic kumascopes may be roughly   
divided into six classes4 ,the first    
class includes all those that depend for
 their action on the coherer principle  
or the reduction of the resistance of a 
metallic microphone by the action of    
electromotive force4 ,as they depend    
upon an imperfect contact1 they may be  
called contact kumascopes4 ,this class  
is furthermore subdivided into the      
self-restoring and the                  
non-self-restoring varieties4 ,the      
second class comprises the magnetic     
kumascopes which depend upon the action 
of an electrical oscillation as a       
magnetising or demagnetising agency4    

,the third class comprises the          
electrolytic responders1 in which the   
action of electric oscillations either  
promotes or destroys the results of     
electrolysis4 ,the fourth class consists
 of the electrothermal detectors1 in    
which the power of an electrical        
oscillation as a high frequency electric
 current to heat a conductor is         
utilised4 ,the fifth class comprises the
 electromagnetic or electro-dynamic     
instruments1 which are virtually very   
sensitive alternating-current ammeters1 
adapted for immensely high frequency4   
,the sixth class must be made to contain
 all those which cannot be well fitted  
at present into any of the others1 such 
as the sensitive responder of ,schaefer1
 the action of which is not very clearly
 made out4  ,we may proceed briefly to  
describe the construction of the        
principal forms of kumascope coming     
under the above headings4 ,in the first 
place1 let us consider those which are  
commonly called the coherers or1 as the 

writer prefers to call them1 the contact
 kumascopes4 ,the simplest of these is  
the crossed needle or single contact1   
which originated with ,professor ,e4    
,branly4#cc ,the pressure of the point  
of a steel needle against an aluminium  
plate was subsequently found by ,sir    
,oliver ,lodge to be a very sensitive   
arrangement when so adjusted that a     
single cell sends little or no current  
through the contact4#cd ,when an        
electric wave passes over it1 good      
conducting contact ensues4 ,the point   
is1 in fact1 welded to the plate1 and   
can only be detached by giving the plate
 or needle a light shock or vibration4  
,a variation of the above form is a pair
 of crossed needles1 one resting on the 
other4  ,professor ,branly found1 in    
#ahia1 that if a pair of                
slightly-oxidised copper wires rest     
across one another the                  
contact-resistance may fall from #h1jjj 
to #g ohms by the impact of an electric 
wave4 ,he has recently devised a tripod 

arrangement1 in which a light metal     
stool with three slightly-oxidised legs 
stands on a polished plate of steel4    
,the contact points must be oxidised1   
but not too heavily1 and the stool makes
 a bad electrical contact until a wave  
falls upon it4#ce ,the decoherence is   
effected by giving the stool a tilt by  
means of an electromagnet4  ,these      
single or multiple-point kumascopes     
labour under the disadvantage that only 
a very small current can be passed      
through the variable contact when used  
as a relay arrangement1 without welding 
them together so much that a            
considerable mechanical shock is        
required to break the contact and reset 
the trap4  ,the logical development of  
the single contact is1 therefore1 the   
infinite number of contacts existing in 
the tube of metallic filings1 which has 
been the form of kumascope most used for
 many years4 ,in its typical form it    
consists of a tube of insulating        
material with metallic plugs at each    

end1 and between them a mass of metallic
 powder1 filings1 borings1 granules or  
small spheres1 lightly touching one     
another4 ,imperfect contact must be     
arranged by light pressure1 and in the  
majority of cases the resistance is very
 large until an electric wave falls upon
 the tube1 when it drops suddenly to a  
small value and remains there until the 
tube is given a slight shake or the     
granules disturbed in any way1 when the 
resistance suddenly rises again4 ,this  
type of responder is a non-restoring    
kumascope1 and requires the continual   
operation of some external agency to    
keep it in a condition in which it is   
receptive or sensitive to electric      
waves4  ,much discussion and            
considerable research have taken place  
in connection with the action and       
improvement of these metallic powder    
kumascopes4 ,as regards materials1 the  
magnetic metals1 nickel1 iron and       
cobalt1 in the order named1 appear to   
give the best results4 ,the noble       

metals1 gold1 silver and platinum1 are  
too sensitive1 and the very oxidisable  
metals too insensitive1 for telegraphic 
work1 but an admixture may be           
advantageously made4  ,omitting the     
intermediate developments of invention1 
it may be said that ,mr4 ,marconi was   
the first to recognise that to secure   
great sensibility in an electric wave   
detector of this type the following     
conditions must be fulfilled3 ,an       
exceedingly small mass of metallic      
filings must be placed in a very narrow 
gap between two plugs1 the whole being  
contained in a vessel which is wholly or
 partly exhausted of its air4 ,mr4      
,marconi devoted himself with great     
success to the development of this      
instrument1 and in a very short time    
succeeded in transforming it from an    
uncertain laboratory appliance1 capable 
of yielding results only in very skilled
 hands1 into an instrument certain and  
simple in its operations as an ordinary 
telegraphic relay4 ,he did this1 partly 

by reducing its size1 and partly by a   
most judicious selection of materials   
for its construction4 ,as made at       
present1 the ,marconi metallic filings  
tube consists of a small glass tube1 the
 interior diameter of which is not much 
more than one-eighth of an inch1 which  
has in it two silver plugs which are    
bevelled off obliquely4 ,these are      
placed opposite to each other1 so as to 
form a wedge-shaped gap1 about a        
millimetre in width at the bottom and   
two1 or at most three1 millimetres in   
width at the top 7see ,fig4 #af74 ,the  
silver plugs exactly fill the aperture  
of the tube1 and are connected to       
platinum wires sealed through the glass4
 ,the tube has a lateral glass tube     
fused into it1 by which the exhaustion  
is made1 which is afterwards sealed off1
 and this tube projects on the side of  
the wider portion of the gap between the
 silver plugs4 ,the sensitive material  
consists of a mixture of metallic       
filings1 five per cent4 silver and      

ninety-five per cent4 nickel1 being     
carefully mixed and sifted to a certain 
standard fineness4 ,in the manufacture  
of these tubes1 great care is taken to  
make them as far as possible absolutely 
identical4 ,each tube when finished is  
exhausted1 but not to a very high       
vacuum4 ,the tube so finished is        
attached to a bone holder1 by which it  
can be held in a horizontal position4   
,the object of bevelling off the plugs  
in the ,marconi tube is to enable the   
sensitiveness of the tube to be varied  
by turning it round1 so that the small  
quantity of filings lie in between a    
wider or narrower part of the gap4#cf   
,illustration3 ,,fig4 #af4--,,marconi   
,,sensitive ,,tube ,,or ,,metallic      
,,filings ,,kumascope4 ,,pp1 silver     
plugs2 ,,tt1 platinum wires2 ,f1 nickel 
and silver filings4  ,other ways of     
adjusting the quantity of the filings to
 the width of the gap have been devised4
 ,sometimes one of the plugs is made    
movable4 ,in other cases1 such as the   

tubes devised by ,m4 ,blondel and ,sir  
,oliver ,lodge1 there is a pocket in the
 glass receptacle to hold square        
filings1 from which more or less can be 
shaken into the gap4  ,an interesting   
question1 which we have not time to     
discuss in full1 is the cause of the    
initial coherence of the metallic       
filings in a ,branly tube4 ,it does not 
seem to be a simple welding action due  
to heat1 and it certainly takes place   
with a difference of potential1 which is
 very far indeed below that which we    
know is required to produce a spark4 ,on
 the other hand1 it seems to be proved  
that in a ,banly tube1 when acted upon  
by electric waves1 chains of metallic   
particles are produced4 ,the effect is  
not peculiar to electric waves4 ,it can 
be accomplished by the application of   
any high electromotive force4 ,thus     
,branly found that coherence may be     
produced by the application of an       
electromotive force of twenty or thirty 
volts1 operating through a very high    

water resistance1 and thus precluding   
the passage of any but an excessively   
small current4 ,again1 the coherence    
seems to take place in some cases when  
metallic particles are immersed in a    
liquid1 or even in a solid1 insulator4  
,processor ,branly has1 therefore1      
preferred to speak of masses of metallic
 granules as radio-conductors1 and      
,professor ,bose has divided substances 
into positive and negative1 according as
 the operation of electromotive force is
 to increase the coherence of the       
particles or to decrease it4  ,it has   
been asserted that for every particular 
,branly tube1 there is a critical       
electromotive force1 in the             
neighbourhood of two or three volts     
which causes the tube to break down and 
pass instantly from a non-conductive to 
a conductive condition1 and that this   
critical electromotive force may become 
a measure of the utility of the tube for
 telegraphic purposes4 ,thus1 ,c4       
,kinsley 7,physical ,review1 ,vol4      

,,xii41 p4 #agg1 #aija7 has made        
measurements of this supposed critical  
potential for different coherers1 and   
subsequently tested the same as         
receivers at a wireless telegraph       
station of the ,u4,s4,a4 ,signal ,corps4
 ,the average of twenty-four experiments
 gave in one case #b4b volts as the     
breaking down potential of one of these 
coherers or ,branly tubes1 #c4h volts   
for a second and #e4e volts for the     
third4 ,these same instruments1 tested  
as telegraphic kumascopes1 showed that  
the first of the three was most         
sensitive4  ,on the other hand1 ,w4 ,h4 
,eccles 7,electrician1 ,vol4 ,,xlvii41  
pp4 #fhb and #gae1 #aija7 has made      
experiments with ,marconi nickel-silver 
sensitive tubes1 using a liquid         
potentiometer made with copper sulphate1
 to apply the potential so that         
infinitesimal spark contacts might be   
avoided and the changes in potential    
made without any abruptness4 ,he states 
that if the coherer tube is continuously

 tapped1 say at the rate of fifty       
vibrations per second1 whilst at the    
same time an increasing potential is    
applied to its terminals and the current
 passing through it measured on a       
galvanometer1 there is no abrupt change 
in current at any point4 ,he found that 
when the current and voltage were       
plotted against each other1 a regular   
curve was obtained1 which after a time  
becomes linear4 ,a decided change occurs
 in the conductivity of the mass of     
metallic filings when treated in this   
manner at voltages lower than the       
critical voltage obtained by previous   
methods4 ,he ascertained that there was 
a complete correspondence between the   
sensitiveness of the tubes used as      
telegraphic instruments and the form of 
the characteristic curve of current and 
voltage drawn by the above-described    
method4  ,in the same manner1 ,k4 ,e4   
,guthe and ,a4 ,trowbridge 7,physical   
,review1 ,vol4 ,,ii41 p4 #bb1 #aijj7    
investigated the action of a simple ball

 coherer formed of half a dozen steel1  
lead or phosphor-bronze balls in slight 
contact4 ,they measured the current i   
passing through the series under the    
action of a difference of potential v   
between the ends1 and found a relation  
which could be expressed in the form    
v  ,v7#a - eki71  where ,v and k are    
constants4  ,the current through this   
ball coherer is1 therefore1 a           
logarithmic function of the potential   
difference between its ends1 of the form
      i  log7v - ,v7  and exhibits no   
discontinuity4  ,the inference was drawn
 that the resistance is due to films of 
water adhering to the metallic particles
 through which electrolytic action      
occurs4  ,a good metallic filings tube  
for use as a receiver in ,hertzian wave 
telegraphy should exhibit a constancy of
 action and should cohere and decohere1 
to use the common terms1 sharply1 at the
 smallest possible tap4 ,it should not  
have a current passed through it by the 
external cell of more than a fraction of

 a milliampere1 or else it becomes      
wounded and unsensitive4  ,the          
investigations which have already taken 
place seem to show pretty clearly that  
the agency causing the masses of filings
 to pass from a non-conductive to a     
conductive condition is electromotive   
force1 and that1 therefore1 it is the   
electromotive force set up in the aerial
 by the incident waves which is the     
effective agent in causing the change in
 the metallic filings tube1 when this is
 used as a telegraphic kumascope4 ,this 
transformation of the tube from a       
non-conductor to a conductor is made to 
act as a circuit-closer1 completing the 
circuit1 by means of which a single cell
 of a local battery is made to send     
current through an ordinary telegraph   
relay1 and so by the aid of a second    
battery operate a telegraphic printer or
 recorder of any kind4 ,hence it is     
clear that after one impact1 the        
metallic filings tube has to be brought 
back to its non-conductive condition1   

and this may be achieved in several     
ways4 7#a7 ,by the administration of    
carefully-regulated taps or shocks or by
 rotating the tube on its axis2 7#b7 by 
the aid of an alternating current2 7#c7 
in those cases where filings of magnetic
 metals are employed1 by magnetism4     
,the decoherence by taps was discovered 
by ,branly1#cg and ,popoff1 following   
the example of ,sir ,oliver ,lodge1     
employed an electric bell arrangement   
for this purpose4#ch  ,mr4 ,marconi1 in 
his original receiving instruments1     
placed an electromagnet under the       
coherer tube with a vibrating armature  
like an electric bell4#ci ,this armature
 carries a small hammer or tapper1      
which1 when set in action1 hits the tube
 on the under side1 and various         
adjusting screws are arranged for       
regulating exactly the force and        
amplitude of the blows4 ,this tapper is 
actuated by the same current as the     
,morse printer1 or other telegraphic    
recorder1 so that when the signal is    

received and the metallic filings tube  
passes into the conductive condition and
 closes the relay circuit1 this latter  
in turn closes the circuit of the ,morse
 printer or other recorder1 and at the  
same time1 a current passes through the 
electromagnet of the tapper and the tube
 is tapped back4 ,this sequence of      
operations requires a certain time which
 limits the speed of receiving4 ,the    
tapper has to be so arranged that it is 
possible to receive and to record not   
only the dot but a dash on the ,morse   
system4 ,the dash is really a series of 
closely adjacent dots1 which run        
together in virtue of the inertia and   
inductance of the different parts of the
 whole receiving apparatus4 ,the        
adjustment has so to be made that1      
whilst the dash is being recorded and a 
continuous tapping is kept up1 yet1     
nevertheless the continued electromotive
 force in the aerial1 due to the        
continually arriving trains of waves1 is
 able to act against the tapping and to 

keep the filings in the tube in the     
conductive condition4 ,hence1 the       
successful operation of the arrangement 
requires attention to a number of       
adjustments1 but these are not more     
difficult1 or even as difficult1 as     
those involved in the use of many       
telegraphic receivers employed in       
ordinary telegraphy with wires4  ,mr4   
,marconi also introduced devices for    
preventing the sparks at the contacts of
 the electromagnetic hammer from        
directly affecting the tube1 and also to
 prevent the electric oscillations which
 are set up in the aerial from being    
partly shunted through other circuits   
than that of the sensitive tube4 ,we    
pass on to notice the remaining devices 
for restoring the metallic filings tube 
to a condition of sensitiveness or      
receptiveness4  ,a method for doing this
 by alternating currents is due to ,mr4 
,s4 ,g4 ,brown4#dj ,the pole pieces of  
the coherer tube are made of iron1 and  
they are enveloped in magnetising coils 

traversed by an alternating electric    
current4 ,between these pole pieces is  
placed a small quantity of nickel or    
iron filings1 and under the action of   
the electromotive force1 due to an      
electric wave acting on them1 may be    
made to cohere in the usual fashion2 but
 the moment that the wave ceases1 the   
alternating magnetism of the electrodes 
causes the filings to drop apart or     
decohere4 ,in place of the alternating  
current1 ,mr4 ,brown finds that a       
revolving permanent magnet can be used  
to produce the alternating magnetisation
 of the pole pieces of the sensitive    
tube or coherer4  ,the third method of  
causing the decoherence of the filings  
is that due to ,t4 ,tommasina4 ,he found
 that when a ,branly tube is made with  
filings of a magnetic metal1 such as    
iron1 nickel and cobalt1 the decoherence
 of the filings can be produced by means
 of an electromagnet placed in a        
suitable position under the tube4#da    
,the explanation of this fact seems to  

be that1 when an electric wave falls    
upon the tube or when any other source  
of electromotive force acts upon it1    
chains of metallic particles are formed1
 stretching from one electrode to the   
other4 ,tommasina contends that he has  
proved the existence of these chains of 
particles by experiments made with iron 
filings2 and ,r4 ,malagoli1#db in       
referring to ,tommasina's assertion1    
states that it can be witnessed in the  
case of brass filings placed between two
 plates of metal and immersed in        
vaseline oil1 when a difference of      
potential is made between the plates4   
,t4 ,sundorph#dc says he has confirmed  
,tommasina's discovery of the formation 
of these chains of metallic particles in
 the coherer4 ,the filings do not all   
cling together1 but certain chains are  
formed which afford a conducting path   
for the current subsequently passed     
through the coherer from an external    
source4 ,accordingly1 ,tommasina's      
method of causing decoherence in the    

case of filings of magnetic metals is to
 pull them apart by an external magnetic
 field2 and he stated that decoherence  
can be effected more easily and         
regularly in this way than by tapping4  
,whilst on this point1 it may be        
mentioned that ,c4 ,tissot#dd says that 
he has found that the sensitiveness of a
 coherer formed of nickel and iron      
filings can be increased by placing it  
in the magnetic field1 the lines of     
which are parallel to the axis of the   
tube4 ,according to ,,mm4 ,a4 ,blondel  
and ,g4 ,dobkevitch1 this is merely the 
result of an increased coherence of the 
particles4         99       99       99 
99       99  ,quite recently1 ,sir      
,oliver ,lodge and ,dr4 ,muirhead have  
employed as a self-restoring coherer or 
kumascope a steel disc revolved by      
clockwork1 the edge of which just       
touches a globule of mercury covered    
with a thin film of paraffin oil4 ,the  
contact is made between the mercury and 
the steel by the electric wave          

generating an electromotive force in the
 aerial1 sufficient to break through the
 thin film of oil4 ,when the wave stops1
 the circuit is again interrupted       
automatically4  ,this device is used    
without a relay to actuate directly a   
syphon recorder as used in submarine    
telegraphy4 ,the working battery        
employed with it must only have an      
electromotive force of about a tenth of 
a volt4 ,it may be used also with a     
telephone in circuit and can1 therefore1
 be employed either for telegraphic or  
telephonic reception4#de  ,illustration3
 ,,fig4 #ag4--;,,italian ,,navy         
,,self-,,restoring ,,kumascope4 ,c1     
carbon plug2 ,i1 iron plug2 ,m1 mercury 
globule2 ,a1 aerial2 ,b1 battery2 ,t1   
telephone2 ,s1 adjusting screw4  ,one of
 the most sensitive of these            
self-restoring kumascopes is the        
carbon-steel-mercury coherer1 the       
invention of which has been attributed  
to ,castelli1 a signalman in the        
,italian ,navy1#df but also stated on   

good authority to have been the         
invention of officers in the ,royal     
,italian ,navy1 and has1 therefore1 been
 called the ,italian ,navy coherer4#dg  
,this instrument has been arranged in   
several forms1 but in the simplest of   
these it consists of a glass tube1      
having in it a plug of iron and a plug  
of arc-lamp carbon1 or two plugs of iron
 with a plug of carbon between them4    
,the plugs of iron1 or of iron and      
carbon1 are separated by an exceedingly 
small globule of mercury1 the size of   
which should be between one and a-half  
and three millimetres4 ,the plugs       
closing the tube must be capable of     
movement1 one of them by means of a     
screw1 as shown in the diagram 7,fig4   
#ag71 taken from a patent specification 
communicated to ,mr4 ,marconi by the    
,marchese ,luigi ,solari1 of the ,royal 
,italian ,navy4 ,one of the plugs of    
this tube is connected to the aerial and
 the other to the earth1 and they are   
also connected through another circuit  

composed of a single dry cell and a     
telephone4 ,the arrangement then forms  
an extremely sensitive detector of      
electric waves or of small electromotive
 forces1 or1 if a wave falls on the     
aerial1 the electromotive force at once 
improves the contact between the mercury
 and the plugs1 and therefore causes a  
sudden increase in the current through  
the telephone1 giving rise to a sound2  
but when the wave ceases1 or the        
electromotive force is withdrawn1 the   
resistance falls back again to its      
origin value1 and the arrangement is1   
therefore1 self-acting1 requiring no    
tapping or other device for restoring it
 to receptivity4  ,a very ingenious form
 of combined telephone and coherer has  
been devised by ,t4 ,tommasina4#dh ,in  
this instrument the diaphragm of an     
ordinary ,bell telephone carries upon it
 a very small carbon or metallic        
coherer4 ,this coherer is connected in  
between the aerial and the earth1 and is
 also in circuit with a battery and the 

electromagnet of a telegraphic relay4   
,when this relay operates it closes the 
circuit of another battery which is     
placed in series with the telephone     
coil4 ,the moment the current passes    
through the telephone coil it attracts1 
and therefore vibrates1 the diaphragm   
and shakes up the metallic filings4 ,if 
an observer1 therefore1 places the      
telephone to his ear1 he hears a sound  
corresponding to every train of waves   
incident upon the aerial4 ,with this    
arrangement1 one can obtain two         
different kinds of results1 according to
 the nature of the cohering powder      
placed in the cavity in the diaphragm4  
,first1 if the powder consists of a     
non-magnetic metal1 gold1 silver1       
platinum or the like1 the receiver will 
be very sensitive2 and at the same time 
the current passing through it when it  
is cohered will be sufficient to work a 
sensive recording apparatus in series   
with the telephone coil4 ,secondly1 if  
the metallic powder placed in the cavity

 is a magnetic metal1 the receiver will 
be somewhat less sensitive1 but will    
work with more precision1 because of the
 magnetic action of the magnet of the   
telephone upon the cohering powder4 ,if 
no recording apparatus is used1 the     
observer must write down the signals as 
heard in the telephone1 since           
corresponding to a short spark at the   
transmitting station1 a single tick or  
short sound is heard at the telephone1  
and corresponding to a series of rapidly
 successive sparks1 a more prolonged    
sound is heard in the telephone4 ,these 
two sounds1 as already explained1       
constitute the dot and the dash of the  
,morse signals4  ,we may1 in the next   
place1 refer to that form of kumascope  
in which the action of the wave or of   
electromotive force is not to decrease  
the resistance of a contact1 but to     
increase that of an imperfect contact4  
,as already mentioned1 ,professor       
,branly discovered long ago that        
peroxide of lead acts in an opposite    

manner to metallic filings1 in that when
 placed in a ,branly tube it increases  
its resistance under the action of an   
electric spark1 instead of decreasing   
it4 ,again1 ,professor ,bose has found  
that fragments of metallic potassium in 
kerosene oil behave in a similar manner1
 and that certain varieties of silver1  
antimony and of arsenic1 and a few other
 metals1 have a similar property4       
,branly tubes1 therefore1 made with     
these materials1 or any arrangements    
which act in a similar manner1 have been
 called anti-coherers4 ,the most        
interesting arragement which has been   
called by this name is that of          
,schaefer4#di ,schaefer's kumascope is  
made in the following manner3 ,a very   
thin film of silver is deposited upon   
glass1 and a strip of this silver is    
scratched across with a diamond1 making 
a fine transverse cut or gap4 ,if the   
resistance of this divided strip of     
silver is measured1 it will be found not
 to be infinite1 but may have a         

resistance as low as forty or fifty ohms
 if the strip is thirty millimetres     
wide4 ,on examining the cut in the strip
 with a microscope1 it will be found    
that the edges are ragged and that there
 are little particles of silver lying   
about in the gap4 ,if1 then1 an         
electromotive force of three volts or   
more is put on the two separated parts  
of the strip1 these little particles of 
silver fly to and fro like the pith     
balls in a familiar electrical          
experiment1 and they convey electricity 
across from side to side4 ,hence a      
current passes having a magnitude of a  
few milliamperes4 ,if1 however1 the     
strip is employed as a kumascope and    
connected at one end to the earth and at
 the other end to an aerial1 when       
electric waves fall upon the aerial1 the
 electrical oscillations thereby excited
 seem to have the property of stopping  
this dance of silver particles and the  
resistance of the gap is increased      
several times1 but falls again when the 

wave ceases4 ,if1 therefore1 a telephone
 and battery are connected between two  
portions of the strip1 the variation of 
this battery current will affect the    
telephone in accordance with the waves  
which fall upon the aerial1 and the     
arrangement becomes therefore a         
wave-detecting device4 ,it is said to   
have been used in wireless telegraph    
experiments in ,germany up to a distance
 of ninety-five kilometres4  ,we must   
next direct attention to those          
wave-detecting devices which depend upon
 magnetisation of iron1 and here we are 
able to record recent and most          
interesting developments4 ,more than    
seventy years ago ,joseph ,henry1 in the
 ,united ,states1 noticed the effect of 
an electric spark at a distance upon    
magnetised needles4#ej ,of recent times1
 the subject came back into notice      
through the researches of ,professor ,e4
 ,rutherford1#ea who carried out at     
,cambridge1 ,england1 in #ahif1 a       
valuable series of experiments on this  

subject4 ,he found that if a magnetised 
steel needle or a very small bundle of  
extremely thin iron wires is magnetised 
and placed in the interior of a small   
coil1 the ends of which are connected to
 two long collecting wires1 then an     
electric wave started from a ,hertz     
oscillator at a distance causes an      
immediate demagnetisation of the iron4  
,this demagnetisation he detected by    
means of the movement of the needle of a
 magnetometer placed near one end of the
 iron wire4 ,although ,rutherford's wave
 detector has been much used in         
scientific research1 it was not1 in the 
form in which he used it1 a telegraphic 
instrument1 and could not record        
alphabetic signals4  ,not long ago ,mr4 
,marconi invented1 however1 a           
telegraphic instrument based upon his   
discovery that the magnetic hysteresis  
of iron can be annulled by electric     
oscillations4 ,in one form1 ,mr4        
,marconi's magnetic receiver is         
constructed as follows#eb 7see ,fig4    

#ah73 ,an endless band of thin iron wire
 composed of several iron wires about   
,no4 #cf gauge1 arranged in parallel1 is
 made to move slowly round on two       
pulleys1 like the driving belt of a     
machine4 ,in one part of its path the   
wire passes through a glass tube1 on    
which are found two coils of wire1 one a
 rather short1 thick coil1 and the other
 a very fine1 long one4 ,the fine1 long 
coil is connected with a telephone1 and 
the shorter coil is connected at one end
 to the earth and the other to the      
aerial4 ,two permanent horse-shoe       
magnets are placed as shown n ,fig4 #ah1
 with their similar poles together1 and1
 as the iron band passes through their  
field1 a certain length of it is        
magnetised1 and owing to the hysteresis 
of the material1 it retains this        
magnetism for a short time after it has 
passed out of the centre of the field4  
,if then an electric oscillation1 coming
 down from the aerial1 is passed through
 the shorter coil1 it changes the       

position of the magnetised portion of   
the iron and1 so to speak1 brings the   
magnetised portion of iron back into the
 position it would have occupied if the 
iron had had no hysteresis4 ,this       
action1 by varying the magnetic flux    
through the secondary coil1 creates in  
it an electromotive force which causes a
 sound to be heard in the telephone     
connected to it4 ,if at a distant place 
a single wave or train of waves is      
started and received by the aerial1 this
 will express itself by making an       
audible tick in the telephone1 and if   
several groups of closely adjacent wave 
trains are sent1 these will indicate    
themselves by producing a rapid series  
of ticks in the telephone1 heard as a   
short continuous noise and taken as     
equivalent to the ,morse dash4          
,illustration3 ,,fig4 #ah4--,,marconi   
,,magnetic ,,receiver4 ,w#a,w#b1 wheels2
 ,i1 iron wire band2 ,p1 primary coil2  
,s1 secondary coil2 ,t1 telephone2 ,a1  
aerial2 ,e1 earthplate4  ,it was by     

means of this remarkably ingenious      
instrument that ,mr4 ,marconi was able1 
in the summer of #aijb1 to detect the   
waves sent out from ,poldhu on the coast
 of ,cornwall1 and receive messages as  
far as ,cronstadt in the ,baltic1 in one
 direction1 and as far as ,spezzia in   
the ,mediterranean in another direction1
 and also to receive messages across the
 ,atlantic from the power stations      
situated in ,glace ,bay1 ,nova ,scotia1 
and from one at ,cape ,cod in           
,massachusetts1 ,u4,s4,a41 in ,december1
 #aijb4  ,there can be no question that 
this magnetic detector of ,mr4          
,marconi's1 used in connection with a   
good telephone and an acute human ear1  
is the most sensitive device yet        
invented for the detection of electric  
waves and their utilisation in          
telegraphy without continuous wires4 ,it
 is marvellously simple1 ingenious and  
yet effective1 as a ,hertzian wave      
telegraphic receiver4  ,whilst on the   
subject of magnetic wave detectors1 the 

author may describe experiments that he 
has been recently making to construct a 
,hertzian wave detector on the          
,rutherford principle1 which shall be   
strictly quantitative4 ,all the         
receivers of the coherer type and       
electrolytic type give no indications   
that are at all proportional to the     
energy of the incident wave4 ,their     
indications are more or less accidental 
and depend upon the manner in which the 
receiver was last left4 ,there is a     
great need for a quantitative wave      
detector1 the indications of which shall
 give us a measure of the energy of the 
arriving wave4 ,it is only by the       
possession of such an instrument that we
 can hope to study properly the sending 
powers of various transmitters or the   
efficiency of different forms of aerial 
or devices by which the wave is         
produced4 ,this magnetic receiver is    
constructed as follows3  ,a coil of fine
 wire is constructed in sections like   
the secondary coil of an induction coil1

 and in the instrument already made1    
this coil contains thirty or forty      
thousand turns of wire4 ,in the interior
 of this coil are placed a number of    
little bundles of fine iron wire wound  
round with two coils1 a fine wire coil  
which is a magnetising coil1 and a      
thicker wire coil which is a            
demagnetising coil4 ,these sets of coils
 are joined up1 respectively1 in series 
or in parallel4 ,then1 associated with  
this form of induction coil is a        
commutator of a peculiar kind1 which    
performs the following functions when a 
battery is connected to it and when it  
is made to revolve by a motor or by     
clockwork4 ,first1 during part of the   
revolution1 the commutator closes the   
battery circuit and magnetises the iron 
cores1 and whilst this is taking place  
the secondary circuit of the induction  
coil is short-circuited and the         
galvanometer is disconnected from it4   
,secondly1 the magnetising current is   
stopped1 and soon after that the        

secondary coil is unshort-circuited and 
connected to the galvanometer1 and      
remains in this condition during the    
remainder of the revolution4 ,this cycle
 of operations is repeated at every     
revolution4 ,if then an electrical      
oscillation is sent into the            
demagnetising coils1 and if it continues
 longer than one revolution of the      
commutator1 it will demagnetise the iron
 core during that period of time in     
which the battery is disconnected and   
the galvanometer connected4 ,the        
demagnetisation of the iron which ensues
 produces an electromotive force in the 
secondary coil and causes a deflection  
of the galvanometer1 and this deflection
 will continue and remain steady if the 
oscillation persists4 ,moreover1 since  
this deflection is due to the passage   
through the galvanometer of a rapid     
series of discharges1 it is large when  
the oscillations continue for a long    
time and are powerful1 and small when   
they continue for a short time or are   

weak4 ,we can1 therefore1 with this     
arrangement1 receive on the             
galvanometer1 just as on the mirror     
galvanometer used in submarine cable    
work1 a dot or dash1 and1 moreover1 the 
magnitude of these deflections is a     
measure of the energy of the wave4  ,it 
is probable that when this arrangement  
is perfected it will become exceedingly 
useful for making all kinds of tests and
 measurements in connection with        
,hertzian telegraphy1 even if it is not 
sensitive enough to use as a long       
distance receiver4  ,of late years a    
variety of wave-detecting devices have  
been brought forward which depend upon  
electrolysis4 ,one of the best known of 
these is that by ,de ,forest and        
,smythe4#ec ,in this arrangement1 a tube
 contains two small electrodes like     
plugs1 which may be made of tin1 silver 
or nickel1 or other metal4 ,the ends of 
these plugs are flat and separated from 
each other by about one two-hundredth of
 an inch4 ,sometimes the end of one of  

these plugs is made cup shaped and the  
cup or recess is filled with a mass of  
peroxide of lead and glycerine4 ,in the 
interval between the electrodes is      
placed an electrolyzable mixture1 which 
consists of glycerine or vaseline mixed 
with water or alcohol1 and a small      
quantity of litharge and metallic       
filings4 ,these metallic filings act as 
secondary electrodes4 ,when a small     
electromotive force is applied between  
the terminals of the electrodes of this 
tube through a very high resistance of  
twenty or thirty thousand ohms1 an      
exceedingly small current passes through
 this mixture1 and it causes an         
electrolytic action which results in the
 production of chains of metallic       
particles connecting the two electrodes 
together4 ,if1 in addition to this1 one 
terminal or electrode of the arrangement
 is connected to an aerial wire and the 
other terminal to the earth1 then on the
 arrival of an electric wave creating   
oscillations in the wire1 these         

oscillations pass down into the         
electrolytic cell1 where they break up  
the chains of metallic particles and    
thus interrupt the current passing      
through the telephone quite suddenly1   
which is heard as a slight tick by an   
ear applied to it4 ,as soon as the wave 
ceases1 the chain of metallic particles 
is re-established1 so that the appliance
 is always in a condition to be affected
 by a wave4 ,it is said that this       
breaking up and reformation of the      
chains of metallic particles is so rapid
 that a short spark made at the         
transmitting station is heard as a tick 
in the telephone1 but a rapid succession
 of oscillatory sparks is heard as a    
short continuous sound2 hence the two   
signals necessary for alphabetical      
conversation can be transmitted4        
,another receiver which has some        
resemblance to the above1 although      
different in principle1 is that of      
,neugschwender4#ed ,in this arrangement1
 which to a certain extent resembles the

 ,schaefer detector1 a glass plate has  
upon it a deposit of silver in the form 
of a strip1 which is cut across at one  
place1 thus interrupting it4 ,if the cut
 is breathed upon or placed in a moist  
atmosphere1 a little dew is deposited   
upon the glass1 which bridges over the  
cut in the metal and creates an electric
 continuity4 ,hence a small current can 
be passed across the gap and through a  
telephone by one or two cells of a      
battery4 ,if1 however1 an electric      
oscillation passes across the gap on its
 way from an aerial to the earth1 then  
the continuity of the liquid film is    
destroyed1 and the current is           
interrupted and a sound created in the  
telephone4  ,the opinion has been       
expressed by ,sir ,oliver ,lodge that in
 this case the interruption of the      
circuit which occurs is really due to   
the coalescence of minute water         
particles into larger drops1 as when    
vapour is condensed into rain1 and hence
 the continuity of the material is      

interrupted4  ,we must then make a brief
 reference to other kumascopes which    
depend upon the heating power of an     
electrical oscillation1 which it        
possesses in common with every other    
form of electric current4 ,professor ,r4
 ,a4 ,fessenden#ee has constructed a    
very ingenious thermal receiver in the  
following manner3 ,an extremely fine    
platinum wire1 about #j4jjc of an inch  
in diameter1 is embedded in the middle  
of a silver wire about one tenth of an  
inch in diameter1 like the wick of a    
candle4 ,this compound wire is then     
drawn down until the diameter of the    
silver wire is only #j4jjb of an inch1  
and hence the platinum wire in its      
interior1 being reduced in the same     
ratio1 will have been drawn to a        
diameter of #j4jjjjf of an inch4 ,a     
short piece of this drawn wire is then  
bent into a loop and the ends fixed to  
wires4 ,the tip of the loop is then     
immersed in nitric acid and dissolved in
 the silver1 leaving an exquisitely fine

 platinum wire a few hundredths of an   
inch in length and having a resistance  
of about thirty ohms4 ,this little loop 
is sealed into a glass bulb like a very 
small incandescent lamp1 or it may be   
enclosed in a small silver bulb and the 
air may be exhausted4 ,if an electrical 
oscillation is sent through this        
exceedingly fine platinum wire it heats 
it and rapidly increases its resistance4
 ,the electrical oscillations produced  
in an aerial are sent through a number  
of these loops arranged in parallel1 and
 the loops are short-circuited by a     
telephone1 joined in series with a      
source of very small electromotive force
 produced by shunting a single cell or  
opposing to one another two cells of    
nearly equal electromotive force4 ,any  
variation of resistance of the little   
platinum loops due to the heat produced 
by the oscillations1 by suddenly        
altering the current flowing through the
 telephone1 will cause a sound to be    
heard in it4 ,the electrical            

oscillations when passing through the   
loops are therefore detected by the heat
 which they generate in these           
exquisitely fine platinum wires4        
,finally1 one word must be said on the  
subject of electrodynamic receivers1 due
 to the same inventor4 ,an exceedingly  
small silver ring is suspended by a     
quartz fibre and has a mirror attached  
to it in the manner of a galvanometer4  
,this ring is suspended between two     
coils joined in series1 which are placed
 either in the circuit of the aerial or 
in the secondary circuit of the small   
air core transformer inserted between   
the aerial and the earth4 ,when         
electrical oscillations travel down the 
aerial they induce other electrical     
oscillations in the silver ring1 and if 
the ring is so placed that its normal   
position is with its plane inclined at  
an angle of forty-five degrees to the   
plane of the fixed coils1 then the ring 
will be slightly deflected every time an
 oscillation occurs in the aerial4      

,omitting further mention of the details
 of the kumascopes in use and the       
receiving aerial1 we must next proceed  
to consider the receiving arrangements  
taken as a whole4  ,in the original     
,marconi system1 the sensitive tube or  
coherer was inserted between the bottom 
of the receiving aerial and the         
earth4#ef ,accordingly1 when the        
incident electric wave strikes the      
receiving aerial and creates in it an   
oscillatory electromotive force1 this   
last will1 if of sufficient amplitude1  
cause the particles of the coherer to   
cohere and become conductive4 ,this     
sudden change from a nearly perfect     
non-conductivity to a conductive        
condition is made to act as a switch or 
relay1 closing or completing the circuit
 of a single cell1 and so sending a     
current through an ordinary telegraphic 
relay1 closing or completing the circuit
 of a single cell1 which may in turn    
actuate another recording telegraphic   
instrument1 such as a ,morse printer4   

,to prevent the oscillations from       
passing into the relay circuit1 small   
choking or inductance coils are inserted
 between the ends of the sensitive tube 
and the relay and cell and serve to     
confine the oscillations to the tube4   
,it has already been pointed out that in
 the transmitting aerial the amplitude  
at the potential vibrations increases   
from the bottom to the top1 and when    
vibrating in its fundamental manner     
there is a potential node at the earth  
connection and a potential loop or      
antinode at the top4 ,the same is true  
of the receiving aerial4 ,hence1 if the 
kumascope employed is a ,branly metallic
 filings tube and is inserted near the  
base of the aerial1 the difference of   
potential between its two ends will be  
small4  ,it has also been mentioned that
 a receiver of this type acts in virtue 
of electromotive force or potential     
difference1 and hence the proper place  
to insert the coherer is not at the base
 of the aerial1 but between the top of  

the aerial and the earth4 ,this1        
however1 could not be done by running up
 another wire from the earth1 as that   
would amount to putting the coherer     
between the tops of two identical       
aerials1 and between its ends there     
would be no difference of potential4    
,professor ,slaby1 in conjunction with  
,count von ,arco1 has given an ingenious
 solution of this problem4 ,if we take  
two equal lengths of wire1 bent at right
 angles1 and connect the point of       
intersection with the earth1 placing one
 of these wires vertically and the other
 horizontally1 we then have an          
arrangement which responds to the impact
 of electric waves1 and has electrical  
oscillations set up in it in such       
fashion that the common point of the two
 wires has a very small amplitude of    
potential1 but the two extremities have 
equal and large variations4 ,if1 then1  
we insert a coherer tube between the    
earth and the outer extremity of the    
horizontal wire1 it is influenced in the

 same manner as it would be by the      
potential variations at the top of the  
vertical wire4 ,in other words1 it is   
acted upon by a large difference of     
potential instead of a small one4 ,it is
 not found necessary to stretch the     
horizontal wire out straight2 it may be 
coiled into a spiral with open turns1   
and the slight decrease in capacity and 
increase in inductance resulting from   
this can be compensated by cutting off a
 short piece of it4  ,illustration3     
,,fig4 #ai4--,,slaby ,,receiver4 ,a1    
aerial2 ,e1 earth plate2 ,f1 coherer2   
,m1 multiplier2 ,c1 condenser2 ,r1      
relay2 ,b1 battery2 ,e1 earth plate4    
,in this way we have an arrangement 7see
 ,fig4 #ai7 in which the outer extremity
 of this open spiral experiences        
variations or potential which exactly   
correspond with those at the summit of  
the vertical aerial4 ,the receiving     
arrangements are then completed as in   
,fig4 #ai1 one end of the coherer being 
attached to the outer end of the spiral 

and the other end through a condenser to
 the earth1 a relay and a voltaic cell  
being arranged as shown in the diagram4 
,the mode of operation of this receiver 
is as follows3 ,when the wave strikes   
the aerial it sets up in it electrical  
oscillations with a potential antinode  
at the summit1 and at the same time a   
potential antinode is created at the    
outer end of the spiral attached near   
the base of the aerial1 this spiral     
being called by ,professor ,slaby a     
multiplicator4 ,as long as the coherer  
tube remains non-conductive1 the local  
cell cannot send a current through the  
relay1 but1 as soon as the resistance is
 broken down by the impact of a wave1   
the local cell sends a current through  
the coherer tube which1 passing down to 
the earth through the base of the aerial
 and up through the earth connection to 
the condenser1 completes its circuit    
through the relay4 ,many variations of  
this arrangement have been made by      
,slaby and ,von ,arco and by the        

,allgemeine ,elektricitaets             
,gesellschaft of ,berlin4  ,in #ahih1   
,mr4 ,marconi made a great advance in   
the construction of his receiving       
apparatus by the insertion of his jigger
 or oscillation transformer in the      
aerial receiving circuit4#eg ,in this   
arrangement1 the primary coil of an air 
core transformer wound in a particular  
way is inserted between the receiving   
aerial and the earth1 and the secondary 
circuit is cut in the middle and        
connected to the two surfaces of a      
condenser1 these surfaces being also    
connected through the circuit of an     
ordinary telegraphic relay and a single 
cell 7see ,fig4 #bj74 ,the ends of the  
secondary circuit of this oscillation   
transformer are also connected to the   
terminals of the coherer tube1 and these
 again are short-circuited by a small   
condenser4  ,illustration3 ,,fig4       
#bj4--,,marconi ,,receiver4 ,a1 aerial2 
,j1 jigger2 ,,cc1 condensers2 ,f1       
filings tube2 ,t1 tapper2 ,r1 relay2 ,b1

 battery2 ,m1 ,morse printer4  ,the     
operation of this receiver is as        
follows3 ,the oscillations set up in the
 aerial pass through the primary circuit
 of the jigger1 and these induce other  
oscillations in the secondary circuit2  
the electromotive force or difference of
 potential between the primary terminals
 being transformed up in any desired    
ratio4 ,it is this exalted electromotive
 force which is made to act on the      
coherer tube1 and1 inasmuch as the      
jigger operates in virtue of a current  
passing through its primary circuit and 
this current is at a maximum at the     
lower end of the aerial1 the arrangement
 is exceedingly effective1 because it1  
so to speak1 converts current into      
voltage4 ,at the lower end of the       
aerial1 although the amplitude of the   
potential oscillations is a minimum1 the
 amplitude of the current oscillations  
is a maximum1 and the jigger transforms 
these large current oscillations into   
large potential oscillations1 provided  

it is constructed in the right manner4  
,we can also transform up or increase   
the amplitude of the small potential    
variations near the bottom of the aerial
 by employing the principle of          
resonance4 ,many devices of this kind1  
due to ,professor ,slaby and others1    
have been suggested and tried but the   
details are rather too technical to be  
fully described here4  ,it will be      
noticed that the receiving aerial may be
 arranged in one of two ways--it may be 
either earthed at the lower end or it   
may be insulated4 ,it has been claimed  
that there is a great advantage in      
earthing the receiving aerial directly  
in that it eliminates atmospheric       
disturbances4  ,we shall allude to this 
point more particularly later on4       
,meanwhile it may be mentioned that the 
receiving arrangements1 as a whole1     
constitute a sensitive arrangement1 as  
shown by ,popoff1 ,tommasina and by all 
the large experience of ,mr4 ,marconi   
himself for detecting changes in the    

electrical condition of the atmosphere1 
which are doubtless of the nature of    
electrical oscillations4 ,on the other  
hand1 the receiving arrangements may be 
perfectly insulated and some            
experimentalists have asserted that by  
this method the greatest freedom is     
secured from atmospheric disturbances4  
,amongst the non-earthed arrangements   
the system invented by ,professor ,f4   
,braun1 of ,strassburg1 and worked by   
,messrs4 ,siemens1 of ,berlin1 may be   
mentioned4#eh  ,illustration3 ,,fig4    
#ba4--;,,braun',s ,,non-,,earthed       
,,receiver4 ,i1 induction coil2 ,,cc1   
condensers2 ,s1 spark gap2 ,j1          
transmitting jigger2 ,k1 receiving      
jigger2 ,f1 filings tube2 ,r1 relay2 ,b1
 battery4  ,professor ,braun's          
arrangements are indicated in the       
diagram in ,fig4 #ba4 ,in this case an  
induction coil is used to create a      
discharge between two spark balls1 and  
to these two balls are connected the two
 outer coatings of two condensers1 the  

inner coatings of which are connected   
together through the primary coil of an 
air core transformer4 ,the secondary    
coil of this transformer is connected to
 two extension wires forming a ,hertz   
resonator1 and the length of these wires
 is so adjusted with reference to the   
time period of the primary circuit that 
they resonate to it1 the whole length   
from end to end of the secondary circuit
 being half a wave-length4 ,the         
receiver1 as shown in the diagram1      
consists of a pair of quarter           
wave-length receiving wires connected   
through two condensers1 which are       
short-circuited by the primary coil of  
an oscillation transformer4 ,the        
secondary circuit of this last          
oscillation transformer has two         
extension wires to it1 turned in the    
same manner1 to respond to the primary  
oscillator2 and in the circuit of one of
 these extension wires is placed a      
coherer tube1 short-circuited by a relay
 and a local battery4  ,it will thus be 

seen that there is an entire abolition  
of ground connection1 which1 ,professor 
,braun claims1 practically avoids all   
atmospheric disturbances4#ei ,the       
details of the receiving arrangement are
 as follows3--,the coherer tube consists
 of an ebonite tube containing hard     
steel particles of a uniform size1      
placed in the adjustable space between  
two polished steel electrodes4 ,it is   
found that with this steel coherer1 a   
small amount of magnetism in the        
particles increases its sensitiveness1  
and to obtain this1 a ring magnet is    
employed in connection with a coherer   
tube4 ,receiving apparatus arranged on  
this system is said to have been used   
for telegraphing between ,heligoland and
 ,cuxhaven1 a distance of thirty-six    
miles4  ,all the immense experience1    
however1 gained by ,mr4 ,marconi and    
those who have worked with his system1  
is in favour of using the earth         
connection4 ,there is no doubt that     
,hertzian wave telegraphy can be        

conducted over short distances by means 
of totally insulated aerials1 but for   
long distances the earth connection is  
essential1 for the reasons that have    
been explained previously4  ,there are  
many of the details of the receiving    
arrangements which remain to be         
considered4 ,if the communication is    
received by a telegraphic instrument    
like the ,morse printer1 which requires 
a current of anything like ten          
milliamperes to work it1 then an        
important element in the receiving      
arrangement is the relay4 ,the relay    
that is generally used is a modified    
form of the ,siemens polarised relay1   
which is so adjusted as to make a single
 contact4 ,for marine work on board     
ship1 it is essential that this relay   
shall be balanced so that variations in 
position shall not affect it4 ,sometimes
 the relay is hung in gimbals like a    
compass1 and at other times suspended   
from a support by elastic bands1 so as  
to avoid jolting4 ,in any case1 the     

relay must be so adjusted that no change
 of position will cause it to close the 
circuit of the telegraphic printer or   
recorder4 ,its sensibility ought to be  
such that it is actuated by a tenth of a
 milliampere1 and1 if possible1 even by 
less4 ,the alteration of sensibility in 
the ordinary contact form of relay is   
the pressure that is necessary to bring 
the platinum points of the circuit      
closer together1 so as to pass the      
minimum current which will work the     
telegraph printer4  ,the important      
matter1 however1 in connection with the 
use of the relay in ,hertzian wave      
telegraphy1 is that it should be capable
 of adjustment without extraordinary    
skill4 ,it is no use to put into the    
hands of an operator a relay which      
requires abnormal dexterity to make it  
work at all4         99       99        
99       99       99  ,it remains1 then1
 to consider some of the questions      
connected with practical ,hertzian wave 
telegraphy and the problem of the       

limitation of communication4 ,these     
matters at the present moment very much 
occupy the public attention1 and many   
conflicting opinions are expressed      
concerning them4  ,it may be observed at
 the outset that the difficulty of      
dealing with the subject as freely as   
many desire is that ,hertzian wave      
telegraphy is no longer merely a subject
 of scientific investigation1 but has   
developed into a business and involves1 
therefore1 other interests than the     
simple advancement of scientific        
knowledge4 ,we can1 however1 discuss in 
a general manner some of the scientific 
problems which present themselves for   
solution4 ,the first of these is the    
independence of communication between   
stations4 ,it is desirable1 at the      
outset1 to clear up a little            
misunderstanding4 ,there is a great     
difference between preventing the       
reception of communication when it is   
not desired by the recipient1 and       
preventing it when it is the object of  

the latter to overhear if he can4 ,it   
is1 therefore1 necessary to distinguish 
between isolation and overhearing4 ,we  
may say that a station is isolated when 
it is not affected by ,hertzian waves   
other than those it desires to receive2 
but that a station overhears when it    
can1 if it chooses1 pick up             
communications not intended for it1 or  
cannot help receiving them against its  
will4  ,this distinction is a perfectly 
fair one4 ,any telegraph or telephone   
wire can be tapped1 if it is desired1   
but unless there is some fault on the   
line1 no station will receive a message 
against its desires4 ,moreover1 it may  
be noted that there are penalties       
attached to tapping a telegraph wire1   
and at present there are none connected 
with the misappropriation of an ether   
wave4  ,we shall1 therefore1 consider in
 the first place the methods so far     
proposed for preventing any given       
receiver from being affected by         
,hertzian waves sent out from other     

stations1 except that of those from     
which it is desired to receive them4    
,the first method is that which has been
 called the method of electrical        
syntony1 and consists in adjusting the  
electrical capacity and inductance of   
the various open and closed circuits of 
the receiving and transmitting stations 
to be put in communication so that they 
have the same electrical time-period4#fj
  ,in the ,cantor ,lectures before the  
,society of ,arts in #aijj1 on          
electrical oscillations and electric    
waves1 the author has discussed at      
length the conditions under which       
powerful electrical oscillations can be 
set up in a circuit4 ,it was there shown
 that every electric circuit having     
capacity and inductance has a particular
 or natural time-period of electrical   
oscillation depending on the product of 
these qualities1 and that1 to accumulate
 powerful electrical oscillations in it1
 the electromotive impulses on it must  
be delivered at this rate4              

,illustrations were drawn from          
mechanics1 such as the examples         
furnished by vibrating pendulums and    
springs1 and from acoustics1 as         
illustrated by the phenomena of         
resonance1 to show that small or feeble 
blows or impulses delivered at the      
proper time intervals have a cumulative 
effect in setting up vibrations in a    
body capable of oscillation4 ,it is a   
familiar fact that if we time our blows1
 we can achieve that which no single    
blow1 however powerful1 can accomplish  
in throwing into vibration a body such  
as a pendulum1 which is capable of      
oscillation under the action of a       
restoring force4 ,precisely the same is 
true of an electric circuit4 ,we have   
already seen that the receiving aerial  
has an alternating electromotive force  
set up in it by the impact of the       
successive electric waves sent out from 
the transmitter4 ,it must1 however1 be  
remembered that the transmitter sends   
out a series of trains of waves1 not by 

any means a continuous train1 but one   
cut up into groups of probably ten to   
fifty waves1 each separated by intervals
 of silence1 long1 compared with the    
duration of a single train of waves4    
,illustration3 ,,fig4 #bb4--,,seibt',s  
,,apparatus ,,for ,,exhibiting          
,,electric ,,resonance4 ,i1 induction   
coil2 ,s1 spark gap2 ,,cc1 condensers2  
,l1 variable inductance2 ,e1 earth      
plate2 ,,ww1 wire spirals2 ,,vv1 vacuum 
tubes4  ,if1 however1 by a suitable     
adjustment of capacity and inductance1  
we make the natural time-period of      
oscillation of the receiving aerial     
circuits agree with those of the        
transmitting aerial1 within certain     
limits the former will only be receptive
 for waves of the frequency sent out by 
the transmitter4 ,it is quite easy to   
illustrate this principle by numerous   
experiments4 ,it can be done by means of
 an apparatus devised by ,dr4 ,georg    
,seibt for showing in an interesting    
manner the syntonisation or tuning of   

two electric circuits4 ,this consists of
 two bobbins1 each consisting of one    
layer of insulated wire wound on a      
wooden rod 7see ,fig4 #bb74 ,each of    
these bobbins has a certain electrical  
capacity with respect to the earth1 when
 considered as an insulated conductor1  
and it has also a certain inductance4   
,if1 therefore1 electromotive impulses  
are applied to one end of the bobbin at 
regular intervals1 electrical           
oscillations will be set up in it1 and1 
as already explained1 if these are timed
 at a certain rate1 the bobbin will act 
like a closed organ-pipe to air impulses
 and oscillations of potential will be  
accumulated at the opposite end1 which  
have much greater amplitude than the    
impressed oscillations at the end at    
which they are applied4 ,we can make the
 existence of the amplitude oscillations
 of potential evident by attaching to   
one end of the bobbin a vacuum tube1    
which will be illuminated thereby1 or by
 terminating it by a pointed piece of   

wire1 so that an electrical brush can be
 formed at the point1 if the potential  
variations have sufficient amplitude4   
,we arrange also another closed         
oscillation circuit1 consisting of two  
,leyden jars and a variable inductance  
coil and a pair of spark balls which are
 connected to an induction coil4 ,in    
this manner we can set up oscillations  
in the discharge circuit of these       
,leyden jars1 and we can vary the time  
period by altering the inductance and   
the capacity4 ,if we denote the capacity
 of the jars in the microfarads by the  
letter ,c and the inductance in         
centimetres of the discharge circuit of 
the jars by the letter ,l1 it can then  
be shown that the number of oscillations
 per second denoted by n is given by the
 expression--#fa      n                 
7#e1jjj1jjj1jjj7 _/ 7sq,,cl74  ,if now  
we adjust the ,leyden jar circuit to a  
particular rate of oscillation1 we have 
between the terminals of the jar or     
condenser an alternating difference of  

potential or electromotive force4 ,if we
 connect one side of the jars to the    
earth and the other side to the foot of 
one of the spirals or bobbins above     
described1 we shall find perhaps that   
the vacuum tube at the other end is not 
rendered luminous4 ,when1 however1 we   
adjust the inductance in the discharge  
circuit of the jar to a certain value to
 make the frequency of the condenser    
oscillations agree with the natural time
 period of the bobbin terminated by the 
vacuum tube1 this latter at once lights 
up brilliantly4 ,again1 if we connect   
both these bobbins at the same time to  
the discharge circuit of the ,leyden    
jar1 we shall find that we can make an  
adjustment of the inductance of that    
circuit1 such that either of the bobbins
 at pleasure can be made to respond and 
be set in electrical vibration1 as shown
 by the illumination of the vacuum tube 
at its upper end or by an electrical    
brush being formed at the terminal4 ,in 
making this adjustment of inductance1 we

 are tuning1 as it is called1 the       
,leyden jar discharge circuit to the    
resonating bobbin4 ,a very small        
variation of the inductance of the jar  
circuit causes the vacuum tube to change
 in luminosity4 ,if1 however1 the       
natural time periods of these bobbins do
 not lie very far apart1 then a faint   
luminosity will make its appearance in  
both the vacuum tubes4 ,supposing1      
therefore1 that we connect to the       
oscillating circuit of the jar a number 
of bobbins having different time periods
 of oscillation1 like organ-pipes1 and  
supply them all with one common         
alternating electromotive force4 ,these 
bobbins1 whose natural time period is   
very different to that of the           
osciilating circuit or impressed        
electromotive force1 will not respond1  
but those bobbins of which the natural  
time period lies near to1 even if not   
quite exactly the same as1 that of the  
impressed electromotive force will give 
evidence of being set in oscillation4 ,a

 very violent electromotive force will  
cause them all to respond to some slight
 extent1 no matter whether the period of
 that impluse is tuned to their common  
period precisely or not4  ,at this point
 questions arise of great practical     
importance4 ,a matter which has been in 
dispute in connection with practical    
,hertzian wave telegraphy is how far    
this electrical tuning is a sufficient  
solution of the practical problem of    
isolation4 ,it is not denied that       
experiments such as those made with     
,seibt's apparatus can be shown on a    
small scale2 and1 on a still larger     
scale1 ,mr4 ,marconi gave to the author 
in ,september1 #aijj1 a demonstration in
 practical telegraphic work of sending  
two independent ,hertzian wave messages 
and receiving them on two independent   
receivers attached to the same aerial4  
,since that date much experience has    
been gained and large power stations    
erected1 and a statement has been       
frequently made that syntony is no      

protection against interference when one
 of the stations is sending out very    
powerful waves4 ,the contention has been
 raised that large power stations       
producing electric waves will therefore 
play havoc with ,hertzian wave          
telegraphy on a smaller scale1 such as  
the ship to shore and intermarine       
communication4 ,under these             
circumstances1 it appeared to the author
 important to subject the matter to a   
special test1 and ,mr4 ,marconi1        
therefore1 offered to give a            
demonstration1 with this object1 in     
support of the opinion that he has      
expressed positively that waves from his
 power stations do not interfere with   
the working of his ship installations4  
,this matter is vital to the whole      
question of practical ,hertzian wave    
telegraphy1 for the ship to shore       
communication is of stupendous          
importance2 and if ,mr4 ,marconi had    
done nothing else except to render this 
possible and effective1 he would have   

earned1 as he has done1 the gratitude of
 humanity for all time4 ,accordingly1   
the author embraced the opportunity of  
making some careful tests to settle the 
question whether the powerful waves sent
 out from a station such as ,poldhu did 
or did not affect the exchange of       
messages between ship and shore stations
 in proximity1 equipped with ,marconi   
apparatus of a suitable type4  ,these   
experiments were carried out on the     
eighteenth of ,march last1 at ,poldhu1  
in ,cornwall1 and a programme was       
arranged by the author of the following 
kind4 ,close to the ,poldhu station is  
an isolated mast1 which was equipped by 
,mr4 ,marconi with a ,hertzian wave     
apparatus1 similar to that he places on 
ships4 ,six miles from ,poldhu is the   
,lizard receiving station1 with which   
ships proceeding up or down the ,english
 ,channel communicate4 ,it was arranged 
that a series of secret messages1 some  
of them in cipher1 should be delivered  
simultaneously at certain known times1  

both to the power station at ,poldhu and
 to the small adjacent ship station2 and
 it was arranged that these messages    
should be sent off simultaneously1 the  
operators being kept in ignorance up to 
the moment of sending as to the nature  
of the messages4 ,at the ,lizard1 ,mr4  
,marconi connected two of his receiving 
instruments to the aerial1 one of them  
tuned to the waves proceeding from the  
power station at ,poldhu1 and the other 
to those proceeding from the small ship 
station4 ,at the appointed time1 these  
two sets of messages were received      
simultaneously in the presence of the   
author1 each message being printed down 
independently on its own receiver2 and  
,mr4 ,marconi read off and interpreted  
all these messages perfectly correctly1 
not having known before what was the    
message that was about to be sent4 ,in  
addition to this1 precautions were taken
 to prove that the power station at     
,poldhu was really emitting waves       
sufficiently powerful to cross the      

,atlantic and not being made to sing    
small for the occasion4 ,to assist in   
proving this1 the messages sent out from
 the power station were also received at
 a station at ,poole1 two hundred miles 
away1 and the assistant there was       
instructed to telegraph back these      
messages by wire as soon as he received 
them4 ,these messages came back         
perfectly correctly1 thus demonstrating 
that the power station was sending out  
power waves4 ,the whole programme was   
carried out with the greatest care to   
avoid any mistakes on the part of the   
assistants1 and provided an absolute    
demonstration of the truth of ,mr4      
,marconi's assertion that the waves from
 one of his power stations1 such as     
,poldhu1 do not in the least degree     
interfere with the transmission and     
reception of messages between ship and  
shore1 effected by means of certain     
forms of ,marconi apparatus for         
producing and detecting waves of a      
different wave length4#fb ,this complete

 independence of transmission1 however1 
is entirely due to the employment of a  
receiving circuit of a certain type in  
,mr4 ,marconi's receivers4 ,it does not 
at all follow that a receiving circuit  
of any kind1 even a ,marconi receiver   
not especially arranged1 set up in      
proximity to a power station would not  
be affected4 ,this1 however1 is not an  
important matter4 ,far more important is
 it to show1 as has been shown1 that    
practically perfect isolation can be    
achieved if it is desired4  ,it must be 
noted1 however1 that1 although the fact 
that electric circuits have a natural   
time-period of oscillation of their own 
is a scientific principle which carries 
us a considerable way towards a solution
 of what is called syntonic ,hertzian   
wave telegraphy1 it is not in itself    
alone in every respect an entire        
solution of the practical problem4 ,the 
degree to which it is a solution depends
 to a considerable extent upon the      
nature of the detecting device1 or      

kumascope1 which we are employing4 ,the 
coherer1 or ,branly filings tube1 has   
the peculiarity that its passage from a 
non-conductive to a conductive condition
 follows immediately when the difference
 of potential between its ends is made  
sufficiently great4 ,in other words1 if 
the tube is acted upon by a sufficient  
electromotive force1 it is not necessary
 that electromotive force should be     
repeated at intervals to make this      
particular form of kumascope responsive4
 ,again1 if we consider the nature of   
the oscillations which are sent out from
 any transmitting aerial1 we find that  
each group of oscillations corresponding
 to a single spark consists of waves    
gradually decreasing in amplitude4 ,in  
other words1 the first wave of the group
 is the strongest1 and the decay in     
amplitude is often very rapid4          
,supposing1 then1 we construct a simple 
receiver consisting of an aerial having 
inserted in its circuit a sensitive     
,branly filings tube4 ,such a receiver  

is almost entirely non-syntonic2 that is
 to say1 it is affected by any wave     
passing over it which is sufficiently   
powerful4 ,we may look upon it that if  
the first wave of the series is         
sufficiently powerful to affect the     
kumascope1 the conductive change takes  
place whether or not the first wave is  
followed by others4 ,accordingly1 it is 
perfectly certain that if a transmitter 
is sending out trains of waves of any   
period1 a simple combination of coherer 
and aerial will be influenced1 if it is 
placed near enough to the transmitter4  
,on the other hand1 it is possible to   
combine a kumascope of a certain type   
with a receiving aerial and other       
circuits in such a manner that when the 
waves that reach it are feeble it shall 
not respond at all unless those waves   
have very nearly a time period of a     
certain value4  ,at this stage1 it may  
be perhaps well to explain a little in  
detail what is meant by an easily       
responsive circuit1 and1 on the other   

hand1 by an irresponsive circuit1 or1 as
 we may call it1 a stiff circuit4       
,supposing that we consider an aerial   
consisting of a simple straight wire    
having small capacity and small         
inductance1 such a circuit admits of    
being sent into electrical oscillation1 
not only by waves of its own natural    
time-period1 but by the sudden          
application of any violent electromotive
 impulse4 ,if1 on the other hand1 we    
bestow upon the circuit in any way      
considerable inductance1 we then obtain 
what may be called a stiff or           
irresponsive circuit1 which is one in   
which electrical oscillations can be    
accumulated only by the prolonged action
 of impulses tuned to a particular      
period4  ,a mechanical analogue of this 
difference may be found in considering  
the different behaviour of elastic      
bodies to mechanical blows4 ,take1 for  
instance1 a piece of elastic steel and  
fix the bottom end in a vice4 ,the steel
 strip may be thrown into vibration by  

deflecting the upper end4 ,it has1      
however1 a very small mass1 and         
therefore any violent blow or blows1    
even although not repeated1 will set it 
in oscillation4 ,if1 however1 we add    
mass to it by fixing at the other end a 
heavy weight1 such as a ball of lead1   
and at the same time make the spring    
stiffer1 we have an arrangement which is
 capable of being sent into considerable
 oscillation only by the action of a    
series of impulses or blows which are   
timed at a particular rate4  ,returning 
then to the electrical problem1 we see  
that in order to preserve a kumascope or
 wave detector from being operated on by
 any vagrant wave or waves having a     
period very different to an assigned    
period1 it must be associated with an   
electrical circuit of the kind above    
called a stiff circuit4  ,we will now   
consider the manner in which the problem
 has been practically attacked by ,mr4  
,marconi1 ,dr4 ,slaby1 ,sir ,oliver     
,lodge and others1 who have invented    

forms of receiver and transmitter1 which
 are syntonic or sympathetic to one     
another4  ,some of the methods which    
,mr4 ,marconi has devised for the       
achievement of syntonic wireless        
telegraphy were fully described by him  
in a ,paper read before the ,society of 
,arts on ,may1 #ag1 #aija4fc            
,illustration3 ,,fig4 #bc4--,,marconi   
,,transmitter ,,and ,,receiver4 ,i1     
induction coil2 ,a1 aerial2 ,e1 earth   
plate2 ,,hh1 choking coils2 ,s1 spark   
gap2 ,j1 transmitting jigger2 ,k1       
receiving jigger2 ,r1 relay2 ,c1        
condenser2 ,f1 filings tube2 ,b1        
battery4 ,many practical details are    
omitted4  ,on referring to his ,paper1  
it will be seen that in one form his    
transmitter consists of an aerial1 near 
the base of which is inserted the       
secondary circuit of an oscillation     
transformer or transmitting jigger4 ,one
 end of this secondary circuit is       
attached to the aerial and the other end
 is connected to the earth through a    

variable inductance coil4 ,the primary  
circuit of this oscillation transformer 
is connected in series with a condenser1
 consisting of a battery of ,leyden     
jars1 and the two together are connected
 across to the spark balls which close  
the secondary circuit of an induction   
coil1 having the usual make and break   
key in the primary circuit4 ,mr4        
,marconi so adjusts the induction of the
 aerial and the capacity of the         
condenser1 or battery of ,leyden jars1  
that the two circuits1 consisting       
respectively of this battery of ,leyden 
jars and the primary circuit of the     
transformer1 and on the other hand of   
the capacity of the aerial and the      
inductance in series with it1 and that  
of the secondary circuit of the         
transformer have the same time period4  
,in other words1 these two inductive    
circuits are tuned together4 ,at the    
receiving end1 the aerial is connected  
in series with a variable inductance and
 with the primary circuit of another    

oscillation transformer1 the second     
terminal of which is connected to the   
earth4 ,the secondary circuit of this   
last oscillation transformer is cut in  
the middle and is connected to the      
terminals of a small condenser4 ,the    
outer terminals of this secondary       
circuit are connected to the metallic   
filings tube or other sensitive receiver
 and to a small condenser in parallel   
with it 7see ,fig4 #bc74 ,the terminals 
of the condenser which is inserted in   
the middle of the secondary circuit of  
the oscillation transformer are         
connected through two small inductance  
coils with a relay and a single cell4   
,this relay in turn actuates a ,morse   
printer by means of a local battery4    
,the two circuits of the oscillation    
transformer are tuned or syntonised to  
one another1 and also to the similar    
circuit of the transmitting arrangement4
 ,when this is the case1 the transmitter
 affects the co-resonant receiving      
arrangement1 but will not affect any    

other similar arrangement1 unless it is 
within a certain minimum range of       
distance4 ,owing to the inductance of   
the oscillation transformer forming part
 of the receiving arrangements1 the     
receiving circuit is1 as before stated1 
very stiff or irresponsive2 the         
sensitive tube is therefore not acted   
upon in virtue merely of the impact of  
the single wave against the aerial1 but 
it needs repeated or accumulated effects
 of a great many waves1 coming in proper
 time1 to break down the coherer and    
cause the recording mechanism to act4   
,an inspection of the diagram will show 
that as soon as the secondary           
electromotive force in the small        
oscillation transformer or jigger of the
 receiving instrument is of sufficient  
amplitude to break down the resistance  
of the coherer1 the local cell in       
circuit with the relay can send a       
current through it and cause the relay  
to act and in turn make the associated  
telegraphic instrument record or sound4 

,mr4 ,marconi described in the          
above-mentioned ,paper some other       
arrangements for achieving the same     
result1 but those mentioned all depend  
for their operation upon the            
construction of a receiving circuit on  
which the time-period of electrical     
oscillations is identical with that of a
 transmitting arrangement4 ,by this     
means he showed experiments during the  
reading of his ,paper1 illustrating the 
fact that two pairs of transmitting and 
receiving arrangements could be so      
syntonised that each receiver responded 
only to its particular transmitter and  
not to the other4  ,with arrangements of
 substantially the same nature1 he made 
experiments in the autumn of #aijj      
between ,niton1 in the ,isle of ,wight1 
and ,bournemouth1 a distance of about   
thirty miles1 in which independent      
messages were sent and received on the  
same aerial4  ,dr4 ,slaby and ,count von
 ,arco1 working in ,germany1 have       
followed very much on the same lines as 

,mr4 ,marconi1 though with appliances of
 a somewhat different nature4 ,as       
constructed by the ,general ,electric   
,company1 of ,berlin1 the ,slaby-,arco  
syntonic system of ,hertzian telegraphy 
is arranged in one form as              
follows3--,the transmitter consists of a
 vertical rod like a lightning          
conductor1 say1 #ajj or #aej feet in    
height4 ,at a point six or nine feet    
above the ground1 a connection is made  
to a spark ball 7see ,fig4 #bd71 and the
 corresponding ball is connected through
 a variable inductance with one terminal
 of a condenser1 the other terminal of  
which is connected to the earth4 ,the   
two spark balls are connected to an     
induction coil1 or alternating current  
transformer1 and by variation of the    
inductance and capacity the frequency is
 so arranged that the wave-length       
corresponding to it is equal to four    
times the length of that portion of the 
aerial which is above the spark ball    
connection4 ,the method by which this   

tuning is achieved is to insert in the  
portion of the aerial below the spark   
balls1 between it and the earth1 a hot  
wire ammeter of some form4 ,it has      
already been shown that in the case of  
such an earthed aerial1 when electrical 
oscillations are set up in it1 there is 
a potential node at the earth and a     
potential anti-node or loop at the      
summit1 if it is vibrating in its       
fundamental manner2 also1 there is a    
node of current at the summit of the    
aerial and an anti-node at the base4    
,this amounts to saying that the        
amplitude of the potential vibrations is
 greatest at the top end of the aerial1 
and the amplitude of the current        
vibrations is greatest at the bottom or 
earthed end4 ,accordingly1 the          
inductance and capacity of the lateral  
branch of the transmitter is altered    
until the hot wire ammeter in the base  
of the aerial shows the largest possible
 current4  ,illustration3 ,,fig4        
#bd4--,,slaby-,,arco ,,syntonic         

,,transmitter ,,and ,,receiver4 ,i1     
induction coil2 ,m1 multiplier2 ,b1     
battery2 ,a1 aerial2 ,f1 filings tube2  
,r1 relay2 ,e1 earth plate2 ,c1         
condenser4  ,the corresponding receiver 
is constructed in a very similar manner4
 ,a lightning conductor or long vertical
 rod of the same height as the          
transmitting aerial is set up at the    
receiving station1 and at a point six or
 nine feet from the ground a circuit is 
taken off1 consisting of a wire loosely 
coiled in a spiral1 the length of which 
is nearly equal to1 although a little   
shorter than1 the height of the vertical
 wire above the point of connection4    
,the outer end of this loose spiral is  
connected to one terminal of the coherer
 tube1 and the other terminal of the    
coherer is connected to the earth       
through a condenser of rather large     
capacity4 ,the terminals of this last   
condenser are short-circuited by a relay
 and a single cell4 ,when the           
adjustments are properly made1 it is    

claimed that the receiver responds only 
to waves coming from its own syntonised 
or tuned transmitter4 ,in this case the 
length of the receiving aerial above the
 point of junction with the coherer     
circuit is one quarter the length of the
 wave4 ,a variation of the above        
arangements consists in making this     
lateral circuit equal in length to      
one-half of a wave1 and connecting the  
coherer to its centre through a         
condenser to the earth4 ,the outer end  
of this lateral circuit is also         
connected to the earth 7see ,fig4       
#bd74fd  ,dr4 ,slaby claims that this   
arrangement is not affected by          
atmospheric electricity1 and that the   
complete and direct earthing of the     
aerial and also in the second           
arrangement1 of the receiver of the     
outer end of the lateral conductor1     
conduces to preserve the receiver immune
 from any electrical disturbances except
 those having a period to which it is   
tuned4  ,illustration3 ,,fig4           

#be4--,,lodge-,,muirhead ,,syntonic     
,,receiver4 ,i1 induction coil2 ,s1     
spark gap2 ,a1 aerial2 ,,cc1 condensers2
 ,e1 earth plate2 ,r1 relay2 ,l1        
variable inductance2 ,f1 filings tube2  
,b1 battery4  ,a method has also been   
arranged by him for receiving on the    
same aerial two messages from different 
transmitting stations simultaneously4   
,in this case1 two lateral wires of     
different lengths are connected to the  
receiving aerial1 and to the outer end  
of each of these is connected a coherer 
tube1 the other end of which is earthed 
through a condenser4 ,one of these      
lateral wires is made equal1 or nearly  
equal1 in length to the aerial1 and the 
other is made longer to fulfil the      
following condition4#fe ,if we call ,h  
the height of the receiving aerial above
 point of junction of the lateral wires1
 then the length of one lateral wire is 
made equal to ,h1 and the height of the 
aerial is adjusted to be equal to       
one-quarter of the wave length of one   

incident wave4 ,the other lateral wire  
may then be made of a length equal to   
one-third of ,h1 and it will then       
respond to the first odd harmonic of    
that wave1 of which the fundamental is  
in syntony with the vertical wire4 ,by  
suitably choosing the relation between  
the wave-lengths of the two transmitting
 stations1 it is possible to receive in 
this manner two different messages at   
the same time on the same aerial4       
,subsequently to the date of the        
above-mentioned demonstration of        
multiplex wireless telegraphy by ,mr4   
,marconi an exhibition of a similar     
nature was given by ,professor ,slaby in
 a lecture given in ,berlin on ,december
 #bb1 #aijj4ff  ,both the               
above-described syntonic systems of ,mr4
 ,marconi and ,dr4 ,slaby are earthed   
systems1 but arrangements for syntonic  
telegraphy have been devised by ,sir    
,oliver ,lodge and ,professor ,braun    
which are non-earthed4  ,sir ,oliver    
,lodge and ,dr4 ,muirhead have devised  

also syntonic systems4 ,according to    
their last methods1 the systonic        
transmitting and receiving arrangements 
are as shown in ,fig4 #be4fg ,on        
examining the diagrams it will be seen  
that the secondary terminals of the     
induction coil are1 as usual1 connected 
to a pair of spark balls1 and that these
 spark balls are connected by a         
condenser and by a variable inductance4 
,one terminal of the condenser is       
earthed through another condenser of    
large capacity1 and the remaining       
terminal of the first condenser is      
connected to an aerial4 ,it should1     
therefore1 be borne in mind in dealing  
with electrical oscillations that a     
condenser of sufficient capacity is     
practically a conductor1 and an         
inductance coil of sufficient inductance
 is practically a non-conductor4 ,hence 
the insertion of a large capacity in the
 path of the aerial wire is no advantage
 whatever and makes no essential        
difference in the arrangement4 ,in order

 to obtain any powerful radiation1 the  
length of the aerial1 or sky wire1 as   
they call it1 must be so adjusted that  
its length is one-quarter the           
wave-length corresponding to the        
oscillation circuit1 consisting of the  
condenser and variable inductance4  ,the
 receiving arrangement consists of a    
similar sky wire or aerial earthed      
through a condenser of large capacity   
and having in the portion above this    
last condenser another condenser of     
similar capacity4 ,at the earthed side  
of this last condenser a connection is  
made to a resonant circuit1 consisting  
of a variable inductance1 and another   
condenser and a sensitive metallic      
filings tube of the ,branly type2 also a
 portion of this resonant circuit is    
shunted by another consisting of a      
battery and telegraphic relay1 as shown 
in the diagram4 ,the circuit1 including 
the coherer1 is tuned to its own aerial 
and also to that of the transmitting    
circuit1 and under these circumstances  

trains of waves thrown off at the       
transmitting aerial will sympathetically
 affect the receiving aerial4  ,there is
 nothing in the arrangement which       
specially calls for notice4 ,it is      
simply a variation of other known forms 
of syntonic transmitter and receiver1   
and possesses all the advantages and    
disadvantages attaching to such         
electrical syntonic methods4  ,professor
 ,braun's syntonic system1 the receiver 
and transmitter of which have been      
described1 is also in one form a        
non-earthed system4 ,innumerable other  
patentees have taken out patents for    
devices which are modifications in small
 degree of the above arrangements4  ,it 
may be well to note at this point the   
disadvantages that are possessed by any 
form of coherer as a telegraphic        
kumascope in connection with proposed   
arrangements for the isolation of       
,hertzian wave stations4 ,all the       
detectors of the coherer type really    
depend for their actuation upon         

electromotive force2 that is to say1    
upon the application to the terminals of
 the detector of a certain electromotive
 force4 ,although there may be no sharp 
and defined critical electromotive      
force1 yet1 nevertheless1 as a matter of
 fact1 if the electromotive force       
applied exceeds a certain value1 then   
the detector passes suddenly from one   
state of conductivity to another4 ,it   
may be of great conductivity1 as in the 
case of the ,branly coherer1 or of      
lesser conductivity1 as in the case of  
the so-called anti-coherers1 of which   
the ,schaefer kumascope may be taken as 
a type4 ,accordingly1 when these        
instruments are subjected to a train of 
waves1 each individual group of which is
 damped1 their operation is largely     
governed by the fact that if the first  
wave or oscillation set up in the       
receiving circuit is powerful enough to 
break down the coherer1 then the        
receiving mechanism acts1 no matter     
whether the first impulse is followed by

 others or not4  ,in comparison with    
so-called coherers1 those depending upon
 the changes in the magnetisation of    
iron by electrical oscillations         
certainly have an advantage1 because    
this is a process which requires the    
application of alternating electric     
currents decreasing in strength for a   
certain time2 and it is found1          
therefore1 that the magnetic receivers  
do not require to be associated with    
such a stiff or irresponsive resonant   
circuit to confine their indications to 
oscillations or waves of one definite   
period1 and that they lend themselves   
much more perfectly to the work of      
tuning or syntonising stations than do  
those kumascopes depending upon the     
contact or coherer principle4  ,we may  
then glance at the alternative solutions
 of the problem offered by other        
investigators4 ,m4 ,blondel has proposed
 to effect the syntonisation of two     
stations1 not by syntonising the        
receiver for the exceedingly            

high-frequency oscillations of the      
individual electric waves1 but to       
syntonise it for the much lower         
frequency1 corresponding to that of the 
intervals between the groups of waves4  
,thus1 for instance1 if an ordinary     
simple transmitting aerial is set up1   
the production of sparks between the    
spark balls results in the emission of  
short trains of waves1 each of which may
 consist of half a dozen or more        
individual waves1 the time of production
 of the whole group being very small    
compared with the interval between the  
groups4 ,m4 ,blondel proposes1 however1 
to syntonise the receiver1 not for the  
high-frequency period of the waves      
themselves1 which may be reckoned in    
millions per second1 but for the        
low-frequency period between the groups 
of waves1 which is reckoned in hundreds 
per second4 ,thus1 for instance1 if     
sparks are made at the rate of fifty or 
a hundred per second1 they can be made  
to actuate the telephone receiver and so

 produce in the telephone a sound       
corresponding to a frequency of #ej or  
#ajj2 in other words1 to make a low     
musical note or hum4 ,this continuous   
sound can be cut up1 by means of a key  
placed in the primary circuit of the    
transmitting arrangement1 into long or  
short periods1 and hence the letters of 
the alphabet signal4  ,m4 ,blondel's    
arrangements comprise a ,mercadier's    
monotone telephone and either a coherer 
or a particular form of vacuum tube as a
 kumascope4 ,on ,august #af1 #ahih1 ,m4 
,blondel deposited with the ,academy of 
,sciences in ,paris a sealed envelope   
containing a description of his         
improvements in syntonic wireless       
telegraphy1 which was opened on ,may    
#ai1 #aijj4fh ,the arrangement of the   
receiving apparatus was as follows3--,a 
single-battery cell keeps a condenser   
charged until the kumascope is rendered 
conductive by the oscillations coming   
down the aerial2 and under these        
circumstances the condenser discharges  

through the telephone and causes a tick 
to be heard in it4 ,if the trains of    
waves are at the rate of #ej or #ajj per
 second1 these small sounds run together
 into a musical note1 and this          
continuous hum can be cut up into long  
and short spaces1 in accordance with the
 ,morse alphabet signals4 ,the telephone
 must not be an ordinary telephone1     
capable of being influenced by any      
frequency1 but be one which responds    
only to a particular note1 and under    
these conditions the receiving          
arrangement is receptive only when the  
trains of waves arrive at certain       
regular predetermined intervals1        
corresponding with the tone to which the
 telephone is sensitive4         99     
99       99       99       99  ,a number
 of more or less imperfect arrangements1
 having the isolation of communications 
for their object1 have been devised or  
patented1 which are dependent upon the  
use of several aerials1 each supposed to
 be responsive only to a particular     

frequency2 and attempts have been made  
to solve the problem of isolation by    
,,mm4 ,tommasi1 ,tesla1 ,jegon1 ,tissot1
 ,ducretet and others4  ,we may then    
pass on to notice the attempts that have
 been made to secure isolation by a plan
 which is not dependent on electrical   
syntony4 ,one of these1 which has the   
appearance of developing into a         
practical solution of the problem1 is   
that due to ,anders ,bull4#fi ,in the   
first arrangements proposed by this     
inventor1 a receiver is constructed     
which is not capable of being acted upon
 merely by a single wave or train of    
waves or even a regularly-spaced train  
of electric waves1 but only by a group  
of wave trains which are separated from 
one another by certain unequal1         
predetermined intervals of time4 ,thus1 
for instance1 to take a simple instance1
 the transmitting arrangements are so   
devised as to send out groups of        
electric waves1 these wave trains       
following one another at time intervals 

which may be represented by the numbers 
#a1 #c and #e2 that is to say1 the      
interval which elapses between the      
second and third is three times that    
between the first two1 and the interval 
between the fourth and fifth is five    
times that between the first two4 ,this 
is achieved by making five electric     
oscillatory sparks with a transmitter of
 the ordinary kind1 the intervals       
between which are settled by the        
intervals between holes punched upon    
strips of paper1 like that used in a    
,wheatstone automatic telegraphic       
instrument4 ,it will easily be          
understood that by a device of this     
kind1 groups of sparks can be made1 say1
 five sparks rapidly succeeding each    
other1 but not at equal intervals of    
time4 ,one such group constitutes the   
,morse dot1 and two or three such groups
 succeeding one another very quickly    
constitute the ,morse dash4 ,these      
waves1 on arriving at the receiving     
station1 are caused to actuate a        

punching arrangement by the             
intermediation of a coherer or other    
kumascope1 and to punch upon a uniformly
 moving strip of paper holes1 which are 
at intervals of time corresponding to   
the intervals between the sparks at the 
transmitting station4 ,this strip of    
paper then passes through another       
telegraphic instrument1 which is so     
constructed that it prints upon another 
strip a dot or a dash1 according to the 
disposition of the holes on the first   
strip4 ,accordingly1 taken as a whole1  
the receiving arrangement is not capable
 of being influenced so as to print a   
telegraphic sign except by the operation
 of a series of wave trains succeeding  
one another at certain assigned         
intervals of time4  ,an improvement has 
been lately described by the same       
inventor1#gj in which the apparatus     
used1 although more complicated1        
performs the same functions4 ,at each   
station two instruments have to be      
employed2 at the transmitting station   

one to effect the conversion of ,morse  
signals into the properly arranged      
series of wave trains1 and at the       
receiving station an instrument to      
effect the re-conversion of the series  
of wave trains into the ,morse signals4 
,these are called respectively the      
dispenser and the collector4 ,the       
details of the arrangements are somewhat
 complicated1 and can only be described 
by the aid of numerous detailed         
drawings1 but the inventor states that  
he has been able to carry on ,hertzian  
wave telegraphy by means of these       
arrangements for short distances4       
,moreover1 the method lends itself to an
 arrangement of multiplex telegraphy1 by
 sending out from different transmitters
 signals which are based upon different 
arrangements of time intervals between  
the electric wave trains4 ,although this
 method may succeed in preventing a     
receiving arrangement from being        
influenced by vagrant waves or waves not
 intended for it1 yet an objection which

 arises is that there is nothing to     
prevent any one from intercepting these 
wave trains1 and with a little skill    
interpreting their meaning4 ,thus1 if   
the record were received in the ordinary
 way on a simple receiver1 corresponding
 to a ,morse dot would be printed five  
dots at unequal intervals1 and          
corresponding to a ,morse dash would be 
printed two such sets of five dots4 ,a  
little skill would then enable an       
operator to interpret these arbitrary   
signals4 ,on the other hand1 the        
inventor asserts that he can overcome   
this difficulty by making intervals of  
time between the impulses in the series 
so long that the latter become longer   
than the intervals between each of the  
series of waves which are despatched in 
continuous succession when the key is   
pressed for a dash4 ,in this case1 when 
telegraphing1 the series of dots would  
overlap and intermingle with each other 
in a way which would make the record    
unintelligible if received in the usual 

manner1 but would be perfectly legible  
if received and interpreted by a        
receiver adapted for the purpose4       
,another way of obliterating the record1
 as far as outsiders are concerned1 is  
to interpolate between the groups of    
signals an irregular series of          
dots--i4e41 of wave trains--which would 
affect an ordinary coherer1 and so make 
an unintelligible record on an ordinary 
receiver1 but these dots are not        
received or picked up by the appropriate
 selecting instrument used in the       
,anders ,bull system4  ,the matter most 
interesting to the public at the present
 time is the long-distance telegraphy by
 ,hertzian waves to the accomplishment  
of which ,mr4 ,marconi has devoted      
himself with so much energy of late     
years4 ,everyone1 except perhaps those  
whose interests may be threatened by his
 achievements1 must accord their hearty 
admiration of the indomitable           
perseverance and courage which he has   
shown in overcoming the immense         

difficulties which have presented       
themselves4 ,five years ago he was      
engaged in sending signals from ,alum   
,bay1 in the ,isle of ,wight1 to        
,bournemouth1 a distance of twelve or   
fourteen miles2 and to-day he has       
conquered twice that number of hundred  
miles and succeeded in sending1 not     
merely signals1 but long messages of all
 descriptions over three thousand miles 
across the ,atlantic4 ,critics there are
 in abundance1 who declare that the     
process can never become a commercial   
one1 that it will destroy short-distance
 ,hertzian telegraphy1 or that the      
multiplication of long-distance stations
 will end in the annihilation of all    
,hertzian wave telegraphy4 ,no one1     
however1 can contemplate the history of 
any development of applied science      
without seriously taking to heart the   
lesson that the obstacles which arise   
and which prove serious in any          
engineering undertaking are never those 
which occur to armchair critics4        

,sometimes the seemingly impossible     
proves the most easy to accomplish1     
whilst difficulties of a formidable     
nature often spring up where least      
expected4  ,the long-distance           
transmission is a matter of peculiar    
interest to the author of these         
articles1 because he was at an early    
stage in connection with it invited to  
render ,mr4 ,marconi assistance in the  
matter4#ga ,the particular work         
entrusted to him was that of planning   
the electrical engineering arrangements 
of the first power station erected for  
the production of electric waves for    
long-distance ,hertzian wave telegraphy 
at ,poldhu1 in ,cornwall4 ,when ,mr4    
,marconi returned from the ,united      
,states in the early part of #aijj1 he  
had arrived at the conclusion that the  
time had come for a serious attempt to  
accomplish wireless telegraphy across   
the ,atlantic4 ,up to that date the     
project had been an inventor's dream1   
much discussed1 long predicted1 but     

never before practically taken in hand4 
,the only appliances1 moreover1 which   
had been used for creating ,hertzian    
waves were induction coils or small     
transformers1 and the greatest distance 
covered1 even by ,mr4 ,marconi himself1 
had been something like #aej miles over 
sea4 ,accordingly1 to grapple with the  
difficulty of creating an electric wave 
capable of making itself felt at a      
distance of #c1jjj miles1 even with the 
delicate receiving appliances invented  
by ,mr4 ,marconi1 seemed to require the 
means of producing at least four hundred
 times the wave-energy that had been    
previously employed4 ,the author was1   
therefore1 requested to prepare plans   
and specifications for an electric      
generating plant for this purpose1 which
 would enable electrical oscillations to
 be set up in an aerial on a scale never
 before accomplished4  ,this work       
involved1 not merely the ordinary       
experience of an electrical engineer1   
but also the careful consideration of   

many new problems and the construction  
of devices not before used4 ,every step 
had to be made secure by laboratory     
experiments before the responsibility   
could be incurred of advising on the    
nature of the machinery and appliances  
to be ordered4 ,many months in the year 
#aija were thus occupied by the author  
in making small-scale experiments in    
,london and in superintendence of       
large-scale experiments at the site of  
the first power station at ,poldhu1 near
 ,mullion1 in ,cornwall1 before the     
plant was erected and any attempt was   
made by ,mr4 ,marconi to commence actual
 telegraphic experiments4 ,as this work 
was of a highly confidential nature1 it 
is obviously impossible to enter into   
the details of the arrangements1 either 
as made by the writer in the first      
instance1 or as they have been          
subsequently modified by ,mr4 ,marconi4 
,the design of the aerial and of the    
oscillation transformers and many of the
 details in the working appliances are  

entirely due to ,mr4 ,marconi1 but as a 
final result1 a power plant was erected 
for the production of ,hertzian waves on
 a scale never before attempted4 ,the   
utilisation of #ej ,h4,p4 or #ajj ,h4,p4
 for electric wave production has       
involved dealing with many difficult    
problems in electrical engineering1 not 
so much in novelty of general           
arrangement as in details4 ,it will     
easily be understood that ,leyden jars1 
spark balls and oscillators1 which are  
quite suitable for use with an induction
 coil1 would be destroyed immediately if
 employed with a large                  
alternating-current plant and immensely 
powerful transformers4  ,illustration3  
,,fig4 #bf4--,,wooden ,,towers          
,,supporting ,,the ,,marconi ,,aerial   
,,at ,,poldhu ,,power ,,station1        
,,cornwall1 ,,england4  ,in the initial 
experiments with this machinery and in  
its first working there was very        
considerable risk1 owing to its novel   
and dangerous nature2 but throughout the

 whole of the work from the very        
beginning1 no accident of any kind has  
taken place1 so great have been the     
precautions taken4 ,the only thing in   
the nature of a mishap was the collapse 
of a ring of tall masts1 erected in the 
first place to sustain the aerial wires1
 but which now have been replaced by    
four substantial timber towers1 #bae    
feet in height1 placed at the corners of
 a square1 #bjj feet in length4 ,these  
four towers sustain a conical           
arrangement of insulated wires 7see     
,fig4 #bf7 which can be used in sections
 and which constitute the transmitting  
radiator or receiver1 as the case may   
be4 ,each of these wires is #bjj feet in
 length and formed of bare stranded     
wire4  ,at the outset1 there was much   
uncertainty as to the effect of the     
curvature of the earth on the           
propagation of a ,hertzian wave over a  
distance of many hundreds of miles4 ,in 
the case of the ,atlantic transmission  
between the station at ,poldhu in       

,cornwall and that at ,cape ,cod in     
,massachusetts1 ,u4,s4,a41 we have two  
stations separated by about #de degrees 
of longitude on a great circle1 or      
one-eighth part of the circumference of 
the world4 ,in this case1 the versine of
 the arc or height of the sea at the    
half-way point above the straight line  
or chord joining the two places is #cjj 
miles4  ,the question has recently      
attracted the attention of several      
eminent mathematical physicists4 ,the   
extent to which a free wave propagated  
in a medium bends round any object or is
 diffracted depends on the relation     
between the length of the wave and the  
size of the object4 ,thus1 for instance1
 an object the size of an orange held   
just in front of the mouth does not     
perceptibly interfere with the          
propagation of the waves produced by the
 speaking or singing voice1 because     
these are from two to six feet in       
length3 but if arrangements are made by 
means of a ,galton whistle to produce   

air waves half an inch in length1 then  
an obstacle the size of an orange causes
 a very distinct acoustic shadow4 ,the  
same thing is true of waves in the      
ether4 ,the amount of bending of light  
waves round material objects is         
exceedingly small1 because the average  
length of light waves is about          
one-fifty-thousandth part of an inch4   
,in the case of ,hertzian wave          
telegraphy1 we are1 however1 dealing    
with ether waves many hundreds of feet  
in length1 and the waves sent out from  
,poldhu have a wave-length of a thousand
 feet or more1 say1 one-fifth to        
one-quarter of a mile4 ,the distance1   
therefore1 between ,poldhu and ,cape    
,cod is only at most about twelve       
thousand wave-lengths1 and stands in the
 same relation to the length of the     
,hertzian wave used as does a body the  
diameter of a pea to the wave-length of 
yellow light4 ,there is unquestionably a
 large amount of diffraction or bending 
of the electric wave round the earth1   

and1 proportionately speaking1 it is    
larger than in the case of light waves  
incident on objects of the same relative
 size4  ,quite recently ,mr4 ,h4 ,m4    
,macdonald 7see ,proc4 ,roy4 ,soc41     
,london1 ,vol4 ,,lxxi41 p4 #bea7 has    
submitted the problem to calculation1   
and has shown that the power required to
 send given electric waves #c1jjj miles 
along a meridian of the earth is greater
 than would be required to send them    
over the same distance if the sea       
surface were flat in the ratio of #aj to
 #c4 ,hence the rotundity of the earth  
does introduce a very important         
reduction factor1 although it does not  
inhibit the transmission4 ,mr4          
,macdonald's mathematical argument has1 
however1 been criticised by ,lord       
,rayleigh and by ,m4 ,h4 ,poincare 7see 
,proc4 ,roy4 ,soc41 ,vol4 ,,lxxii41 p4  
#dj1 #aijc74  ,the accomplishment of    
very long distances by ,hertzian wave   
telegraphy is1 however1 not merely a    
question of power1 it is also a question

 of wave-length4 ,having regard1        
however1 to the possibility that the    
propagation which takes place in        
,hertzian wave telegraphy is not that   
simply of a free wave in space1 but the 
transmission of a semi-loop of electric 
strain with its feet tethered to the    
earth1 it is quite possible that if it  
were worth while to make the attempt1 an
 ether disturbance could be made in     
,england sufficiently powerful to be    
felt in ,new ,zealand4  ,leaving1       
however1 these hypothetical questions   
and matters of pure conjecture1 we may  
consider some of the facts which have   
resulted from ,mr4 ,marconi's           
long-distance experiments4 ,one of the  
most interesting of these is the effect 
of daylight upon the wave propagation4  
,in one of his voyages across the       
,atlantic1 when receiving signals from  
,poldhu on board the ,s4,s4             
,philadelphia1 he noticed that the      
signals were received by night when they
 could not be detected by day4#gb ,in   

these experiments ,mr4 ,marconi         
instructed his assistants at ,poldhu to 
send signals at a certain rate from #ab 
to #a a4m41 from #f to #g a4m41 from #ab
 to #a p4m41 and from #f to #g p4m41    
,greenwich mean time1 every day for a   
week4 ,he has stated that on board the  
,philadelphia he did not notice any     
apparent difference between the signals 
received in the day and those received  
at night until after the vessel had     
reached a distance of #ejj statute miles
 from ,poldhu4 ,at distances of over    
#gjj miles1 the signals transmitted     
during the day failed entirely1 while   
those sent at night remained quite      
strong up to #a1eea miles1 and were     
clearly decipherable up to a distance of
 #b1jii miles from ,poldhu4 ,mr4        
,marconi also noted that at distances of
 over #gjj miles1 the signals at #f     
a4m41 in the week between ,february #bc 
and ,march #a1 were quite clear and     
distinct1 whereas by #g a4m4 they had   
become weak almost to total             

disappearance4 ,this fact led him at    
first to conclude that the cause of the 
weakening was due to the action of the  
daylight upon the transmitting aerial1  
and that as the sun rose over ,poldhu1  
so the wave energy radiated1 diminished1
 and he suggested as an explanation the 
known fact of the dissipating action of 
light upon a negative charge4  ,although
 the facts seem to support this view1   
another explanation may be suggested4   
,it has been shown by ,professor ,j4 ,j4
 ,thomson that gaseous ions or electrons
 can absorb the energy of an electric   
wave1 if present in a space through     
which waves are being transmitted4#gc   
,if it be a fact1 as suggested by       
,professor ,j4 ,j4 ,thomson1 that the   
sun is projecting into space streams of 
electrons1 and if these are continually 
falling in a shower upon the earth1 in  
accordance with the fascinating         
hypothesis of ,professor ,arrhenius1    
then that portion of the earth's        
atmosphere which is facing the sun will 

have present in it more electrons or    
gaseous ions than that portion which is 
turned towards the dark space1 and it   
will therefore be less transparent to   
long ,hertzian waves4#gd ,in other      
words1 clear sunlit air1 though         
extremely transparent to light waves1   
acts as if it were a slightly turbid    
medium for long ,hertzian waves4 ,the   
dividing line between that portion of   
the earth's atmosphere which is         
impregnated with gaseous ions or        
electrons is not sharply delimited from 
the part not so illuminated1 and there  
may be1 therefore1 a considerable       
penetration of these ions into the      
regions which ,i may call the twilight  
areas4 ,accordingly1 as the earth       
rotates1 a district in which ,hertzian  
waves are being propagated is brought1  
towards the time of sunrise1 into a     
position in which the atmosphere begins 
to be ionised1 although far from as     
freely as is the case during the hours  
of bright sunshine4  ,mr4 ,marconi      

states that he has found a similar      
effect between inland stations1 signals 
having been received by him during the  
night between ,poldhu and ,poole with an
 aerial the height of which was not     
sufficient to receive them by day4 ,it  
has been found1 however1 that the effect
 simply amounts to this1 that rather    
more power is required by day than by   
night to send signals by ,hertzian waves
 over long distances4  ,some interesting
 observations have also been made by    
,captain ,h4 ,b4 ,jackson1 ,r4,n41#ge on
 the influence of various states of the 
atmosphere upon ,hertzian wave          
telegraphy4 ,these experiments were all 
made between ships of the ,british      
,royal ,navy1 furnished with ,hertzian  
wave telegraphy apparatus on the        
,marconi system4 ,some of his           
observations concerned the effect of the
 interpositon of land between two ships4
 ,he found that the interposition of    
land containing iron ores reduced the   
signalling distances1 compared with the 

maximum distance at open sea1 to about  
#cj per cent4 of the latter2 whilst hard
 limestone reduced it to nearly #fj per 
cent4 and soft sandstone or shale to #gj
 per cent4 ,these results show that     
there is a considerable absorption      
effect when waves of certain wave-length
 pass through or over hard rocks        
containing iron ores4 ,it would be      
interesting to know1 however1 whether   
this reduction was in any degree        
proportional to the dryness or moisture 
of the soil4 ,earth conductivity is far 
more dependent upon the presence or     
absence of moisture than upon the       
particular nature of the material which 
composes it other than water4  ,the     
observations of ,captain ,jackson1      
however1 only confirm the already       
well-known fact that ,hertzian waves1 as
 employed in the ,marconi system of     
wireless telegraphy1 within a certain   
range of wave-length1 are considerably  
weakened by their passage through land1 
over land or round land4 ,in some cases 

he noticed that quite sharp electric    
shadows were produced by rocky          
promontories projecting into the line of
 transmission4 ,his attention was also  
directed 7loc4 cit47 to the more        
important matter of the effect of       
atmospheric electrical conditions upon  
the transmission4 ,the effect of all    
lightning discharges1 whether visible or
 invisible1 is to make a record on the  
telegraphic receiver4 ,on the approach  
of an atmospheric electrical disturbance
 towards the receiving station on a     
ship1 the first visible indications     
generally are the recording of dots at  
intervals from a few minutes to a few   
seconds on the telegraphic tape4        
,captain ,jackson states that the most  
frequent record is that of three dots1  
the first being separated from the other
 two by a slight interval like the      
letters ,e ,i on the ,morse code1 and   
this is the sign most frequently        
recorded by distant lightning4 ,but in  
addition to this1 dashes are recorded   

and irregular signs1 which1 however1    
sometimes spell out words in the ,morse 
code4 ,he noted that these disturbances 
are more frequent in summer and autumn  
than in winter and spring1 and in the   
neighbourhood of high mountains more    
than in the open sea4 ,in settled       
weather1 if present1 they reach their   
maximum between #h p4m4 and #aj p4m41   
and frequently last during the whole of 
the night1 with a minimum of disturbance
 between #i a4m4 and #a p4m4 ,another   
important matter noted by ,captain      
,jackson is the shorter distance at     
which signals can usually be received   
when any electrical disturbances are    
present in the atmosphere1 compared with
 the distance at which they can be      
received when none are present4 ,this   
reduction in signalling distance may    
vary from #bj to #gj per cent1 of that  
obtainable in fine weather4 ,it does not
 in any way decrease with the number of 
lightning flashes1 but rather the       
reverse1 the loss in signalling distance

 generally preceding the first          
indications on the instrument of the    
approaching electrical disturbance4 ,it 
is clear that these observations fit in 
very well with the theory outlined      
above1 viz41 that the atmosphere when   
impregnated with free electrons or      
negatively-charged gaseous ions is more 
opaque to ,hertzian waves than when they
 are absent4 ,captain ,jackson gives an 
instance of ships whose normal          
signalling distance was #fe miles1      
failing to communicate at #bb miles when
 in the neighbourhood of a region of    
electrical disturbance4 ,these effects  
in the case of wireless telegraphy have 
their parallel in the disturbances      
caused to telegraphy with wires by earth
 currents and magnetic storms4  ,another
 effect which he states reduces the     
usual maximum signaling distance is the 
presence of material particles held in  
suspension by the water spherules in    
moist atmosphere4 ,the effect has been  
noticed in the ,mediterranean ,sea when 

the sirocco wind is blowing4 ,this is a 
moist wind conveying dust and salt      
particles from the ,african coast4 ,a   
considerable reduction in signalling    
distance is produced by its advent4     
,another interesting observation due to 
,captain ,jackson is the existence of   
certain zones of weak signals4 ,thus1   
for instance1 two ships at a certain    
distance may be communicating well2 if  
their distance increases1 the signalling
 falls off1 but is improved again at a  
still greater distance4 ,he advances an 
ingenious theory to show that this fact 
may be due to the interference between  
two sets of waves sent out by the       
transmitter having different            
wave-lengths4  ,finally1 in the ,paper  
referred to1 he emphasises the          
well-known fact that long-distance      
signalling can only be accomplished by  
the aid of an aerial wire and a good    
earth4 ,summing up his results1 he      
concludes3 7#a7 ,that intervening land  
of any kind reduces the practical       

signalling distance between two ships or
 stations1 compared with that which     
would be obtainable over the open sea1  
and that this loss in distance varies   
with the height1 thickness1 contour1 and
 nature of the land2 7#b7 material      
particles1 such as dust and salt1 held  
in suspension in a moist atmosphere also
 reduce the signalling distance1        
probably by dissipating and absorbing   
the waves2 7#c7 that electrical         
disturbances in the atmosphere also act 
most adversely in addition to affecting 
the receiving instrument and making     
false signals or strays1 as they are    
called2 7#d7 that with certain forms of 
transmitting arrangement1 interference  
effects may take place which have the   
result of creating certain areas of     
silence very similar to those which are 
observed in connection with sound       
signals from a siren4  ,it is clear1    
therefore1 from all the above           
observations1 that ,hertzian-wave       
telegraphy taking place through the     

terrestrial atmosphere is not by any    
means equivalent to the propagation of a
 wave in free or empty space2 and that  
just as the atmosphere varies in its    
opacity to rays of light1 sometimes     
being clear and sometimes clouded1 so it
 varies from time to time in            
transparency to ,hertzian waves1 the    
cause of this variation in transparency 
probably being the presence in the      
atmosphere of negatively-charged        
corpuscles or electrons4 ,if there are  
present in the atmosphere at certain    
times clouds of electrons or electronic 
fogs1 these may have the effect of      
producing a certain opacity1 or rather  
diminution in transparency to ,hertzian 
waves1 just as water particles do in the
 case of sunlight4  ,we may1 therefore1 
in conclusion1 review a few of the      
outstanding problems awaiting solution  
in connection with ,hertzian wave       
wireless telegraphy4 ,in spite of the   
fact that this new telegraphy has not   
been accorded a very hearty welcome by  

the representatives of official or      
established telegraphy in ,great        
,britain1 it has reached a point1       
unquestionably owing to ,mr4 ,marconi's 
energy and inventive power1 at which it 
is bound to continue its progress4 ,but 
that progress will not be assisted by   
shutting our eyes to facts4 ,many       
problems of great importance remain to  
be solved4 ,we have not yet reached a   
complete solution of all the            
difficulties connected with isolation of
 stations4 ,in the next place1 the      
question of localising the source of the
 signals and waves is most important4   
,our kumascopes and receiving appliances
 at present are like the rudimentary    
eyes of the lower organisms1 which are  
probably sensitive to mere differences  
in light and darkness1 but which are not
 able to see or visualise1 in the sense 
of locating the direction and distance  
of a radiating or luminous body4 ,just  
as we have1 as little children1 to learn
 to see1 so a similar process has to be 

accomplished in connection with         
,hertzian telegraphy1 and the           
accomplishment of this does not seem by 
any means impossible or even distant4   
,we are dealing with hemispherical waves
 of electric and magnetic force1 which  
are sent out from a certain radiating   
centre1 and in order to localise that   
centre we have to determine the position
 of the plane of the wave and also the  
curvature of the surface at the         
receiving point4 ,something1 therefore1 
equivalent to a range finder in         
connection with light is necessary to   
enable us to locate the distance and the
 direction of the radiant point4        
,lastly1 there are important            
improvements possible in connection with
 the generation of the waves themselves4
 ,at the present moment1 our mode of    
generating ,hertzian waves involves a   
dissipation of energy in the form of the
 light and heat of the spark4 ,just as  
in the case of ordinary artificial      
illuminants1 such as lamps of various   

kinds1 we have to manufacture a large   
amount of ether radiation of long wave  
length1 which is of no use to us for    
visual purposes--in fact1 creating      
ninety-five per cent1 of dark and       
useless waves for every five per cent4  
of luminous or useful waves--so in      
connection with present methods of      
generating ,hertzian waves1 we are bound
 to manufacture by the discharge spark a
 large amount of light and heat rays    
which are not wanted1 in order to create
 the ,hertzian waves we desire4 ,it is  
impossible yet to state precisely what  
is the efficiency1 in the ordinary sense
 of the word1 of a ,hertzian wave       
radiator2 how much of the energy        
imparted to the aerial falls back upon  
it and contributes to the production of 
the spark1 and how much is discharged   
into the ether in the form of a wave4   
,nothing is more remarkable1 however1   
than the small amount of energy which1  
if properly utilised in electric wave   
making1 will suffice to influence a     

sensitive receiver at a distance of even
 one or two hundred miles4 ,suppose1 for
 instance1 that we charge a condenser   
consisting of a battery of ,leyden jars1
 having a capacity of one seventy-fifth 
of a microfarad1 to a potential of      
#ae1jjj volts2 the energy stored up in  
this condenser is then equal to #a4e    
joules1 or a little more than one       
foot-pound4 ,if this energy is          
discharged in the form of a spark five  
millimetres in length through the       
primary coil of an oscillation          
transformer1 associated with an aerial  
#aej feet in height1 the circuits being 
properly tuned by ,mr4 ,marconi's       
method1 then such an aerial will affect1
 as he has shown1 one of ,mr4 ,marconi's
 receivers1 including a nickel silver   
filings coherer tube1 at a distance of  
over two hundred miles over sea4        
,consider what this means4 ,the energy  
stored up in the ,leyden jars cannot all
 be radiated as wave energy by the      
aerial1 probably only half of it is thus

 radiated4 ,hence the impartation to the
 ether at any one locality of about half
 a foot-pound of energy in the form of a
 long ,hertzian wave is sufficient to   
affect sensitive receivers situated at  
any point on the circumference of a     
circle of #bjj miles radius described on
 the open sea4 ,hertzian wave telegraphy
 is sometimes described as being        
extravagant in power1 but1 as a matter  
of fact1 the most remarkable thing about
 it is the small amount of power really 
involved in conducting it4 ,on the other
 hand1 ,hertzian wave manufacture is not
 altogether a matter of power4 ,it is   
much more dependent upon the manner in  
which the ether is struck4 ,just as half
 an ounce of dynamite in exploding may  
make more noise than a ton of gunpowder1
 because it hits the air more suddenly1 
so the formation of an effective wave in
 the ether is better achieved by the    
right application of a small energy than
 by the wrong mode of application of a  
much larger amount4 ,if we translate    

this fact into the language of          
electronic theory1 it amounts simply to 
this4 ,it is the electron alone which   
has a grip of the ether4 ,to create an  
ether wave1 we have to start or stop    
crowds of electrons very suddenly4 ,if  
in motion1 their motion implies energy1 
but it is not only their energy which is
 concerned in the wave making1 but the  
acceleration1 positive or               
negative--i4e41 the quickness with which
 they are started or stopped4 ,it is    
possible we may discover in time a way  
of manufacturing long ether waves       
without the use of an electric spark1   
but at present we know only one way of  
doing this--viz41 by the discharge of a 
condenser1 and in the discharge of large
 condensers of very high potentials it  
is difficult to secure that extreme     
suddenness of starting the discharge    
which we can do in the case of smaller  
capacities and voltages4  ,how strange  
it is that the discharge of a ,leyden   
jar studied so profoundly by ,franklin1 

,henry1 ,faraday1 ,maxwell1 ,kelvin and 
,lodge should have become an electrical 
engineering appliance of great          
importance6  ,whilst there are many     
matters connected with the commercial   
aspect of ,hertzian wave telegraphy with
 which we are not here concerned1 there 
is one on which a word may properly be  
said4 ,the ability to communicate over  
long distances by ,hertzian waves is now
 demonstrated beyond question1 and even 
if all difficulties are not overcome at 
once1 it has a field of very practical  
utility1 and may even become of national
 importance4 ,under these circumstances1
 we may consider whether it is          
absolutely necessary to place the       
signalling stations so near the coast4  
,the greater facility of transmission   
over sea has already been discussed and 
explained1 but in time of war1 the masts
 and towers which are essential at      
present in connection with transmitting 
stations could be wrecked by shot or    
shell from an enemy's battleship at a   

distance of five or six miles out at    
sea1 and would certainly be done within 
territorial waters4 ,should not this    
question receive attention in choosing  
the location of important signalling    
stations8 ,for if they can1 without     
prejudice to their use1 be placed inland
 by a distance sufficient to conceal    
them from sight1 their value as a       
national asset in time of war might be  
greatly increased4  ,it has been often  
contended that whilst cables could be   
cut in time of war no one can cut the   
ether2 but wireless telegraph stations  
in exposed situations on high           
promontories1 where they are visible for
 ten to fifteen miles out at sea and    
undefended by any forts1 could easily be
 destroyed4 ,the great towers which are 
essential to carry large aerials are a  
conspicuous object for ten miles out at 
sea2 and a single well-placed shell from
 a six-inch gun would wreck the place   
and put the station completely out of   
use for many months4 ,hence if oceanic  

telegraphy is ever to be conducted in a 
manner in which the communication will  
be inviolable or1 at any rate1 not be   
capable of interruption by acts of war1 
the careful selection of the sites for  
stations is a matter of importance4 ,a  
small station consisting of a single    
#aej-;foot mast and a wooden hut can    
easily be removed or replaced1 but an   
expensive power station1 the mere aerial
 of which may cost several thousand     
pounds1 is not to be put up in a short  
time4#gf  ,meanwhile1 whatever may be   
the future achievements of this new     
supermarine wireless telegraphy         
conducted over long distances1 there can
 be no question as to its enormous      
utility and present value for           
intercommunication between ships on the 
ocean and ships and the shore4 ,at the  
present time1 there are some forty or   
more of the transatlantic ocean liners  
and many other ships equipped with this 
,hertzian wave wireless telegraph       
apparatus on the ,marconi system4       

,provided with this latest weapon of    
applied science1 they are able to chat  
with one another1 though a hundred miles
 apart on the ocean1 with the ease of   
guests round a dinner table1 to exchange
 news or make demands for assistance4   
,ships that pass in the night1 and speak
 each other in passing--     ,only a    
signal shown1 and a distant voice in the
 darkness2     ,so1 on the ocean of     
life1 we pass and speak one another1    
,only a look and a voice1 then darkness 
again1 and a silence4  ,abundant        
experience has been gathered to show the
 inexpressible value of this means of   
communication in case of accident1 and  
it can hardly be doubted that before    
long the possession of this apparatus on
 board every passenger vessel will be   
demanded by the public1 even if not made
 compulsory4 ,although the privacy of an
 ocean voyage may have been somewhat    
diminished by this utilisation of ether 
waves1 there is a vast compensation in  
the security that is thereby gained to  

human life and property by this latest  
application of the great energies of    
nature for the use and benefit of       
mankind4  ,,geo4 ,,tueker1 ,,printer1   
,,salisbury ,,court1 ,,fleet ,,street1  
,,london4  #a ,this series of articles  
is based on the ,cantor ,lectures       
delivered before the ,society of ,arts1 
,london1 in ,march1 #aijc4 ,the lectures
 were attended by many of the leading   
,british scientific men and electrical  
engineers1 and attracted wide attention 
as the most complete and authoritative  
statement hitherto made of wireless     
telegraphy4 ,in writing the articles for
 the ,popular ,science ,monthly1 the    
author has omitted advanced             
technicalities in order that the        
substance may be suitable for the       
general reader4--,,editor4  #b ,for a   
more detailed account of this           
hypothesis1 the reader is referred to an
 article by the present writer1 entitled
 ,the ,electronic ,theory of            
,electricity1 published in the ,popular 

,science ,monthly for ,may1 #aijb4  #c  
,see ,j4 ,j4 ,thomson1 ,recent          
,researches in ,electricity and         
,magnetism1 chap4 ,i41 p4 #af4  #d ,see 
,o4 ,heaviside1 ,electromagnetic        
,theory1 ,vol4 ,i41 p4 #ed4  #e         
,wiedemann's ,annalen1 #cf1 p4 #a1      
#ahhi2 or in his republished ,papers1   
,electric ,waves1 p4 #acg1 ,english     
translation by ,d4 ,e4 ,jones4  #f ,the 
fraction #g_/bb here denotes a stranded 
wire formed of seven strands1 each      
single wire having a diameter expressed 
by the number #bb on the ,british       
standard wire gauge4  #g ,g4 ,marconi1  
,syntonic ,wireless ,telegraphy1        
,journal of the ,society of ,arts1 ,vol4
 ,,xlix41 p4 #eja1 #aija4  #h           
,instruction for the manufacture of     
large induction coils may be obtained   
from a ,treatise on the ,construction of
 ,large ,induction ,coils1 by ,a4 ,t4   
,hare4 7,methuen  ,co41 ,london47  ,also
 see ,vol4 ,,ii4 of ,the                
,alternate-,current ,transformer1 by ,j4

 ,a4 ,fleming1 chap4 ,i4 7,the          
,electrician ,printing and ,publishing  
,co41 #a1 #b and #c1 ,salisbury-court1  
,fleet-street1 ,london1 ,e4,c47  #i ,see
 ,the ,alternate-,current ,transformer1 
by ,j4 ,a4 ,fleming4 ,vol4 ,i41 p4 #ahd4
  #aj ,du ,moncel states that           
,mac,gauley of ,dublin independently    
invented the form of hammer break as now
 used4 ,see ,the ,alternate-,current    
,transformer1 ,vol4 ,,ii4 chap4 ,i4 ,j4 
,a4 ,fleming4  #aa ,see ,professor ,j4  
,trowbridge1 ,on the ,induction ,coil   
,phil4 ,mag41 ,april1 #aijb ,vol4       
,,iii41 ,series #f1 p4 #cic4  #ab ,see  
,dr4 ,wehnelt's article in the          
,elektrotechnische ,zeitschrift1        
,january1 #ahii4  #ac ,see ,the         
,electrician1 ,vol4 ,,xlii41 #ahii1 pp4 
#gba1 #gbh1 #gca1 #gcb and #hda2        
communications from ,mr4 ,campbell      
,swinton1 ,professor ,s4 ,p4 ,thompson1 
,dr4 ,marchant1 the author and others2  
also p4 #hfd1 same volume1 for a leader 
on the subject2 also p4 #hgj1 letters by

 ,m4 ,blondel and ,professor ,e4        
,thomson4 ,see also ,the ,electrician1  
,vol4 ,,xliii41 p4 #e1 #ahii1 extracts  
from a ,paper by ,p4 ,barry2 ,comptes   
,rendus1 ,april1 #ahii4 ,see also the   
,electrical ,review1 ,vol4 ,,xliv41 p4  
#bce1 #ahii1 ,february #ag4  #ad ,see   
,the ,electrician1 ,vol4 ,,xlii41 #ahii4
  #ae ,for a discussion of the function 
of the condenser in an ordinary         
induction coil1 see ,the                
,alternate-,current ,transformer1 by ,j4
 ,a4 ,fleming4 ,vol4 ,,ii41 p4 #ea4  #af
 ,see ,lord ,rayleigh1 ,phil4 ,mag41    
,december1 #aija4  #ag ,it has sometimes
 been stated that the spark balls must  
be solid metal and no hollow1 but this  
is a fallacy1 and has been disproved by 
,mr4 ,c4 ,a4 ,chant4 ,see ,an           
,experimental ,investigation into the   
,skin ,effect in ,electrical            
,oscillators1 ,phil4 ,mag41 ,vol4       
,,iii41 ,sec4 #f1 p4 #dbe1 #aijb4  #ah  
,see ,proc4 ,roy4 ,soc41 ,london1       
,february #bc and ,april #ab1 #ahfj2 or 

reprint of ,papers on electrostatics and
 magnetism1 p4 #bdg4  #ai ,see ,phil4   
,mag41 ,august1 #aijb1 ,vol4 ,,iv41 p4  
#bbd1 #fth ,series4 ,mr4 ,jervis-,smith 
has also described an experiment to show
 how much the use of compressed air     
round a spark gap is of advantage in    
working an ordinary ,tesla coil4 ,in his
 ,british specification1 ,no4 #ab1jci of
 #ahif1 ,mr4 ,marconi had long          
previously mentioned the use of         
compressed air round the spark gap4  #bj
 ,this energy storage is at the rate of 
#dd foot-pounds per cubic foot of glass4
 ,this figure shows what a relatively   
small amount of energy is capable of    
being stored up in the form of electric 
strain in glass4 ,in the case of an air 
condenser1 it is only stored at the rate
 of #a foot-pound per cubic foot4  #ba  
,see ,british specification ,no4 #g1ggg 
of #aijj4--;,g4 ,marconi4 ,improvements 
in ,apparatus for ,wireless ,telegraphy4
  #bb ,that this number really does     
represent the order of this oscillation 

frequency in an aerial has been shown by
 ,c4 ,tissot1 ,comptes ,rendus1 #acb1 p4
 #gfc1 ,march #be1 #aija1 by photographs
 taken of the oscillatory spark of a    
,hertzian wave telegraphic transmitter4 
7,see ,science ,abstracts1 ,vol4 ,,iv41 
,abs4 #a1eah47 ,he found frequencies    
from #j4e million to #a4f million4  #bc 
,the term jigger is one of those slang  
terms which contrive to effect a        
permanent attachment to various arts and
 crafts4 ,similarly1 the word booster is
 now used for a step-up or              
voltage-raising transformer or dynamo1  
inserted in series with an electric     
supply main4 ,the word boost is a slang 
term signifying to raise or lift up4 ,to
 give a real good boost is an expression
 for lending a helping hand4 ,the term  
jigger1 in the same manner1 is an       
adaptation of a seaman's term for       
hoisting tackle or lift4  #bd ,the earth
 itself probably only conducts          
electrolytically4 ,all such materials as
 sand1 clay1 chalk1 etc41 and most      

surface soils are fairly good insulators
 when very dry1 but conduct in virtue of
 moisture present in them4  #be ,the    
,electrician1 ,vol4 ,,xl41 p4 #hf       
7leader74  #bf ,british ,patent         
,specification1 ,c4 and ,s4 ,a4 ,varley1
 ,no4 #afe1 #ahff4  #bg ,see also       
,journal de ,physique1 ,vol4 ,v41 p4    
#egc1 #ahhf4  #bh ,see ,comptes ,rendus1
 ,vol4 ,,cxi41 p4 #ghe2 ,vol4 ,,cxii41  
p4 #aab1 #ahia2 or ,la ,lumiere         
,electrique1 ,vol4 ,,xl41 pp4 #cja1     
#ejf1 #ahia2 or ,the ,electrician1 ,vol4
 ,,xxvii41 #ahia1 pp4 #bba1 #ddh4  #bi  
,see ,the ,electrician1 ,vol4 ,,xxix41  
#ahib1 pp4 #cig and #dcb4  #cj ,mr4 ,w4 
,b4 ,croft1 ,proc4 ,phys4 ,soc41 ,vol4  
,,xii41 p4 #dba4 ,report of meeting on  
,october #bg1 #ahic4  #ca ,see          
,professor ,minchin1 ,proc4 ,phys4      
,soc41 ,november #bd1 #ahic2 or ,the    
,electrician1 ,vol4 ,,xxxii41 #ahic1 p4 
#abc4 ,see also ,professor ,minchin1    
,phil ,mag41 ,january1 #ahid1 ,vol4     
,,xxxvii41 p4 #ij1 ,on the ,action of   

,electromagnetic ,radiation on ,films   
containing ,metallic ,powders4  #cb     
,this lecture was afterwards published  
as a book1 the first edition bearing the
 same title as the lecture--viz41 ,the  
,work of ,hertz and ,some of ,his       
,successors4 ,in the second edition1    
published in #ahih1 an appendix was     
added 7p4 #ei7 containing ,the ,history 
of the ,coherer ,principle1 and the     
original title of the work had prefixed 
to it ,signalling ,without ,wires4  #cc 
,see ,the ,electrician1 ,vol4 ,,xxvii41 
p4 #bbb1 #ahia4 ,e4 ,branly1 ,variations
 of ,conductivity under ,electrical     
,influence4  #cd ,see ,the ,electrician1
 ,vol4 ,,xl41 p4 #ij4 ,sir ,oliver      
,lodge1 ,the ,history of the ,coherer   
,principle4  #ce ,see ,professor ,e4    
,branly1 ,a ,sensitive ,coherer1        
,comptes ,rendus1 ,vol4 ,,cxxxiv41 p4   
#a1ahg1 #aijb2 or ,science ,abstracts1  
,vol4 ,v41 p4 #heb1 #aijb4  #cf ,this   
device of making the inter-electrode gap
 in a tubular filings coherer           

wedge-shaped has been patented again and
 again by various inventors4 ,see       
,german patent ,no4 #aaf1aac1 ,class    
#ba;a1 #aijj4 ,it has also been claimed 
by ,m4 ,tissot4  #cg ,see ,the          
,electrician1 ,vol4 ,,xxvii41 #ahia1 p4 
#ddh4  #ch ,journal of the ,russian     
,physical and ,chemical ,society1 ,vol4 
,,xxviii41 ,division of ,physics1 ,part 
,i41 ,january1 #ahif4  #ci ,see ,british
 ,patent ,specification ,no4 #ab1jci1   
,june #b1 #ahif4  #dj ,british ,patent  
,specification ,no4 #ai1gaj of #ahii4   
#da ,comptes ,rendus41 ,vol4 ,,cxxviii41
 p4 #a1bbe1 #ahhi2 ,science ,abstracts1 
,vol4 ,,ii41 p4 #eba4  #db ,il ,nuovo   
,cimento1 ,vol4 ,x41 p4 #bgi1 #ahii4    
#dc ,wied ,ann41 ,vol4 ,,lxviii41 p4    
#eid1 #ahii2 ,science ,abstracts1 ,vol4 
,,ii41 p4 #geg4  #dd ,comptes ,rendus1  
,vol4 ,,cxxx41 p4 #ijb1 #aijj2 ,science 
,abstracts1 ,vol4 ,,iii41 p4 #fae4  #de 
,see ,proc4 ,roy4 ,soc41 ,london1 ,vol4 
,,lxxi41 p4 #djb4  #df ,see ,report by  
,capt4 ,quintino ,bonomo1 ,telegrafia   

,senza ,fili1 ,rome1 #aijb2             
,l',elettricista1 ,ser4 ,,ii41 ,vol4    
,i41 pp4 #aah1 #agc4  #dg ,see ,royal   
,institution1 ,friday evening discourse1
 by ,mr4 ,marconi1 ,june #ac1 #aijb2    
also ,the ,electrician1 ,vol4 ,,xlix41  
p4 #dij2 also a letter to ,the ,times of
 ,july #c1 #aijb1 by the ,marchese      
,luigi ,solari4  #dh ,see ,u4,s4,a4     
,patent ,specification ,no4 #gjj1afa1   
,may #bd1 #aijj4  #di ,see ,e4 ,marx1   
,phys4 ,zeitschrift1 ,vol4 ,,ii41 p4    
#bdi2 ,science ,abstracts1 ,vol4 ,,iv41 
p4 #dga4 ,see also ,german ,patent      
,specification ,no4 #aba1ffc1 ,class    
#ba;a4  #ej ,see ,the ,scientific       
,writings of ,professor ,joseph ,henry4 
#ea ,phil4 ,trans4 ,roy4 ,soc41 ,london1
 #ahig1 ,vol4 ,,clxxxix4,a1 p4 #a4  #eb 
,see ,proc4 ,roy4 ,soc41 ,london1 ,june 
#ab1 #aijb4 ,note on a ,magnetic        
,detector for ,electric ,waves which can
 be employed as a ,receiver for ,space  
,telegraphy1 by ,g4 ,marconi4  #ec ,see 
,u4,s4,a4 ,patent ,specification ,no4   

#gaf1jjj1 ,application of ,july #e1     
#aija4  #ed ,see the ,electrical        
,review1 ,vol4 ,,xliv41 #ahii1 ,may #bf2
 ,wied ,ann41 ,vol4 ,,lxviii41 p4 #ib2  
or ,german ,patent ,specification ,no4  
#ajg1hdc4  #ee ,u4,s4,a4 ,patent        
,specification ,no4 #gjf1gdb1 #aijb4    
#ef ,see ,british ,patent               
,specification1 ,g4 ,marconi1 ,no4      
#ab1jci1 ,june #b1 #ahif4  #eg ,see ,g4 
,marconi1 ,british ,patent              
,specification ,no4 #ab1cbf1 of ,june   
#a1 #ahih4  #eh ,see the ,electrical    
,review1 ,september #bf1 #aijb1 ,vol4   
,,li41 p4 #edc4  #ei ,there is a good   
deal of contradiction between various   
inventors on this point1 some saying    
that earthed aerials obviate atmospheric
 electrical disturbances1 and others    
that insulated aerials are in this      
respect superior4 ,the truth appears to 
be that1 neither form is absolutely free
 from risk of disturbance by this cause4
  #fj ,the capacity of an electrical    
circuit corresponds to the elastic      

pliability1 or what is commonly called  
the elasticity1 of a material substance1
 and the inductance to mass or inertia4 
,hence capacity and inductance are      
qualities of an electric circuit which  
are analogous to the elasticity and     
inertia of such a body as a heavy       
spring4  #fa ,see ,cantor ,lectures1 on 
,electrical ,oscillations and ,electric 
,waves1 delivered before the ,society of
 ,arts1 ,london1 ,november #bf1         
,december #d1 #aj1 #ag1 #aijj4 ,lecture 
,i41 p4 #ab1 of reprint4  #fb ,a fuller 
account of these experiments was given  
by the author in a letter to the ,london
 ,times published on ,april #ad1 #aijc4 
#fc ,see ,journal of the ,society of    
,arts1 ,vol4 ,,xlix41 p4 #eje4 ,syntonic
 ,wireless ,telegraphy1 by ,g4 ,marconi4
  #fd ,see ,german ,patent              
,specifications1 ,class #ba;a1 ,no4     
#g1deb of #aijj1 and also ,no4 #h1jhg of
 #aija4  #fe ,see ,german ,patent       
,specification1 ,class #ba;a1 ,no4      
#g1dih of #aijj1 applied for ,november  

#i1 #aijj4 ,the above-mentioned patent  
is subsequent in date to ,mr4 ,marconi's
 experiments on the same subject4  #ff  
,see ,the ,electrician1 ,january #ah1   
#aijj1 ,vol4 ,,xlvi41 p4 #dge4 ,also    
reprint of a ,paper of ,professor ,a4   
,slaby1 ,abgestimmte und mehrfache      
,funkentelegraphie4  #fg ,see ,british  
,specification ,no4 #aa1cdh of #aija4   
#fh ,see ,comptes ,rendus1 ,may #ba1    
#aijj2 ,rapports du ,congres            
,international d',electricite1 ,paris1  
#aijj1 p4 #cda4  #fi ,see ,the          
,electrician1 ,vol4 ,,xlvi41 p4 #egc1   
,february #h1 #aija4  #gj ,see ,the     
,electrician1 ,vol4 ,l41 p4 #dah1       
,january #b1 #aijc4  #ga ,see ,mr4      
,marconi's ,friday evening discourse at 
the ,royal ,institution1 ,june #ac1     
#aijb2 also ,the ,electrician1 ,vol4    
,,xlix41 p4 #cij4  #gb ,see ,proc4 ,roy4
 ,soc41 ,june #ab1 #aijb4 ,a ,note on   
the ,effect of ,daylight upon the       
,propagation of ,electromagnetic        
,impulses over ,long ,distances1 by ,g4 

,marconi4  #gc ,see ,phil4 ,mag41 ,vol4 
,,iv41 p4 #bec1 ,series #f1 ,august1    
#aijb4 ,j4 ,j4 ,thomson1 ,on ,some      
,consequences of the ,emission of       
,negatively-electrified ,corpuscles by  
,hot ,bodies4  #gd ,the opinion that    
ionisation of the air by sunlight is a  
cause of obstruction to ,hertzian waves 
propagated over long distances has also 
been expressed by ,mr4 ,j4 ,e4 ,taylor4 
,see ,proc4 ,roy4 ,soc41 ,vol4 ,,lxxi41 
p4 #bbe1 #aijc4 ,characteristics of     
,earth ,current ,disturbances and their 
,origin4  #ge ,see ,proc4 ,roy4 ,soc41  
,may #ae1 #aijb4 ,on ,some ,phenomena   
affecting the ,transmission of ,electric
 ,waves over the ,surface of the ,sea   
and ,earth1 by ,captain ,h4 ,b4         
,jackson1 ,r4,n41 ,f4,r4,s4  #gf ,mr4   
,marconi has informed the writer that   
these strategic questions have received 
attention in selecting the sites for    
large ,marconi power stations in ,italy4
                    99       99       99
       99       99   ,detailed          

,transcriber's ,notes   ,the text has   
been made to match the original text as 
much as possible  retaining all apparent
 printer's errors and inconsistencies4  
,the  following1 detail the apparent    
printer's errors etc4 identified in  the
 original text4   ,variation in         
spelling1 ,strasburg and ,strassburg for
 ,strasbourg4   ,there are a number of  
inconsistencies in hyphenation present  
in the  original text4 ,those concerned 
with the variation between one word or  
a hyphenated word are detailed below4   
,those concerned with the  variation    
between multiple words and hyphenated   
words are too  numerous to detail       
individually4   ,inconsistent           
hyphenation of word1 'anti-node' and    
'antinode' both  present in original    
text4   ,inconsistent hyphenation of    
word1 'electro-dynamic' and             
'electrodynamic' both present in        
original text4   ,inconsistent          
hyphenation of word1 'horse-shoe' and   
'horseshoe' both  present in original   

text4   ,inconsistent hyphenation of    
word1 'over-blowing' and 'overblowing'  
both present in original text4   ,page  
#e1 possible printer's error1 a for at1 
'consisting when a rest'4   ,page #f1   
printer's error1 comma rather than full 
stop at end of  sentence1 'ether        
constituting electric radiation1'4      
,page #aj1 printer's error1 millmetre   
for millimetre1 'three thousand  volts  
per millmetre1'4   ,page #ac1 possible  
printer's error1 set for sets1 'there   
are three set  of phenomena'4   ,page   
#ac1 printer's error1 duplicate word1   
'detached and and travel  away4'4       
,page #ac1 brackets added to in-line    
equation to aid clarity1 ',f            
7#c_/h7;,,cv#b_/ajf4'4   ,page #ac1 both
 equations originally multi-line        
fraction1 rendered into  one line for   
clarity4   ,page #ae1 both equations    
originally multi-line fraction1 rendered
 into  one line for clarity4   ,page    
#bb1 printer's error1 correponding for  
corresponding1  'correponding to this   

frequency'4   ,page #bb1 printer's      
error1 consist for consists1 'due to    
,braun1 consist  of attaching'4   ,page 
#bd1 printer's error1 one-hundreth for  
one-hundredth1 'capacity of             
one-hundreth of a microfarad1'4   ,page 
#bh1 printer's error1 missing full stop 
at end of sentence added1  'in the case 
of the hammer break4'4   ,page #cc1     
printer's error1 supppse for suppose1   
',let us supppse'4   ,page #dd1 equation
 originally multi-line fraction1        
rendered into one  line for clarity4    
,page #df1 printer's error1 comma rather
 than full stop at end of  sentence1 'to
 the transmitting aerial1'4   ,page #dh1
 possible printer's error1 alterations  
for alternations1  'alterations of      
electric strain'4   ,page #ed1 printer's
 error1 ,banly for ,branly1 'proved that
 in a ,banly  tube1'4   ,page #ef1      
variation in spelling1 unsensitive for  
insensitive1 'wounded  and              
unsensitive4'4   ,page #ei1 possible    
printer's error1 sensive for sensitive  

'to work a  sensive recording           
apparatus'4   ,page #ei1 possible       
printer's error1 arragement for         
arrangement1 'most  interesting         
arragement'4   ,page #fa1 printer's     
error1 missing letter i1 'as shown n    
,fig4 #ah1'4   ,page #gj1 equation      
originally multi-line fraction1 rendered
 into one  line for clarity4   ,page    
#ga1 printer's error1 osciilating for   
oscillating1 'to that of the            
osciilating circuit'4   ,page #ga1      
printer's error1 impluse for impulse1   
'the period of that  impluse'4   ,page  
#gd1 possible printer's error1 extra    
comma in date1 'on ,may1 #ag1  #aija4'4 
,page #gf1 printer's error1 arangements 
for arrangements1 'variation of  the    
above arangements'4   ,page #gg1        
printer's error1 systonic for syntonic1 
'the systonic  transmitting'4   ,page   
#hf1 printer's error1 interpositon for  
interposition1 'effect of  the          
interpositon of land'4   ,page #hg1     
printer's error1 signaling for          

signalling1 'the usual  maximum         
signaling'4   ,footnote #ag1 printer's  
error1 missing letter t1 'must be solid 
metal and no hollow1'4   ,footnote #ca1 
printer's error1 missing full stop after
 abbreviation1  ',phil ,mag4'4          
,footnote #da1 printer's error1 extra   
full stop after reference1  ',comptes   
,rendus4'4