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LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

GIFT  OF 

MRS.  MARTHA  E.   HALLIDIE. 
Class 


SOME  OPINIONS   OF  THE   PRESS, 


"  Mr  Fahie  is  doing  good  work  as  the  historian  of  telegraphy,  but 
this  book  is  more  than  a  history,  in  that  it  gives  some  graphic  descrip- 
tions of  the  recent  investigations  of  Hughes,  Hertz,  Preece,  Lodge, 
Marconi,  and  others." — The  Electrical  Engineer. 

"  Both  the  scientific  and  general  reader  will  find  Mr  Fahie's  'History 
of  Wireless  Telegraphy '  a  very  excellent  book  on  a  most  interesting 
subject."— The  Electrician. 

"  This  book  contains  all  that  is  worth  knowing  about  the  history  of 
wireless  telegraphy.  The  author  has  spared  no  pains  in  collecting 
the  materials,  and  we  should  think  that  very  little  that  is  of  any 

importance  has   been  overlooked Everybody   interested   in   the 

subject  should  read  Mr  Fahie's  book." — The  Electrical  Review. 

"  Contains  matter  of  great  interest,  and  is  written  by  an  authority 

on  the  history  of  telegraphy The  book  has  a  collection  of  small 

but  excellent  portraits  of  'The  Arch -builders  of  Wireless  Teleg- 
raphy.'  The  appendices  are  worthy  of  the  most  careful  reading 

in  the  light  of  recent  events.  In  fact,  the  book  teems  with  interesting 
matter  from  cover  to  cover. " — Nature. 

"An  interesting,  timely,  and  valuable  volume  on  the  new  art,  full 

of  references  to  inventors   in    this  field Should  be  ordered  at 

once." — Electrical   World  and  Engineer,  New  York. 

"  To  one  at  all  interested  in  the  subject  the  book  makes  over  300 
pages  of  valuable  reading.  The  author  has  gone  to  a  great  amount 
of  trouble  in  obtaining  details  of  the  work  of  the  earlier  experi- 
menters."— Science  Gossip. 

"  In  his  desire  to  write  a  popular  treatise  Mr  Fahie  has  succeeded 
admirably The  book  will  have  a  place  on  the  shelves  of  all  inter- 
ested in  the  subject." — Industries  and  Iron. 

"  Much  credit  is  due  to  the  author  for  industry  in  collecting  and 
ability  in  presenting  his  facts  in  an  eminently  readable  form.  An 
attractive  subject  is  on  the  whole  ably  and  most  successfully  treated, 
and  we  have  no  hesitation  in  strongly  recommending  this  handsome 
volume  to  our  readers." — The  Surveyor. 

"  An  extremely  able  and  comprehensive  treatise  on  the  development 

of  wireless  telegraphy Perhaps  its  greatest  charm  is  that  lay 

readers  can  from  beginning  to  end  not  only  understand  but  enjoy 
the  careful  and  instructive  record  of  this  great  development  of  the 
century. " — Transport. 

' '  We  welcome  this  book.  It  is  lucid,  comprehensive,  and  accurate, 
and  will  no  doubt  receive  the  recognition  to  which  its  merits  entitle 
it." — Feilderis  Magazine. 


* '  With  Mai-coni's  successes  fresh  in  everybody's  remembrance  Mr 
Fahie's  '  History  of  Wireless  Telegraphy  '  is  published  at  an  opportune 
moment.  Some  of  his  readers  will  probably  be  surprised  to  discover 
that  the  idea  is  almost  as  old  as  electric  telegraphy  itself." — The 
Times. 

"  A  succinct  and  well-informed  account  of  the  origin  and  develop- 
ment of  the  idea. " — Literature. 

"The  record  presented  by  Mr  Fahie  is  interesting  and  instructive, 
and  his  book  should  be  read  by  all  who  are  interested  in  the  develop- 
ment of  the  latest  idea  in  science." — Illustrated  London  News. 

"Students  of  electrical  science  cannot  do  better  than  read  Mr 
Fahie's  book,  which  is  well  illustrated  and  has  a  good  index." — The 
Morning  Post. 

11  Mr  Fahie  is  to  be  thanked  for  supplying  an  account  so  full  and 
so  accurate  of  the  gradual  development  of  a  discovery  which  may 
play  an  important  part  in  the  sociology  of  the  immediate  future." — 
The  Globe. 

' '  Of  the  practical  introduction  of  wireless  telegraphy  Mr  Fahie's 
new  book  gives  a  clear  and  interesting  account." — The  Spectator. 

"For  most  of  us  this  compendium  of  information  on  aerial  teleg- 
raphy will  be  full  of  interesting  surprises The  reputation  and 

career  of  the  writer  are  sufficient  guarantees  for  his  ability  to  deal 
with  the  question,  and  that  he  has  chosen  to  do  so  in  so  popular  a 
form  is  a  matter  of  congratulation  for  the  general  public." — St  James's 
Gazette. 

"  A  succinct  and  well-informed  account  not  only  of  Marconi's 
system  but  of  other  systems  and  of  many  guesses." — (Edinburgh) 
Scotsman. 

"To  the  reader  with  a  fair  smattering  of  electrical  science  Mr 
Fahie's  book  will  be  very  informing,  while  as  a  work  of  reference  and 
a  text-book  it  ought  to  survive  through  many  editions." — Birming- 
ham Daily  Post. 

\  "  Mr  Fahie's  account  of  the  rise  and  progress  of  the  discoveries  is 
excellent,  and  not  too  technical  for  an  ordinary  educated  reader." — 
Bristol  Times. 

"  The  author — he  is  more  than  a  compiler — has  deserved  well  for 
bringing  forward  the  names  of  those  worthy  pioneers  but  for  whose 
skill  and  perseverance  the  successful  outcome  of  the  methods  of 
Preece,  Willoughby  Smith,  and  Marconi  would  have  been  an  impos- 
sibility  The  volume  is  one  that  ought  to  be  found  in  the  library 

of  every  engineer  and  electrician." — North  British  Daily  Matt. 

"Distinctly  a  popular  treatise Will  be  found  indispensable  for 

an  understanding  of  what  is  certain  to  be  one  of  the  great  fields  of 
scientific  progress  in  the  future." — Aberdeen  Free  Press. 

"  Those  interested  in  this  modern  development  of  practical  science 
should  not  miss  this  book." — The  Bookman. 


A    HISTORY 


OF 


WIRELESS    TELEGRAPHY 


(*  *  e  e  c  6 


WIU.OUCH0Y    SMiTH 

THE   ARCH-BUILDERS   OF  WIRELESS   TELEGRAPHY 


A    HISTORY 

OF 

WIRELESS     TELEGRAPHY 

INCLUDING   SOME    BARE-WIRE    PROPOSALS 
FOR   SUBAQUEOUS   TELEGRAPHS 


BY 


J.     J.    FAHIE 
v) 

MF.MBRR  OK  THE   INSTITUTION  OF  ELECTRICAL  ENGINEERS,   LONDON,    AND  OF 
THK   SOC1ETE   INTRRNATIONALE   DKS   ELECTRIC!  ENS,    PARIS; 

AUTHOR   OF 
*A    HISTORY   OK   ELECTRIC   TELEGRAPHY    TO  THK   YEAR   1837,'    ETC. 


WITH  FRONTISPIECE  AND  ILLUSTRATIONS 


SECOND    EDITION,    REVISED 


WILLIAM    BLAOKWOOD    AND    SONS 

EDINBURGH    AND    LONDON 

MCMI 


All  Jliyltts  reserved 


HALLIDIE 

"  Every  student  of  science  should  be  nn  antiquary  in  liis 
subject."— CLERK-MAXWELL. 


Betofcatefc 


TO 


SIK  WILLIAM   II.   PEEECE,   K.C.B,   F.E.S., 

Past  President,  Institution  of  Electrical  Engineers ; 
President,  Institution  of  Civil  Engineers, 

&c.,  &c., 

The  First  Constructor  of  a  Practical 
Wireless  Telegraph, 

AS   A   SLIGHT   TOKEN   OF   ESTEEM   AND   FRIENDSHIP, 
AND    IN    ACKNOWLEDGMENT    OF    MANY 

KINDNESSES 
EXTENDING   OVER   MANY  YEARS. 


99004 


PREFACE  TO  SECOND  EDITION. 


FROM  the  fact  that  two  impressions  of  this  work  have  been 
sold  out  in  fifteen  months  and  that  a  second  edition  is  now 
called  for,  the  author  is  glad  to  think  that  he  has  met  a 
want,  and,  judging  by  the  press  notices,  has  met  it  in  a 
satisfactory  manner. 

^While  acknowledging  with  thanks  the  numerous  and, 
with  one  exception,  altogether  favourable  reviews  of  his 
book,  the  author  begs  leave  to  notice  two  objections  which 
have  been  advanced  by  more  than  one  of  his  critics. 

Firstly,  it  has  been  thought  that  a  history  of  wireless 
telegraphy  now  is  premature — that  the  subject  is  still  in 
a  more  or  less  embryonic,  or  at  least  infantile,  stage,  and 
that  the  time  for  writing  its  history  has  not  yet  come. 
But  a  beginning  has  to  be  made  at  some  time,  and  as  well 
now  as  later,  and  for  this  reason :  While  (as  stated  in  the 
Preface  to  the  first  edition)  the  book  is  intended  to  be  a 
popular  account  of  the  origin  and  progress  of  the  subject, 
the  author  thought  that  it  would  also  be  useful  to  students 
arid  inventors,  as  showing  them  what  has  been,  so  far,  dono 


Vlll  PREFACE  TO   SECOND   EDITION. 

or  attempted,  so  that  they  may  not  waste  their  ingenuity  on 
ways  and  means  that  have  already  been  exploited. 

Secondly,  ifc  has  been  objected  that  there  is  much  in 
the  book — especially  in  the  First  Period — that  might  be 
omitted,  or  still  further  condensed.  But  here  again  the 
author  had  in  view  the  requirements  of  the  inventive 
reader,  for  whom  the  crudities  and  failures  of  previous 
experimenters  are  in  their  way  as  instructive  as  their 
successes 

In  this  new  edition  he  has  made  some  alterations  and 
additions  (chiefly  in  the  pages  dealing  with  the  Marconi 
system),  with  a  view  of  (1)  correcting  inaccuracies  of  ex- 
pression in  some  places,  and  making  the  meaning  more 
clear  in  others  ;  (2)  bringing  out  more  some  points  of  the 
theory  and  practice  of  Hertzian  -  wave  telegraphy  ;  and 
(3)  bringing  up  to  date  the  record  of  Mr  Marconi's  public 
demonstrations. 

A  new  and  fuller  index  is  appended,  in  which  every 
subject  is  noted  both  under  the  authors'  names  and  under 
the  subjects  themselves.  This  should  make  easy  the 
reader's  search  for  any  matter  that  may  specially  interest 
him. 

In  the  way  of  practical  applications  of  wireless  teleg- 
raphy since  the  first  edition  was  published  in  October 
1899,  Sir  William  Preece's  system  has  found  new  employ- 
ment, as  mentioned  at  p.  160.  As  regards  the  Hertzian- 
wave  form,  we  have  many  new  experimenters  in  the  field, 
whose  "  inventions,"  although  generally  said  to  be  unlike 
Marconi's,  seem  to  differ  from  it  chiefly  in  points  of  con- 
structive detail ;  many  new  demonstrations  by  Marconi  and 


PREFACE   TO    SECOND    EDITION.  ix 

his  imitators  of  the  value  of  their  system  or  systems,  which, 
within  limits,  nobody  contests ;  many  paragraphs  in  the 
newspapers  as  to  what  each  one  is  going  to  do ;  but  so  far 
as  actual  installations  under  the  rough-and-tumble  con- 
ditions of  everyday  working,  it  must  be  confessed  that 
progress  has  been  slow — disappointingly  so  to  some  people, 
Sir  William  Preece,  for  instance,  who  is  "getting  tired 
of  wireless  telegraphy,"  and  asks  "  where  is  there  at  present 
a  single  circuit  worked  commercially  on  a  practical  system 
of  wireless  telegraphy1?" 

Well,  the  position  is  not  so  bad  as  Sir  William  would 
have  us  infer.  To  begin  with,  there  is  no  longer  any 
question  of  its  value  to  governments  for  naval  and  military 
purposes,  or  of  its  commercial  value  for  outlying  islands, 
lightships,  lighthouses,  and  for  shipping  generally.  To 
have  thus  convinced  the  general  public,  in  the  short 
period  of  four  years,  of  the  soundness  of  its  scientific  basis 
and  of  its  practical  utility  is  no  slight  achievement,  and  is 
all  in  the  way  of  progress.  Then,  as  a  matter  of  fact,  Mr 
Marconi's  system,  or  some  modification  of  it,  lias  been 
adopted  in  the  navies  of  all  the  great  Powers,  and  on  some 
Germairand  Belgian  trading  vessels.  That  it  has  not  yet 
been  employed  on  British  vessels  of  the  same  kind  is  not 
entirely  Mr  Marconi's  fault,  but  seems  more  to  be  due  to 
official  obstacles. 

Then  again,  in  May  of  last  year,  the  Marconi  apparatus 
was  installed  at  Borkum,  Germany,  on  a  semi-commercial 
basis  ('  Electrician,'  July  20,  p.  488),  and  about  the  same 
time  it  was  introduced  into  Hawaii  as  a  permanent  means 
of  intercommunication  between  the  five  islands  of  the  group 


X  PREFACE   TO   SECOND   EDITION. 

('Electrician,'  March  2,  p.  680).  Quite  recently  a  Marconi 
station  has  been  established  at  La  Panne  (Belgium),  between 
Ostend  and  Dunkirk,  and  about  61  miles  from  Dover. 
The  Princess  Clementine,  one  of  the  Belgian  mail  packets 
running  between  Ostend  and  Dover,  has  also  been  fitted 
up,  and  keeps  up  communication  with  La  Panne  in  her 
daily  trips  across  channel.  Not  only  this,  but  wireless 
messages  have  been  exchanged  between  the  ship  at  Dover 
and  the  Marconi  station  at  Dovercourt,  near  Harwich,  a 
distance  of  over  80  miles  of  sea  and  land  (London  daily 
papers,  November  5-10).  Progress,  therefore,  there  has 
been — slow  perhaps,  but  solid  and,  all  things  considered, 
satisfactory.  And  now  we  seem  to  be  on  the  eve  of 
further  extensions,  as  to  which  those  interested  will  find 
some  indication  in  the  addresses  of  the  Marconi  Company's 
chairman  reported  in  the  '  Electrician,'  March  2,  August  3, 
and  December  21  of  last  year. 

January  1901. 


PREFACE  TO  FIRST  EDITION 


EARLY  in  1897  there  was  a  great  flutter  in  the  dove-cotes 
of  telegraphy,  and  holders  of  the  many  millions  of  telegraph 
securities,  and  those  interested  in  the  allied  industries, 
began  to  be  alarmed  for  the  safety  of  their  property. 
Mysterious  paragraphs  about  the  Kew,  Wireless,  or  Space 
Telegraphy,  as  it  was  variously  called,  kept  appearing  in 
the  papers  ;  and  the  electrical  profession  itself — certainly 
some  leading  members  of  it — seemed  disposed  to  accept 
implicitly  the  new  marvels,  without  the  grain  of  salt  usual 
and  proper  on  such  occasions. 

In  a  lecture  on  Submarine  Telegraphy  at  the  Imperial 
Institute  (February  15,  1897),  Professor  Ayrton  said:  "I 
have  told  you  about  the  past  and  about  the  present.  What 
about  the  future  ?  Well,  there  is  no  doubt  the  day  will 
come,  maybe  when  you  and  I  are  forgotten,  when  copper 
wires,  gutta-percha  coverings,  and  iron  sheathings  will  be 
relegated  to  the  Museum  of  Antiquities.  Then,  when  a 
person  wants  to  telegraph  to  a  friend,  he  knows  not  where, 
he  will  call  in  an  electro-magnetic  voice,  which  will  be 


Xll  PREFACE   TO    FIRST   EDITION. 

hoard  loud  by  him  who  has  the  electro-magnetic  ear,  but 
will  be  silent  to  every  one  else.  He  will  call,  '  Where  are 
you  1 '  and  the  reply  will  come,  '  I  am  at  the  bottom  of  the 
coal-mine,'  or  *  Crossing  the  Andes,'  or  '  In  the  middle  of 
the  Pacific ' ;  or  perhaps  no  reply  will  come  at  all,  and  he 
may  then  conclude  the  friend  is  dead." 

Soon  after,  in  the  course  of  a  debate  in  the  House  of 
Commons  (April  2,  1897)  on  the  Telephone  monopoly,  one 
of  the  speakers  said  :  "  It  would  be  unwise  on  the  part  of 
the  Post  Office  to  enter  into  any  very  large  undertakings  in 
respect  of  laying  down  telephone  wires  until  they  had  as- 
certained what  was  likely  to  be  the  result  of  the  Eontgen 
form  of  telegraph,  which,  if  successful,  would  revolutionise 
our  telephonic  and  telegraphic  systems." 

When  cautious  men  of  science  spoke,  or  should  I  not 
say  dreamt  thus,  and  when  sober  senators  accepted  the 
dream  as  a  reality  and  proceeded  to  legislate  upon  it,  we 
can  imagine  the  ideas  that  were  passing  in  the  minds  of 
those  of  the  general  public  who  gave  the  subject  a  thought. 
Well,  two  years  and  more  have  now  elapsed,  and  the  un- 
bounded potentialities  of  the  new  telegraphy  have  been 
whittled  down  by  actual  experiment  to  small  practical 
though  still  very  important  proportions;  and  so,  those 
interested  in  the  old  order  can  sleep  in  peace,  and  can 
go  on  doing  so  for  a  long  time  yet  to  come. 

Having  in  the  course  of  many  years'  researches  in  electric 
lore  collected  a  mass  of  materials  on  this  subject — for  the 
idea  embodied  in  the  new  telegraphy  is  by  no  means  new — 
and  having  been  a  close  observer  of  its  recent  and  startling 
developments,  I  have  thought  that  a  popular  account  of  its 


PKEFACE   TO   FIRST   EDITION.  xiii 

origin  and  progress  would  not  now  be  uninteresting.  This 
I  have  accordingly  attempted  in  the  following  pages. 

At  an  early  stage  in  the  evolution  of  our  subject,  objec- 
tion was  taken  to  the  epithet  Telegraphy  without  Wires, 
or,  briefly,  Wireless  Telegraphy,  as  a  misnomer  (e.g.,  the 
*  Builder/  March  17,  1855,  p.  132),  and  in  recent  times 
the  objection  has  been  repeated.  Induction,  Space,  and 
Ethereal  Telegraphy  have  been  suggested,  but  though 
accurate  for  certain  forms,  they  are  not  comprehensive 
enough.  A  better  name  would  be  Telegraphy  without 
Connecting  Wires,  which  has  also  been  suggested,  but  it  is 
too  cumbrous — an  awkward  mouthful.  Pending  the  dis- 
covery of  a  better  one,  I  have  adhered  to  the  original 
designation,  Wireless  Telegraphy,  which  actually  is  the 
popular  one,  and  for  which,  moreover,  I  have  the  high 
sanction  of  her  Majesty's  Attorney-General. 

In  the  course  of  a  discussion  on  Mr  (now  Sir  Wm.) 
Preece's  paper  on  Electric  Signalling  without  Wires 
('  Journal  Society  of  Arts,'  February  23,  1894),  Sir 
Ixichard  Webster  laid  down  the  law  thus :  "I  think  the 
objection  to  the  title  of  the  paper  is  rather  hypercritical, 
because  ordinary  people  always  understand  telegraphing  by 
wire  as  meaning  through  the  wire,  going  from  one  station 
to  the  other;  and  these  parallel  wires, .not  connected, 
would  rather  be  looked  upon  as  parts  of  the  sending  and 
receiving  instruments.  I  hope,  therefore,  that  the  same 
name  will  be  adhered  to  in  any  further  development 
of  the  subject."  If  thus  the  name  be  allowable  in 
Preece's  case  where,  to  bridge  a  space  of,  say,  one  mile, 
two  parallel  wires,  each  theoretically  one  mile  long,  are 


XIV  PREFACE   TO   FIRST  EDITION. 

requisite,  or  double  the  amount  required  in  the  old  form 
of  telegraphy,  it  cannot  be  objected  to  in  any  of  the  other 
proposals  which  are  described  in  these  pages,  certainly 
not  to  the  Marconi  system,  where  a  few  yards  of  wire 
at  each  end  suffice  for  one  mile  of  space,  or,  to  put  it 
accurately,  where  the  height  of  the  vertical  wires  (in 
yards)  varies  as  the  square  root  of  the  distance  (in  miles) 
to  be  signalled  over. 

At  the  outset  of  my  task  I  was  met  with  the  difficulty 
of  arranging  my  materials — whether  in  simple  chronological 
order,  or  classified  under  heads,  as  Conduction,  Induction, 
"Wave,  and  Other  or  Miscellaneous  Methods.  Both  have 
their  advantages  and  disadvantages,  but  after  consideration 
I  decided  to  follow  in  the  main  the  chronological  order  as 
the  better  of  the  two  for  a  history  which  is  intended  to  be 
a  simple  record  of  what  has  been  done  or  attempted  in  the 
last  sixty  years  by  the  many  experimenters  who  have 
attacked  the  problem  or  contributed  in  any  way  to  its 
solution. 

Having  settled  this  point,  the  further  question  of  sub- 
division presented  itself,  and  as  the  materials  did  not  lend 
themselves  to  arrangement  in  chapters,  I  decided  to  divide 
the  text  into  periods.  The  first  I  have  called  The  Possible 
Period,  which  deals  with  first  suggestions  and  empirical 
methods  of  experiment,  and  which,  by  reason  of  the  want 
of  delicacy  in  the  instruments  then  available,  may  not 
inaccurately  be  compared  with  the  Palaeolithic  period  in 
geology.  The  second  is  The  Practicable  (or  Neolithic) 
Period,  when  the  conditions  of  the  problem  came  to  be 
better  understood,  and  more  delicate  instruments  of  research 


PREFACE   TO   FIRST   EDITION.  XV 

were  at  hand.  The  third — The  Practical  Period — brings 
the  subject  up  to  date,  and  deals  with  the  proposals  of 
Preece  (Electro  -  Magnetic),  of  Willoughby  Smith  (Con- 
ductive), and  of  Marconi  (Hertzian),  which  are  to-day  in 
actual  operation. 

The  whole  concludes  with  five  Appendices,  containing 
much  necessary  information  for  which  I  ,could  not  conveni- 
ently find  room  in  the  body  of  the  work.  Appendix  A 
deals  with  the  philosophic  views  of  the  relation  between 
electricity  and  light  before  and  after  Hertz,  who,  for  the 
first  time,  showed  them  to  be  identical  in  kind,  differing 
only  in  the  degree  of  their  wave-lengths.  Appendix  B 
gives  in  a  popular  form  the  modern  views  of  electric 
currents  consequent  on  the  discoveries  of  Clerk-Maxwell, 
Hertz,  and  their  disciples.  Appendix  C  reproduces  the 
greater  part  of  Professor  Branly's  classic  paper  on  his 
discovery  of  the  Coherer  principle,  which  is  one  of  the 
foundation-stones  of  the  Marconi  system.  Appendix  1) 
contains  a  very  interesting  correspondence  between  myself 
and  Prof.  Hughes,  F.R.S.,  which  came  too  late  for  insertion 
in  the  body  of  the  work,  and  which  is  too  important  from 
the  historical  point  of  view  to  be  omitted. 

In  Appendix  E  Mr  Marconi's  patent  specification  is 
reproduced,  as,  besides  being  historically  interesting  as  the 
first  patent  for  a  telegraph  of  the  Hertzian  order,  it  is  in 
itself  a  marvel  of  completeness.  As  the  apparatus  is  there 
described,  so  it  is  used  to-day  after  three  years'  rigorous 
experimentation,  the  only  alterations  being  in  points  of 
detail — a  finer  adjustment  of  means  to  ends.  This  says 
much  for  the  constructive  genius  of  the  young  inventor, 


XVI  PREFACE   TO   FIRST   EDITION. 

and  bodes  well  for  the  survival  of  his  system  in  the 
struggle  for  existence  in  which  it  is  now  engaged. 

In  the  presentation  of  my  materials  I  have  allowed,  as 
far  as  possible,  the  various  authors  to  speak  in  their  own 
words,  merely  condensing  freely  and,  where  necessary, 
translating  obsolete  words  and  phrases  into  modern  technical 
language.  This  course  in  a  historical  work  is,  I  think, 
preferable  to  obtruding  myself  as  their  interpreter.  For 
the  same  reason  I  have  given  in  the  text,  or  in  footnotes 
thereto,  full  references,  so  that  the  reader  who  desires  to 
consult  the  original  sources  can  readily  do  so. 

I  seem  to  hear  the  facetious  critic  exclaim,  "  Why,  this 
is  all  scissors  and  paste."  So  it  is,  good  sir,  much  of  it ; 
and  so  is  all  true  history  when  you  delete  the  fictions  with 
which  many  historians  embellish  their  facts.  What  one 
person  said  or  what  another  did  is  not  altered  by  the  pres- 
ence or  absence  of  quotation  marks.  However,  the  only 
credit  I  claim  is  that  due  to  collecting,  condensing,  and  pre- 
senting my  facts  in  a  readable  form — no  light  task, — and  if 
my  critics  will  award  me  this  I  MTill  be  satisfied. 

Since  the  following  pages  were  written,  two  excellent 
contributions  have  been  made  by  Prof.  Oliver  Lodge 
and  Mr  Sydney  Evershed  in  papers  read  before  the  Insti- 
tution of  Electrical  Engineers,  December  8  and  22,  1898. 
These  will  be  found  in  No.  137  of  the  'Journal/  and, 
together  with  the  discussion  which  followed,  should  be 
studied  by  all  interested  in  this  fascinating  subject.  Mr 
Marconi  has  followed  up  these  papers  with  one  on  his  own 
method,  which  was  read  before  the  Institution  on  the  2nd 
of  March  last,  and  was  repeated  by  general  request  on  the 


PREFACE   TO   FIRST   EDITION.  XVli 

IGth  idem.  He  does  not  carry  the  matter  farther  than  I 
have  done  in  the  text,  but  still  the  paper  is  worth  reading 
— if  only  as  an  exposition  in  a  nutshell  of  his  beautiful 
system. 

As  a  Frontispiece  I  give  a  group  of  twelve  portraits  of 
eminent  men  who  may  be  fitly  called  the  Arch-builders  of 
Wireless  Telegraphy.  At  the  top  stands  Oersted  (Den- 
mark), who  first  showed  the  connection  between  electricity 
and  magnetism.  Then  follow  in  order  of  time  Ampere 
(France),  Faraday  (England),  and  Henry  (America),  who 
explained  and  extended  the  principles  of  the  new  science  of 
electro-magnetism.  Then  come  Clerk-Maxwell  (England) 
and  Hertz  (Germany),  who  showed  the  relation  between 
electricity  and  light,  the  one  theoretically,  and  the  other 
by  actual  demonstration.  These  are  followed  by  Lranly 
(France),  Lodge  (England),  and  Eighi  (Italy),  whose  dis- 
coveries have  made  possible  the  invention  of  Marconi. 
The  last  three  are  portraits  of  Preece  and  Willoughby 
Smith  (England)  and  Marconi  (Italy),  who  divide  between 
them  the  honour  of  establishing  the  first  practical  lines  of 
wireless  telegraph — each  typical  of  a  different  order. 

ST  HELIER'S,  JERSEY, 
September  1899. 


CONTENTS. 


FIRST   PERIOD— THE  POSSIBLE. 

PACK 
PROFESSOR   C.  A.  STEINHEIL — 1838  ...  1 

EDWARD   DAVY— 1838  .....  6 

PROFESSOR  MORSE — 1842    .....  10 

JAMES   BOWMAN   LINDSAY — 1843      .  .  .  .13 

J.  W.  WILKINS — 1845          .  .  .  .          .  .33 

DR  O'SHAUGHNESSY  (AFTERWARDS  SIR  WILLIAM  o'SHAUGH- 

NESSY  BROOKE)— 1849  .  .  .  .39 

E.  AND   H.  HIGHTON— 1852-72  .  .  .  .40 

G.  E.  DERING — 1853  .  .  .  .  .48 

JOHN   HAWORTH — 1862          .  .  .  .  .56 

J    H.  MOWER — 1868  .  .  .  .  .65 

M.  BOURBOUZE — 1870  .  .  .  .  .06 

MAHLON   LOOMIS— 1872         .....  68 

SECOND  PERIOD— THE   PRACTICABLE. 

PRELIMINARY  :   NOTICE   OF  THE  TELEPHONE  IN  RELATION 

TO   WIRELESS   TELEGRAPHY       .  .  .  .74 

PROFESSOR   JOHN   TROWBRIDGE — 1880  80 


XX  CONTENTS. 

PROFESSOR   GRAHAM   BELL — 1882  .  .                                   .91 

PROFESSOR   A.  E.  DOLBEAR — 1882  .  94 

T.  A.  EDISON— 1885                  .  .100 

W.  F.  MELHUISH — 1890          .  .111 

CHARLES   A.  STEVENSON — 1892         .  .119 

PROFESSOR   ERICH    RATHENAU — 189-1  .                                   .130 

THIRD  PERIOD— THE   PRACTICAL. 

SYSTEMS   IN   ACTUAL   USE. 

«Bt  w.  H.  PREECE'S  METHOD          .  .  .  .135 

WILLOUGHBY  SMITH'S  METHOD      .  .  .  .161 

G.  MARCONI'S  METHOD        ...  .      176 

APPENDIX   A. 

THE     RELATION     BETWEEN     ELECTRICITY     AND     LIGHT  — 

BEFORE  AND   AFTER   HERTZ     .  .  .         262 

APPENDIX   B. 

PROF.  HENRY  ON  HIGH  TENSION  ELECTRICITY  BEING 
CONFINED  TO  *THE  SURFACE  OF  CONDUCTING  BODIES, 
WITH  SPECIAL  REFERENCE  TO  THE  PROPER  CON- 
STRUCTION OF  LIGHTNING-RODS  .  .  .  277 

ON  MODERN  VIEWS  WITH  RESPECT  TO  THE  NATURE  OF 

ELECTRIC  CURRENTS  .....  280 

APPENDIX   C. 

VARIATIONS  OF  CONDUCTIVITY  UNDER  ELECTRICAL  IN- 
FLUENCE 292 


CONTENTS.  XX  i 

APPENDIX   D. 

RESEARCHES  OF  PROF.  D.  E.  HUGHES,  F.K.S.,  IX  ELECTRIC 
WAVES  AND  THEIR  APPLICATION  TO  WIRELESS  TELEG- 
RAPHY, 1879-1886  ,  .  .  .  .  3U5 

APPENDIX   E. 
REPRINT  OF  SIGNOR  G.  MARCONI'S  PATENT          .  .316 

INDEX:         .  .  341 


A  HISTORY  OF 
WIRELESS   TELEGRAPHY. 

FIRST   PERIOD— THE   POSSIBLE. 

"Awhile  forbear, 

Nor  scorn  man's  efforts  at  a  natural  growth, 
Which  in  some  distant  age  may  hope  to  find 
Maturity,  if  not  perfection. " 

PROFESSOR  C.   A.   STEINHEIL— 1838. 

JUST  mentioning  en  passant  the  sympathetic  needle  and 
sympathetic  flesh  telegraphs  of  the  sixteenth  and  seven- 
teenth centuries,  a  full  account  of  which  will  be  found  in 
my  'History  of  Electric  Telegraphy  to  1837 '  (chap,  i.),1  we 
come  to  the  year  1795  for  the  first  glimmerings  of  teleg- 
raphy without  wires.  Salva,  who  was  an  eminent  Spanish 
physicist,  and  the  inventor  of  the  first  electro-chemical  tele- 
graph, has  the  following  bizarre  passage  in  his  paper  "  On 
the  Application  of  Electricity  to  Telegraphy,"  read  before 
the  Academy  of  Sciences,  Barcelona,  December  16,  1795. 
After  showing  how  insulated  wires  may  be  laid  under 

1  E.  &  F.  N.  Spon,  London,  1884. 
A 


2  FIRST   PERIOD — THE   POSSIBLE. 

the  seas,  and  the  water  used  instead  of  return  wires,  he 
goes  on  to  say :  "If  earthquakes  be  caused  by  electricity 
going  from  one  point  charged  positively  to  another  point 
charged  negatively,  as  Bertolon  has  shown  in  his  '  Elec- 
tricite  des  Me"teores'  (vol.  i.  p.  273),  one  does  not  even  want 
a  cable  to  send  across  the  sea  a  signal  arranged  beforehand. 
One  could,  for  example,  arrange  at  Mallorca  an  area  of 
earth  charged  with  electricity,  and  at  Alicante  a  similar 
space  charged  with  the  opposite  electricity,  with  a  wire 
going  to,  and  dipping  into,  the  sea.  On  leading  another 
wire  from  the  sea-shore  to  the  electrified  spot  at  Mallorca, 
the  communication  between  the  two  charged  surfaces  would 
be  complete,  for  the  electric  fluid  would  traverse  the  sea, 
which  is  an  excellent  conductor,  and  indicate  by  the  spark 
the  desired  signal."1 

Another  early  telegraph  inventor  and  eminent  physi- 
ologist, Sommerring  of  Munich,  has  an  experiment  which, 
under  more  favourable  conditions  of  observation,  might 
easily  have  resulted  in  the  suggestion  at  this  early  date 
of  signalling  through  and  by  water  alone.  Dr  Hamel2 
tells  us  that  Sommerring,  on  the  5th  of  June  1811,  and 
at  the  suggestion  of  his  friend,  Baron  Schilling,  tried  the 
action  of  his  telegraph  whilst  the  two  conducting  cords 
were  each  interrupted  by  water  contained  in  wooden  tubs. 
The  signals  appeared  just  as  well  as  if  no  water  had  been 
interposed,  but  they  ceased  as  soon  as  the  water  in  the 
tubs  was  connected  by  a  wire,  the  current  then  returning 
by  this  shorter  way. 

Now  here  we  have,  in  petto,  all  the  conditions  necessary 

1  Later  on  (p.  81  infra)  we  shall  see  that  Salve's  idea  is  after 
all  not  so  extravagant  as  it  seems.     We  now  know  that  large  spaces 
of  the  earth  can  be  electrified,  giving  rise  to  the  phenomenon  of 
"bad  earth,"  so  well  known  to  telegraph  officials. 

2  '  Historical  Account  of  the  Introduction  of   the  Galvanic  and 
Electro-magnetic  Telegraph  into  England,'  Cooke's  Reprint,  p.  17. 


PROFESSOR   C.   A.    STEINHEIL.  3 

for  an  experiment  of  the  kind  with  which  we  are  dealing, 
and  had  it  been  possible  for  Sommerring  to  have  employed 
a  more  delicate  indicator  than  his  water-decomposing  appar- 
atus he  would  probably  have  noticed  that,  notwithstanding 
the  shorter  way,  some  portion  of  the  current  still  went  the 
longer  way  ;  and  this  fact  could  hardly  have  failed  to  suggest 
to  his  acute  and  observant  mind  further  experiments,  which, 
as  I  have  just  said,  might  easily  have  resulted  in  his  recog- 
nition of  the  possibility  of  wireless  telegraphy. 

Leaving  the  curious  suggestion  of  Salva,  which,  though 
seriously  meant,  cannot  be  regarded  as  more  than  a  jeu 
d'esprit  —  a  happy  inspiration  of  genius  —  arid  the  what- 
might-have-come-of-it  experiment  of  Sommerring,  we  come 
to  the  year  1838,  when  the  first  intelligent  suggestion  of  a 
wireless  telegraph  was  made  by  Steinheil  of  Munich,  one  of 
the  great  pioneers  of  electric  telegraphy  on  the  Continent. 

The  possibility  of  signalling  without  wires  was  in  a 
manner  forced  upon  him.  While  he  was  engaged  in  estab- 
lishing his  beautiful  system  of  telegraphy  in  Bavaria,  Gauss, 
the  celebrated  German  philosopher,  and  himself  a  telegraph 
inventor,  suggested  to  him  that  the  two  rails  of  a  railway 
might  be  utilised  as  telegraphic  conductors.  In  July  1838 
Steinheil  tried  the  experiment  on  the  Nurmberg-Furth 
railway,  but  was  unable  to  obtain  an  insulation  of  the  rails 
sufficiently  good  for  the  current  to  reach  from  one  station 
to  the  other.  The  great  conductibility  with  which  he 
found  that  the  earth  was  endowed  led  him  to  presume  that 
it  would  be  possible  to  employ  it  instead  of  the  return  wire 
or  wires  hitherto  used.  The  trials  that  he  made  in  order 
to  prove  the  accuracy  of  this  conclusion  were  followed  by 
complete  success  ;  and  he  then  introduced  into  electric  teleg- 
raphy one  of  its  greatest  improvements — the  earth  circuit.1 

1  For  the  use  of  the  earth  circuit  before  Steinheil's  accidental  dis- 
covery, see  my  '  History  of  Electric  Telegraphy,'  pp.  343-345. 


4  FIRST   PERIOD — THE   POSSIBLE. 

Steinheil  then  goes  on  to  say :  "  The  inquiry  into  the 
laws  of  dispersion,  according  to  which  the  ground,  whose 
mass  is  unlimited,  is  acted  upon  by  the  passage  of  the 
galvanic  current,  appeared  to  be  a  subject  replete  with  in- 
terest. The  galvanic  excitation  cannot  be  confined  to  the 
portions  of  earth  situated  between  the  two  ends  of  the  wire ; 
on  the  contrary,  it  cannot  but  extend  itself  indefinitely,  and 
it  therefore  only  depends  on  the  law  that  obtains  in  this 
excitation  of  the  ground,  and  the  distance  of  the  exciting 
terminations  of  the  wire,  whether  it  is  necessary  or  not  to 
have  any  metallic  communication  at  all  for  carrying  on 
telegraphic  intercourse. 

"  An  apparatus  can,  it  is  true,  be  constructed  in  which 
the  inductor,  having  no  other  metallic  connection  with  the 
multiplier  than  the  excitation  transmitted  through  the 
ground,  shall  produce  galvanic  currents  in  that  multiplier 
sufficient  to  cause  a  visible  deflection  of  the  bar.  This  is  a 
hitherto  unobserved  fact,  and  may  be  classed  amongst  the 
most  extraordinary  phenomena  that  science  has  revealed  to 
us.  It  only  holds  good,  however,  for  small  distances  ;  and 
it  must  be  left  to  the  future  to  decide  whether  we  shall  ever 
succeed  in  telegraphing  at  great  distances  without  any 
metallic  communication  at  all.  My  experiments  prove  that 
such  a  thing  is  possible  up  to  distances  of  50  feet.  For 
greater  distances  we  can  only  conceive  it  feasible  by  aug- 
menting the  power  of  the  galvanic  induction,  or  by  ap- 
propriate multipliers  constructed  for  the  purpose,  or,  in 
conclusion,  by  increasing  the  surface  of  contact  presented 
by  the  ends  of  the  multipliers.  At  all  events,  the  phe- 
nomenon merits  our  best  attention,  and  its  influence  will  not 
perhaps  be  altogether  overlooked  in  the  theoretic  views  we 
may  form  with  regard  to  galvanism  itself."  1 

In  another  place,  discussing  the  same  subject,  Steinheil 
1  Sturgeon's  'Annals  of  Electricity,'  vol.  iii.  p.  450. 


PROFESSOR  C.   A.   STEINHETL.  5 

says :  "  We  cannot  conjure  up  gnomes  at  will  to  convey 
our  thoughts  through  the  earth.  Nature  has  prevented 
this.  The  spreading  of  the  galvanic  effect  is  proportional, 
not  to  the  distance  of  the  point  of  excitation,  but  to  the 
square  of  this  distance  ;  so  that,  at  the  distance  of  50  feet, 
only  exceedingly  small  effects  can  be  produced  by  the  most 
powerful  electrical  effect  at  the  point  of  excitation.  Had 
we  means  which  could  stand  in  the  same  relation  to  elec- 
tricity that  the  eye  stands  to  light,  nothing  would  prevent 
our  telegraphing  through  the  earth  without  conducting 
wires ;  but  it  is  not  probable  that  we  shall  ever  attain 
this  end."1 

Steinheil  proposed  another  means  of  signalling  without 
wires,  which  is  curiously  apropos  of  Professor  Graham 
Bell's  photophone.  In  his  classic  paper  on  "Telegraphic 
Communication,  especially  by  Means  of  Galvanism,"  he 
says :  "  Another  possible  method  of  bringing  about 
transient  movements  at  great  distances,  without  any  inter- 
vening artificial  conductor,  is  furnished  by  radiant  heat, 
when  directed  by  means  of  condensing  mirrors  upon  a 
thermo-electric  pile.  A  galvanic  current  is  called  into  play, 
which  in  its  turn  is  employed  to  produce  decimations  of  a 
magnetic  needle.  The  difficulties  attending  the  construc- 
tion of  such  an  instrument,  though  certainly  considerable, 
are  not  in  themselves  insuperable.  Such  a  telegraph, 
however,  would  only  have  this  advantage  over  those 
[semaphores]  based  on  optical  principles — namely,  that  it 
does  not  require  the  constant  attention  of  the  observer  • 
but,  like  the  optical  one,  it  would  cease  to  act  during 
cloudy  weather,  and  hence  partakes  of  the  intrinsic  defects- 
of  all  semaphoric  methods."  2 

1  '  Die  Anwendung  des  Electromagnetismus,'  1873,  p.  172.   "We  now 
have  these  means  in  "the  electric  eye"of  Hertz !   See  pp.  180, 27Qinfra. 

2  'Sturgeon's  Annals  of  Electricity,'  March  1839. 


6  FIRST   PERIOD — THE   POSSIBLE. 

Acting  on  this  suggestion,  in  June  1880  the  present 
writer,  while  stationed  at  Teheran,  Persia,  and  while  yet 
ignorant  of  Professor  Bell's  method,  worked  out  for  himself 
a  photophone,  or  rather  a  tele-photophone,  which  will  be 
found  described  in  the  'Electrician/  February  26,  1881. 
On  my  temporary  return  to  England  in  1882,  I  found 
that  as  early  as  1878  Mr  A.  C.  Brown,  of  the  Eastern 
Telegraph  Company,  was  working  at  the  photophone.  In 
September  of  that  year  he  submitted  his  plans  to  Prof.  Bell, 
who  afterwards  said  of  them  :  "  To  Mr  Brown  is  undoubtedly 
due  the  honour  of  having  distinctly  and  independently  for- 
mulated the  conception  of  using  an  undulatory  beam  of 
light,  in  contradistinction  to  a  merely  intermittent  one,  in 
connection  with  selenium  and  a  telephone,  and  of  having 
devised  apparatus,  though  of  a  crude  nature,  for  carrying  it 
into  execution"  ('Jour.  Inst.  Elec.  Engs.,'  vol.  ix.  p.  404). 
Indeed  the  photophone  is  as  much  the  invention  of  Mr 
Brown  as  of  Prof.  Bell,  who,  however,  has  all  the  credit  for 
it  in  popular  estimsltion. 


EDWARD    DAVY— 1838. 

While  arranging,  in  1883,  the  Edward  Davy  MSS.,  now 
in  the  library  of  the  Institution  of  Electrical  Engineers, 
the  present  writer  discovered  two  passages  which  he  at  first 
took  to  have  reference  to  some  kind  of  telephonic  relay; 
but  on  closer  consideration  it  would  appear  that  Davy  had 
in  view  some  contrivance  based  on  the  conjoint  use  of 
sound  and  electricity,  much  as  Steinheil  suggested  the  joint 
use  of  electricity  and  heat.  The  following  are  the  passages 
to  which  I  refer : — 

At  the  end  of  a  long  critical  examination  of  Cooke  and 
Wheatstone's  first  patent  of  June  12,  1837,  he  says:  "I 


EDWAKD   DAVY.  7 

have  lately  found  that  there  is  a  peculiar  way  of  propagat- 
ing signals  between  the  most  distant  places  by  self-acting 
means,  and  without  the  employment  of  any  conducting 
wires  at  all.  It  is  to  be  done  partly  by  electricity,  but 
combined  with  another  principle,  of  the  correctness  of 
which  there  can  be  no  doubt.  But  until  I  know  what 
encouragement  the  other1  will  meet  with  I  shall  take  no 
steps  in  this,  as  it  may  happen  there  will  be  other  rivals. 
To  give  you  a  general  idea  of  it,  a  bell  may  be  rung  at 
the  first  station,  and  then  in  the  next  instant  a  bell  will 
ring  at  the  next  station  a  mile  off,  and  so  on  for  an 
unlimited  series,  though  there  is  nothing  between  them 
but  the  plain  earth  and  air !  At  the  termination  of  the 
series,  the  signals  may  be  given  in  letters,  as  in  the  present 
contrivance." 

Again,  in  a  paper  of  numbered  miscellaneous  memor- 
anda, No.  20  reads  as  follows :  "  20.  The  plan  proposed 
(101)  of  propagating  communications  by  the  conjoint 
agency  of  sound  and  electricity — the  griginal  sound  pro- 
ducing vibrations  which  cause  sympathetic  vibrations  in  a 
unison -sounding  apparatus  at  a  distance,  this  last  vibra- 
tion causing  a  renewing  wire  to  dip2  and  magnetise  soft 
iron  so  as  to  repeat  the  sound,  and  so  on  in  unlimited 
succession." 

It  is  not  easy  to  say  from  these  passages  (which  are  all 
we  could  find  on  the  subject)  what  plan  Davy  had  in 
contemplation.  In  the  first  quotation  he  speaks  of  bells, 
for  which  we  may  read  a  powerful  trumpet  at  one  end, 
and  a  concave  reflector  to  focus  the  sound  at  the  other 

1  That  is,  his  chemical  recording  telegraph.     See  my  '  History  of 
Electric  Telegraphy,'  p.  379. 

2  I.e.,  causing  a  relay  to  close  a  local  circuit  containing  an  electro- 
magnet.    Davy  always  spoke  of  the  relay  as  the  "  renewer "  or  the 
"  renewing  wire  "  ;  and  by  dip  he  meant  to  dip  into  mercury,  or,  as 
we  say  nowadays,  to  close  the  cireuit. 


8  FIRST  PERIOD — THE  POSSIBLE. 

end ;  or  some  arrangement  like  the  compressed-air  tele- 
phone, proposed  by  Captain  Taylor,  RK,  in  1844 ;  or 
the  modern  siren;  or,  in  short,  any  means  of  producing 
sharp  concussions  of  the  air,  such  as  were  known  in  his 
day.  Let  us  suppose  he  used  any  of  these  methods  for 
projecting  sound  waves,  then,  at  the  focus  of  the  distant 
reflector  he  may  have  designed  a  "renewing  wire,"  so 
delicately  poised  as  to  respond  to  the  vibration,  and  so 
close  a  local  circuit  in  which  was  included  the  electro- 
magnetic apparatus  for  recording  the  sound,  or  for  renewing 
it  as  required. 

In  the  second  passage  he  speaks  of  something  on  the 
principle  of  the  tuning-fork.  Now,  tuning-forks  in  com- 
bination with  reflectors  may  be  practicable  for  short  dis- 
tances, but  it  is  difficult  to  see  how  their  vibrations  could 
be  utilised,  at  the  distance  of  a  mile,  for  "causing  a 
renewing  wire  to  dip." 

However  this  may  be,  Davy's  idea  deserves  at  least 
this  short  notice  in  a  history  of  early  attempts  at  wireless 
telegraphy ;  for,  although  hardly  possible  of  realisation 
with  the  apparatus  at  his  command,  it  is  perfectly  feasible 
in  these  days  of  megaphones  and  microphones.  As  regards 
its  practical  utility,  that  is  a  question  for  the  future,  as 
to  which  we  prefer  not  to  prophesy.1 

Davy's  idea  was  probably  the  result  of  an  incautious 
dose  of  the  Auticatelephor  of  Edwards,  which  made  a 
great  stir  a  few  years  previously,  and  which,  at  first  sight, 
might  be  taken  to  be  a  telegraph  without  apparently  any 

1  Such  a  plan  as  Davy's  was  again  suggested,  in  1881,  by  Signor 
Senlicq  d' Andres  ('  Telegraphic  Journal,'  vol.  ix.  p.  126),  who,  however, 
proposed  to  use,  instead  of  a  renewing  wire  or  relay,  the  mouthpiece 
of  a  microphonic  speaker,  rendered  more  sensitive  by  a  contact  lever 
with  unequal  arms.  Mr  A.  R.  Sennett  has  also  worked  at  the  idea 
in  more  recent  years.  His  method  is  very  clearly  described  in  the 
'Jour.  Inst.  Elec.  Engs.,'  No.  137,  p.  908. 


EDWARD   DAVY. 

connecting  medium.     We  take  the  following  announcement 
from  the  'Kaleidoscope'  of  June  30,  1829  (p.  430)  :— 

"THE    AUTICATELBPHOR. 

"  We  have  received  several  papers  descriptive  of  a  new 
and  curious  engine,  with  the  above  name,  invented  by  Mr 
T.  W.  C.  Edwards,  Lecturer  on  Experimental  Philosophy 
and  Chemistry,  and  designed  for  the  instantaneous  convey- 
ance of  intelligence  to  any  distance.  After  noticing  some 
of  the  greatest  inventions  of  preceding  times,  Mr  Edwards 
undertakes  to  demonstrate  clearly  and  briefly,  in  the  work 
which  he  has  now  in  the  press,1  the  practicability  and 
facility  of  transmitting  from  London,  instantaneously,  to  an 
agent  at  Edinburgh,  Dublin,  Paris,  Vienna,  St  Petersburg, 
Constantinople,  the  Cape  of  Good  Hope,  Madras,  Calcutta, 
&c.,  any  question  or  message  whatever,  and  of  receiving 
back  again  at  London,  within  the  short  space  of  one  minute, 
an  acknowledgment  of  the  arrival  of  such  question  or 
message  at  the  place  intended,  and  a  distinct  answer  to  it  in 
a  few  minutes.  In  principle  this  engine  is  altogether 
different  from  every  kind  of  telegraph  or  semaphore,  and 
requires  neither  intermediate  station  nor  repetition.  In  its 
action  it  is  totally  unconnected  with  electricity,  magnetism, 
galvanism,  or  any  other  subtle  species  of  matter;  and 
although  the  communication  from  place  to  place  is  instan- 
taneous, and  capable  of  ringing  a  bell,  firing  a  gun,  or 
hoisting  a  flag  if  required,  yet  this  is  not  effected  by  the 
transit  of  anything  whatever  to  and  fro  ;  nor  in  the  opera- 
tion is  aught  either  audible  or  visible,  except  to  the  persons 

1  In  1883  we  searched  for  this  book  in  vain.  Under  the  name  T. 
W.  C.  Edwards  we  found  in  the  British  Museum  Catalogue  no  less 
than  twenty  entries  of  translations  from  Greek  authors,  and  of  Greek 
and  Latin  grammars,  &c.  ;  but  nothing  to  show  that  the  writer  was 
either  a  natural  philosopher  or  a  chemist. 


10  FIRST  PERIOD — THE   POSSIBLE. 

communicating.  It  may  be  proper,  however,  to  state  that  a 
channel  or  way  must  previously  be  prepared,  by  sinking  a 
series  of  rods  of  a  peculiar  description  in  the  ground,  or 
dropping  them  in  the  sea ;  but  these,  after  the  first  cost, 
will  remain  good  for  ages  to  come,  if  substantial  when  laid 
down."  J 

From  the  concluding  words  of  this  paragraph  it  would 
seem  that  the  Auticatelephor  was  simply  an  application  to 
telegraphy  of  pneumatic  or  hydraulic  pressure  in  pipes — 
cautiously  styled  "  rods  of  a  peculiar  description."  On  this 
supposition  the  last  sentence  may  be  paraphrased  thus  : 
"  It  may  be  proper,  however,  to  state  that  a  channel  or  way 
must  previously  be  prepared,  by  laying  down  a  continuous 
series  of  hollow  rods  or  tubes  under  the  ground  or  along  the 
sea-bottom."  If  our  supposition  be  correct,  and  if  Edwards 
contemplated  the  use  of  compressed  air,  his  proposal  was 
certainly  novel ;  but  if  he  designed  the  use  of  compressed 
water,  the  idea  was  by  no  means  new.  Without  going 
back  to  the  old  Roman  plan  of  ^Eneas  Tacticus,  we  have  its 
revival  by  Brent  and  others  towards  the  close  of  the  last 
century,  and  the  still  more  practical  arrangements  of  Joseph 
Bramah  in  1796,  of  Yallance  in  1825,  and  of  Jobard  in 
1827. 

PROFESSOR  MORSE— 1842. 

The  idea  of  a  wireless  telegraph  next  appears  to  have 
presented  itself  to  Professor  Morse.  In  a  letter  to  the 
Secretary  of  the  Treasury,  which  was  laid  before  the 
House  of  Representatives  on  December  23,  1844,  he 
says : — 

"In  the  autumn  of  1842,  at  the  request  of  the  American 

1  See  also  the  'Mechanics'  Magazine,'  vol.  xiii.,  First  Series, 
p.  182. 


PROFESSOR  MORSE.  11 

Institute,  I  undertook  to  give  to  the  public  in  New  York 
a  demonstration  of  the  practicability  of  my  telegraph,  by 
connecting  Governor's  Island  with  Castle  Garden,  a  dis- 
tance of  a  mile ;  and  for  this  purpose  I  laid  my  wires 
properly  insulated  beneath  the  water.  I  had  scarcely 
begun  to  operate,  and  had  received  but  two  or  three 
characters,  when  my  intentions  were  frustrated  by  the 
accidental  destruction  of  a*  part  of  my  conductors  by  a 
vessel,  which  drew  them  up  on  her  anchor,  and  cut  them 
off.  In  the  moments  of  mortification  I  immediately  de- 
vised a  plan  for  avoiding  such  an  accident  in  future,  by 
so  arranging  my  wires  along  the  banks  of  the  river  as  to 
cause  the  water  itself  to  conduct  the  electricity  across. 
The  experiment,  however,  was  deferred  till  I  arrived  in 
Washington;  and  on  December  16,  1842,  I  tested  my 
arrangement  across  the  canal,  and  with  success.  The 
simple  fact  was  then  ascertained  that  electricity  could  be 
made  to  cross  a  river  without  other  conductors  than  the 
water  itself;  but  it  was  not  until  the  last  autumn  that 
I  had  the  leisure  to  make  a  series  of  experiments  to  ascer- 
tain the  law  of  its  passage.  The  following  diagram  will 
serve  to  explain  the  experiment : — 


Fig.  1. 

"A,  B,  c,  D,  are  the   banks  of  the  river;  N,  P,  is  the 
battery  ;  G  is  the  galvanometer ;  w  w,  are  the  wires  along 


12 


FIRST   PERIOD — THE   POSSIBLE. 


the  banks,  connected  with  copper  plates,  /,  17,  h,  i,  which 
are  placed  in  the  water.  When  this  arrangement  is  com- 
plete, the  electricity,  generated  by  the  battery,  passes  from 
the  positive  pole,  p,  to  the  plate  h,  across  the  river  through 
the  water  to  plate  i,  and  thence  around  the  coil  of  the 
galvanometer  to  plate  /,  across  the  river  again  to  plate  g, 
and  thence  to  the  other  pole  of  the  battery,  N. 

"  The  distance  across  the  canal  is   80  feet ;  on  August 
24  the  following  were  the  results  of  the  experiment : — 


No.  of  the  experiment. 

1st. 

2nd. 

3rd. 

4th. 

5th. 

6th. 

No.  of  cups  in  battery 

14 

14 

14 

7 

7 

7 

Length  of  conductors,  w,  w 

400 

400 

400 

400 

300 

200 

Degrees  of  motion  of  gal- 

vanometer 

32&24 

13£  &  4£ 

1  &1 

24&13 

29&21 

2H&15 

Size  of  the  copper  plates,  ) 

/,  g,  ft,  i                     \ 

5  by 
2*  ft. 

16  by 
13  in. 

6  by 
5  in. 

5  by 

2^  ft. 

5  by 
2^  ft. 

5  by 
2ift. 

"  Showing  that  electricity  crosses  the  river,  and  in  quan- 
tity in  proportion  to  the  size  of  the  plates  in  the  water.  The 
distance  of  the  plates  on  the  same  side  of  the  river  from 
each  other  also  affects  the  result.  Having  ascertained  the 
general  fact,  I  was  desirous  of  discovering  the  best  practical 
distance  at  which  to  place  my  copper  plates,  and  not  having 
the  leisure  myself,  I  requested  my  friend  Professor  Gale  to 
make  the  experiments  for  me.  I  subjoin  his  letter  and  the 
results.1 

"  '  NEW  YORK,  Nov.  5th,  1844. 

" '  MY  DEAR  SIR,  —  I  send  you  herewith  a  copy  of  a 
series  of  results,  obtained  with  four  different-sized  plates, 
as  conductors  to  be  used  in  crossing  rivers.  The  batteries 
used  were  six  cups  of  your  smallest  size,  and  one  liquid 

1  We  omit  the  tables  of  results,  as  of  no  present  value.     They  can 
be  seen  in  Vail's  book,  quoted  infra. 


JAMES   BOWMAN   LINDSAY.  13 

used  for  the  same  throughout.  I  made  several  other  series 
of  experiments,  but  these  I  most  rely  on  for  uniformity  arid 
accuracy.  You  will  see,  from  inspecting  the  table,  that  the 
distance  along  the  shores  should  be  three  times  greater  than 
that  from  shore  to  shore  across  the  stream  ;  at  least,  that 
four  times  the  distance  does  not  give  any  increase  of 
power.  I  intend  to  repeat  all  these  experiments  under 
more  favourable  circumstances,  and  will  communicate  to 
you  the  results. — Very  respectfully,  L.  D.  GALE. 

"  <  Professor  S.  F.  B.  MORSE, 

Superintendent  of  Telegraphs' 

"  As  the  results  of  these  experiments,  it  would  seem  that 
there  may  be  situations  in  which  the  arrangements  I  have 
made  for  passing  electricity  across  rivers  may  be  useful, 
althouglT^experience  alone  can  determine  whether  lofty 
spars,  on  which  the  wires  may  be  suspended,  erected  in  the 
rivers,  may  not  be  deemed  the  most  practical.  The  experi- 
ments made  were  but  for  a  short  distance ;  in  which,  how- 
ever, the  principle  was  fully  proved  to  be  correct.  It  has 
been  applied  under  the  direction  of  my  able  assistants, 
Messrs  Vail  and  Rogers,  across  the  Susquehanna  river,  at 
Havre-de-Grace,  with  complete  success,  a  distance  of  nearly 
a  mile." l 


JAMES   BOWMAN   LINDSAY— 1843. 

The  next  to  pursue  the  subject  was  J.  B.  Lindsay  of 
Dundee,  whose  extensive  labours  in  this,  as  well  as  in  the 
department  of  electric  lighting,  have  hitherto  been  little 
appreciated  by  the  scientific  world.  Through  the  kind 
assistance  of  Dr  Robert  Sinclair  of  Dundee,  I  have  lately 

1  Vail's '  American  Electro- Magnetic  Telegraph,'  Philadelphia,  1845, 


14  FIRST   PERIOD — THE   POSSIBLE. 

collected  a  number  of  facts  relating  to  this  extraordinary 
man,  and  as  I  believe  they  will  be  new  to  most  of  my 
readers,  I  will  draw  largely  from  them  in  what  follows.1 

James  Bowman  Lindsay  was  born  at  Carmyllie,  near 
Arbroath,  on  September  8,  1799,  and  but  for  the  delicacy 
of  his  constitution  would  have  been  bred  a  farmer.  At  an 
early  age  he  evinced  a  great  taste  for  reading,  and  every 
moment  that  he  could  spare  from  his  work  as  a  linen- 
weaver  was  devoted  to  his  favourite  books.  Often,  indeed, 
he  would  be  seen  on  his  way  to  Arbroath  with  a  web  of 
cloth  tied  on  his  back  and  an  open  book  in  his  hands  ;  and, 
after  delivering  the  cloth  and  obtaining  fresh  materials  for 
weaving,  he  would  return  to  Carmyllie  in  the  same  fashion. 
Encouraged  by  these  studious  habits,  Lindsay's  parents 
wisely  arranged  that  he  should  go  to  St  Andrews  Uni- 
versity. Accordingly,  in  1821  he  entered  on  his  studies, 
and,  self-taught  though  he  had  hitherto  been,  he  soon  made 
for  himself  a  distinguished  place  among  his  fellow-students, 
particularly  in  the  mathematical  and  physical  sciences,  in 
which  departments,  indeed,  he  became  the  first  student  of 
his  time.  Having  completed  the  ordinary  four  years' 
course,  Lindsay  entered  as  a  student  of  theology,  and  duly 
completed  his  studies  in  the  Divinity  Hall ;  but  he  never 
presented  himself  for  a  licence,  his  habits  of  thought  in- 
clining more  to  scientific  than  to  theological  pursuits.  In 
the  long  summer  vacations  he  generally  returned  to  his 
occupation  of  weaving,  though  latterly  he  took  up  teaching, 
and  thus  enjoyed  more  time  for  the  prosecution  of  his  own 
studies. 

Coming  to  Dundee  in  1829,  he  was  appointed  Science 
and  Mathematical  Lecturer  at  the  Watt  Institution,  then 
conducted  by  a  Mr  M'Intosh.  Soon  after,  Alexander 

1  Extracts  from  the  writer's  articles  in  the  '  Electrical  Engineer,' 
vol.  xxiii.  pp.  21,  51. 


JAMES   BOWMAN   LINDSAY.  15 

Maxwell,  the  historian  of  Dundee,  became  a  pupil,  and  this 
is  the  picture  he  has  left  us  of  Lindsay  : — 

"  When  I  was  with  Mr  M'Intosh,  I  attended  classes  that 
were  taught  by  Mr  Lindsay,  a  man  of  profound  learning 
and  untiring  scientific  research,  who,  had  he  been  more 
practical,  less  diffident,  and  possessed  of  greater  worldly 
wisdom,  would  have  gained  for  himself  a  good  place 
amongst  distinguished  men.  As  it  was,  he  remained  little 
more  than  a  mere  abstraction,  a  cyclopaedia  out  of  order, 
and  went  through  life  a  poor  and  modest  schoolmaster. 

"  By  the  time  I  knew  him  he  was  devoting  much  of  his 
attention  to  electricity,  to  the  celerity  with  which  it  was 
transmitted  to  any  distance,  and  to  the  readiness  with 
which  its  alternating  effects  may  be  translated  into  speech 
— and  I  have  no  doubt  he  held  in  his  hand  the  modern 
system  of  the  telegraph,  but  it  needed  a  wiser  man  than  he 
to  turn  it  to  practical  use.  He  also  produced  from  galvanic 
cells  a  light  which  burned  steadily  for  a  lengthened  period. 

"  His  acquaintance  with  languages  was  extraordinary, 
and  almost  equalled  that  of  his  famous  contemporary,  the 
Cardinal  Mezzofanti.  In  1828  he  began  the  compilation  of 
a  dictionary  in  fifty  languages,  the  object  of  which  was  to 
discover,  if  possible,  by  language  the  place  where,  and  the 
time  when,  man  originated.  This  stupendous  undertaking, 
which  occupied  the  main  part  of  his  life's  work,  he  left 
behind  in  a  vast  mass  of  undigested  manuscript,  consist- 
ing of  dissertations  on  language  and  cogitations  on  social 
science — a  monument  of  unpractical  and  inconclusive  in- 
dustry. In  1845  he  published  'A  Pentecontaglossal 
Paternoster,'  intended  to  serve  as  a  specimen  of  his  fifty- 
tongued  lexicon. 

"In  1858  he  published  'The  Chrono  -  Astrolabe,'  for 
determining  with  certainty  ancient  chronology — a  work  on 
which  he  had  been  engaged  for  many  years ;  and  in  1861 


16  FIRST   PERIOD — THE   POSSIBLE. 

'  A  Treatise  on  Baptism,'  which  is  a  curious  record  of  his 
philosophical  knowledge.  .  .  . 

"In  1832  he  obtained  a  situation  as  travelling  tutor, 
which  was  to  take  him  abroad  for  some  time.  We  loved 
him  as  much  as  consists  with  a  boy's  nature  to  love  his 
teacher,  and  subscribed  for  a  silver  snuff-box  as  a  slight 
mark  of  our  regard.  .  .  . 

"  I  am  afraid  that  the  situation  of  travelling  tutor  did 
not  turn  out  well,  for  within  two  years  Lindsay  was  back 
again  in  Dundee,  and  resumed  his  position  of  assistant 
teacher,  arduously  following  at  the  same  time  his  favourite 
studies." 

The  scope  of  his  teaching  at  this  time  is  shown  by  the 
following  notice  which  appeared  in  the  '  Dundee  Advertiser ' 
of  April  11,  1834:— 

"  J.  B.  Lindsay  resumes  classes  for  cultivating  the  intel- 
lectual and  historical  portions  of  knowledge  and  instruction 
on  April  14,  1834,  in  South  Tay  Street,  Dundee. 

"  In  a  few  weeks  hence  a  course  of  lectures  will  be  formed 
on  frictional,  galvanic,  and  voltaic  electricity  ;  magnetism ; 
and  electro-magnetism.  The  battery,  already  powerful,  is 
undergoing  daily  augmentation.  The  light  obtained  from 
it  is  intensely  bright,  and  the  number  of  lights  may  be 
increased  without  limit. 

' '  A  great  number  of  wheels  may  be  turned  [by  electricity], 
and  small  weights  raised  over  pulleys. 

"  Houses  and  towns  will  in  a  short  time  be  lighted  by 
electricity  instead  of  gas,  and  heated  by  it  instead  of  coal ; 
and  machinery  will  be  worked  by  it  instead  of  steam — all 
at  a  trifling  expense. 

"  A  miniature  view  of  all  these  effects  will  be  exhibited, 
besides  a  number  of  subordinate  experiments,  including  the 
discoveries  of  Sir  Humphry  Davy." 

In  March  1841,  Lindsay  was  appointed  teacher  in  the 


JAMES   BOWMAN   LINDSAY.  17 

Dundee  Prison  on  a  salary  of  <£50  a-year,  a  post  which  he 
held  for  upwards  of  seventeen  years,  till  October  1858. 
It  is  stated  that  shortly  after  taking  up  this  office  he  could 
have  obtained  an  appointment  in  the  British  Museum,  a 
situation  which  would  have  been  most  congenial  to  his 
tastes,  and  which  would  certainly  have  led  to  a  lasting 
recognition  of  his  great  abilities ;  but,  being  unwilling  to 
leave  his  aged  mother,  he  declined  the  offer — a  rare  example 
of  devotion  and  self-denial.  .  .  . 

Lindsay  was  a  bachelor,  and  lived  alone,  buried,  it  might 
be  said,  in  his  books,  collections  of  which,  in  history  and 
philosophy,  science  and  languages,  were  heaped  in  every 
corner  of  his  dwelling — a  small  house  of  three  apartments 
(11  South  Union  Street).  The  kitchen  was  filled  with 
electrical  apparatus,  mostly  the  work  of  his  own  hands  ;  and 
his  little  parlour  was  so  crowded  with  books,  philosophical 
apparatus,  and  other  instruments  of  his  labour,  that  it  was 
difficult  to  move  in  it.  To  provide  these  things,  he  denied 
himself  through  life  the  ordinary  comforts  and  conveniences, 
— bread  and  coffee,  and  other  simple  articles,  forming  the 
principal  part  of  his  diet.  His  house  in  time  acquired  a 
celebrity  as  one  of  the  curiosities  of  Dundee,  and  men  of 
learning  from  distant  parts,  not  only  of  the  kingdom  but  of 
the  world,  often  came  to  pay  him  a  visit. 

In  July  1858,  on  the  recommendation  of  Lord  Derby, 
then  Prime  Minister,  her  Majesty  granted  Lindsay  an 
annual  pension  of  .£100  a-year,  "in  recognition  of  his 
great  learning  and  extraordinary  attainments."  This  well- 
deserved  bounty  relieved  him  from  the  drudgery  of  a  prison 
teacher,  and  henceforth  to  the  close  of  his  life  he  devoted 
himself  entirely  to  literary  and  scientific  pursuits.  " 

Although  never  robust,  Lindsay  on  the  whole  enjoyed 
tolerably  good  health  through  life,  but  trouble  came  at  last. 


18  FIRST   PERIOD — THE   POSSIBLE. 

On  June  24,  1862,  he  was  seized  with  diarrhoea,  which 
carried  him  off  on  June  29,  1862,  in  the  sixty -third  year  of 
his  age.1 

Although  languages  and  chronology  took  up  much  (I  am 
inclined  to  think  too  much)  of  Lindsay's  time,  still  electricity 
and  its  applications  were  his  first,  as  they  were  always  his 
favourite,  study.  Amongst  some  notes  and  memoranda, 
bound  up  with  his  manuscripts  in  the  Albert  Institute, 
Dundee,  he  says  : — 

"  Previous  to  the  discovery  of  Oersted,  I  had  made  many 
experiments  on  magnetism,  with  the  view  of  obtaining  from 
it  a  motive  power.  No  sooner,  however,  was  I  aware  of  the 
deflection  of  the  needle  and  the  multiplication  of  the  power 
by  coils  of  wire  than  the  possibility  of  power  appeared 
certain,  and  I  commenced  a  series  of  experiments  in  1832. 
The  power  on  a  small  scale  was  easily  obtained,  and  during 
these  experiments  I  had  a  clear  view  of  the  application  of 
electricity  to  telegraphic  communication.  The  light  also 
drew  my  attention,  and  I  was  in  a  trilemma  whether  to  fix 
upon  the  power,  the  light,  or  the  telegraph.  After  reflection 
I  fixed  upon  the  light  as  the  first  investigation,  and  had 
many  contrivances  for  augmenting  it  and  rendering  it 
constant.  Several  years  were  spent  in  experiments,  and  I 
obtained  a  constant  stream  of  light  on  July  25,  1835. 
Having  satisfied  myself  on  this  subject,  I  returned  to  some 
glossological  investigations  that  had  been  left  unfinished, 
and  was  engaged  with  these  till  1843.  In  that  year  I  pro- 
proposed  a  submarine  telegraph  across  the  Atlantic,  after 
having  proved  the  possibility  by  a  series  of  experiments. 
Inquiries  on  other  subjects  have  since  that  time  engaged 
my  attention,  but  I  eagerly  desire  to  return  to  electricity." 

The  first  public  announcement  of  Lindsay's  success  in 

1  Nome's  '  Dundee  Celebrities  of  the  Nineteenth  Century, '  Dundee 
1873. 


JAMES   BOWMAN    LINDSAY.  19 

electric  lighting  was  contained  in  a  short  paragraph  in  the 
'Dundee  Advertiser'  of  July  31,  1835  ;  and  on  October  30 
following  the  same  paper  published  a  letter  on  the  subject 
from  Lindsay  himself  :— 

"ELECTRIC  LIGHT. 

"  SIR, — As  a  notice  of  my  electric  light  has  been  exten- 
sively circulated,  some  persons  may  be  anxious  to  know  its 
present  state,  and  my  views  respecting  it.,  ' 

"  The  apparatus  that  I  have  at  present  is  merely  a  small 
model.  It  has  already  cost  a  great  deal  of  labour,  and  will 
yet  cost  a  good  deal  more  before  my  room  is  sufficiently 
lighted.  Had  circumstances  permitted,  it  would  have  been 
perfected  two  years  ago,  as  my  plans  were  formed  then.  I 
am  writing  this  letter  by  means  of  it,  at  6  inches  or  8  inches 
distant ;  and,  at  the  present  moment,  can  read  a  book  at 
the  distance  of  1 J  foot.  From  the  same  apparatus  I  can  get 
two  or  three  lights,  each  of  which  is  fit  for  reading  with.  I 
can  make  it  burn  in  the  open  air,  or  in  a  glass  tube  without 
air,  and  neither  wind  nor  water  is  capable  of  extinguishing 
it.  It  does  not  inflame  paper  nor  any  other  combustible. 
These  are  facts. 

"  As  I  intend  in  a  short  time  to  give  a  lecture  on  the 
subject,  my  views  on  the  further  progress  will  be  unfolded 
then.  A  few  of  these,  however,  may  be  mentioned  just 
now. 

"  Brilliant  illumination  will  be  obtained  by  a  light  incap 
able  of  combustion  ;  and,  on  its  introduction  to  spinning 
mills,  conflagrations  there  will  be  unheard  of.  Its  beauty 
will  recommend  it  to  the  fashionable ;  and  the  producing 
apparatus,  framed,  may  stand  side  by  side  with  the  piano  in 
the  drawing-room.  Requiring  no  air  for  combustion,  and 
emitting  no  offensive  smell,  it  will  not  deteriorate  the 


20  FIRST   PERIOD — THE   POSSIBLE. 

atmosphere  in  the  thronged  hall.  Exposed  to  the  open 
day,  it  will  blaze  with  undiminished  lustre  amidst  tempests 
of  wind  and  rain  ;  and,  being  capable  of  surpassing  all  lights 
in  splendour,  it  will  be  used  in  lighthouses  and  for  telegraphs. 
The  present  generation  may  yet  have  it  burning  in  their 
houses  and  enlightening  their  streets.  Nor  are  these  pre- 
dictions the  offshoots  of  an  exuberant  fancy  or  disordered 
imagination.  They  are  the  anticipated  results  of  laborious 
research  and  of  countless  experiments.  Electricity,  moreover, 
is  destined  for  mightier  feats  than  even  universal  illumina- 
tion. J.  B.  LINDSAY. 

"DUNDEE,  Oct.  28,  1835." 


Lindsay's  connection  with  electric  telegraphy  forms  a 
very  interesting  episode.  We  have  seen  that  from  about 
the  year  1830  he  was  familiar  with  telegraphic  projects, 
and  that  he  made  them  the  subject  of  illustration  in  his 
classes.  At  this  date  electric  telegraphs  were  distinctly 
in  the  air,  but,  like  electric  lighting,  they  had  hardly 
advanced  beyond  the  laboratory  stage.1  Lindsay  does 
not  appear  to  have  carried  them  much  further  for  several 
years,  for  it  was  not  until  1843  that  he  conceived  the  bold 
idea  of  a  submarine  telegraph  to  America  by  means  of  a 
naked  wire  and  earth-batteries,  "after  having  proved  the 
possibility  by  a  series  of  experiments." 

It  is  true  that  at  this  time  the  earth-battery  was  known. 
It  was  first  proposed  by  Kemp,  of  Edinburgh,  in  1828; 
Prof.  Gauss  in  1838  suggested  its  employment  for  tele- 
graphic purposes,  and  Steinheil,  acting  on  the  suggestion, 
actually  used  it  with  some  success  on  the  Munich-Nanhofen 

1  From  the  public  exhibition  of  Baron  Schilling's  needle  instru- 
ment in  Germany  in  1835-36  dates  the  first  real  start  of  electric 
telegraphy*  See  my  'History  of  Electric  Telegraphy,'  chap.  ix. 


JAMES   BOWMAN   LINDSAY.  21 

Railway,  twenty-two  miles  long ;  and  Bain  in  October  1842 
employed  it  for  working  clocks.  Similarly,  the  idea  of 
signalling  with  uninsulated  wire  and  without  any  wire  at 
all  was  not  new,  for,  as  we  have  seen,  the  possibility  of 
doing  so  was  in  a  manner  forced  on  the  notice  of  Steinheil 
in  1838  and  on  Morse  in  1842,  but  Lindsay  was  certainly 
the  first  to  combine  the  two  principles  in  his  daring  pro- 
posal of  an  Atlantic  telegraph ;  and  this,  be  it  remembered, 
at  a  time  when  electric  telegraphy  was  still  a  young  and 
struggling  industry,  and  when  submarine  telegraphy  was 
yet  a  dream. 

On  June  19,  1845,  a  short  paragraph  appeared  in  the 
'  Northern  Warder,'  Dundee,  referring  to  a  New  York 
project  of  communicating  between  England  and  America 
by  means  of  a  submerged  copper  wire  "properly  covered 
and  of  sufficient  size."  This  called  forth  the  following 
letter  from  Lindsay,  which  was  published  in  the  same 
paper  on  June  26  following  : — 

"ELECTKIC  TELEGRAPH  TO  AMERICA. 

"  SIR, — The  few  lines  I  now  send  you  have  been  occa- 
sioned by  a  notice  in  your  last  in  reference  to  an  electric 
telegraph  to  America.  Should  the  plan  be  carried  into 
effect  the  following  hints  should  be  attended  to  :  The  wire 
should  be  of  pure  copper,  as  otherwise  it  would  be  injured 
by  the  electro-chemical  action  of  the  water.  The  wire 
must  not  be  composed  of  parts  joined  by  soldering,  but 
welded  together ;  this  welding  can  be  performed  by  elec- 
tricity. In  order  to  prevent  the  action  of  water  on  the 
wire,  a  button  of  a  more  oxidable  metal  should  be  welded 
to  it  at  short  distances;  the  best  metal  for  this  purpose 
would  be  lead.  If  soldered  to  the  wire,  it  must  be  soldered 
by  lead  alone.  No  third  metal  must  be  used.  If  welded, 


22  FIRST  PERIOD — THE   POSSIBLE. 

it  may  be  done  by  electricity.  In  this  way  the  wire  resting 
on  the  bottom  of  the  sea  might  last  a  long  time.  The  one 
end  of  the  wire  is  then  to  be  soldered  or  welded  to  a  plate 
of  zinc  immersed  in  the  ocean  on  the  coast  of  Britain,  and 
the  other  end  similarly  joined  to  a  plate  of  copper  deposited 
in  the  same  ocean  on  the  coast  of  America.  In  reference 
to  the  expense,  suppose  the  wire  to  be  a  ninth  or  tenth  of 
an  inch  diameter,  then  the  length  of  100  inches  would  con- 
tain a  cubic  inch  of  copper,  and  three  miles  of  wire  would 
contain  a  cubic  foot,  weighing  9000  ounces,  of  the  value 
of  about  .£36  sterling.  Owing  to  the  inequalities  in  the 
bottom  of  the  ocean,  the  distance  to  America  might  be 
3000  miles,  and  the  expense  £36,000  sterling  — a  trifle 
when  compared  with  the  resulting  benefit.  The  only 
injury  that  the  wire  is  likely  to  undergo  is  from  sub- 
marine eruptions.  It  may  be  broken  by  these.  The  two 
ends,  however,  being  accessible,  the  greater  part  of  the 
wire  may  be  drawn  up,  and  the  necessary  length  of  wire 
welded  to  it.  It  should  be  remembered  that  this  welding 
must  be  done  by  electricity.  To  Calcutta,  by  the  Cape  of 
Good  Hope,  the  expense  would  be  £200,000.  The  wire 
from  Calcutta  to  Canton  would  cost  £70,000,  to  New 
Zealand  £120,000,  to  Tahiti  nearly  £200,000.  A  wire 
might  be  placed  round  the  coast  of  Britain,  and  another 
along  the  coast  of  America.  There  might  be  stations  at 
different  towns  and  electric  clocks  agreeing  with  each  other 
to  a  second  of  time.  Each  town  might  have  a  specific  time 
for  intelligence.  Suppose  Dundee  to  have  the  hour  from 
nine  to  ten.  From  nine  to  ten  minutes  past  nine,  mes- 
sages are  sent  and  answers  received  between  Dundee  and 
JSTew  York.  From  ten  minutes  to  twenty  minutes  past 
nine  communication  is  made  between  Dundee  and  Quebec. 
The  rest  of  the  hour  is  for  intercourse  between  Dundee 
and  other  towns.  The  same  is  done  with  Edinburgh, 


JAMES   BOWMAN   LINDSAY.  23 

Glasgow,   Liverpool,   &c.,   each  town  having  an  hour  for 
itself.— L. 

"DUNDEE,  June  21,  1845." 

From  this  letter  it  is  clear  that  Lindsay  then  contem- 
plated an  uninsulated  wire  across  the  Atlantic  in  connection 
with  what  have  come  to  be  known  as  earth -batteries  at 
the  stations  along  the  coasts.  His  plan  of  protecting  the 
wire  from  the  corrosive  action  of  the  sea-water  was  evidently 
borrowed  from  Sir  Humphry  Davy's  proposal  of  1824  for 
the  protection  of  the  copper  sheathing  of  ships  by  strips  of 
zinc ;  while  the  further  suggestion,  on  which  he  insists  so 
much,  of  welding  the  various  lengths  of  wire  by  electricity, 
if  not  original  with  him,  was  at  all  events  a  very  early 
recognition  of  a  process  which  has  cropped  up  again  in 
recent  years,  and  which  is  now  largely  employed.1 

Between  1845  and  1853  Lindsay  does  not  appear  to  have 
done  anything  in  furtherance  of  his  Atlantic  project,  being 
probably  wholly  absorbed  in  his  linguistic  and  chronological 
studies.  At  all  events,  we  hear  nothing  from  him  until 
March  11,  1853,  when  a  notice  appeared  in  the  'Dundee 
Advertiser '  of  a  lecture  which  he  proposed  to  give  on  the 
ensuing  Tuesday  at  the  Thistle  Hall. 

In  the  same  paper  a  week  later  a  report  of  the  lecture  is 
given  as  follows  : — 

"  TELEGRAPHIC  COMMUNICATION. 

"  On  Tuesday  evening  our  learned  and  ingenious  towns- 
man, Mr  J.  B.  Lindsay,  delivered  a  lecture  on  the  above 
subject,  one  with  which  he  has  an  acquaintance  second  to 

1  Electric  welding  was  proposed  by  Joule  in  1856 ;  by  Wilde  in 
1865  ;  and  by  Prof.  Elihu  Thomson  (America)  and  Dr  Benardos 
(Russia)  in  1887. 


24  FIRST   PERIOD — THE   POSSIBLE. 

no  man  in  the  kingdom.  It  would  be  impossible,  in  the 
limited  space  at  our  disposal,  to  give  any  vidimus  of  the 
lecture ;  we  can  only  indicate  the  outline  of  a  recent  dis- 
covery made  by  Mr  Lindsay,  involving  a  principle  which,  if 
capable  of  acting  irrespective  of  distance  (and  we  see  no 
reason  to  doubt  that  it  is),  must  by-and-by  revolutionise 
all  our  ideas  of  time  and  space.  Mr  Lindsay  stated  the 
principle  to  be  that  submerged  wires,  such  as  those  now 
used  for  telegraphic  intelligence  between  this  country  and 
Ireland  and  France,  were  no  longer  necessary.  By  a 
peculiar  arrangement  of  the  wires  at  the"  sides  of  rivers  or 
seas,  the  electric  influence  can  be  made  to  pass  on  through 
the  water  itself.  This  proposition  was  certainly  startling, 
but  he  illustrated  it  on  a  small  scale  by  means  of  a  water- 
trough,  and,  so  far  as  the  experiment  went,  it  faithfully 
developed  the  principle.  Mr  Lindsay,  after  concluding 
these  experiments,  proceeded  to  point  out  the  lines  which 
appeared  to  him  most  eligible  for  transmitting  telegraphic 
intelligence  throughout  the  world ;  and,  having  done  so,  he 
wound  up  with  a  peroration  of  great  beauty,  in  which  the 
wonders  to  be  achieved  by  electric  influence  in  the  days  to 
come  were  eloquently  set  forth.  It  is  a  fine  sight  to  see 
this  learned  and  philosophic  man  pursuing  the  studies  of 
science  and  literature,  not  for  the  sake  of  any  empty 
applause,  but  for  those  pure  pleasures  they  are  in  themselves 
so  well  fitted  to  bestow.  At  the  same  time,  it  is  gratifying 
to  know  that  there  are  many  people  capable  of  appreciating 
the  modest  and  retiring  character  of  Mr  Lindsay, — a  fact 
which  was  clearly  evidenced  on  Tuesday  evening  by  the 
numerous  and  most  respectable  meeting  which  then 
assembled  to  hear  his  scientific  lecture." 

In   the   following   August    Lindsay    delivered    another 
lecture  (probably  the  same)  in  Glasgow,  and  so  sanguine 


JAMES  BOWMAN  LINDSAY.  25 

was  he  at  this  time  of  the  practicability  of  his  method  that 
he  actually  patented  it  on  June  5,  1854.  The  following 
account,  which  I  have  condensed  from  the  specification  of 
his  patent,  explains  the  modus  operandi,  and  also  shows 
how  well  he  understood  the  conditions  of  the  problem  : — 

"  My  invention  consists  of  a  mode  of  transmitting  tele- 
graphic messages  by  means  of  electricity  or  magnetism 
through  and  across  water  without  submerged  wires,  the 
water  being  made  available  as  the  connecting  and  conduct- 
ing medium  by  the  following  means  : — 

"  On  the  land,  on  the  side  from  which  the  message  is  to 
be  sent,  I  place  a  battery  and  telegraph  instrument,  to 
which  are  attached  two  wires  terminating  in  metal  balls, 
tubes,  or  plates  placed  in  the  water  or  in '  moist  ground 
adjacent  to  the  water  at  a  certain  distance  apart,  according 
to  the  width  of  the  water  to  be  crossed  (the  distance 
between  the  two  balls,  plates,  or  tubes  to  be  greater  than 
across  the  water  when  practicable).  On  the  land  which  is 
situated  on  the  opposite  side  of  the  water,  and  to  which 
the  message  is  to  be  conveyed,  I  place  two  similar  metal 
balls,  plates,  or  tubes,  immersed  as  above  stated,  and 
having  wires  attached  to  them  which  lead  to,  and  are  in 
connection  with,  another  battery  and  needle  indicator,  or 
other  suitable  telegraphic  instrument.  A,  A  in  the  diagram 
(fig.  2)  show  the  position  of  the  battery  and  instru- 
ment on  one  side  of  the  water,  z ;  B,  B,  the  battery  and 
instrument  on  the  opposite  side ;  c,  D,  E,  F,  metallic  or 
charcoal  terminators;  G,  H,  i,  K,  wires  insulated  in  the  usual 
way,  and  connecting  the  terminators,  batteries,  and  instru- 
ments, as  shown. 

"As  regards  the  power  or  primary  agent,  it  may  be 
either  voltaic,  galvanic,  or  magnetic  electricity,  and  the 
apparatus  for  evolving  the  same,  such  as  is  used  for  ordi- 
nary telegraphic  purposes. 


26 


FIRST   PERIOD — THE   POSSIBLE. 


"As  regards  the  indicating  apparatus,  I  propose  to 
employ  any  of  the  instruments  in  known  use  which  are 
most  efficient  for  my  purpose,  observing  that  the  needle 
indicator  may  be  arranged  either  in  a  vertical  or  in  a  hori- 
zontal position,  and  that  the  coil  of  wire  which  actuates 
the  needle  may  be  increased  or  diminished  according  to 
circumstances. 


Water 

Z 


"  Suppose  it  is  required  to  transmit  a  message  from  A, 
the  operator  completes  the  circuit  of  the  electric  current  as 
ordinarily  practised.  It  will  be  evident  that  the  current 
will  have  two  courses  open  to  it,  the  one  being  directly 
back  through  the  water  from  c  to  D,  and  the  other  across  the 
water  from  c  to  B,  along  the  wires  I  K,  through  the  instru- 
ment B,  and  back  from  F  to  D.  Now,  I  have  found  that  if 
each  of  the  two  distances  c  D  and  E  F  be  greater  than  c  E 


JAMES   BOWMAN   LINDSAY.  27 

and  D  F,  the  resistances  through  c  E  and  D  p  will  be  so 
much  less  than  that  through  the  water  between  c  and  D, 
that  more  of  the  current  will  pass  across  the  water,  through 
the  opposite  wires,  and  recross  at  P,  than  take  the  direct  course 
CD;  or,  more  correctly  speaking,  the  current  will  divide 
itself  between  the  two  courses  in  inverse  ratio  to  their 
resistances.  As  cases  may  arise,  from  local  or  other  causes, 
such  as  not  to  admit  of  the  distance  between  the  immersed 
plates  being  greater  than  the  distance  across  the  water,  I 
propose,  then,  to  augment  the  force  of  the  batteries,  and  to 
increase  the  size  of  the  plates,  so  as  to  compel  a  sufficient 
portion  of  the  current  to  cross.  I  prefer,  however,  when 
circumstances  admit  of  it,  employing  the  first  method." 

Lindsay's  first  public  trials  were  across  the  Earl  Grey 
Docks  at  Dundee,  and  then  across  the  Tay  at  Glencarse, 
where  the  river  is  nearly  three -quarters  of  a  mile  wide. 
Of  the  few  friends  who  assisted  at  these  experiments  Mr 
London  of  Dundee  is,  I  believe,  the  only  one  now  left. 
He  tells  us  that  Lindsay  would  station  them  on  one  side 
of  the  Tay,  enjoining  them  to  watch  the  galvanometer  and 
note  down  how  the  needle  moved.  He  would  then  insert 
his  plates  in  the  water  on  their  side  of  the  river,  and,  cross- 
ing over  to  the  opposite  side,  would  complete  his  arrange- 
ments. With  a  battery  of  twenty -four  Bunsen  cells  he 
would  make  a  few  momentary  contacts,  reversing  the  con- 
nections a  few  times  so  as  to  produce  right  and  left  deflec- 
tions of  the  galvanometer  needle.  Then  he  would  return 
and  compare  the  deflections  of  the  needle  which  they  had 
noted  with  the  order  in  which  he  had  himself  made  the 
battery  contacts,  and  on  finding  them  to  correspond  he 
would  be  supremely  happy.1 

In  1854  Lindsay  was  in  London,  and  brought  his  plans 
to  the  notice  of  the  Electric  Telegraph  Company.  It  is 
1  Kerr,  'Wireless  Telegraphy,'  1898,  p.  40. 


28  FIEST   PERIOD — THE   POSSIBLE. 

now  curious  to  remark  that  Sir  W.  H.  Preece,  who,  as 
we  shall  see  later  on,  became  himself  in  after  years  an 
eminent  wireless -telegraph  inventor,  was  the  officer  who 
was  deputed  to  assist  him  and  report  on  his  method.  Sir 
William  tells  us  that  these  were  almost  the  first  electrical 
experiments  of  any  importance  in  which  he  ever  took  part, 
and  in  a  letter  to  the  writer,  dated  October  15,  1898,  he 
adds :  "  I  remember  Lindsay  very  well.  He  came  up 
to  London  with  his  'great  invention,'  and  I  assisted  him 
in  making  his  experiments  in  our  gutta-percha  testing  tank 
at  Percy  Wharf  on  the  Thameo.  We  used  the  old  sand 
battery  and  galvanometers — ohms  and  volts  were  not  in- 
vented then — and  showed  that  by  varying  the  distance 
apart  of  the  plates  on  each  side  of  the  tank  we  varied 
the  strength  of  the  signals.  I  have  no  record  of  the 
results,  but  they  showed  the  feasibility  of  the  plan.  I 
had,  however,  to  crush  poor  Lindsay  by  telling  him  that  it 
was  not  new.  Morse  in  1842  had  done  the  same  thing, 
and  Alexander  Bain  had  also  tried  about  the  same  time 
a  similar  experiment  on  the  Serpentine,  but  I  have  not 
found  any  published  record  of  it."  * 

In  August  1854  Lindsay  carried  out  a  series  of  experi- 
ments at  Portsmouth,  in  which,  according  to  a  notice  in 
the  '  Morning  Post '  (August  28),  he  completely  succeeded 
in  transmitting  signals  across  the  mill  dam,  where  it  is 
about  500  yards  wide.2 

1  In  this,  I  think,  his  memory  betrays  him.     Bain's  experiments 
had  to  do  with  an  insulated  wire  in  connection  with  earth-batteries. 
See  'The  Artisan,'  June  30,  1843,  p.  147. 

2  These  experiments  were  also  noticed  in  '  Chambers's  Journal '  for 
September  1854,  as  follows:  "Again  has  an  attempt  been  made  to 
send  a  signal  through  water  without  a  wire — this  time  at  Ports- 
mouth, where  it  was  attended  with  partial  success.     The  thing  has 
often  been  tried  :  a  few  years  ago,  a  couple  of  savants  might  have 
been  seen  sending  their  messages  across  those  minor  lakes  known  to 


JAMES   BOWMAN   LINDSAY.  29 

Lindsay  repeated  these  experiments  at  intervals  and  at 
various  places,  indeed  whenever  and  wherever  he  had  the 
chance,  his  greatest  performance  being  across  the  Tay,  from 
Dundee  to  Woodhaven,  where  the  river  is  nearly  two  miles 
broad.  On  one  of  these  occasions,  and  when  an  Atlantic 
telegraph  began  to  be  seriously  debated,  the  difficulty  of 
finding  a  steamer  large  enough  to  carry  the  cable  was 
discussed,  when  Lindsay  quietly  remarked,  "If  it  were 
possible  to  provide  stations  at  not  more  than  twenty  miles 
distant  all  the  way  across  the  Atlantic,  I  would  save  them 
the  trouble  of  laying  any  cable." 

In  September  1859  Lindsay  read  a  paper  before  the 
British  Association  at  Aberdeen  "  On  Telegraphing  without 
Wires,"  which  drew  from  Lord  Rosse,  the  president  of  the 
section,  special  commendation.  Prof.  Faraday  and  (Sir) 
G.  B.  Airy,  then  Astronomer  -  Royal,  also  added  their 
approval  of  the  views  enunciated.  Prof.  Thomson  (now 
Lord  Kelvin)  was  also  present,  and,  as  is  well  known, 
was  then  deeply  engaged  with  Atlantic  cable  projects. 
History  does  not  say  what  he  thought  of  the  poor  Dundee 
lecturer,  but,  with  the  experience  of  forty  years,  we  can 
easily  guess. 

A  brief  abstract  of  the  paper  was  published  in  the 
Annual  Report  of  the  Association  for  1859,  but  a  fuller 
account  appeared  in  the  'Dundee  Advertiser,'  from  which 
I  take  the  following  interesting  details : — 

"  The  author  has  been  engaged  in  experimenting  on  the 

Londoners  as  the  Hampstead  Ponds  ! "     Can  any  reader  tell  me  who 
these  savants  were  ? 

About  this  time  experiments  in  wireless  telegraphy  were  evidently 
popular.  Van  Reese  at  Portsmouth  ;  Gintl,  the  first  inventor  of  a 
duplex  telegraph,  in  Austria ;  Bonelli  in  Italy,  and  Bouchotte  and 
Douat  in  France  (and  doubtless  others),  all  were  engaged  on  the 
problem,  but  with  what  results  I  do  not  know,  as  I  have  not  met 
with  any  detailed  accounts  of  their  experiments. 


30  FIRST  PERIOD — THE   POSSIBLE. 

subject,  and  in  lecturing  on  it  in  Dundee,  Glasgow,  and 
other  places  since  1831.  Recently  he  had  made  addi- 
tional experiments,  and  succeeded  in  crossing  the  Tay 
where  it  was  three-quarters  of  a  mile  broad.  His  method 
had  always  been  to  immerse  two  plates  or  sheets  of  metal 
on  the  one  side,  and  connect  them  by  a  wire  passing 
through  a  coil  to  move  a  needle,  and  to  have  on  the 
other  side  two  sheets  similarly  connected,  and  nearly 
opposite  the  two  former.  Experiments  had  shown  that 
only  a  fractional  part  of  the  electricity  generated  goes 
across,  and  that  the  quantity  that  thus  goes  across  can 
be  increased  in  four  ways :  (1)  by  an  increased  battery 
power;  (2)  by  increasing  the  surface  of  the  immersed 
sheets ;  (3)  by  increasing  the  coil  that  moves  the  receiving 
needle ;  and  (4)  by  increasing  the  lateral  distance  of  the 
sheets.  In  cases  where  lateral  distance  could  be  got  he 
recommended  increasing  it,  as  then  a  smaller  battery  power 
would  suffice.  In  telegraphing  by  this  method  to  Ireland 
or  France  abundance  of  lateral  distance  could  be  got,  but 
for  America  the  lateral  distance  in  Britain  was  much  less 
than  the  distance  across.  In  the  greater  part  of  his  experi- 
ments the  distance  at  the  sides  had  been  double  the  dis- 
tance across ;  but  in  those  on  the  Tay  the  lateral  distance 
was  the  smaller,  being  only  half  a  mile,  while  the  distance 
across  was  three-quarters  of  a  mile. 

"  Of  the  four  elements  above  mentioned,  he  thought 
that  if  any  one  were  doubled  the  portion  of  electricity 
that  crossed  would  also  be  doubled,  and  if  all  the  elements 
were  doubled  the  quantity  transmitted  would  be  eight 
times  as  great.  In  the  experiments  across  the  Tay  the 
battery  was  of  4  square  feet  of  zinc,  the  immersed  sheets 
contained  about  90  square  feet  of  metal,  the  weight  of  the 
copper  coil  was  about  6  lb.,  and  the  lateral  distance  was, 
as  just  stated,  less  than  the  transverse ;  but  if  it  had  been 


JAMES   BOWMAN    LINDSAY.  31 

a  mile,  and  the  distance  across  also  a  mile,  the  signals 
would,  no  doubt,  have  been  equally  distinct.  Should  this 
law  (when  the  lateral  distance  is  equal  to  the  transverse) 
be  found  correct,  the  following  table  might  then  be 
formed :  — 

Zinc  for  battery.     Immersed  sheets.       Weight  of  coil.         Distance  crossed, 

sq.  ft.  sq.  ft.  Ib.  miles. 

4  90  6  1 

8  180  12  8 

16  360  24  64 

32  720  48  512 

64  1440  96  4096 

128  2880  192  32,768 

"But  supposing  the  lateral  distance  to  be  only  half  the 
transverse,  then  the  space  crossed  might  be  16,000  miles; 
and  if  it  was  only  a  fourth,  then  there  would  be  8000 
miles — a  much  greater  distance  than  the  breadth  of  the 
Atlantic.  Further  experiments  were,  however,  necessary 
to  determine  this  law,  but,  according  to  his  calculations, 
he  thought  that  a  battery  of  130  square  feet,  immersed 
sheets  of  3000  square  feet,  and  a  coil  of  200  Ib.,1  would 
be  sufficient  to  cross  the  Atlantic  with  the "  lateral  distance 
that  could  be  obtained  in  Great  Britain." 

After  the  reading  of  the  paper  Lindsay  carried  out  some 
very  successful  experiments  across  the  river  Dee,  in  the 

1  My  readers  will  smile  at  the  suggestion  of  such  galvanometer 
coils,  but  they  should  remember  that  forty  years  ago  matters  electri- 
cal were  largely  ordered  by  the  rule  of  thumb.  The  electro-magnet 
first  used  by  Morse  on  the  Washington-Baltimore  line  (1844),  and 
exhibited  in  Europe,  weighed  185  Ib.  The  arms  were  3^  inches 
long  and  18  inches  diameter,  the  wire  (copper)  being  that  known  as 
No.  16 — the  same  size  as  the  line  wire,  it  being  then  supposed  that 
the  wire  of  the  coils  and  of  the  line  should  be  of  the  same  size 
throughout.  Down  to  1860  not  a  few  practical  telegraphists  held 
this  view.  See  D.  G.  FitzGerald  in  the  London  'Electrical  Review,' 
August  9,  1895,  p.  157. 


32  FIRST   PERIOD — THE   POSSIBLE. 

presence  of  Lord  Kosse,  Prof.  Jacob!  of  St  Petersburg,  and 
other  members  of  the  Association.  In  February  1860  he 
made  Liverpool  the  scene  of  his  operations,  but  there, 
strange  to  say,  he  had  not  the  success  which  hitherto 
attended  him.  The  experiments  failed,  being  "counter- 
acted by  some  unaccountable  influence  which  he  had  not 
before  met  with."  However,  in  the  following  July  he 
was  again  successful  at  Dundee  in  his  experiments  across 
the  Tay,  below  the  Earn,  where  the  river  is  more  than 
a  mile  wide.  In  communicating  these  results  to  the 
'Dundee  Advertiser'  (July  10,  1860),  he  says:  "The 
experiment  was  successful,  and  the  needle  was  strongly 
moved ;  but  as  I  had  no  person  with  me  capable  of  sending 
or  reading  a  message,  it  [regular  telegraphic  signalling]  was 
not  attempted." 

This  was  Lindsay's  last  public  connection  with  the  tele- 
graph, but  to  the  end  of  his  life  (June  29,  1862)  he  re- 
mained perfectly  convinced  of  the  soundness  of  his  views 
and  of  their  ultimate  success.1 

1  On  the  eve  of  the  centenary  of  Lindsay's  birth  the  'Dundee 
Advertiser'  (September  7, 1899)  published  a  very  appreciative  sketch 
of  "  the  famous  Scottish  inventor,"  which  is  largely  based  on  my 
articles  quoted  on  p.  14,  supra.  As  a  result  we  are  gratified  to  learn 
that  "  a  bust  of  James  Bowman  Lindsay,  a  pioneer  of  wireless  teleg- 
raphy by  the  conductive  method,  is  to  be  placed  in  the  Victoria  Art 
Galleries  of  Dundee.  The  bust  is  to  be  of  white  Carrara  marble, 
and  will  be  the  gift  of  Lord  Provost  M'Grady,  Mr  George  Webster 
of  Edinburgh  being  the  sculptor.  It  has  further  been  proposed  to 
erect  a  monument  over  Lindsay's  grave  V>v  public  subscription." — 
'Electrician,'  vol.  xliii.  p.  795. 


J.   W.   WILKINS.  33 


J.  W.  WILKINS— 1845. 

In  the  New  York  'Electrical  Engineer'  of  May  29,  1895, 
it  was  claimed  for  Prof.  Trowbridge  (of  whom  we  shall 
have  more  to  say  later  on)  that  he  was  the  first  to  telegraph 
without  wires  in  1880. 

The  paragraph  in  which  this  claim,  unfounded  as  we 
already  see,  was  advanced,  besides  drawing  renewed  atten- 
tion to  Prof.  Trowbridge's  experiments,  had  the  merit  of 
calling  forth  an  interesting  communication  from  our  own 
Mr  J.  W.  Wilkins,  one  of  the  very  few  telegraph  officers  of 
Cooke  &  Wheatstone's  days  still  with  us,  and  whose  early 
and  interesting  reminiscences  I  hope  we  may  yet  see.1 

Writing  in  'The  Electrician,'  July  19,  1895,  Mr  Wilkins 


"Nearly  fifty  years  ago,  and  thirty  years  before  Prof. 
Trowbridge  '  made  original  researches  between  the  Observa- 
tory at  Cambridge  and  the  City  of  Boston,'  the  writer  of 
these  lines  had  also  researched  on  the  same  subject,  and  a 
year  or  two  later  published  the  results  of  his  investigations 
in  an  English  periodical — the  '  Mining  Journal '  of  March 
31,  1849 — under  the  heading  'Telegraph  communication 
between  England  and  France.'  In  that  letter,  after  going 
into  the  subject  very  much  like  the  American  Professor  in 
1880,  there  will  be  found  my  explanation — also  not  differing 
much  from  the  Professor's — as  to  how  the  thing  was  to  be 
done ;  except  that,  in  my  case,  I  proposed  a  new  and  delicate 
form  of  galvanometer  or  telegraph  instrument  for  the  pur- 
pose, while  he  made  use  of  the  well-known  telephone.  I 
suggested  the  erection  of  lengths  of  telegraph  wires  on  the 

1  Mr  Wilkins  is  the  author  of  two  English  patents  :  (1)  Improve- 
ments in  Electric  Telegraphs,  January  13,  1853  ;  and  (2)  Improve- 
ments in  obtaining  power  by  Electro- Magnetism,  October  28,  1853. 

0 


34  FIRST  PERIOD — THE  POSSIBLE. 

English  and  French  coasts,  with  terminals  dipping  into  the 
earth  or  sea,  and  as  nearly  parallel  as  possible  to  one  another; 
and  I  suggested  a  form  of  telegraph  instrument  consisting  of 
'  coils  of  finest  wire,  of  best  conductibility,'  with  magnets  to 
deflect  them  on  the  passage  of  a  current  of  electricity  through 
them,  which  I  expected  would  take  place  on  the  discharge  of 
electricity  through  the  circuits  on  either  side  of  the  water ; 
anticipating,  of  course,  that  a  portion  of  the  current  would 
flow  from  the  one  pair  of  earth-plates — terminals  of  one 
circuit — to  the  other  pair  of  terminals  on  the  opposite  shore. 

"  It  may  be  interesting  to  relate  how  I  came  to  think 
that  telegraphy  without  wires  was  a  possibility,  and  that  it 
should  have  appeared  to  me  to  have  some  value,  at  a  time 
when  gutta-percha  as  an  insulator  was  not  imagined,  or 
the  ghost  of  a  proposition  for  a  submarine  wire  existed. 
At  that  time,  too,  it  was  with  the  utmost  difficulty  that 
efficient  insulation  could  be  maintained  in  elevated  wires 
if  they  happened  to  be  subject  to  a  damp  atmosphere. 

"It  was  in  the  year  1845,  and  while  engaged  on  the 
only  long  line  of  telegraph  then  existing  in  England — 
London  to  Gosport  —  that  my  observations  led  me  to 
question  the  accepted  theory  that  currents  of  electricity, 
discharged  into  the  earth  at  each  end  of  a  line  of  telegraph, 
sped  in  a  direct  course — instinctively,  so  to  say — through 
the  intervening  mass  of  ground  to  meet  a  current  or  find  a 
corresponding  earth-plate  at  the  other  end  of  it  to  complete 
the  circuit.  I  could  only  bring  myself  to  think  that  the 
earth  acted  as  a  reservoir  or  condenser — in  fact,  receiving 
and  distributing  electricity  almost  superficially  for  some 
certain  or  uncertain  distance  around  the  terminal  earths, 
and  that  according  to  circumstances  only.  A  year  later, 
while  occupied  with  the  installation  of  telegraphs  for 
Messrs  Cooke  &  Wheatstone  (afterwards  the  Electric  Tele- 


J.   W.   WILKINS.  35 

graph  Company),  a  good  opportunity  offered  of  testing  this 
matter  practically  upon  lengths  of  wire  erected  on  both 
sides  of  a  railway.  To  succeed  in  my  experiment,  and 
detect  the  very  small  amount  of  electricity  likely  to  be 
available  in  such  a  case,  I  evidently  required  the  aid  of  a 
very  sensitive  galvanometer,  much  more  so  indeed  than  the 
long  pair  of  astatic  needles  and  coil  of  the  Cooke  &  Wheat- 
stone  telegraph,  which  was  then  in  universal  use  as  a 
detector.  The  influence  of  magnetism  upon  a  wire  con- 
veying an  electric  current  at  once  suggested  itself  to  me, 
and  I  constructed  a  most  sensitive  instrument  on  this 
principle,  by  which  I  succeeded  in  obtaining  actual  signals 
between  lengths  of  elevated  wires  about  120  ft.  apart. 
This,  however,  suggested  nothing  more  at  the  moment  than 
that  the  current  discharged  from  the  earth-plates  of  one 
line  found  its  way  into  the  earth-plates  of  another  and 
adjacent  circuit,  through  the  earth.  Later  on,  I  had  other 
opportunities  of  verifying  this  matter  with  greater  distances 
between  the  lines  of  wire,  and  ultimately  an  instance  in 
which  the  wires  were  a  considerable  distance  apart,  and 
with  no  very  near  approach  to  parallelism  in  their  situa- 
tion. Then  it  was  that  it  entered  my  head  that  telegraph- 
ing without  wires  might  be  a 


The  following  extracts  from  the  letter  in  the  'Mining 
Journal,'  above  referred  to,  may  now  be  reproduced  with 
interest.  I  have  slightly  altered  the  phraseology  with  a 
view  of  making  the  writer's  meaning  more  clear  and 
connected  :  * — 

"Allow   me,    through    the    medium   of    your   valuable 

1  Mr  Charles  Bright  has  reprinted  this  letter  verbatim  in  Jour. 
Inst.  Elec.  Engs.,'  vol.  xxvii.  p.  958,  as  containing  "  the  first  really  prac- 
tical suggestion  in  the  direction  of  inductive  telegraphy  " ;  but,  as  we 
now  see,  it  is  not  the  first  suggestion,  and  it  is  certainly  not  inductive. 


36  FIRST   PERIOD — THE   POSSIBLE. 

journal,  to  draw  attention  to  a  principle  upon  which  a 
telegraphic  communication  may  be  made  between  England 
and  France  without  wires.  I  take  for  certain  (as  experi- 
ments I  have  made  have  shown  me)  that  when  the  poles 
of  a  battery  are  connected  with  any  extended  conducting 
medium,  the  electricity  diffuses  itself  in  radial  lines  between 
the  poles.  The  first  and  larger  portion  will  pass  in  a 
straight  line,  as  offering  the  least  resistance ;  the  rays  will 
then  form  a  series  of  curves,  growing  larger  and  larger, 
until,  by  reason  of  increasing  distance,  the  electricity 
following  the  outer  curves  is  so  infinitesimal  as  to  be  no 
longer  perceptible. 

"  These  rays  of  electricity  may  be  collected  within  a 
certain  distance — focussed  as  it  were — by  the  interposition 
of  a  metallic  medium  that  shall  offer  less  resistance  than 
the  water  or  earth ;  and,  obviously,  the  nearer  the  battery, 
the  greater  the  possibility  of  collecting  them.  I  do  not 
apprehend  the  distance  of  twenty  miles  being  at  all  too 
much  to  collect  a  sufficient  quantity  of  electricity  to  be 
useful  for  telegraphic  purposes.  If,  then,  it  is  possible,  as 
I  believe,  to  collect  in  France  some  portion  of  the  elec- 
tricity which  has  been  discharged  from  a  battery  in 
England,  all  that  is  required  is  to  know  how  to  deal  with 
it  so  that  it  shall  indicate  its  presence. 

"The  most  delicate  of  the  present  telegraph  apparatus, 
the  detector,  being  entirely  unsuited  for  the  purpose,  I  pro- 
pose the  following  arrangement :  Upon  one  shore  I  propose 
to  have  a  battery  that  shall  discharge  its  electricity  into  the 
earth  or  sea,  with  a  distance  between  its  poles  of  five,  ten, 
or  twenty  miles,  as  the  case  may  be.  Let  a  similar  length 
of  wire  be  erected  on  the  opposite  coast,  as  near  to,  and 
parallel  with,  it  as  possible,  with  its  ends  also  dipping  into 
the  earth  or  sea.  In  this  circuit  place  an  instrument  con- 
sisting of  ten,  twenty,  or  more  round  or  square  coils  of  the 


J.   W.   WILKINS.  37 

finest  wire  of  best  conductibility,  suspended  on  points  or 
otherwise  between,  or  in  front  of,  the  poles  of  an  electro-, 
or  permanent,  magnet  or  magnets.  Any  current  passing 
through  the  coil  would  be  indicated  by  its  moving  or  shift- 
ing its  position  with  reference  to  the  poles  of  the  magnet. 
This  would  constitute  a  receiving  apparatus  of  the  most 
delicate  character,  for  its  efficiency  would  depend  not  so 
much  on  the  strength  of  the  current  passing  as  on  the 
power  of  the  magnet,  which  may  be  increased  at  pleasure. 

"  I  hope  some  one  will  take  up  this  suggestion  and  carry 
it  out  practically  to  a  greater  extent  than  my  limited  experi- 
ments have  enabled  me  to  do.  Of  its  truth  for  long  as  well 
as  for  short  distances  I  am  satisfied,  and  only  want  of 
means  and  opportunity  prevent  me  carrying  it  out  myself." 

In  a  recent  letter  to  the  writer  apropos  of  this  early  pro- 
posal, Mr  Wilkins  says  : — 

"  I  will  just  say  that  all  thought  of  induction  was  absent 
in  my  first  experiments.  I  modified  my  views  in  this 
respect  a  year  or  two  later,  but  I  did  not  attach  sufficient 
importance  to  the  matter  to  follow  up  my  communication  to 
the  '  Mining  Journal,'  especially  as  at  that  time  a  cable  was 
actually  laid  across  the  Channel,  which  I  could  not  doubt 
would  be  a  success,  and  a  permanent  one  too.  I  rather 
courted  forgetfulness  of  the  proposition.  Whatever  my 
opinion  at  the  time  was  as  to  the  source  of  the  electricity 
that  I  discovered  in  the  far  removed  and  disconnected 
circuit,  the  result  was  the  same,  and  the  means  I  used  to 
obtain  it  the  same  in  principle  as  those  which  make  the 
matter  an  accomplished  fact  to-day — viz.,  elevated  lengths  of 
wire,  and  the  discharge  of  electricity  from  the  one  on  to  a 
delicate  receiving  apparatus  in  the  circuit  of  the  other. 

"As  regards  the  form  of  receiving  apparatus  which  I 
suggested  for  indicating  the  signals,  I  did  then,  and  do  now, 
attach  great  importance  to  the  happy  idea.  It  happens  to 


38  FIRST   PERIOD — THE   POSSIBLE. 

be  the  most  delicate  form  of  detector  or  galvanometer,  and 
is  identical  in  principle  with  Lord  Kelvin's  apparatus  for 
long  cable  working,  which,  in  his  Siphon  Recorder  Patent, 
he  says  is  as  sensitive  as  his  Mirror  Galvanometer." 

This  principle,  as  the  practical  reader  knows,  has  been 
largely  used  in  telegraphy.  Besides  Lord  Kelvin's  appli- 
cation of  it,  we  have  the  Brown  and  Allan  Relay,  the 
Weston  Relay,  and  Voltmeter,  and  other  contrivances  of  a 
similar  nature ; l  but  Mr  Wilkins  was  himself  the  first  to 
put  it  in  practice,  and  under  the  following  interesting  cir- 
cumstances:  In  1851  he  went  to  America  to  assist  Henry 
O'Reilly  of  New  York,  a  well-known  journalist,  who  had  a 
concession  from  the  patentees  of  the  Morse  system  for  the 
erection  of  telegraph  lines,  at  a  royalty  per  mile.  Disputes 
soon  arose,  and  the  Morse  Syndicate  sought  to  prevent 
O'Reilly  from  using  their  relay,  without  which  the  Morse 
instruments  would  be  useless  for  long  distances.  In  this 
difficulty  O'Reilly  adopted  Bain's  electro-chemical  apparatus, 
and  employed  it  for  a  time  on  the  People's  Telegraph  from 
New  York  to  Boston,  via  Albany.  But  finding  that  it  was 
impossible  to  use  this  instrument  in  connection  with  inter- 
mediate stations,  O'Reilly  was  again  in  a  difficulty,  when  Mr 
Wilkins  came  to  the  rescue  by  saying  he  could  devise  a 
relay  which  did  not  require  an  iron  armature,  or  electro- 
magnet of  the  ordinary  form,  and  which  would  therefore  be 
independent  of  the  Morse  patent.  Very  soon  relays  con- 
sisting of  movable  coils  of  wire,  suspended  between  the 
poles  of  a  magnet,  were  constructed  in  the  workshop  of 
John  Gavitt,  a  friend  of  O'Reilly's,  and  then  famous  as  a 
bank-note  engraver.  The  instruments  were  placed  in  the 

1  The  germ  of  all  these  instruments,  as  well  as  the  Axial  Magnets 
of  Prof.  Page  and  Royal  E.  House,  was  sown  by  Edward  Davy  in 
England  in  1837.  See  my  'History  of  Electric  Telegraphy,'  pp.  356, 
357. 


DR  O'SHAUGHNESSY.  39 

circuit  of  the  People's  Telegraph,  and  O'Reilly  was  saved — 
but  only  for  a  time,  as  in  the  end  he  was  beaten  by  his 
powerful  opponents.  The  Wilkins  relay  was  put  aside  and 
soon  forgotten,  but  forty-three  years  later  it  was  brought 
forward  again  by  Mr  Weston  as  an  original  invention.1 


DR  O'SHAUGHNESSY  (AFTERWARDS  SIR  WILLIAM 
O'SHAUGHNESSY  BROOKE)— 1849. 

One  of  the  first  difficulties  encountered  in  the  early  days 
of  the  telegraph  in  India  was  the  crossing  of  the  great 
water-ways  that  abound  in  that  country ;  and  it  was  this 
difficulty  which  first  directed  the  attention  of  Dr  O'Shaugh- 
nessy,  the  introducer  of  the  system  in  India,  to  the  subject 
of  subaqueous  telegraphy. 

In  1849  he  laid  a  bare  iron  rod  under  the  waters  of  the 
river  Huldee,  4200  feet  wide,  with  batteries  and  delicate 
needle  instruments  in  connection  on  each  bank.  Signals 
were  passed,  but  "  it  was  found  that  the  instruments 
required  the  attention  of  skilful  operators,  and  that  in 
practice  such  derangements  occurred  as  caused  very  frequent 
interruptions." 

He  next  tried  the  experiment  without  any  metallic  con- 
ductor, using  the  water  alone  as  the  sole  vehicle  of  the 
electric  impulses,  but,  though  he  again  succeeded  in  passing 
intelligible  signals,  he  found  that  the  battery  power  for 
practical  purposes  would  be  enormous  (he  used  up  to  250 
cells  of  the  nitric  acid  and  platinum  form),  and  therefore 
prohibitively  expensive. 

Although  for  practical  purposes  he  soon  abandoned  the 
idea  of  signalling  across  rivers  with  naked  wires,  and  with- 
out any  wires  at  all,  O'Shaughnessy  for  many  years  took 
1  See  the  New  York  '  Electrical  Engineer,'  February  21,  1894. 


40  FIRST  PERIOD — THE  POSSIBLE. 

great  interest  in  the  subject.  Thus  as  late  as  1858  we  find 
him  performing  some  careful  experiments  in  the  lake  at 
Ootacamund,  and  in  his  Administration  Eeport  of  the  Tele- 
graph Department  for  that  year  he  says :  "  I  have  long  since 
ascertained  that  two  naked  uncoated  wires,  kept  a  moderate 
distance — say  50  or  100  yards — apart,  will  transmit  electric 
currents  to  considerable  distances  (two  to  three  miles)  suf- 
ficiently powerful  for  signalling  with  needle  instruments." 


E.  AND  H.  HIGHTON— 1852-72. 

The  brothers  Edward  and  Henry  Highton,  who  were 
well-known  inventors  in  the  early  years  of  electric  teleg- 
raphy, took  up  the  problem  of  transaqueous  communica- 
tion about  1852.  In  Edward  Highton's  excellent  little  book, 
4  The  Electric  Telegraph :  Its  History  and  Progress,'  pub- 
lished in  that  year,  he  says  :  "  The  author  and  his  brother 
have  tried  many  experiments  on  this  subject.  Naked 
wires  have  been  sunk  in  canals,  for  the  purpose  of  ascer- 
taining the  mathematical  law  which  governs  the  loss  of 
power  when  no  insulation  was  used.  Communications 
were  made  with  ease  over  a  distance  of  about  a  quarter 
of  a  mile.  The  result,  however,  has  been  to  prove  that 
telegraphic  communications  could  not  be  sent  to  any  con- 
siderable distance  without  the  employment  of  an  insulated 
medium." 

On  the  other  hand,  Henry  Highton  long  continued  to 
believe  in  its  practicability,  and  made  many  further  experi- 
ments to  that  end.  These  were  embodied  in  a  paper  read 
before  the  Society  of  Arts  on  May  1,  1872  (Telegraphy 
without  Insulation),  from  which  I  condense  the  following 
account : — 

"  I  have  for  many  years  been  convinced  of  the  possibility 


E.   AND   H.   HIGHTON.  41 

of  telegraphing  for  long  distances  without  insulation,  or 
with  wires  very  imperfectly  insulated ;  but  till  lately  I  had 
not  the  leisure  or  opportunity  of  trying  sufficient  experi- 
ments bearing  on  the  subject.  I  need  hardly  say  that 
the  idea  has  been  pronounced  on  all  hands  to  be  entirely 
visionary  and  impossible,  and  I  have  been  warned  of  the 
folly  of  incurring  any  outlay  in  a  matter  where  every 
attempt  had  hitherto  failed.  But  I  was  so  thoroughly 
convinced  of  the  soundness  of  my  views,  and  of  the 
certainty  of  being  able  to  go  a  considerable  distance  with- 
out any  insulation,  and  any  distance  with  very  imperfect 
insulation,  that  I  commenced,  some  three  or  four  months 
since,  a  systematic  series  of  experiments  with  a  view  to 
test  my  ideas  practically. 

"  I  began  by  trying  various  lengths  of  wire,  dropped  in 
the  Thames  from  boats,  and  found  that  I  could,  without 
the  slightest  difficulty,  exceed  the  limits  allowed  hitherto 
as  practicable.  This  method,  however,  was  attended  with 
much  difficulty  and  inconvenience,  owing  to  the  rapidity  of 
the  tides  and  the  motion  of  the  boats.  I  next  tried  wires 
across  the  Thames,  but  had  them  broken  five  or  six  times 
by  the  strength  of  the  current  and  by  barges  dragging  their 
anchors  across  them. 

"  1  then  put  the  instrument  in  my  own  room,  on  the 
banks  of  the  river,  and  sent  a  boat  down  stream  with  a 
reel  of  wire  and  a  battery  to  signal  to  me  at  different  dis- 
tances. The  success  was  so  much  beyond  my  expectations, 
that  I  next  obtained  leave  to  lay  down  wires  in  Wimbledon 
Lake.  As  the  result  of  all  these  experiments  I  found  that 
water  is  so  perfect  an  insulator  for  electricity  of  low  tension 
that  wires  charged  with  it  retained  the  charge  with  the 
utmost  obstinacy;  and,  whether  from  the  effect  of  polar- 
isation (so-called),  or,  as  I  am  inclined  to  suppose,  from 
electrisation  of  the  successive  strata  of  water  surrounding 


42  FIRST   PERIOD — THE   POSSIBLE. 

the  wire,  a  long  wire,  brought  to  a  state  of  low  electrical 
tension,  will  retain  that  tension  for  minutes,  or  even  hours. 
Notwithstanding  attempts  to  discharge  the  wire  every  five 
seconds,  I  have  found  that  a  copper  surface  of  10  or  12 
square  feet  in  fresh  water  will  retain  a  very  appreciable 
charge  for  a  quarter  of  an  hour ;  and  even  when  we  attempt 
to  discharge  it  continuously  through  a  resistance  of  about 
thirty  units  [ohms],  it  will  retain  an  appreciable  though 
gradually  decreasing  charge  for  five  or  six  minutes.1 

"  Since  that  time  I  have  constructed  an  artificial  line, 
consisting  of  resistance  coils,  condensers,  and  plates  of 
copper  in  liquids,  acting  at  once  as  faults  and  as  condensers, 
so  that  I  might  learn  as  far  as  possible  to  what  extent  the 
principle  of  non- insulation  can  be  carried,  and  I  have 
satisfied  myself  that,  though  there  are  difficulties  in  very 
long  lengths  absolutely  uninsulated,  yet  it  is  quite  feasible 
to  telegraph,  even  across  the  Atlantic,  with  an  insulation  of 
a  single  unit  instead  of  the  170,000  units  [absolute]  of  the 
present  cables. 

"  The  instrument  with  which  I  propose  to  work  is  the 
gold-leaf  instrument,  constructed  by  me  for  telegraphic 
purposes  twenty-six  years  ago,2  acted  upon  by  a  powerful 
electro-magnet,  and  with  its  motions  optically  enlarged. 
The  exclusive  use  of  this  instrument  in  England  was 
purchased  by  the  Electric  and  International  Telegraph 
Company,  but  it  was  never  practically  used,  except  in 
Baden,  where  a  Government  commission  recommended  it 
as  the  best.  One  of  its  chief  merits  is  its  extreme  light- 
ness and  delicacy.  Judging  by  the  resistance  it  presents 

1  It  does  not  appear  to  have  struck  our  author  that  these  effects 
would  militate  against  the  practical  application  of  his  method. 

2  A  special  arrangement  of  this  instrument,  adapting  it  for  long 
and  naked  (or  badly  insulated)  lines,  was  patented   February  13, 
1873.     For  reports  of  its  great  delicacy  see  'Telegraphic  Journal,' 
February  15,  1874. 


E.  AND   H.   HIGHTON.  43 

to  the  electric  current,  it  would  appear  that  the  piece  of 
gold-leaf  in  the  instrument  now  before  us  does  not  weigh 
more  than  -^Vrrtii  part  of  a  grain ;  let  us  even  say  that  it 
weighs  four  times  more,  or  -B^rth  Par^  °f  a  grain.  In 
order,  then,  to  make  a  visible  signal  we  only  have  to  move 
a  very,  very  small  fraction  of  a  grain  through  a  very,  very 
small  fraction  of  an  inch.  You  may  judge  of  its  delicacy 
when  I  show  you  that  the  warmth  of  the  hand,  or  even  a 
look,  by  means  of  the  warmth  of  the  face  turned  towards 
a  thermopile,  can  transmit  an  appreciable  signal  through  a 
resistance  equal  to  that  of  the  Atlantic  cable  (experiment 
performed).  Another  great  merit  of  this  instrument  is  its 
ready  adaptability  to  the  circumstances  in  which  it  may  be 
placed,  as  it  is  easy  to  increase  or  diminish  the  length,  or 
breadth,  or  tension  of  the  gold-leaf.  Thus,  increase  of 
length  or  diminution  of  breadth  increases  the  resistance, 
but  also  increases  the  sensitiveness ;  and  again,  par- 
taking as  it  does  partly  of  the  character  of  a  pen- 
dulum and  partly  of  a  musical  string,  the  rapidity  of 
vibration  is  increased  by  giving  it  greater  tension  and 
greater  shortness  (though  by  doing  so  the  sensitiveness  is 
diminished),  so  that  you  can  adjust  it  to  the  peculiar  cir- 
cumstances of  any  circuit.  Again,  you  notice  the  deadness 
of  the  movements  and  the  total  absence  of  swing,  which, 
whenever  a  needle  is  used,  always  more  or  less  tends  to 
confuse  the  signals.  The  greatest  advantage  of  all  is  that 
we  can  increase  the  sensitiveness  without  increasing  the 
resistance,  simply  by  increasing  the  power  of  the  electro- 
magnet 

"  Having  now  explained  the  construction  of  the  instru- 
ment, and  pointed  out  its  merits,  I  proceed  to  show  by 
experiment  how  tenaciously  a  piece  of  copper  in  water  will 
retain  a  state  of  electrical  tension.  Here  is  a  tub  of  fresh 
water,  with  copper  plates  presenting  to  each  other  about 


44  FIRST  PERIOD — THE  POSSIBLE. 

14  square  feet  of  surface.  I  charge  these  plates  with  a 
Daniell  cell,  and  you  see  how  they  retain  the  charge ;  in  fact, 
they  will  go  on  gradually  discharging  for  several  minutes 
through  the  small  resistance  of  the  gold-leaf  instrument.  I 
now  do  the  same  with  a  tub  of  salt  water,  and  the  result 
is  still  the  same,  though  less  marked.  In  fact,  these 
plates,  with  the  water  between,  represent  the  two  metallic 
surfaces  of  a  Leyden  jar,  and  the  water  retains  the  elec- 
tricity of  this  small  tension  with  much  more  obstinacy  than 
the  glass  of  a  Leyden  jar  does  the  electricity  of  a  higher 
tension.1 

"  Indeed,  it  is  a  fact  of  the  highest  importance  in  teleg- 
raphy that  when  there  is  a  fault,  electricity  of  a  high 
tension,  say  of  twenty  or  thirty  Daniell  cells,  will  almost 
wholly  escape  by  it,  and  leave  nothing  for  the  instrument ; 
whereas  electricity  of  a  small  tension,  as  from  a  single  cell 
of  large  surface,  will  pass  through  the  instrument  with  very 
little  loss  of  power.  This  is  strikingly  shown  by  the  use 
of  an  ordinary  tangent  galvanometer.  I  cannot  well  show 
it  to  a  large  audience  like  the  present,  therefore  I  will 
only  inform  you  that  when  I  have  taken  two  currents, 
each  marking  30°  on  the  galvanometer,  the  one  of  high 
tension  from  thirty  Daniell  cells,  and  the  other  of  low 
tension  from  a  single  cell  of  small  internal  resistance,  a 
fault  equivalent  to  the  exposure  of  a  mile  of  No.  16  wire 
in  sea- water  will  annihilate  all  appreciable  effects  on  the 
galvanometer  when  using  the  current  of  high  tension, 
whereas  the  current  of  low  tension  will  still  show  as  much 
as  20°.  You  see,  then,  the  importance  of  using  currents 
of  low  tension  from  a  battery  of  large  surface,  and  how  a 

1  These  experiments  are  not  clearly  described  in  the  report  from 
which  we  are  quoting.  If  we  understand  them  aright,  they  are 
rather  electrolytic  than  Leyden-jar  effects.  In  any  case,  as  the  tubs 
were  presumably  fairly  well  insulated,  they  have  no  bearing  ad  rem. 


E.    AND   H.   HIGHTON.  45 

faulty  cable  can  be  worked  with  such  currents  when  it  is 
absolutely  useless  with  currents  of  high  tension. 

"  There  are  three  ways  of  signalling  without  insulation  : 
one,  only  feasible  for  short  distances ;  a  second,  which  I 
think  will  be  found  the  most  practicable ;  and  a  third,  in 
the  practical  working  of  which  for  very  long  distances 
several  difficulties  (though  by  no  means  insuperable)  pre- 
sent themselves. 

"To  explain  the  first  plan,  we  will  take  the  case  of  a 
river,  and  in  the  water  near  one  bank  place  the  copper 


Fig.  3. 

plates  A  B,  and  connect  them  with  a  wire,  including  the 
battery  p.  Near  the  opposite  bank  submerge  similar  plates, 
c  D,  connected  by  a  wire,  in  the  circuit  of  which  is  placed 
the  galvanometer  g.  Between  A  and  B  the  current  will 
pass  by  every  possible  route,  in  quantities  inversely  pro- 
portional to  their  resistances ;  parts  will  pass  direct  by  A  B  ; 
and  other  portions  by  A,  c,  D,  B,  and  by  A,  c,  g,  D,  B. 
Now,  if  the  plates  be  large,  and  A  c  and  B  D  respectively 
comparatively  near  to  each  other,  an  appreciable  current 
will  pass  from  A  to  c,  through  g,  and  back  from  D  to  B  ; 
but  if  the  plates  be  small,  the  battery  power  small,  and 


46  FIRST   PERIOD — THE   POSSIBLE. 

the  distance  from  A  to  B  and  from  c  to  D  comparatively 
short,  no  appreciable  amount  will  pass  through  the  galvan- 
ometer circuit.  I  do  not  hesitate  to  say  that  it  is  possible, 
by  erecting  a  very  thick  line  wire  from  the  Hebrides  to 
Cornwall,  by  the  use  of  enormous  plates  at  each  extremity, 
and  by  an  enormous  amount  of  battery  power — i.e.,  as 
regards  quantity — to  transmit  a  current  which  would  be 
sensibly  perceived  in  a  similar  line  of  very  thick  wire,  with 
very  large  plates,  on  the  other  side  of  the  Atlantic.  But 
the  trouble  and  expense  would  probably  be  much  greater 
than  that  of  laying  a  wire  across  the  ocean. 

"The  second  is  the  simplest  and  most  feasible  plan — 
namely,  laying  across  the  sea  two  wires  kept  from  metallic 
contact  with  each  other,  and  working  with  that  portion  of 
the  current  which  prefers  to  pass  through  this  metallic 
circuit  instead  of  passing  across  the  liquid  conductor,  using 
currents  of  low  tension  from  batteries  of  large  surface. 

"The  third  method  is  to  lay  a  single  wire  imperfectly 
insulated,  and  to  place  at  the  opposite  end  beyond  the 
instrument  a  very  large  earth-plate.  Any  electrical  tension 
thrown  on  this  wire  transmits  itself  more  or  less  to  the 
opposite  end,  and  will  be  shown  on  any  instrument  of 
small  resistance  and  sufficient  delicacy.1  There  are  certain 
difficulties  in  this  way  of  working,  such  as  the  effects  of 
earth-currents  and  currents  of  polarisation  which  keep  the 
needle  or  gold-leaf  permanently  deflected  from  zero,  neces- 
sitating special  means  of  counteraction.  I  have  no  doubt, 
from  my  experiments,  that  these  difficulties  may  be  over- 
come ;  but  still  I  think  the  simplest  and  most  feasible,  and 
not  more  expensive,  plan  will  be  to  work  with  two  naked 
wires  kept  apart  from  metallic  contact,  using  electricity  of 
a  very  low  tension." 

1  The  following  cutting  from  '  Once  a- Week '  (February  26,  1876) 
is  given  here  in  the  hope  that  some  American  reader  will  kindly  sup- 


E.   AND  H.   HIGHTON.  47 

Soon  after  this  Mr  Highton  turned  a  complete  volte 
face,  and  went  back  to  wires  perfectly  insulated,  but  at  a 
ridiculously  small  cost !  On  April  20,  1873,  he  sent  the 
following  letter  to  the  '  Times ' : — 


"  CHEAP  TELEGRAPHY. 

"  SIR, — Some  months  ago  I  read  a  paper  to  the  Society 
of  Arts  on  the  possibility  of  telegraphing  for  great  distances 
without  insulation,  for  which  they  were  good  enough  to 
vote -me  a  medal.  I  now  find,  however,  that  by  the  dis- 
covery of  a  new  insulating  material  perfect  insulation  can 
be  provided  at  a  ridiculously  small  cost. 

"  I  find  by  the  addition  of  this  material,  which  is  simply 
tar  chymically  modified,  nearly  200,000  per  cent  is  added 
to  the  insulating  power  of  a  thin  coating  of  gutta-percha.  I 
hope  the  result  will  shortly  be  found  in  the  great  cheapening 
of  telegraphy. — Yours,  &c.,  H.  HIGHTON." 

The  new  material  here  referred  to  was  a  preparation  of 
vegetable  tar  and  oxide  of  lead,  which  almost  instantly 
solidified  on  application.  In  some  experiments  at  the 
Silvertown  Works,  it  was  found  that  No.  18  copper  wire, 
covered  with  gutta-percha  weighing  only  21  Ib.  to  the  mile, 
had  its  insulation  increased  nearly  200,000  per  cent, 
representing  an  insulation  per  mile  of  nearly  three  billion 
ohms ! — enough,  as  the  inventor  needlessly  remarked,  for 
any  lengths  possible  on  the  surface  of  the  earth.1 

ply  details,  if  any  are  procurable  :  "The  '  New  York  Tribune'  gives 
an  account  of  what  appears  to  be  a  very  remarkable  discovery  in 
electrical  science  and  telegraphy.  It  is  claimed  that  a  new  kind  of 
electricity  has  been  obtained,  differing  from  the  old  in  several  partic- 
ulars, and  notably  in  not  requiring  for  transmission  that  the  conduct- 
ing wires  shall  be  insulated." 

1  For  reports  on  this  cable  see  'Telegraphic  Journal,'  vol.  ii.  pp. 


48  FIRST   PERIOD — THE   POSSIBLE. 


G.  E.  BERING— 1853. 

The  problem  of  wireless  telegraphy  was  taken  up  about 
this  time  by  Mr  George  Dering  of  Lockleys,  Herts,  who 
was,  like  his  old  Rugby  tutor,  Henry  Highton,  a  prolific 
inventor  of  electrical  and  telegraphic  appliances,  patents  for 
which  he  took  out  on  eleven  separate  occasions  between 
1850  and  1858,  and  many  of  which  came  into  practical 
use  in  the  early  Fifties.  His  needle  telegraph,  patented 
December  27,  1850,  was  in  use  in  the  Bank  of  England 
early  in  1852,  connecting  the  governor's  room  with  the 
offices  of  the  chief  accountant,  chief  cashier,  secretary, 
engineer,  and  other  officials.  About  the  same  time  it 
was  partially  used  on  the  Great  Northern  Eailway,  and 
exclusively  so  on  the  first  Dover-Calais  cable  (1851),  where 
it  did  excellent  service,  working  direct  between  London 
and  Paris  for  a  long  time  (including  the  busy  period  of  the 
Crimean  war),  until  supplanted  by  the  Morse  recording 
instrument. 

In  the  same  specification  of  1850,  Dering  patented  three 
methods  of  carrying  off  atmospheric  electricity  from  the  line- 
wires  :  (a)  "  Two  roughened  or  grooved  metallic  surfaces 
separated  by  fine  linen,  one  of  which  is  included  in  the 
line-wire  circuit,  and  the  other  is  in  connection  with  the 
earth."  This  was  afterwards  (in  1854)  repatented  by  (Sir) 
William  Siemens,  and  is  now  known  as  Siemens'  Serrated- 

104,  129.  The  Hightons  received  several  Society  of  Arts'  medals  for 
the  excellence  of  their  telegraphic  appliances  which  were  largely  used 
fifty  years  ago.  Indeed  a  company,  The  British  Electric  Telegraph 
Co.,  was  expressly  formed  in  1850  to  work  their  instruments,  and 
was  afterwards  merged  in  the  British  and  Irish  Magnetic  Telegraph 
Co.  A  few  years  before  his  death  (December  1874)  Henry  Highton 
invented  an  artificial  stone,  which  I  believe  is  largely  used  in  build- 
ing and  paving. 


G.   E.   DERING.  49 

Plate  Lightning-Guard,  (b)  "  The  attraction  or  repulsion 
occurring  between  dissimilarly  or  similarly  electrified  bodies 
respectively.  Thus  metal  balls  may  be  suspended  from  the 
line-wire  by  wires,  which  on  separating  under  the  influ- 
ence of  the  lightning-discharge  make  contact  with  plates 
connected  with  the  earth ;  or  the  separation  may  simply 
break  connection  between  the  line-wire  and  the  instrument." 
(e)  "Introducing  a  strip  of  metallic  leaf  into  the  circuit,  this 
being  fused  by  the  passage  of  the  atmospheric  electricity." 
This  very  effective  method  has  also  been  reintroduced  in 
later  years,  and  always  as  a  novelty,  by  various  telegraph 
engineers. 

Bering's  telegraphic  appliances  made  a  goodly  show  at 
the  Great  Exhibition  of  1851,  side  by  side  with  Henley's 
colossal  magnets,  and  received  "  honourable  mention." 
They  were  again  on  view  at  the  Paris  International  Exhi- 
bition of  1855,  where  they  were  awarded  a  medal  for 
general  excellence. 

Bering's  proposals  for  a  transmarine  telegraph  are  con- 
tained in  his  patent  specification  of  August  15,  1853,  from 
which  we  condense  the  following  account : — 

"  The  present  invention  is  applicable  to  submarine  tele- 
graphs, and  also  to  the  means  of  communication  by  under- 
ground or  over-ground  wires.  Heretofore,  in  constructing 
electric  telegraphs  where  the  whole  circuit  has  been  made 
of  metal,  and  also  where  the  conducting  property  of  the 
earth  has  been  employed  as  a  part  of  the  circuit,  it  has 
been  usual,  and  it  has  been  considered  absolutely  necessary, 
to  cause  the  wires  to  be  thoroughly  insulated,  the  con- 
sequence of  which  has  been  that  the  expense  of  laying 
down  electric  circuits  has  been  very  great,  particularly 
where  the  same  have  crossed  the  sea  or  other  waters,  where 
not  only  have  the  wires  been  insulated,  but  in  order  to 
protect  the  insulating  matter  from  injury  further  great  cost 

D 


50  FIRST   PERIOD — THE   POSSIBLE. 

has  been  caused  by  the  use  of  wire  rope,  or  other  means  of 
protection. 

"  Now,  I  have  discovered  that  a  metallic  circuit  formed 
of  wires,  either  wholly  uninsulated  or  partially  so,  may  be 
employed  for  an  electric  telegraph,  provided  that  the  two 
parts  of  the  circuit  are  at  such  a  distance  apart  that  the 
electric  current  will  not  all  pass  direct  from  one  wire  to  the 
other  by  the  water  or  earth,  but  that  a  portion  will  follow 
the  wire  to  the  distant  end. 

"  To  carry  out  my  invention,  I  cause  two  uninsulated  or 
partially  insulated  wires  to  be  placed  in  the  water  or  in  the 
earth,  at  a  distance  apart  proportionate  to  the  total  length 
of  the  circuit,  the  said  wires  being  insulated  where  they 
approach  one  another  to  communicate  with  the  instruments, 
in  order  to  prevent  the  current  passing  through  the  dimin- 
ished water  or  earth  space  between  them.  The  batteries 
(or  other  suitable  source  of  electricity)  employed  are  to  be 
constructed  in  the  proportion  of  their  parts  in  conformity 
with  the  well-known  laws  which  regulate  the  transmission 
of  electric  currents  through  multiple  circuits — that  is,  they 
should  possess  the  properties  generally  understood  by  the 
term  quantity  in  a  considerably  greater  degree  than  is  usual 
for  telegraphing  through  insulated  wires,  which  may  be 
effected  (in  the  case  of  galvanic  batteries)  by  using  plates 
of  larger  dimensions,  or  by  other  alterations  in  the  exciting 
liquids  or  plates.  The  proper  distance  at  which  to  place 
the  conductors  from  one  another  is  also  determined  by  the 
same  laws,  all  of  which  will  be  readily  understood  by  per- 
sons conversant  with  the  principles  of  electrical  science.  In 
practice  I  find  that  from  one-twentieth  to  one-tenth  the 
length  of  the  line-wires  is  a  sufficient  distance. 

"  Another  method  of  carrying  out  my  invention  consists 
in  establishing  circuits  composed  in  part  of  the  uninsulated 
or  partially  insulated  conductors,  and  in  part  of  the  con- 


G.   E.   PEKING.  51 

ducting  property  of  the  sea,  across  which  the  communication 
is  to  be  made,  or  of  the  earth  or  the  moisture  contained 
therein  in  the  case  of  land  telegraphs.  For  this  purpose 
the  connections  are  effected  at  such  a  distance  in  a  lateral 
direction  that  a  sufficient  portion  of  the  current  will  pass 
across  the  water  or  earth  space  and  enter  the  corresponding 
wire  connection  at  the  other  extremity.  The  connecting 
wires  at  the  termini  must  be  effectually  insulated  as  in  the 
first  method. 

"  A  third  method  consists  in  placing  in  the  sea  or  earth 
two  wires  of  dissimilar  metal  having  the  quality  of  generat- 
ing electricity  by  the  action  of  the  water  or  moisture  with 
which  they  are  in  contact.  If  at  one  extremity  the  wires 
be  attached  respectively  to  the  two  ends  of  the  coil  of  an 
electro -magnet  or  other  telegraphic  apparatus,  it  will  be 
found  that  the  instrument  is  acted  on  by  the  current 
generated  by  the  wires.  If  now  at  the  other  extremity  the 
wires  be  connected,  a  portion  of  the  current  will  complete 
its  circuit  through  this  connection,  instead  of  all  passing 
through  the  electro-magnet,  where  consequently  the  effect 
will  be  diminished;  and  if  means  be  adopted  to  indicate 
this  greater  or  less  power,  signals  may  be  indicated  at  one 
end  by  making  and  breaking  contact  at  the  other.  If  de- 
sirable, currents  derived  from  galvanic  batteries,  or  other 
source,  may  be  employed  as  auxiliary  to  those  generated  in 
the  outstretched  wires. 

"  In  the  different  means  of  communication  which  I  have 
described,  if  strong  conductors  are  required,  as  in  submarine 
lines,  wire  rope  may  be  employed,  either  alone  or  attached 
to  chains  for  greater  strength  and  protection,  or  the  con- 
ducting wires  may  be  attached  to  hempen  ropes,  or  envel- 
oped within  them.  The  metal  composing  the  wires  may  be 
iron  or  copper  or  any  other  suitable  kind,  and  it  may  be 
coated  with  varnish,  by  which  means  the  amount  of  exposed 


52  FIRST  PERIOD — THE  POSSIBLE. 

surface  will  be  diminished,  and  the  metal  preserved  from 
corrosion. 

"  I  will  now  suppose  the  case  of  a  line  to  be  carried  out 
upon  the  principle  which  I  have  described,  say  from  Holy- 
head  to  Dublin,  a  distance  of  about  sixty  miles.  It  would 
be  necessary,  first,  to  select  two  points  on  each  coast  from 
three  to  six  miles  apart,  and  to  connect  these  points  on  each 
coast  by  insulated  wires.  Next,  the  two  northern  points 
are  to  be  connected  by  a  submerged  uninsulated  conduc- 
tor, and  the  two  southern  points  by  a  similar  conductor, 
unless  the  water  be  employed  as  a  substitute  in  the  manner 
before  described.  Thus  an  oblong  parallelogram  of  con- 
tinuous conductors  is  formed,  having  for  its  longer  sides 
the  uninsulated  conductors,  and  for  its  shorter  sides  the 
insulated  wires  along  the  coasts.  If  now  these  latter  wires 
be  cut  at  any  parts,  and  instruments  and  batteries  be  con- 
nected in  circuit,  signals  may  be  transmitted  by  any  of  the 
means  ordinarily  employed  with  insulated  wires. 

"  Or,  to  take  the  case  of  a  longer  line,  say  from  England 
to  America,  I  should  select  two  points,  as  the  Land's  End 
in  Cornwall  and  the  Giant's  Causeway  in  Ireland  or  some 
suitable  place  on  the  west  coast  of  Scotland,  and  corre- 
sponding points  on  the  American  shore.  Next,  I  should 
unite  the  two  points  in  each  country  by  insulated  wires, 
and,  finally,  submerge  two  uninsulated  conductors  across 
the  Atlantic,  or  one  if  the  water  be  employed  to  complete 
the  circuit.  Then  by  introducing,  as  before,  suitable  tele- 
graphic instruments  and  batteries  the  communication  will 
be  established. 

rt  From  the  foregoing  description  it  will  be  seen  that  the 
cost  of  laying  down  electric  telegraphs,  whether  submarine 
or  otherwise,  is,  by  this  invention  of  employing  distance 
between  the  conductors  as  a  means  of  insulation,  reduced 
to  little  more  than  the  mere  cost  of  the  wires,  together 


G.   E.   BERING.  53 

with  that  of  an  insulated  wire  at  each  end ;  while  the 
numerous  difficulties  which  attend  the  insulation  of  long 
lengths  of  wire  are  avoided,  as  also  the  chances  of  the 
communication  being  interrupted  by  accidents  to  the 
insulation." 

At  the  time  of  this  patent,  and  for  many  years  after,  the 
difficulties  just  referred  to  were  only  too  real.  Many  of 
the  cables  laid  between  1850  and  1860  failed  after  a  longer 
or  shorter  period,  and  chiefly  through  defective  insulation. 
Hence,  no  doubt,  the  persistency  with  which  telegraph 
engineers  in  the  Fifties  sought  in  telegraphy  without  in- 
sulation, and  telegraphy  without  wires,  other  and  more 
economical  ways  of  solving  the  great  problem  of  trans- 
marine communication. 

Dering's  experiments  were  performed  across  the  river 
Mimram  at  Lockleys,  Herts,  with  bare  parallel  wires  of 
No.  8  galvanised  iron,  laid  at  a  distance  apart  of  about 
30  feet,  or  one-tenth  of  the  space  to  be  traversed.  With 
a  small  battery  power  of  only  two  or  three  Smee  cells  the 
signals  were  easily  readable. 

At  one  of  these  performances  on  August  12,  1853,  the 
chairman  and  directors  of  the  Electric  Telegraph  Com- 
pany of  Ireland  (one  of  several  mushroom  companies  then 
started)  were  present,  and  so  impressed  were  they  with 
the  results  obtained  that  they  there  and  then  decided  to 
adopt  the  system  for  their  intended  line  between  Port- 
patrick  and  Donaghadee.  This  is  a  fact  not  generally 
known  in  the  history  of  early  submarine  telegraph  enter- 
prises ;  and  what  is  still  less  known,  for  there  is  no  record 
of  it,  is  that  the  project  was  actually  attempted.  In  a 
recent  letter,  Mr  Dering,  who  I  am  glad  to  say  is  still 
with  us,  has  given  me  some  interesting  details  of  the 
attempt  which  I  now  publish,  feeling  sure  that  they  will 
be  new  to  the  reader. 


54  FIRST   PERIOD — THE   POSSIBLE. 

On  September  23,  1853,  the  necessary  wire  in  bundles 
was  shipped  to  Belfast,  which,  "for  the  sake  of  ultra 
economy,"  consisted  of  single  No.  1  galvanised  iron  instead 
of  twisted  strand  wire  as  Dering  had  recommended.  On 
examination  the  wire  proved  to  be  so  unreliable,  with 
numerous  weak  and  brittle  places — chiefly  at  the  factory 
welds — that  Dering  urged  delay  and  the  substitution  of 
stranded  wire.  "  Had  we  been  wise,"  writes  Mr  Dering, 
"  we  should  have  abandoned  the  attempt  with  this  un- 
suitable material,  but  it  was  resolved  to  go  on  and  risk  it — 
testing  the  wire  as  far  as  might  be  beforehand  and  removing 
the  weak  parts.  I,  however,  addressed  a  formal  letter  to  the 
board  of  directors  in  London,  stating  that  the  wire  was  so 
unreliable  I  must  decline  all  responsibility  as  to  the  laying 
it  down,  but  that  I  would  do  the  best  I  could." 

After  carefully  testing  the  various  lengths,  removing  all 
weak  parts  and  bad  welds  as  far  as  they  could  be  discovered, 
and  jointing  and  tarring  the  whole  into  one  long  length,  the 
wire  was  paid  into  the  hold  of  the  Albert.  On  November 
21  a  start  was  made,  a  shore-end  wire  was  laid  from  Milisle, 
carried  out  to  sea,  and  buoyed.  Next  morning  the  Albert,1 
piloted  by  H.M.S.  Asp  (Lieut.  Aldridge),  picked  up  the 
buoyed  end,  joined  it  to  the  wire  on  board,  and  paid  out 
successfully  for  about  3J  miles,  when  the  wire  broke  at  a 
factory  weld,  and  the  ship  returned  to  Donaghadee  "  in  a 
gale  of  wind." 

The  next  few  days  were  occupied  in  some  alterations  to 
the  paying-out  machinery,  found  by  experience  to  be  de- 
sirable, and  on  the  26th  another  start  was  made.  The 
wire  on  board  was  joined  to  the  buoyed  end  at  4  miles 
from  shore,  and  paying-out  proceeded  successfully  as  far  as 
mid-channel  (about  12  miles)  when  the  wire  broke,  again 

1  With  Dr  Hamel  on  board,  the  famous  Russjan  scientist  of  Alpine 
celebrity,  as  the  representative  of  his  Government. 


G.   E.   DERING.  55 

at  a  factory  weld,  and  the  end  was  lost  in  82  fathoms  of 
water.  The  ship  then  returned  to  the  buoy  and  tried  to 
underrun  the  wire,  but  it  soon  broke  again,  and  for  the 
moment  further  attempts  were  abandoned. 

Previous  to  this  two  unsuccessful  attempts  had  already 
been  made  to  connect  Great  Britain  and  Ireland  by  cables 
made  on  the  lines  of  the  Dover-Calais  cable  of  1851 — one, 
undertaken  by  Messrs  Newall  &  Co.,  between  Holyhead 
and  Howth,  June  1,  1852,  which  failed  three  days  after; 
and  the  other,  a  heavy  six-wired  cable,  undertaken  by  the 
same  firm,  between  Portpatrick  and  Donaghadee,  October  9, 
1852,  which  broke  in  a  gale  after  sixteen  miles  had  been 
paid  out. 

In  June  1854  Messrs  Newall  recovered  the  whole  of  this 
sixteen  miles  of  cable,  and  completed  the  laying  to  Port- 
patrick, thus  rendering  another  attempt  at  a  bare  wire  cable 
unnecessary,  if,  indeed,  it  was  still  thought  desirable. 

Mr  Bering's  faith  in  the  soundness  of  his  views  is  still 
unshaken,  for  he  goes  on  to  say  :  "  Instead  of  a  single 
wire,  as  in  1853,  I  should  now  advocate  the  use  of  a  bare 
strand  of  wires  for  each  of  the  conductors.  And  I  must 
add,  considering  the  craving  there  is  at  present  for  Wireless 
Telegraphs,  that  it  seems  to  me  not  altogether  improbable 
that  the  less  ambitious  but  (for,  at  all  events,  long  dis- 
tances) far  more  feasible  plan  of  using  bare  wires  will  yet 
have  its  innings."  And  who,  in  these  days  of  electrical 
marvels,  will  dare  to  say  him  nay?  I,  for  my  part,  will 
not,  for  I  have  seen  more  unlikely  things  come  to  pass. 
The  dream  of  to-day,  "  idle  and  ridiculous  "  as  it  may  seem, 
has  been  so  often  realised  on  the  morrow,  that  the  cautious 
historian  of  science  must  not  look  for  finality  in  any  of 
its  applications.1 

1  For  recent  applications  of  the  bare-wire  principle,  see  Melhuish, 
p.  Ill, infra. 


56  FIRST  PERIOD — THE  POSSIBLE. 


JOHN  HAWORTH— 1862. 

On  March  27,  1862,  Mr  Haworth  patented  "An  im- 
proved method  of  conveying  electric  signals  without  the 
intervention  of  any  continuous  artificial  conductor,"  in 
reference  to  which  a  lecturer  of  the  period  said  : 1  "I  have 
not  met  one  single  gentleman  connected  with  the  science  of 
telegraphy  who  could  understand  his  process,  or  its  proba- 
bility of  success.  I  applied  to  him  for  some  information, 
but  he  is  unwilling  to  communicate  any  particulars  until 
experiment  has  sufficiently  demonstrated  the  practicability 
of  his  plans." 

In  the  discussion  which  followed,  Mr  Cromwell  Varley, 
electrician  of  the  old  Electric  and  International  Telegraph, 
and  the  old  Atlantic  Telegraph,  Companies,  said :  "  Being 
informed  that  Sir  Fitzroy  Kelly  and  the  learned  chairman 
(Mr  Grove)  had  seen  Haworth's  system  in  operation,  and 
that  the  latter  gentleman  was  a  believer  in  it,  he  had  tried 
the  experiment  upon  a  very  small  scale  in  his  own  garden, 
with  apparatus  constructed  according  to  the  instructions  of 
Mr  Haworth.  His  two  stations  were  only  8  yards  apart, 
and,  although  he  used  a  very  sensitive  reflecting  galvano- 
meter, and  twelve  cells  of  Grove's  nitric  acid  battery,  he 
could  not  get  any  signals,  although  the  experiments  were 
varied  in  every  conceivable  way." 

Under  these  circumstances  it  will  not  be  surprising  if  I, 
too,  after  a  careful  study  of  the  specification,  and  with  the 
light  thrown  upon  it  by  a  further  patent  of  October  30, 
1863,  have  failed  to  understand  the  author's  method.  In- 
deed, I  feel  in  much  the  same  mental  condition  towards  it 
as  Tristram  Shandy's  connoisseurs,  who,  "  by  long  friction, 
incumbition,  and  electrical  assimilation,  have  the  happiness, 
1  T.  A.  Masey,  Society  of  Arts,  January  28,  1863. 


:     l 

«!i'i!il4a!  I'ft. 


58 


FIRST   PERIOD — THE   POSSIBLE. 


at  length,  to  get  all  be-virtu'd,  be-pictured,  be-butterflied, 
and  be-fuddled."  However,  I  will  do  my  best  to  translate 
the  terrible  phraseology  of  the  letters  patent  into  plain 
English ;  and  if  after  this  my  readers  cannot  divine  the 
mode  of  action  I  will  not  blame  them — nor  must  they 
blame  me !  My  description  of  the  apparatus  is  based  on 
the  complete  specification  and  drawings  of  the  second  patent, 
which  were  lodged  in  the  Patent  Office  on  April  30,  1864, 
and  which  must  therefore  be  supposed  to  contain  the  in- 
ventor's last  word  on  the  subject. 

A,   z  (fig.    4)  are  copper   and   zinc   plates  respectively, 
curved  as  shown,  and  buried  in  the  earth   about  3  feet 


Tiiir 


Fig.  5. 

apart.  The  superficies  varies  according  to  distance  and 
other  circumstances :  thus,  for  distances  up  to  75  miles 
plates  1  foot  square  suffice ;  over  75  and  up  to  440  miles, 
plates  24  by  16  inches  are  required.  G,  F  are  copper 
cylinders,  24  by  4  inches,  buried  in  earth,  which  is 
always  moist.  At  a  point  distant  about  3  feet  from  the 
centres  of  A  and  z  a  wooden  box  j  is  buried,  containing  a 
coil  of  insulated  copper  wire,  No.  16  gauge,  wound  upon  a 
wooden  reel.  The  ends  of  the  coil  are  attached  to  binding 
screws  shown  on  top  of  the  box.  B  is  a  wooden  box  con- 
taining a  wooden  reel  divided  into  three  compartments,  xt 
y,  z  (fig.  5).  x  is  filled  with  fine  covered-copper  wire,  the 


JOHN   HAWORTH.  59 

ends  of  which  are  brought  together  and  secured  on  the  out- 
side of  the  reel,  y  is  filled  with  thicker  covered-copper 
wire,  wound  in  the  same  direction  as  x,  and  the  ends  are 
severally  connected  to  binding-screws,  shown  on  the  out- 
side, z  is  half  filled  with  insulated  iron  wire,  wound  in  the 
same  direction  as  x  and  y ;  the  ends  are  fastened  together 
on  the  outside  of  the  reel  as  with  coil  x.  The  compartment 
is  then  filled  with  more  of  the  same  iron  wire,  wound 
double,  and  in  the  reverse  direction  to  the  coil  below  it. 
These  double  wires  are  not  twisted,  nor  bound  together,  nor 
allowed  to  cross  one  another,  but  are  wound  evenly  in 
layers  side  by  side ;  and  the  ends  of  each  coil  are  secured 
together  on  the  outside  of  the  reel  as  in  the  case  of  the 
lower  coil,  and  adjacent  thereto.  Usually  the  wire  of  coil 
x  is  No.  32  gauge  ;  y,  No.  16  ;  and  2,  No.  20  \  but  the  sizes 
and  quantities  required  must  vary  according  to  distance  and 
other  circumstances. 

c  is  any  suitable  telegraph  instrument  of  the  needle 
pattern. 

D  is  a  condenser  of  a  kind  which  an  electrical  Dominie 
Sampson  would  call  prodigious !  A  wooden  box  divided 
lengthwise  into  two  compartments  well  coated  with  shellac. 
In  each  compartment  is  placed  a  band  of  stout  gold-foil — 
both  well  insulated,  and  connected  at  their  ends  to  the 
binding-screws  a,  g,  and  &,  h,  respectively  (fig.  6).  Each 
compartment  is  filled  with  sixty  rectangular  plates  of  gutta- 
percha,  on  which  insulated  copper  wire,  No.  32  gauge,  is 
wound  in  one  continuous  length  from  the  first  plate  to  the 
last,  and  the  ends  are  attached  to  the  binding-screws  a,  g, 
and  b,  7i,  respectively.  "I  fix  binding-screws  c,  d,  e,f,  Jc, 
and  I  in  the  positions  shown,  and  connect  them  with  the 
wire  upon  the  plates  in  its  passage  through  the  box.  I 
then  pass  from  end  to  end  of  each  compartment  over  the 
plates,  and  lying  on  them,  but  well  insulated  from  them, 


60 


FIRST   PERIOD — THE   POSSIBLE. 


another  band  of  stout  gold-foil,  and  connect  each  end  of  it 
with  the  screws  a,  g,  and  bt  h,  respectively." 

E  is  another  wooden  box,  containing  a  reel  similar  to  B, 
but  divided  into  only  two  compartments,  each  of  which  is 
filled  with  two  copper  wires,  one  covered  and  the  other 
uncovered,  wound  side  by  side,  and  all  four  of  different 
gauges  from  No.  18  to  30.  The  ends  of  one  of  the  covered 
coils  are  brought  to  the  screws  p,  p,  shown  on  top  of 
the  box  ;  the  ends  of  the  other  covered  coil  are  fastened 


Fig.  6. 

on  the  outside  of  the  reel ;  and  the  ends  of  the  two 
uncovered  coils  are  likewise  fastened  on  the  outside 
of  the  reel,  "but  in  such  a  position  that  they  can 
never  come  in  contact  with  any  uncovered  part  of  the 
coated  wire.  Between  each  of  the  layers  of  wire  I  place  a 
strip  of  non-metallic  paper  to  insulate  it  from  the  layers 
above  and  below,  and  when  in  winding  I  arrive  within  an 
inch  of  the  circumference  of  the  reel  I  employ  gutta-percha 
tissue  in  addition  to  the  non-metallic  paper." 

H  is  a  Smee's  battery,  the  size  and  power  of  which  will 
depend  on  circumstances,  such  as  the  distance  to  which  it 


JOHN   HAWORTH.  61 

is  intended  to  convey  the  message ;  the  strength  and 
direction  of  earth -currents;  and  even  the  state  of  the 
weather — more  power  being  required  in  dry  than  in  damp 
weather.  "  For  a  distance  of  ten  miles,  from  dotting  Hill 
to  Croydon,  I  have  found  a  Smee's  battery  of  two  cells 
at  each  end,  containing  plates  3  by  5  inches,  to  suffice. 
For  about  fifty  miles,  from  Netting  Hill  to  Brighton,  I 
have  used  with  success  a  battery  of  three  cells  at  each 
end ;  and  from  Netting  Hill  to  Bangor,  in  Wales,  I  have 
required  six  cells  at  each  end.  Generally  speaking,  I  have 
found  that  less  power  is  required  to  convey  a  message  from 
north  to  south  and  from  south  to  north  than  from  east 
to  west,  or  from  west  to  east." 

The  connections  of  the  various  instruments  are  shown  by 
lines,  and  an  exactly  similar  set  of  instruments  is  arranged 
at  the  place  with  which  it  is  desired  to  correspond. 

And  now  as  to  the  modus  operandi:  when  the  handle 
of  the  needle  instrument,  c,  is  worked  in  the  act  of  signal- 
ling, what  happens1?  Here  the  trouble  comes  in.  The 
author,  I  regret  to  say,  is  silent  as  to  what  happens,  and 
I  won't  be  so  rash  as  to  make  a  guess ;  but  I  would  suggest 
the  question  as  a  safe  prize-puzzle  for  the  Questions  arid 
Answers  column  of  some  technical  journal !  Seriously,  it 
seems  to  me  that  the  results,  if  any,  must  be  a  perfect 
chaos  of  battery  currents,  earth -battery  currents,  earth- 
currents,  induction  currents,  and  currents  of  polarisation 
— all  fighting  in  a  feeble  way  for  the  mastery ;  and  yet 
some  men,  besides  the  author,  believed  these  effects  to 
be  intelligible  signals ! 

The  remarks  of  Mr  Varley,  quoted  above,  drew  that 
gentleman  into  an  angry  correspondence  in  the  pages  of 
the  old  'Electrician'  journal,  from  which  I  need  only 
extract  Mr  Yarley's  letter  and  Mr  Haworth's  reply.  In 
the  number  for  February  27,  1863,  Mr  Varley  writes:  — 


62  FIRST   PERIOD — THE   POSSIBLE. 

"  I  make  it  a  rule  never  to  pay  any  attention  to  anony- 
mous correspondents.  As  Mr  Haworth,  however,  has  com- 
mented upon  the  remarks  I  made  a  short  time  since  at  the 
Society  of  Arts,  allow  me  to  draw  attention  to  the  fact 
that,  the  discussion  having  been  prolonged  beyond  the  time 
allotted  for  that  purpose,  the  detail  of  the  experiments 
could  not  then  be  fully  entered  into. 

"Mr  Haworth  paid  me  'one'  visit  a  short  time  ago, 
when  I  asked  him  if  he  had  any  objection  to  his  invention 
being  tested  by  actual  experiment :  he  said  he  had  not,  and 
pointed  out  to  me  how  to  arrange  the  various  parts  of  the 
apparatus.  I  have  preserved  the  pencil  sketch  made  at  the 
time,  as  indicated  and  approved  by  him.  This  was  strictly 
followed  in  the  experiments. 

"The  apparatus  used  was  constructed  especially  for  this 
purpose.  The  primary  coils  were  thoroughly  insulated  with 
gutta-percha,  the  secondary  coils  by  means  of  a  resinous 
compound  and  india-rubber.  The  plates  of  copper  and  zinc 
at  each  station  were  but  an  inch  and  a  half  from  each 
other ;  they  were  each  6  inches  square.  The  two  stations 
were  only  8  yards  apart. 

"The  apparatus  at  each  station  consisted  of  a  plate  of 
copper  and  a  plate  of  zinc,  connected  to  a  flat  secondary 
coil  containing  nearly  a  mile  of  No.  35  copper  wire.  The 
secondary  coil  was  placed  immediately  behind  the  plates, 
and  behind  this  was  placed  a  flat  primary  coil. 

"  At  the  sending  station  the  primary  coil  was  connected 
with  six  cells  of  Grove's  battery,  and  contact  intermitted. 
At  the  receiving  station  the  primary  coil  was  connected 
with  one  of  Thomson's  reflecting  galvanometers,  of  small 
resistance,  no  more  than  that  of  an  ordinary  telegraph 
instrument. 

"  With  this  disposition  of  apparatus  no  current  could  be 
obtained. 


JOHN   HA  WORTH.  63 

"  Crossing  a  river  without  wires  is  an  old  experiment. 
In  March  1847  I  tried  experiments  in  my  own  garden, 
and  also  across  the  Eegent's  Canal,  with  a  single  cell  of 
Grove's  hattery.  Feeble  but  evident  currents  were  sent 
across  the  canal  50  feet  wide.  The  current  received  was 
but  a  minute  fraction  of  that  leaving  the  battery.  In  this 
case  the  distance  across  the  canal  was  but  one  quarter  of 
that  separating  the  plates  on  each  bank.  When,  however, 
these  plates  were  brought  near  together,  as  in  Haworth's 
specification,  no  visible  signal  could  be  obtained. 

"  This  experiment  has  been  repeated  by  numbers  in  vari- 
ous parts  of  the  world,  and  with  the  same  well-known 
results.  When  tried  by  me  in  1847,  I  was  unaware  that 
the  idea  had  occurred  to  Professor  Morse,  or  any  one  else. 

"To  account  for  Mr  Haworth's  assertions  that  he  has 
worked  from  Ireland  to  London,  and  between  other  distant 
places,  I  can  only  suppose  that  he  has  mistaken  some 
irregularity  in  the  currents  generated  by  his  copper  and 
zinc  plates  for  signals.1 

"If  he  can  telegraph  without  wires,  why  does  he  not 
connect  England  with  America,  when  he  can  earn  .£1000 
per  diem  forthwith,  and  confer  upon  the  world  a  great 
blessing  1 

"  Before  speaking  at  the  Society  of  Arts,  I  called  at  Mr 
Haworth's  house  several  times,  and  found  him  out  on  all 
occasions.  I  wrote  him  more  than  once,  giving  him  the 
negative  results  of  my  experiments,  &c.  He,  however, 
paid  no  attention  to  any  of  my  communications. 

1  "  I  have  seen  Mr  Haworth's  apparatus  at  work  repeatedly,  and 
have  myself  read  off  from  the  indicator  the  messages  which  have 
arrived  ;  and  these  '  irregular  currents  mistaken  for  signals '  have 
consisted  of  words  and  sentences  transmitted  as  correctly  as  by  the 
electric  telegraph.  My  house  has  been  one  station,  and  Brighton,  or 
Kingstown  in  Ireland,  the  other." — J.  M.  Holt,  'Electrician,'  March 
6, 1863. 


64  FIRST   PERIOD— THE   POSSIBLE. 

"  I  have  not  been  able  to  meet  with  a  single  individual 
who  has  seen  a  message  transmitted  by  Mr  Haworth ;  and 
every  one  of  those  who  are  reported  to  have  seen  it,  and 
with  whom  I  have  come  in  contact,  positively  deny  it  when 
questioned. 

"I  have  no  hesitation  in  stating — 1st,  That  Mr  Haworth' s 
specification  is  unintelligible :  it  is  a  jumble  of  induction 
1  lates,  induction  coils,  and  coils  of  wire  connected  together 
in  a  way  that  can  have  no  meaning. 

"  2ndly,  That  he  cannot  send  electric  signals  without 
wires  to  any  useful  distance. 

"3rdly,  From  my  acquaintance  with  the  laws  of  elec- 
tricity, I  cannot  believe  it  possible  that  he  has  ever  com- 
municated between  distant  stations  as  stated  in  his  speci- 
fication, No.  843,  1862. 

"  4thly,  Supposing  for  a  moment  that  he  could  work,  as 
stated,  any  person  constructing  a  similar  apparatus  in  the 
neighbourhood  would  be  able  to  read  the  communications, 
and  they  no  longer  would  be  private." 

In  the  following  number  (March  6,  1863)  Mr  Haworth 
says  : — 

"Will  you  kindly  allow  me  space  for  a  line  in  reply 
to  Mr  Varley]  I  never  received  his  letter  of  the  27th  of 
January,  and  am  truly  sorry  for  any  apparent  discourtesy 
on  my  part.  I  fear  other  letters  have  shared  the  same 
fate. 

"From  Mr  Yarley's  account  of  his  experiments  I  find 
several  particulars  in  which  there  has  been  considerable 
misapprehension  on  his  part ;  but  I  cannot  spare  the  time 
— nor  can  I  ask  you  for  the  space — to  give  further  explana- 
tions. It  certainly  is  a  new  feature  in  electricity,  if  the 
earth's  currents  alone  can  register  words  and  sentences  on 
the  dial-plate.  I  hope  shortly  to  be  able  to  convince  the 
most  sceptical  by  ocular  demonstration.  For  the  present  I 


J.   H.    MOWER.  65 

am  content  to  wait,  being  anxious  rather  to  perfect  my  dis- 
covery than  to  push  it." 

After  this  we  hear  nothing  more  of  Mr  Haworth,  though 
no  doubt  the  publication  and  discussion  of  his  views  kept 
the  subject  alive  for  a  time.1 


J.  H.  MOWER— 1868. 

Of  the  next  proposal  with  which  we  have  to  deal  in 
these  pages,  I  find  amongst  my  notes  only  a  single 
cutting  from  the  New  York  'Bound  Table'  of  (August 
or  September)  1868.  I  give  it,  in  extenso,  for  what  it 
is  worth,  and  hope  some  American  reader  may  be  able 
to  furnish  details  and  further  developments  if  any : — 

"Mr  Mower  has  elaborated  a  discovery  which,  if  the 
description  given  by  the  'New  York  Herald  *  is  to  be 
relied  upon,  will  revolutionise  trans-oceanic,  and  generally 
all  subaqueous,  telegraphy.  For  some  years  he  had  been 
engrossed  in  electrical  experiments,  when  the  Atlantic 
cable  gave  a  special  direction  to  his  investigations  into 
generating  and  conducting  substances,  the  decomposition 
of  water,  the  development  of  the  electrical  machine,  &c.,  &c. 
By  this  summer  his  arrangements  had  been  so  far  perfected 
that,  a  few  weeks  ago,  he  was  able  to  demonstrate  to 
himself  and  his  coadjutor  the  feasibility  of  his  project, 
on  a  scale  approximate  to  that  which  it  is  designed  to 
assume. 

"Selecting  the  greatest  clear  distance  on  an  east  and 
west  line  in  Lake  Ontario — from  a  point  near  Toronto, 

1  See,  for  example,  'The  Electrician,'  January  23,  1863.  Also 
Boron's  '  Me'te'orologie  Simplified,'  Paris,  1863,  pp.  936,  937,  where 
there  is  a  hazy  description  of  a  wireless  telegraph,  apparently  on  the 
same  lines  as  Haworth's. 

E 


66  FIRST   PERIOD — THE   POSSIBLE. 

Canada  West,  to  one  on  the  coast  of  Oswego  County,  New 
York — at  his  first  attempt  he  succeeded  in  transmitting  his 
message,  without  a  wire,  from  the  submerged  machine  at 
one  end  of  the  route  to  that  at  the  other.  The  messages 
and  replies  were  continued  for  two  hours,  the  average  time 
of  transmission  for  the  138  miles  being  a  little  less  than 
three-eighths  of  a  second. 

"The  upshot  of  the  discovery — on  what  principle  Mr 
Mower  is  not  yet  prepared  to  disclose — is,  that  electric 
currents  can  be  transmitted  through  water,  salt  or  fresh, 
without  deviation  vertically,  or  from  the  parallel  of  lati- 
tude. The  difficulty  from  the  unequal  level  of  the  tidal 
waves  in  the  two  hemispheres  will  be  obviated,  it  is 
claimed,  by  submerging  the  apparatus  at  sufficient  depth. 
The  inventor,  we  are  told,  is  preparing  to  go  to  Europe 
to  secure  there  the  patent  rights  for  which  the  caveats  have 
been  filed  here.  At  the  inconsiderable  cost  of  10,000 
dollars  he  expects  within  three  months  to  establish  tele- 
graphic communication  between  Montauk  Point,  the  eastern 
extremity  of  Long  Island,  and  Spain,  the  eastern  end  of  the 
line  striking  the  coast  of  Portugal  at  a  point  near  Oporto. 

"The  statement  of  the  discovery  is  enough  to  take  away 
one's  breath ;  but,  with  the  history  of  the  telegraph  before 
us,  we  no  more  venture  to  deny  than  we  do  to  affirm 
its  possibility." 


M.  BOURBOUZE— 1870. 

During  the  investment  and  siege  of  Paris  by  the  German 
forces  in  the  winter  of  1870-71,  many  suggestions  were 
made  for  the  re-establishment  of  telegraphic  communica- 
tion between  Paris  and  the  provinces.  Acoustic  methods 
were  tried,  based  on  the  transmission  of  sound  by  earth 


M.   BOUKBOUZE.  67 

and  water.  A  Mr  Granier  proposed  a  form  of  aerial  line 
which  was  thought  to  be  feasible  by  the  distinguished 
aeronaut,  Gaston  Tissandier.  The  wire  (to  be  paid  out 
from  balloons)  was  to  be  enclosed  in  gutta-percha  tubing, 
inflated  with  hydrogen  gas  so  as  to  float  1000  to  1500 
metres  above  the  earth.1 

Amongst  other  suggestions  was  one  by  M.  Bourbouze, 
a  well-known  French  electrician,  which  only  need  concern 
us  in  these  pages.  His  proposal  was  to  send  strong 
currents  into  the  river  Seine  from  a  battery  at  the  nearest 
approachable  point  outside  the  German  lines,  and  to  receive 
in  Paris  through  a  delicate  galvanometer  such  part  of  these 
currents  as  might  be  picked  up  by  a  metal  plate  sunk  in 
the  river.  After  some  preliminary  experiments  between 
the  Hotel  de  Ville  and  the  manufactory  of  M.  Claparede 
at  St  Denis,  it  was  decided  to  put  the  plan  in  practice. 
Accordingly,  on  December  17,  1870,  M.  d' Almeida  left  the 
beleaguered  city  by  balloon,  descended  after  many  perils 
at  Champagne  outside  the  enemy's  lines,  and  proceeded 
via  Lyons  and  Bordeaux  to  Havre.  Thence  the  necessary 
apparatus  was  ordered  from  England  and  conveyed  to 
Poissy,  where  M.  d'Almeida  regained  the  banks  of  the 
Seine  on  January  14,  1871.  Here,  however,  the  river 
was  found  to  be  completely  frozen  over,  and  the  attempt 
at  communicating  with  Paris  was  deferred  to  January  24. 
Meanwhile  the  armistice  was  proclaimed,  and  the  project 
was  allowed  to  drop.2 

1  Such  a  plan  was  patented  in  England  more  than  twenty  years 
previously.      See   patent  specification,  No.   2907,  of  November  19, 
1857. 

2  On  March  27,  1876,  Bourbouze  requested  to  be  opened  at  the 
Academy  of  Sciences  a  sealed  packet  which  he  had  deposited  on 
November  28,  1870.     It  was  found  to  contain  a  note  entitled  "  Sur 
les  Communications  a  Distance  par  les  Cours  d'Eau."     The  contents 
of  the  document,  so  far  as  I  know,  have  not  been  published. 


68  FIRST   PERIOD — THE   POSSIBLE. 

M.  Bourbouze  did  not,  however,  abandon  his  idea,  and, 
thinking  he  found  in  the  principle  of  La  Cour's  phonic  wheel 
telegraph  a  better  means  of  indicating  the  signals  than  the 
galvanometer,  he  again  took  up  the  problem.  Between  1876 
and  1878  an  occasional  notice  of  his  experiments  appeared 
in  the  technical  journals,  but  they  are  all  provokingly  silent 
on  the  point  of  actual  results  over  considerable  distances.1 


MAHLON  LOOMIS— 1872. 

In  1872  Mr  Mahlon  Loomis,  an  American  dentist,  pro- 
posed to  utilise  the  electricity  of  the  higher  atmosphere  for 
telegraphic  purposes  in  a  way  which  caused  some  excite- 
ment in  America  at  the  time. 

It  had  long  been  known  that  the  atmosphere  is  always 
charged  with  electricity,  and  that  this  charge  increases 
with  the  ascent :  thus,  if  at  the  surface  of  the  earth  we 
represent  the  electrical  state  or  charge  as  1,  at  an  elevation 
of  100  feet  it  may  be  represented  as  2  ;  at  200  feet  as  3  ; 
and  so  on  in  an  ascending  series  of  imaginary  strata. 
Hitherto  this  had  been  considered  as  a  rough-and-ready 
way  of  stating  an  electrical  fact,  just  as  we  say  that  the 
atmosphere  itself  may,  for  the  sake  of  illustration,  be 
divided  into  strata  of  100  or  any  agreed  number  of  feet, 
and  that  its  density  decreases  pro  rata  as  we  ascend  through 
each  stratum.  But  Mr  Loomis  appears  to  have  made  the 
further  discovery  that  these  electrical  charges  are  in  some 
way  independent  of  each  other,  and  that  the  electricity  of 
any  one  stratum  can  be  drawn  off  without  the  balance  being 

1  See,  amongst  other  accounts,  the  '  English  Mechanic,'  September 
8,  1876  ;  'Engineering,'  April  13,  1878  ;  and  the  French  journal,  '  La 
Nature,' July  8,  1876.  For  Bourbouze' s  earlier  experiments,  see  'La 
Lumiere  Electrique,'  August  19,  1879. 


MAHLON  LOOMIS.  69 

immediately  restored  by  a  general  redistribution  of  elec- 
tricity from  the  adjacent  strata.  On  this  assumption, 
which  is  a  very  large  one,  he  thought  it  would  be  easy  to 
tap  the  electricity  at  any  one  point  of  a  stratum,  preferably 
an  elevated  one  where  the  atmosphere  is  comparatively 
undisturbed,  which  tapping  would  be  made  manifest  at 
any  distant  point  of  the  same  stratum  by  a  corresponding 
fall  or  disturbance  there  of  the  electrical  density ;  and  thus, 
he  argued,  an  aerial  telegraph  could  be  constructed. 

The  following  is  an  extract  from  his  (American)  patent, 
dated  July  30,  1872  :— 

"  The  nature  of  my  discovery  consists  in  utilising  natural 
electricity,  and  establishing  an  electrical  current  or  circuit 
for  telegraphic  and  other  purposes  without  the  aid  of  wires, 
artificial  batteries,  or  cables,  and  yet  capable  of  communi- 
cating from  one  continent  of  the  globe  to  another. 

"As  it  was  found  possible  to  dispense  with  the  double 
wire  (which  was  first  used  in  telegraphing),  making  use  of 
but  one,  and  substituting  the  earth  instead  of  a  wire  to 
form  the  return  half  of  the  circuit ;  so  I  now  dispense  with 
both  wires,  using  the  earth  as  one-half  the  circuit  and  the 
continuous  electrical  element  far  above  the  earth's  surface 
for  the  other  half.  I  also  dispense  with  all  artificial  bat- 
teries, but  use  the  free  electricity  of  the  atmosphere,  co- 
operating with  that  of  the  earth,  to  supply  the  current  for 
telegraphing  and  for  other  useful  purposes,  such  as  light, 
heat,  and  motive  power. 

"As  atmospheric  electricity  is  found  more  and  more 
abundant  when  moisture,  clouds,  heated  currents  of  air, 
and  other  dissipating  influences  are  left  below  and  a  greater 
altitude  attained,  my  plan  is  to  seek  as  high  an  elevation  as 
practicable  on  the  tops  of  high  mountains,  and  thus  establish 
electrical  connection  with  the  atmospheric  stratum  or  ocean 
overlying  local  disturbances.  Upon  these  mountain-tops  I 


70  FIRST  PERIOD — THE  POSSIBLE. 

erect  suitable  towers  and  apparatus  to  attract  the  electricity, 
or,  in  other  words,  to  disturb  the  electrical  equilibrium,  and 
thus  obtain  a  current  of  electricity,  or  shocks  or  pulsations, 
which  traverse  or  disturb  the  positive  electrical  body  of  the 
atmosphere  between  two  given  points  by  connecting  it  to 
the  negative  electrical  body  of  the  earth  below." 

To  test  this  idea,  he  selected  two  lofty  peaks  on  the 
mountains  of  West  Virginia,  of  the  same  altitude,  and  about 
ten  miles  apart.  From  these  he  sent  up  two  kites,  held  by 
strings  in  which  fine  copper  wires  were  enclosed.  To  the 
ground  end  of  the  wire  on  one  peak  he  connected  an  electrical 
detector — presumably  of  the  electrometer  kind — and  on  the 
other  peak  a  key  for  connecting  the  kite  wire  to  earth  when 
required.  With  this  arrangement  we  are  told  that  messages 
were  sent  and  received  by  making  and  breaking  the  earth 
connection,  "the  only  electro-motor  being  the  atmospheric 
current  between  the  kites,  and  which  was  always  available 
except  when  the  weather  was  violently  broken." 

So  well  did  this  idea  "  take  on "  in  the  States  that  we 
learn  from  the  New^York  'Journal  of  Commerce '  (February 
5,  1873)  that  a  bill  had  passed  Congress  incorporating  a 
company  to  carry  it  out.  The  article  then  goes  on  to  say  : 
"  We  will  not  record  ourselves  as  disbelievers  in  the  Aerial 
Telegraph,  but  wait  meekly  and  see  what  the  Doctor  will 
do  with  his  brilliant  idea  now  that  both  Houses  of  Congress 
have  passed  a  bill  incorporating  a  company  for  him.  Con- 
gressmen, at  least,  do  not  think  him  wholly  visionary ;  and 
it  is  said  that  the  President  will  sign  the  bill ;  all  of  which 
is  some  evidence  that  air  telegraphy  has  another  side  than 
the  ridiculous  one.  The  company  receive  no  money  from 
the  Government,  and  ask  none.  As  we  understand  the 
Loomis  plan,  it  is  something  to  this  effect — and  readers  are 
cautioned  not  to  laugh  too  boisterously  at  it,  as  also  not  to 
believe  in  it  till  demonstrated.  The  inventor  proposes  to 


MAHLON  LOOMIS.  71 

build  a  very  tall  tower  on  the  highest  peak  of  the  Eocky 
Mountains.  A  mast,  also  very  tall,  will  stand  on  this 
tower,  and  an  apparatus  for  '  collecting  electricity '  will  top 
the  whole.  From  the  loftiest  peak  of  the  Alps  will  rise 
another  very  tall  tower  and  ditto  mast,  with  its  coronal 
electrical  affair.  At  these  sky-piercing  heights  Dr  Loomis 
contends  that  he  will  reach  a  stratum  of  air  loaded  with 
electricity;  and  we  cannot  say  that  he  will  not.  Then, 
establishing  his  ground-wire  connections  the  same  as  in 
ordinary  telegraphs,  he  feels  confident  that  he  can  send 
messages  between  the  mast-tops,  the  electrified  stratum  of 
air  making  the  circuit  complete.  The  inventor  claims  to 
have  proved  the  feasibility  of  this  grand  scheme  on  a  small 
scale.  We  are  told  that,  from  two  of  the  spurs  of  the  Blue 
Ridge  Mountains,  twenty  miles  apart,  he  sent  up  kites, 
using  small  copper  wire  instead  of  pack-thread,  and  tele- 
graphed from  one  point  to  the  other." 

At  intervals  in  the  next  few  years  brief  notices  of  the 
Loornis  method  appeared  in  the  American  journals,  some 
of  which  were  copied  into  English  papers.  The  last  that 
I  have  seen  is  contained  in  the  '  Electrical  Eeview '  of 
March  1,  1879,  where  it  is  stated  that  "with  telephones  in 
this  aerial  circuit  he  [Loomis]  can  converse  a  distance  of 
twenty  miles,"  to  which  the  editor  significantly  adds  a 
note  of  interrogation. 

The  fact  is,  however  much  Mr  Loomis  and  his  Wall 
Street  friends  believed  that  dollars  were  in  the  idea,  the 
technical  press  never  took  it  very  seriously.  This  is  shown 
by  the  following  cutting,  which  we  take  from  the  New 
York  'Journal  of  the  Telegraph,'  March  15,  1877: 
"The  never-ending  procession  of  would-be  inventors  who 
from  day  to  day  haunt  the  corridors  and  offices  of  the 
Electrician's  department  at  195  Broadway,  bringing  with 
them  mysterious  packages  tied  up  in  newspapers,  was 


72  FIRST  PERIOD — THE  POSSIBLE. 

varied  the  other  day  by  the  appearance  of  a  veritable 
lunatic.  He  announced  that  that  much -talked -of  great 
discovery  of  a  few  years  ago,  aerial  telegraphy,  was  in 
actual  operation  right  here  in  New  York.  A.  M.  Palmer, 
of  the  Union  Square  Theatre,  together  with  one  of  his 
confederates,  alone  possessed  the  secret !  They  had  un- 
fortunately chosen  to  use  it  for  illegitimate  purposes,  and 
our  visitor,  therefore,  felt  it  to  be  his  solemn  duty  to  expose 
them.  By  means  of  a  $60,000  battery,  he  said,  they  trans- 
mitted the  subtle  fluid  through  the  aerial  spaces,  read 
people's  secret  thoughts,  knocked  them  senseless  in  the 
street;  ay,  they  could  even  burn  a  man  to  a  crisp,  miles 
and  miles  away,  and  he  no  more  know  what  had  hurt  him 
than  if  he  had  been  struck  by  a  flash  of  lightning,  as  indeed 
he  had  ! l  The  object  of  our  mad  friend  in  dropping  in  was 
merely  to  ascertain  how  he  could  protect  himself  from 
Palmer's  illegitimate  thunderbolts.  Here  the  legal  gentle- 
man, lifting  his  eyes  from  '  Curtis  on  Patents,'  remarked : 
'Now,  I'll  tell  you  what  you  do.  Bring  a  suit  against 
Palmer  for  infringement  of  Mahlon  Loomis's  patent.  Here 
it  is '  (taking  down  a  bound  volume  of  the  'Official  Gazette '), 
1  No.  129,971.  That'll  fix  Palmer.' " 

In  conclusion  of  this  period  of  our  history,  it  will  suffice 
to  say  that  between  1858  and  1874  many  patents  were 
taken  out  in  England  for  electric  signalling  on  the  bare 
wire  system  of  Highton  and  Bering,  with  or  without  the 
use  of  the  so-called  "earth  battery."  As  they  are  all  very 
much  alike,  and  all  unsupported,  so  far  as  I  have  seen,  by 
any  experimental  proofs,  it  would  be  a  tiresome  reiteration 
to  describe  them,  even  in  the  briefest  way.  I  therefore 
content  myself  with  giving  the  following  list,  which  will 

1  This  lunatic  must  be  still  abroad,  for  we  occasionally  hear  much 
the  same  thing  of  the  diabolic  practices  of  Tesla  and  Marconi. 


MAHLON   LOOMIS. 


73 


be  useful  to  those  of  my 
them. 

Name  of  patentee. 

B.  Nickels  . 

A.  V.  Newton     . 

A.  Barclay . 

Do. 

J.  Moleswortli    . 
H.  S.  Kosser 
W.'E.  Newton    . 
H.  Wilde    . 
Lord  A.  S.  Churchill  . 
H.  Wilde    . 

Do.        ... 
T.  Walker  . 

Do. 


readers  who  desire  to  consult 

No.  and  date  of  patent. 

2317  October  16,  1858. 

2514  November  9,  1858. 

56  January  7,  1859. 

263  January  28,  1859. 

687  March  18,  1859. 

2433  October  25,  1859. 

1169  May  11,  1860. 

2997  November  28,  1861. 

458  February  20,  1862. 

3006  December  1,  1863. 

2762  October  26,  1865. 

2870  November  6,  1866. 

293  January  23,  1874 


74 


SECOND  PERIOD— THE  PEACTICABLE. 

PRELIMINARY  :  NOTICE  OF  THE  TELEPHONE  IN  RELATION 
TO  WIRELESS  TELEGRAPHY. 

"  Give  me  the  ocular  proof, 
Make  me  see't ;  or,  at  least,  so  prove  it, 
That  the  probation  bear  no  hinge,  nor  loop, 
To  hang  a  doubt  on." 

WE  have  now  arrived  at  a  period  in  the  history  of  our 
subject  at  which  experiments  begin  to  assume  a  character 
more  hopeful  of  practical  results.  All  that  went  before 
was  more  or  less  crude  and  empirical,  and  could  not  be 
otherwise  from  the  very  necessities  of  the  case.  The  intro- 
duction of  the  telephone  in  1876  placed  in  the  hands  of  the 
electrician  an  instrument  of  marvellous  delicacy,  compared 
with  which  the  most  sensitive  apparatus  hitherto  employed 
was  as  the  eye  to  the  eye  aided  by  the  microscope.  Thus, 
Prof.  Pierce  of  Providence,  Rhode  Island,  has  found  that 
the  Bell  telephone  gives  audible  signals  with  considerably 
less  than  the  one-huudred-thousandth  part  of  the  current 
of  a  single  Leclanche  cell.  In  testing  resistances  with  a 
Wheatstone  bridge,  the  telephone  is  far  more  sensitive  than 
the  mirror  galvanometer ;  in  ascertaining  the  continuity  of 
fine  wire  coils  it  gives  the  readiest  answers ;  and  for  all  the 
different  forms  of  atmospheric  electrical  discharges — and 


THE  TELEPHONE  AND  WIRELESS  TELEGRAPHY.   75 

they  are  many — it  has  a  language  of  its  own,  and  opens  up 
to  research  a  new  field  in  meteorology. 

The  sound  produced  in  the  telephone  by  lightning,  even 
when  so  distant  that  only  the  flash  can  be  seen  in  the  hori- 
zon, and  no  thunder  can  be  heard,  is  very  characteristic — 
something  like  the  quenching  of  a  drop  of  molten  metal  in 
water,  or  the  sound  of  a  distant  rocket ;  but  the  remarkable 
circumstance  for  us  in  this  history  is,  that  this  sound  is 
always  heard  just  before  the  flash  is  seen,  showing  that 
there  is  an  inductive  disturbance  of  the  electricity  overhead, 
due  to  the  distant  concentration  preceding  the  disruptive 
discharge.  Thus,  on  November  18,  1877,  these  peculiar 
sounds  were  heard  in  Providence,  and  the  papers  next 
morning  explained  them  by  reporting  thunderstorms  in 
Massachusetts.  Sounds  like  those  produced  by  lightning, 
but  fainter,  are  almost  always  heard  many  hours  before  a 
thunderstorm  actually  breaks.1 

The  Bell  telephone  was  tried  for  the  first  time  on  a  wire 
from  New  York  to  Boston  on  April  2,  1877,  and  soon  after- 
wards its  extraordinary  sensitiveness  to  induction  currents, 
and  currents  through  the  earth  (leakages)  from  distant 
telegraph  circuits,  began  to  be  observed.2  Thus,  in  August 
1877,  Mr  Charles  Eathbone  of  Albany,  KY.,  had  been  ex- 
perimenting with  a  Bell  telephone  which  was  attached  to  a 
private  telegraph  line  connecting  his  house  with  the  Ob- 

14  Journal  of  the  Telegraph,'  N.Y.,  December  1,  1877.  See  also 
4  Jour.  Inst.  Elec.  Engs.,'  vol.  vi.  p.  523,  vol.  vii.  p.  329  ;  'The  Elec- 
trician,' vol.  ix.  p.  362. 

2  The  disturbing  effects  of  induction  on  ordinary  telegraph  wires  on 
the  same  poles  had  long  before  this  been  noticed.  See  Culley's  paper 
and  the  discussion  thereon  in  the  'Jour.  Inst.  Elec.  Engs.,'  vol.  iv. 
p.  54.  See  also  p.  427  for  Winter's  interesting  observations  in  India 
in  1873.  As  far  back  as  1868  Prof.  Hughes,  at  the  request  of  the 
French  Telegraph  Administration,  undertook  a  series  of  experiments 
with  a  view  of  finding  a  remedy.  The  results  are  given  in  his  paper 
read  before  the  Inst.  Elec.  Engs.,  March  12,  1879. 


76       SECOND  PERIOD — THE  PRACTICABLE. 

servatory.  One  evening  he  heard  some  singing  which  he 
thought  came  from  the  Observatory,  but  found  on  inquiry 
that  that  was  not  the  case.  He  then  carefully  noted  what 
followed,  and  next  morning  sent  a  note  to  the  newspapers 
stating  the  facts  and  giving  the  names  of  the  tunes  which 
he  had  heard.  This  elicited  the  information  that  the  tunes 
were  those  of  an  experimental  concert  with  Edison's  singing 
telephone  over  a  telegraph  wire  between  New  York  and 
Saratoga  Springs.  It  was  then  resolved  to  follow  up  this 
curious  discovery,  and,  accordingly,  when  Edison's  agent 
gave  another  concert  in  Troy,  arrangements  were  made  to 
observe  the  effects.  A  wire  running  from  Albany  to  Troy 
alongside  the  Edison  wire  was  earthed  with  a  Bell  telephone 
in  circuit  at  each  end.  The  concert  was  heard  as  before, 
the  music  coming  perfectly  clear,  and  the  tunes  distinguish- 
able without  the  least  difficulty. 

Later  in  the  evening  the  instruments  were  put  in  circuit 
on  one  of  the  wires  running  from  Albany  to  New  York. 
Again  the  music  was  heard,  and  much  louder,  so  that  by 
placing  the  telephone  in  the  centre  of  the  room  persons 
seated  around  could  hear  with  perfect  distinctness. 

These  observations  were  made  on  six  separate  occasions 
between  August  28  and  September  11,  and,  strangely  enough, 
two  other  and  independent  observers  in  Providence,.  200 
miles  away,  noted  the  same  effects  on  five  out  of  the  six 
dates  given  by  Mr  Eathbone.1 

Dr  Channing,  one  of  the  observers  in  Providence,  has 
published  a  very  interesting  account 2  of  his  observations, 
from  which  I  will  make  a  few  extracts.  During  five 

1  'Journal  of  the  Telegraph,'  N.Y.,  October  1  and  16,  and  No- 
vember 1,  1877.     For  other  early  observations  of  the  same  kind  see 
'The  Telegraphic  Journal,'  March  1,  1878,  p.  96;  'Journal  of  the 
Telegraph,'  March  16,  1878  ;  'The  Electrician,'  vol.  vi.  pp.  207,  303. 

2  'Journal  of  the  Telegraph,'  December  1,  1877,  and  reproduced 
in  the  'Jour.  Inst.  Elec.  Engs.,'  vol.  vi.  p.  545. 


THE  TELEPHONE  AND  WIRELESS  TELEGRAPHY.   77 

evenings  in  the  latter  part  of  August  and  first  part  of 
September  1877  concerts  were  given  in  the  Western  Union 
Office,  N.Y.,  for  the  benefit  of  audiences  in  Saratoga, 
Troy,  and  Albany  respectively.  The  performers  sang  or 
played  into  an  Edison  musical  telephone,  actuated  by  a 
powerful  battery,  and  connected  with  one  or  other  of  the 
above-named  places  by  an  ordinary  telegraph  line,  with 
return  through  the  ground. 

In  Providence,  on  the  evening  of  the  first  concert,  Dr 
Channing  and  a  friend  were  conversing  through  Bell  tele- 
phones over  a  shunt  wire,  made  by  grounding  one  of  the 
American  District  Telegraph  wires  at  two  places,  a  quarter 
of  a  mile  apart,  through  the  telephones  and  several  hun- 
dred ohms  resistance.  At  about  half-past  eight  o'clock 
they  were  surprised  by  hearing  singing  on  the  line,  at  first 
faint,  but  afterwards  becoming  clear  and  distinct.  After- 
wards, during  that  and  subsequent  evenings,  various  airs 
were  heard,  sung  by  a  tenor  or  soprano  voice,  or  played 
on  the  cornet.  On  investigation,  the  music  heard  proved 
to  be  the  same  as  that  of  the  Edison  concerts  performed 
in  New  York. 

The  question  how  this  music  passed  from  the  New  York 
and  Albany  wire  to  a  shunt  on  the  District  wire  in  Provi- 
dence is  of  scientific  importance.  The  Edison  musical 
telephone  consists  of  an  instrument  which  converts  sound 
waves  into  galvanic  waves  at  the  transmitting  station,  and 
another  apparatus  which  reconverts  galvanic  waves  into 
sound  waves  at  the  receiving  station.  The  battery  used 
in  these  concerts  consisted  of  125  carbon-bichromate  cells 
(No.  1J),  with  from  1000  to  3000  ohms  resistance  inter- 
posed between  the  battery  and  the  line.  The  line  wire 
extended  from  the  Western  Union  office,  via  the  Harlem 
Eailway,  to  Albany.  On  the  same  poles  with  this  Albany 
wire,  for  sixteen  miles,  are  carried  four  other  wires,  all 


78       SECOND  PERIOD — THE  PRACTICABLE. 

running  to  Providence,  and  also,  for  eight  miles,  a  fifth 
wire  from  Boston,  via  New  London,  to  Providence.  All 
these  lines,  including  the  Albany  wire,  are  understood  to 
have  a  common  earth  connection  at  New  York,  and  to  be 
strung  at  the  usual  distance  apart,  and  with  the  ordinary 
insulation. 

At  Providence  six  New  York  and  Boston  wires  run 
into  the  Western  Union  office  on  the  same  poles  and 
brackets  for  the  last  975  feet  with  an  American  District 
wire.  This  wire  belongs  to  an  exclusively  metallic  circuit 
of  four  and  a  half  miles,  having,  therefore,  no  earth  con- 
nection. Finally,  in  a  shunt  on  this  wire,  the  telephones 
were  placed  as  before  described. 

It  will  thus  be  seen  that  the  music  from  the  Albany 
wire  passed  first  to  the  parallel  New  York -Providence 
wires;  secondly,  from  these  to  a  parallel  District  wire  in 
Providence ;  and  thirdly,  through  a  shunt  on  the  District 
wire  to  the  telephones. 

This  transfer  may  have  taken  place  by  induction,  by 
cross-leakage,  or,  in  the  first  instance,  in  New  York  by 
a  crowded  ground  connection ;  but  in  the  transfer  in  Provi- 
dence from  the  New  York-Boston  to  the  District  wire  there 
was  no  common  ground  connection,  and  it  is  difficult  to 
suppose  that  sufficient  leakage  took  place  on  the  three 
brackets  and  three  poles  (common  to  the  New  York  'and 
District  wires)  to  account  for  it.  "Without  wholly  reject- 
ing the  other  modes  of  transfer,  Dr  Channing  ascribes  to 
induction  the  principal  part  in  the  effects. 

The  next  question  arises,  What  proportion  of  the  electri- 
cal force  set  in  motion  in  New  York  could  have  reached  the 
listeners  on  the  short  shunt  line  in  Providence  1  Whether 
induction  or  cross-leakage  or  crowded  ground  was  concerned, 
who  will  say  that  the  New  York -Providence  wires  had 
robbed  the  Albany  wire  of  one-tenth  or  even  one-hundredth 


THE  TELEPHONE  AND  WIRELESS  TELEGRAPHY.   79 

of  its  electrical  force  1  When  this  reached  Providence,  did 
the  New  York  wires  in  the  course  of  975  feet  give  up  to 
the  District  wire  one-tenth  or  one-hundredth  of  their  force  ] 
Lastly,  when  the  District  circuit  had  secured  this  minute 
fraction,  did  the  shunt,  with  its  500  ohms  resistance  as 
against  the  few  ohms  of  the  shunted  quarter-mile,  divert 
one-hundredth  part  of  this  minute  fraction  from  the  Dis- 
trict wire  1  Plainly,  the  music  reproduced  in  the  Providence 
telephone  did  not  require  one  ten  -  thousandth,  nor  one 
hundred-thousandth,  of  the  force  originally  imparted  to  the 
Albany  wire. 

In  December  1877  Prof.  E.  Sacher  of  Vienna  undertook 
some  careful  investigations  with  a  view  of  measuring  the 
inductive  effect  in  telephone  circuits.  He  found  that 
signals  from  three  Smee  cells  sent  through  one  wire,  120 
metres  long,  could  be  distinctly  heard  in  the  telephone  on 
another  and  parallel  wire  20  metres  distant  from  it.1 

Early  in  1879  M.  Henri  Dufour  tried  similar  experi- 
ments, and  with  the  same  results.  Two  covered  copper 
wires  were  stretched  parallel  over  a  length  of  1 5  metres,  and 
at  distances  apart  varying  from  15  to  45  centimetres.  In 
connection  with  one  of  the  wires  were  the  battery  and  the 
ordinary  Morse  apparatus,  the  gas -pipes  being  used  to  com- 
plete the  circuit.  The  ends  of  the  other  wire  were  joined 
to  the  telephone  so  as  to  form  a  complete  metallic  circuit. 
The  current  employed  produced  a  deflection  of  60°  on  the 
galvanometer.  Under  these  conditions  all  the  motions  of 
the  key  were  distinctly  heard  in  the  telephone,  and  the 
author  was  satisfied  that  a  telegraphist  would  have  under- 
stood the  signals,  even  when  the  distance  between  the  two 
wires  was  45  centimetres.2 

When  we  consider  the  shortness  of  these  wires,  the 
effects  are  sufficiently  striking ;  but  before  this,  equally 

1  'Electrician,'  vol.  i.  p.  194.  2  Ibid.,  vol.  ii.  p.  182. 


80       SECOND  PERIOD — THE  PRACTICABLE. 

striking  results  had  been  obtained  on  actual  telegraph  lines, 
where  there  was  no  battery,  and  where  the  infinitesimal 
currents  produced  by  speaking  into  a  Bell  telephone  on  one 
wire  were  able  to  induce  currents  in  a  parallel  wire  sufficient 
to  render  the  words  audible  in  another  telephone  in  its 
circuit.  Dr  Channing  found  this  to  be  possible  "under 
very  favourable  conditions."  * 

Another  striking  illustration  is  furnished  by  Prof.  Blake, 
of  Brown  University,  U.S.,  who  talked  with  a  friend  for 
some  distance  along  a  railway  (using  the  two  lines  of  rails 
for  the  telephonic  circuit),  hearing  at  the  same  time  the 
Morse  signals  passing  along  the  telegraph  wires  overhead.2 


PROFESSOR   JOHN    TROWBRIDGE— 1880. 

Such  are  a  few  of  the  early  instances  noted  of  the 
extreme  sensitiveness  of  the  telephone,  by  the  aid  of  which 
the  problem  of  wireless  telegraphy  was  now  to  be  attacked 
with  a  fair  measure  of  success,  and  advanced  a  long  way 
towards  a  practical  solution. 

Mr  J.  Gott,  then  superintendent  of  the  Anglo-American 
Telegraph  Company  at  St  Pierre,  was,  I  believe,  the  first  to 
suggest  the  employment  of  the  telephone  in  this  connection. 
In  a  brief  communication,  published  in  the  '  Jour.  Inst. 
Elec.  Engs.'  (vol.  vi.  p.  523),  he  says  :  "  The  island  of 

1  For  a  curiously  similar  case,  the  result  of  a  wrong  connection  of 
the  line  wires,  see  the  '  Telegraphic  Journal,'  vol.  ix.  p.  68. 

2  The  absence  of  insulation  in  this  experiment  recalls  the  fact  that 
a  telephone  line  using  the  earth  for  the  return  circuit  often  works 
better  when  the  insulation  is  defective,  as  it  is  then  less  affected  by 
extraneous  currents.     Thus,  in  1882,  the  Evansville  (Ind.)  Telephone 
Exchange  Company  worked  400  miles  of  line  without  insulators  of  any 
kind  (the  wires  being  simply  attached  to  the  poles),  and  generally 
with  better  results  than  when  insulators  were  used.     ('  Electrician,' 
vol.  ix.  p.  481.) 


PKOFESSOR  JOHN  TROWBRIDGE.  81 

St  Pierre  is,  perhaps,  better  insulated  than  most  places. 
Hundreds  of  yards  from  the  station,  if  a  wire  be  connected 
to  earth,  run  some  distance,  and  put  to  earth  again,  with  a 
telephone  in  circuit,  the  signals  passing  through  the  cables 
can  be  heard." 

There  are  two  offices  on  the  island, — one  used  for 
repeating  the  cable  business  on  the  short  cables  between 
Sydney,  C.B.,  and  Placentia,  N.F.,  and  operated  by  the 
Morse  system,  with  a  comparatively  powerful  battery ;  the 
other  is  the  office  at  which  the  Brest  and  Duxbury  cables 
terminate,  and  is  furnished  with  very  delicate  instruments 
— the  Brest  cable,  which  is  upwards  of  2500  miles  long, 
being  operated  by  Thomson's  exceedingly  sensitive  dead- 
beat  mirror  galvanometer ;  whilst  on  the  Duxbury  cable  the 
same  inventor's  instrument,  the  siphon  recorder,  is  used. 
The  Brest  instrument  was  found  seriously  affected  by  earth- 
currents,  which  flowed  in  and  out  of  the  cable,  interfering 
very  much  with  the  true  currents  or  signals,  and  rendering 
it  a  difficult  task  for  the  operator  to  decipher  them  ac- 
curately. The  phenomenon  is  not  an  uncommon  one ;  and 
the  cause  being  attributed  to  the  ground  used  at  the 
office,  a  spare  insulated  wire,  laid  across  the  island,  a 
distance  of  nearly  three  miles,  and  a  metal  plate  connected 
to  it  and  placed  in  the  sea,  was  used  in  lieu  of  the  office 
ground.  This  had  a  good  effect,  but  it  was  now  found  that 
part  of  the  supposed  earth-currents  had  been  due  to  the 
signals  sent  by  the  Morse  operator  into  his  wire,  for  when 
the  recorder  was  put  in  circuit  between  the  ground  at  the 
cable  office  and  the  sea  ground — three  miles  distant — the 
messages  sent  by  the  Morse  were  clearly  indicated, — so 
clearly,  in  fact,  that  they  were  automatically  recorded  on 
the  tape. 

It  must  be  clearly  understood  that  the  two  offices  were  in 
no  way  connected,  nor  were  they  within  some  200  yards  of 

F 


82       SECOND  PERIOD — THE  PRACTICABLE. 

each  other;  and  yet  messages  sent  at  one  office  were 
distinctly  read  at  the  other,  the  only  connection  between 
the  two  being  through  the  earth,  and  it  is  quite  evident 
that  they  could  be  so  read  simultaneously  at  many  offices  in 
the  same  neighbourhood.  The  explanation  is  clear  enough. 
The  potential  of  the  ground  at  the  two  offices  is  alternately 
raised  and  lowered  by  the  Morse  battery.  The  potential  of 
the  sea  remains  almost,  if  not  wholly,  unaffected  by  these, 
and  the  island  thus  acts  like  an  immense  Leyden  jar,  con- 
tinually charged  by  the  Morse  battery  and  discharged,  in 
part,  through  the  short  insulated  line.  Each  time  the 
Morse  operator  depressed  his  key  he  not  only  sent  a  current 
into  his  cable,  but  electrified  the  whole  island,  and  this 
electrification  was  detected  and  indicated  on  the  recorder.1 

As  the  result  of  these  experiences,  Mr  Gott  gave  it  as  his 
opinion  that  "speaking  through  considerable  distances  of 
earth  without  wires  is  certainly  possible  with  Bell's  tele- 
phone, with  a  battery  and  Morse  signals." 

Professor  John  Trowbridge  of  Harvard  University, 
America,  was,  however,  the  first  to  systematically  study 
the  problem,  and  to  revive  the  daring  project  of  an  Atlantic 
telegraph  without  connecting  wires,  and  the  less  ambitious 
but  equally  useful  project  of  intercommunication  between 
ships  at  sea.2  In  fact,  Trowbridge's  researches  may  truly  be 

1  See  now  Salvti's  curious  anticipation  in  1795  of  this  phenomenon, 
p.  2,  ante.     The  peculiarity,  due  to  geological  formation,  is  not  con- 
fined to  St  Pierre  ;  it  is  often  met  with  in  practice,  though  usually  in 
lesser  degrees.     See  some  interesting  cases,  noted  by  G.  K.  Winter 
and  James  Graves,  '  Jour.  Inst.  Elec.  Engs.,'  vol.  i.  p.  88,  and  vol. 
iv.  p.  34. 

2  Mr  H.  C.  Strong  of  Chicago,  Illinois,  claims  to  have  suggested 
in  1857,  in  a  Peoria,  111.,  newspaper,  the  possibility  of  communication 
between  ships  at  sea  by  means  of  a  wireless  telegraph  then  recently 
invented  by  his  friend  Henry  Nelson  of  Galesburg.     See  Mr  Strong's 
letter  in  the  New  York  '  Journal  of   the   Telegraph,'   August   15, 
1877. 


PROFESSOR  JOHN   TROWBRIDGE.  83 

said  to  form  a  new  starting-point  in  the  history  of  our 
subject,  for,  as  we  shall  see  later  on,  it  is  chiefly  to  him 
that  Messrs  Preece,  Bell,  and  probably  other  experimenters 
in  this  field,  owe  their  inspirations.1  His  investigations, 
therefore,  deserve  to  be  carefully  followed. 

The  observatory  at  Harvard  transmits  time-signals  from 
Cambridge  to  Boston,  a  distance  of  about  four  miles,  and 
the  regular  recurrence  of  the  beats  of  the  clock  afforded 
a  good  means  of  studying  the  spreading  of  the  electric 
currents  from  the  terminal  of  the  battery  which  is  grounded 
at  the  observatory.  In  all  the  telephone  circuits  between 
Boston  and  Cambridge,  in  the  neighbourhood  of  the  observ- 
atory line,  the  ticking  of  the  clock  could  be  heard.  This 
ticking  had  been  attributed  to  induction,  but  this,  according 
to  Prof.  Trowbridge,  is  an  erroneous  conclusion,  as  he  shows 
by  a  mathematical  analysis  into  which  we  need  not  enter. 
The  result  goes  to  show  that,  with  telephones  of  the  resist- 
ance usually  employed,  no  inductive  effect  will  be  perceived 
by  the  use  of  even  ten  quart  Bunsen  cells  between  wires 
running  parallel,  a  foot  apart,  for  a  distance  of  30  or  40  feet. 

For  this  and  other  reasons,  he  says,  it  is  impossible  to 
hear  telephonic  messages  by  induction  from  one  wire  to 
another,  unless  the  two  run  parallel  and  very  close  to  each 
other  for  a  long  distance.  This  distance  generally  exceeds 
the  limit  at  which  the  ordinary  Bell  telephone  ceases  to 
transmit  articulate  speech.  The  effects  which  have  usually 
been  attributed  to  induction  are  really,  he  says,  due  to  the 
earth  connections  and  to  imperfect  insulation. 

Having  determined  in  this  manner  that  the  echoes  of  the 

1  See  pp.  92  and  137,  infra.  Professor  Trowbridge's  researches 
are  given  at  length  in  a  paper,  "  The  Earth  as  a  Conductor  of  Elec- 
tricity," read  before  the  American  Academy  of  Arts  and  Sciences  in 
1880.  See  also  '  Silliman's  American  Journal  of  Science,'  August 
1880,  which  I  follow  in  the  text. 


84       SECOND  PERIOD — THE  PRACTICABLE. 

time-signals  observed  on  the  telephone  lines  were  not  due 
to  induction,  but  to  leakage  from  the  clock  circuit,  Prof. 
Trowbridge  proceeded  to  study  the  extent  of  the  equally 
electrified  or  equi- potential  surfaces  of  the  ground  sur- 
rounding the  clock  battery.  His  method  of  exploration 
was  to  run  a  wire  500  or  600  feet  long  to  earth  at  each 
end,  including  a  telephone  of  50  to  60  ohms  resistance. 
Evidence  of  a  current  in  this  exploratory  circuit  was  plainly 
shown  by  the  ticking  sound  which  making  and  breaking 
the  circuit  caused  in  the  telephone,  and  the  time-signals 
could  be  distinctly  heard  in  a  field  220  yards  from  the 
observatory  where  one  earth  of  the  time-signal  wire  is 
located.  At  a  distance  of  a  mile  from  the  observatory,  and 
not  in  the  direct  line  between  that  place  and  the  Boston 
telephone  office,  the  time-signals  were  heard  by  connecting 
through  a  telephone  the  gas-pipes  of  one  building  with  the 
water-pipes  of  another  only  50  feet  apart.  In  another  ex- 
periment at  the  Fresh  Pond  lake  in  Cambridge,  signals 
sent  from  Boston  to  Waltham  (ten  to  twelve  miles)  were 
heard  by  simply  dipping  the  terminal  wires  of  the  telephone 
in  the  lake,  and  some  distance  apart,  where  they  must  have 
been  far  away  (?  four  miles)  from  the  battery  earth. 

Prof.  Trowbridge  performed  a  large  number  of  similar 
experiments,  varied  in  every  way,  all  going  to  prove  (1) 
that  a  battery  terminal  discharging  electricity  to  earth  is 
the  centre  of  waves  of  electrical  energy,  ever  widening, 
and  ever  decreasing  in  strength  or  potential  as  they  widen ; 
and  (2)  that  on  tapping  the  earth  in  the  way  described  at 
two  points  of  different  potentials  (not  very  distant,  if  near 
the  central  source,  and  more  removed  the  farther  we  recede 
from  the  source)  we  can  obtain  in  the  telephone  evidence 
of  their  existence.  Prof.  Trowbridge  then  goes  on  to 
say: — 

"  In  a  discussion  on  the  earth  as  a  conductor,  Steinheil 


PROFESSOR  JOHN  TROWBRIDGE.  85 

says :  '  We  cannot  conjure  up  gnomes  at  will  to  convey 
our  thoughts  through  the  earth.  Nature  has  prevented 
this.  The  spreading  of  the  galvanic  effect  is  proportional 
...  to  the  square  of  the  distance ;  so  that,  at  the  distance 
of  50  feet,  only  exceedingly  small  effects  can  be  produced. 
.  .  .  Had  we  means  which  could  stand  in  the  same  relation 
to  electricity  that  the  eye  stands  to  light,  nothing  would 
prevent  our  telegraphing  through  the  earth  without  con- 
ducting wires.' 1 

"  The  telephone  of  Prof.  Bell,  though  far  from  fulfilling 
the  conditions  required  by  Steinheil,  is  nevertheless  our 
nearest  approach  to  the  desideratum. 

"The  theoretical  possibility  of  telegraphing  across  the 
Atlantic  without  a  cable  is  evident  from  the  survey  which 
I  have  undertaken.  The  practical  possibility  is  another 
question.  Powerful  dynamo  -  electric  machines  could  be 
placed  at  some  point  in  Nova  Scotia,  having  one  end  of 
their  circuit  grounded  near  them  and  the  other  end  grounded 
in  Florida,  the  connecting  wire  being  of  great  conductivity 
and  carefully  insulated  throughout.  By  exploring  the  coast 
of  France,  two  points  on  surface  lines  not  at  the  same 
potential  could  be  found;  and  by  means  of  a  telephone 
of  low  resistance,  Morse  signals  sent  from  Nova  Scotia 
to  Florida  could  be  heard  in  France.  Theoretically,  this 
is  possible;  but  practically,  with  the  light  of  our  present 
knowledge,  the  expenditure  of  energy  on  the  dynamo- 
electric  machines  would  be  enormous." 2 

Professor  Trowbridge  has  suggested  the  applicability  of 
this  method  to  the  intercommunication  of  ships  at  sea. 

1  See  p.  5,  ante. 

2  A  writer  in  the  'Electrician'  (vol.  v.  p.  212),  commenting  on 
this  passage,  says  :  "  Prof.  Trowbridge  seems  to  overlook  the  advan- 
tage of  employing  large  condensers  between  the  dynamo  machines 
and  the  earth.     They  would  prove  of  great  service  in  exalting  the 
earth  potentials  at  the  terminal  stations." 


86       SECOND  PERIOD — THE  PRACTICABLE. 

Let,  he  says,  a  steamer  be  provided  with  a  powerful 
dynamo.  Connect  one  terminal  of  the  dynamo  with  the 
water  at  the  bow  of  the  steamer,  and  the  other  to  a  long 
wire,  insulated  except  at  its  extreme  end,  dragging  over  the 
stern,  and  buoyed  so  as  not  to  sink.  The  current  from  the 
dynamo  will  thus  pass  into  the  water  and  spread  out  over 
a  large  area,  as  before  explained,  saturating,  so  to  speak, 
the  water  with  electricity.  Suppose  this  current  be  inter- 
rupted by  any  suitable  means,  say  one  hundred  times  a 
second.  Let  the  approaching  steamer  be  provided  with 
a  telephone  wire,  the  ends  of  which  dip  into  the  water 
at  her  bow  and  stern  respectively.  On  entering  the  sat- 
urated area  the  telephone  will  respond  to  the  interruptions 
of  the  dynamo  by  giving  out  a  continuous  buzzing  sound. 
If  now  in  the  dynamo  circuit  we  have  a  manipulating 
arrangement  for  breaking  up  the  electric  impulses  into 
long  and  short  periods,  corresponding  to  the  Morse  alpha- 
bet, one  ship  can  speak  to  the  other.  It  is  hardly  neces- 
sary to  add  that  by  providing  each  steamer  with  a  dynamo 
circuit  and  a  telephone  circuit  reciprocal  correspondence 
could  be  maintained,  it  being  only  necessary  for  the 
steamer  desiring  to  listen  to  stop  and  disconnect  the 
dynamo.  The  success  of  this  method  of  communicating 
between  ships  in  a  fog  depends  upon  the  distance  between 
the  ends  of  the  dynamo  circuit  and  upon  the  strength  of 
the  current,  or  electrical  impulses  imparted  to  the  water. 

It  is  probable  that  a  dynamo  capable  of  maintaining 
one  hundred  incandescent  lamps  could  establish  a  sufficient 
difference  of  potential  between  the  water  at  the  bow  and 
at  the  end  of  a  trailing  wire,  half  a  mile  long,  to  affect 
a  telephone  on  an  approaching  ship  while  yet  half  a  mile 
distant. 

In  a  discussion  on  Prof.  Graham  Bell's  paper,  read  before 
the  American  Association  for  the  Advancement  of  Science, 


PROFESSOR  JOHN  TROWBRIDGE.  87 

1884,  Prof.  Trowbridge  described  another  plan,  using  in- 
stead of  the  telephone  circuit  a  sensitive  galvanometer  con- 
nected up  to  a  cross-arm  of  wire,  whose  ends  dip  into  the 
water  at  each  side  of  the  ship.  When  one  vessel  comes 
within  the  area  electrically  saturated  by  another,  the  galvan- 
ometer will  show  how  the  equipotential  lines  are  disturbed, 
and  if  a  map  of  these  lines  be  carefully  traced  we  can  fix 
the  position  of  the  approaching  ship.  He  adds:  "The 
method  could  also  be  applied  to  saturating  the  water  around 
a  rock,  and  you  could  take  electrical  soundings,  so  to  speak, 
and  ascertain  your  position  from  electrical  maps  carefully 
made  out." 

In  a  later  paper  published  in  the  *  Scientific  American 
Supplement/  February  21,  1891,  Prof.  Trowbridge  discusses 
the  phenomena  of  induction,  electro-magnetic  and  static, 
as  distinguished  from  leakage  or  earth  conduction,  and  with 
reference  to  their  employment  in  wireless  telegraphy. 

The  hope,  he  says,  that  we  shall  be  able  to  transmit 
messages  through  the  air  by  electricity  without  the  use 
of  connecting  wires  is  supposed  by  some  to  indicate  its 
realisation  at  a  future  day.  Let  us  examine  how  near  we 
are  at  present  to  the  realisation  of  this  hope. 

He  supposes  that  the  chief  use  of  any  method  by  which 
connecting  wires  could  be  dispensed  with  would  be  at  sea 
in  a  fog.  On  land  for  considerable  distances  it  is  hardly 
probable  that  any  electrical  method  could  be  devised  in 
which  air  or  the  ether  of  space  could  advantageously  re- 
place a  metallic  conductor.  The  curvature  of  the  earth 
would  probably  demand  a  system  of  frequent  repetition, 
which  is  entirely  obviated  by  the  use  of  a  wire.  If,  how- 
ever, an  electrical  or  magnetic  system  could  be  made  to  work 
through  the  air  even  at  the  distance  of  a  mile,  it  would 
be  of  very  great  use  at  sea  in  averting  collisions ;  for  any 
system  of  signals  depending  upon  the  use  of  fog-horns  or 


88 


SECOND  PERIOD — THE  PRACTICABLE. 


fog- whistles  i^  apt  to  mislead  on  account  of  the  reflection 
of  the  sound  from  layers  of  air  of  different  densities  and 
from  the  surface  of  the  water.  The  difficulty  of  ascertain- 
ing the  direction  of  a  fog-horn  in  a  thick  fog  is  well  known. 
The  waves  of  sound,  even  if  they  are  carefully  directed  by 
a  trumpet  or  by  parabolic  reflectors,  diverge  so  rapidly  that 
there  is  no  marked  difference  in  the  intensity  between  a 
position  in  the  direct  line  and  one  far  to  one  side. 

The  most  obvious  method  of   signalling  by  electricity 
through  the  air  is  by  electro-magnetic  induction.     Suppose 


Fig.  7. 

we  have  a  coil  of  copper  wire  consisting  of  many  convolu- 
tions, the  ends  of  which  are  connected  with  a  telephone 
(fig.  7).  If  we  place  a  similar  coil,  the  ends  of  which 
are  connected  to  a  battery  through  a  key,  within  a  few 
feet  of  the  first  and  parallel  to  it,  each  time  the  current 
is  made  and  broken  in  the  battery  coil  instantaneous  cur- 
rents are  produced  by  induction  in  the  other  coil,  as  can  be 
heard  by  the  clicks  in  the  telephone. 

To  illustrate  induction  at  a  distance,  Prof.  Joseph  Henry 


PROFESSOR  JOHN  TROWBRIDGE.  89 

placed  a  coil  of  wire,  5J  feet  in  diameter,  against  a  door, 
and  at  a  distance  of  7  feet  another  coil  of  4  feet  diameter. 
When  contact  was  made  and  broken  with  a  battery  of 
eight  cells  in  the  first  coil,  shocks  were  felt  when  the 
terminal  wires  of  the  second  were  placed  close  together 
on  the  tongue. 

In  all  such  methods  the  wires  or  coils  which  produce 
an  electrical  disturbance  in  a  neighbouring  coil  are  never 
more  than  a  few  feet  apart.  Now  let  us  suppose  that 
a  wire  is  stretched  ten  or  twelve  times,  to  and  fro,  from 
yard-arm  to  yard-arm  of  a  steamer's  foremast,  and  con- 
nected at  the  ends  either  with  a  powerful  battery  or 
dynamo,  or  with  a  telephone,  as  may  be  required  either 
for  signalling  or  for  listening.  Let  an  approaching  steamer 
have  a  similar  arrangement.  If  now  the  current  on  one 
vessel  be  interrupted  a  great  number  of  times  per  second,  a 
musical  note  will  be  heard  in  the  telephone  of  the  other 
vessel,  and  vice  versa.  The  sound  will  be  strongest  when 
the  two  coils  are  parallel  to  each  other.  If,  therefore,  the 
coils  be  movable  the  listener  can  soon  find  the  position 
of  greatest  effect,  and  so  fix  the  direction  in  which  the 
signalling  steamer  is  approaching. 

It  may  not  even  be  necessary  to  connect  the  telephone 
with  the  coil,  for  it  has  been  found  that  if  a  telephone, 
pure  and  simple,  be  held  to  the  ear  and  pointed  towards 
a  coil  in  which  a  current  of  electricity  is  rapidly  inter- 
rupted, the  makes  and  breaks  will  be  heard,  and  this  even 
when  the  wire  coil  of  the  telephone  is  removed,  leaving 
only  the  iron  core  and  the  diaphragm.1 

1  Mr  Willoughby  Smith  was,  I  believe,  the  first  in  recent  times  to 
observe  these  effects.  See  his  paper  on  "  Volta-Electric  Induction," 
'Jour.  Inst.  Elec.  Engs.,'  vol.  xii.  p.  457.  But  exactly  similar 
effects,  mutatis  mutandis,  were  described  by  Page  in  1837,  to  which 
he  gave  the  name  of  Galvanic  Music,  and  which  he  found  to  be  due 
to  the  fact  that  iron  when  magnetised  and  demagnetised  gave  out  a 


90  SECOND    PERIOD — THE   PRACTICABLE. 

Nothing  could  seem  simpler  than  this,  but,  unfortunately, 
calculation  shows  that  under  the  best  conditions  the  size  of 
the  coils  would  have  to  be  enormous.  Prof.  Trowbridge 
has  computed  that  to  produce  an  audible  note  in  the  tele- 
phone at  a  distance  of  half  a  mile,  a  coil  of  ten  turns  of 
800  feet  radius  would  be  necessary ;  but  it  is  evident  that 
a  coil  of  this  size  would  be  out  of  the  question.  Instead, 
however,  of  increasing  the  size  of  the  coil  beyond  the 
practical  limits  of  the  masts  and  yard-arms,  we  could  in- 
crease the  strength  of  the  current  so  as  to  be  effective  at 
the  distance  of  half  a  mile;  but,  again,  calculation  shows 
that  this  strength  of  current  would  be  beyond  all  practical 
limits  of  dynamo  construction,  unless  we  discover  some 
method  of  tuning,  so  to  speak,  two  coils  so  that  the  elec- 
trical oscillations  set  up  in  one  may  be  able  to  evoke  in 
the  other  sympathetic  vibrations.1 

Since,  then,  we  have  little,  apparently,  to  hope  for  from 
electro  -  magnetic  induction  in  signalling  through  a  fog, 
cannot  we  expect  something  from  static  induction?  This 
form  of  induction  can  be  well  illustrated  by  an  early 
experiment  of  Prof.  Henry.  An  ordinary  electrical  machine 
was  placed  in  the  third  storey  of  his  house,  and  a  metal 
plate  4  feet  in  diameter  was  suspended  from  the  prime 
conductor.  On  the  first  floor  or  basement,  30  feet  below 
in  a  direct  line,  was  placed  a  similar  plate,  well  insulated. 
When  the  upper  plate  was  charged  by  working  the 
machine,  the  lower  plate  showed  signs  of  electrification, 
as  was  evidenced  by  its  effect  on  the  pith-ball  electroscope.2 

sound.  De  la  Rive,  in  1843,  rightly  traced  this  sound  to  the  slight 
elongation  of  iron  under  the  magnetic  strain — a  fact  which,  in  its 
turn,  was  first  observed  by  Joule  in  1842.  For  Page's  discovery  see 
the  'Magazine  of  Popular  Science,'  1837,  p.  237. 

1  Prof.  Oliver  Lodge  is  now  engaged  on  this  very  problem.     See 
'Jour.  Inst.  Elec.  Engs.,'  No.  137,  p.  799. 

2  See  an  excellent  account  of  Henry  and  his  work  in  the  New 


PROFESSOR  GEAHAM  BELL.  91 

The  distance  to  which  this  electrical  influence  can  be  ex- 
tended depends  upon  the  charging  power  of  the  machine 
and  the  dimensions  of  the  plate.  If  we  could  erect  an 
enormous  metal  plate  on  a  hill,  insulated  and  powerfully 
charged,  it  is  probable  that  its  electrical  influence  could  be 
felt  at  the  distance  of  the  horizon ;  but  here,  again,  the 
question  of  practical  limits  conies  in  as  a  bar,  so  that,  at  the 
present  time  (February  1891),  this  method  of  signalling 
without  wires  seems  as  little  practicable  as  the  others. 

After  following  me  in  this  study  of  Prof.  Trowbridge, 
the  reader  may  well  begin  to  despair,  for  while  the  learned 
Professor's  investigations  are  extremely  interesting,  his  con- 
clusions are  very  disappointing.  But  the  darkest  hour  is 
just  before  the  dawn,  and  so  it  is  in  this  case. 


PROFESSOR    GRAHAM    BELL— 1882. 

Following  the  lines  suggested  by  Prof.  Trowbridge,  Prof. 
Bell  carried  out  some  successful  experiments,  an  account  of 
which  is  given  in  his  paper  read  before  the  American  Asso- 
ciation for  the  Advancement  of  Science  in  1884. 

"  A  few  years  ago,"  he  says,  "  I  made  a  communication 
on  the  use  of  the  telephone  in  tracing  equipotential  lines 
and  surfaces.  I  will  briefly  give  the  chief  points  of  the 
experiment,  which  was  based  on  experiments  made  by  Prof. 
Adams  of  King's  College,  London.  Prof.  Adams  used  a 
galvanometer  instead  of  a  telephone. 

"  In  a  vessel  of  water  I  placed  a  sheet  of  paper.  At  two 
points  on  that  paper  were  fastened  two  ordinary  sewing 

York  'Electrical  Engineer,'  January  13,  1892,  and  succeeding 
numbers,  from  the  pen  of  his  daughter,  Mary  A.  Henry.  Abstracts 
of  these  papers  are  given  in  the  '  Electrician,'  vol.  xxviii.  pp.  327, 
348,  407,  661. 


92       SECOND  PERIOD — THE  PRACTICABLE. 

needles,  which  were  also  connected  with  an  interrupter  that 
interrupted  the  circuit  about  one  hundred  times  a  second. 
Then  I  had  two  needles  connected  with  a  telephone :  one 
needle  I  fastened  on  the  paper  in  the  water,  and  the  moment 
I  placed  the  other  needle  in  the  water  I  heard  a  musical 
sound  from  the  telephone.  By  moving  this  needle  around 
in  the  water,  I  would  strike  a  place  where  there  would  be  no 
sound  heard.  This  would  be  where  the  electric  tension  was 
the  same  as  in  the  needle ;  and  by  experimenting  in  the 
water  you  could  trace  out  with  perfect  ease  an  equipotential 
line  around  one  of  the  poles  in  the  water. 

"  It  struck  me  afterwards  that  this  method,  which  is  true 
on  the  small,  is  also  true  on  the  large  scale,  and  that  it 
might  afford  a  solution  of  a  method  of  communicating  elec- 
trical signals  between  vessels  at  sea. 

"  I  made  some  preliminary  experiments  in  England,  and 
succeeded  in  sending  signals  across  the  river  Thames  in  this 
way.  On  one  side  were  two  metal  plates  placed  at  a  dis- 
tance from  each  other,  and  on  the  other  two  terminals 
connected  with  the  telephone.  A  current  was  established 
in  the  telephone  each  time  a  current  was  established 
through  the  galvanic  circuit  on  the  opposite  side,  and  if 
that  current  was  rapidly  interrupted  you  would  get  a  musical 
tone. 

"  Urged  by  Prof.  Trowbridge,  I  made  some  experiments 
which  are  of  very  great  value  and  suggestiveness.  The  first 
was  made  on  the  Potomac  river. 

"I  had  two  boats.  In  one  boat  we  had  a  Leclanche' 
battery  of  six  elements  and  an  interrupter  for  interrupting 
the  current  very  rapidly.  Over  the  bow  of  the  boat  we  made 
water  connection  by  a  metallic  plate,  and  behind  the  boat  we 
trailed  an  insulated  wire,  with  a  float  at  the  end  carrying  a 
metallic  plate,  so  as  to  bring  these  two  terminals  about  100 
feet  apart.  I  then  took  another  boat  and  sailed  off.  In 


PROFESSOR   GRAHAM   BELL.  93 

this  boat  we  had  the  same  arrangement,  but  with  a  tele- 
phone in  the  circuit.  In  the  first  boat,  which  was  moored, 
I  kept  a  man  making  signals  ;  and  when  my  boat  was  near 
his  I  would  hear  those  signals  very  well — a  musical  tone, 
something  of  this  kind  :  turn,  turn,  turn.  I  then  rowed  my 
boat  down  the  river,  and  at  a  distance  of  a  mile  and  a 
quarter,  which  was  the  farthest  distance  I  tried,  I  could 
still  distinguish  those  signals. 

"It  is  therefore  perfectly  practicable  for  steam -vessels 
with  dynamo  machines  to  know  of  each  other's  presence  in  a 
fog  when  they  come,  say,  within  a  couple  of  miles  of  one 
another,  or,  perhaps,  at  a  still  greater  distance.  I  tried  the 
experiment  a  short  time  ago  in  salt  water  of  about  20  fathoms 
in  depth.  I  used  then  two  sailing-boats,  and  did  not  get  so 
great  a  distance  as  on  the  Potomac.  The  distance,  which 
we  estimated  by  the  eye,  seemed  to  be  about  half  a  mile  ; 
but  on  the  Potomac  we  took  the  distance  accurately  on  the 
shore." 

Later,  in  urging  a  practical  trial  of  his  method,  Prof.  Bell 
further  said :  "  Most  of  the  passenger  steamships  have  dynamo 
engines,  and  are  electrically  lighted.  Suppose,  for  instance, 
one  of  them  should  trail  a  wire  a  mile  long,  or  any  length, 
which  is  connected  with  the  dynamo  engine  and  electrically 
charged.  The  wire  would  practically  have  a  ground  connec- 
tion by  trailing  in  the  water.  Suppose  you  attach  a  telephone 
to  the  end  on  board.  Then  your  dynamo  or  telephone  end 
would  be  positive,  and  the  other  end  of  the  wire  trailing 
behind  would  be  negative.  All  of  the  water  about  the  ship 
will  be  positive  within  a  circle  whose  radius  is  one-half  of 
the  length  of  the  wire.  All  of  the  water  about  the  trailing 
end  will  be  negative  within  a  circle  whose  radius  is  the 
other  half  of  the  wire.  If  your  wire  is  one  mile  long,  there 
is  then  a  large  area  of  water  about  the  ship  which  is  affected 
either  positively  or  negatively  by  the  dynamo  engine  and  the 


94  SECOND   PERIOD — THE   PRACTICABLE. 

electrically  charged  wire.  It  will  be  impossible  for  any  ship 
or  object  to  approach  within  the  water  so  charged  in  relation 
to  your  ship  without  the  telephone  telling  the  whole  story 
to  the  listening  ear.  Now,  if  a  ship  coming  in  this  area  also 
has  a  similar  apparatus,  the  two  vessels  can  communicate 
with  each  other  by  their  telephones.  If  they  are  enveloped 
in  a  fog,  they  can  keep  out  of  each  other's  way.  The  ship 
having  the  telephone  can  detect  other  ships  in  its  track,  and 
keep  out  of  the  way  in  a  fog  or  storm.  The  matter  is  so 
simple  that  I  hope  our  ocean  steamships  will  experiment 
with  it."  l 


PROFESSOR  A.  E.  DOLBEAR— 1882. 

Prof.  Dolbear  of  Tuft's  College,  Boston,  was  also,  about 
the  same  time  as  Graham  Bell,  engaged  on  the  problem  of  a 
wireless  telegraph,  and  produced  a  very  simple  and  workable 
apparatus,  which  he  patented  in  the  United  States  (March 
1882),  and  of  which  he  gave  a  description  at  a  meeting  of 
the  American  Association  for  the  Advancement  of  Science 
in  the  following  August.  I  take  the  following  account 
from  his  specification  as  published  in  the  '  Scientific  Ameri- 
can Supplement,'  December  11,  1886  : — 

"  In  the  diagram,  A  represents  one  place  (say  Tuft's  College) 
and  B  a  distant  place  (say  my  residence). 

"  c  is  a  wire  leading  into  the  ground  at  A,  and  D  a  wire 
leading  into  the  ground  at  B. 

"  Q  is  an  induction  coil,  having  in  the  primary  circuit  a 
microphone  transmitter  T,  and  a  battery  /',  which  has  a 
number  of  cells  sufficient  to  establish  in  the  wire  c,  which 
is  connected  with  one  terminal  of  the  secondary  coil,  an 
electro-motive  force  of,  say,  100  volts.  The  battery  is  so 
1  'Public  Opinion,'  January  31,  1886. 


PROFESSOR  A.    E.    DOLBEAR. 


95 


connected  that  it  not  only  furnishes  the  current  for  the 
primary  circuit,  hut  also  charges  or  electrifies  the  secondary 
coil  and  its  terminals  c  and  H'.1 

"  Now,  if  words  be  spoken  in  proximity  to  transmitter  T, 
the  vibration  of  its  diaphragm  will  disturb  the  electric  con- 
dition of  the  coil  G,  and  thereby  vary  the  potential  of  the 
ground  at  A,  and  the  variations  of  the  potential  at  A  will 
cause  corresponding  variations  of  the  potential  of  the  ground 
at  B,  and  the  receiver  R  will  reproduce  the  words  spoken 
in  proximity  to  the  transmitter,  as  if  the  wires  c  D  were  in 
contact,  or  connected  by  a  third  wire. 


Fig.  8. 

"  There  are  various  well-known  ways  of  electrifying  the 
wire  c  to  a  positive  potential  far  in  excess  of  100  volts,  and 
the  \vire  D  to  a  negative  potential  far  in  excess  of  100  volts. 

"  In  the  diagram,  H  H'  H2  represent  condensers,  the  con- 
denser H'  being  properly  charged  to  give  the  desired  effect. 
The  condensers  H  and  H2  are  not  essential,  but  are  of  some 
benefit ;  nor  is  the  condenser  H'  essential  when  the  second- 
ary coil  is  otherwise  charged.  I  prefer  to  charge  all  these 
condensers,  as  it  is  of  prime  importance  to  keep  the  grounds 
of  wires  c  and  D  oppositely  electrified,  and  while,  as  is 

1  The  diagram,  which  we  have  carefully  copied,  does  not  show  how 
this  is  done,  but  the  practical  reader  will  easily  supply  the  necessary 
connections. 


96       SECOND  PERIOD — THE  PRACTICABLE. 

obvious,  this  may  be  done  by  either  the  batteries  or  the 
condensers,  I  prefer  to  use  both." 

In  the  article  from  which  I  am  quoting  the  author  gives 
some  additional  particulars  which  are  worth  repeating. 
"  My  first  results,"  he  says,  "  were  obtained  with  a  large 
magneto-electric  machine  with  one  terminal  grounded  through 
a  Morse  key,  the  other  terminal  out  in  free  air  and  only  a 
foot  or  two  long  ;  the  receiver  having  one  terminal  grounded, 
the  other  held  in  the  hand  while  the  body  was  insulated, 
the  distance  between  grounds  being  about  60  feet.  After- 
ward, much  louder  and  better  effects  were  obtained  by  using 
an  induction  coil  having  an  automatic  break  and  with  a 
Morse  key  in  the  primary  circuit,  one  terminal  of  the 
secondary  grounded,  the  other  in  free  air,  or  in  a  condenser 
of  considerable  capacity,  the  latter  having  an  air  discharge 
of  fine  points  at  its  opposite  terminal.  At  times  I  have 
employed  a  gilt  kite  carrying  a  fine  wire  from  the  secondary 
coil.  The  discharges  then  are  apparently  nearly  as  strong 
as  if  there  was  an  ordinary  circuit. 

"  The  idea  is  to  cause  a  series  of  electrical  discharges  into 
the  earth  at  a  given  place  without  discharging  into  the  earth 
the  other  terminal  of  the  battery  or  induction  coil — a  feat 
which  I  have  been  told  so  many,  many  times  was  impossible, 
but  which  certainly  can  be  done.  An  induction  coil  isn't 
amenable  to  Ohm's  law  always  !  Suppose  that  at  one  place 
there  be  apparatus  for  discharging  the  positive  pole  of  the 
induction  coil  into  the  ground,  say  100  times  per  second, 
then  the  ground  will  be  raised  to  a  certain  potential  100 
times  per  second.  At  another  point  let  a  similar  apparatus 
discharge  the  negative  pole  100  times  per  second ;  then 
between  these  two  places  there  will  be  a  greater  difference 
of  potential  than  in  other  directions,  and  a  series  of  earth- 
currents,  100  per  second,  will  flow  from  the  one  to  the  other. 
Any  sensitive  electrical  device,  a  galvanometer  or  telephone, 


PROFESSOR   A.    E.    DOLBEAR.  97 

will  be  disturbed  at  the  latter  station  by  these  currents,  and 
any  intermittence  of  them,  as  can  be  brought  about  by  a 
Morse  key  in  the  first  place,  will  be  seen  or  heard  in  the 
second  place.  The  stronger  the  discharges  that  can  be  thus 
produced,  the  stronger  will  the  earth-currents  be  of  course, 
and  an  insulated  tin  roof  is  an  excellent  terminal  for  such  a 
purpose.  I  have  generally  used  my  static  telephone  receiver 
in  my  experiments,  though  the  magneto  will  answer. 

"  I  am  still  at  work  upon  this  method  of  communication, 
to  perfect  it.  I  shall  soon  know  better  its  limits  on  both 
land  and  water  than  I  do  now.  It  is  adapted  to  telegraphing 
between  vessels  at  sea. 

"Some  very  interesting  results  were  obtained  when  the 
static  receiver  with  one  terminal  was  employed.  A  person 
standing  upon  the  ground  at  a  distance  from  the  discharging 
point  could  hear  nothing;  but  very  little,  standing  upon 
ordinary  stones,  as  granite  blocks  or  steps ;  but  standing  on 
asphalt  concrete,  the  sounds  were  loud  enough  to  hear  with 
the  telephone  at  some  distance  from  the  ear.  By  grounding 
the  one  terminal  of  the  induction  coil  to  the  gas  or  water 
pipes,  leaving  the  other  end  free,  telegraph  signals  can  be 
heard  in  any  part  of  a  big  building  and  its  neighbourhood 
without  any  connection  whatever,  provided  the  person  be 
well  insulated." 

When  we  come  to  speak  of  the  Marconi  system,  we  shall 
see  how  near  Dolbear  got  to  that  discovery,  or  perhaps  I 
should  say  how  nearly  he  anticipated  it.  Comparing  the 
arrangement,  fig.  8  (especially  when,  as  stated,  a  Morse  key 
and  automatic  interrupter  were  used  in  place  of  the  micro- 
phonic  transmitter),  with  Marconi's,  fig.  40,  it  will  be  seen 
that  they  are  practically  identical  in  principle.  Dolbear's 
acute  observation  of  the  heightened  effects  obtained  by  pro- 
jecting into  free  air  the  ungrounded  terminals  of  the  sending 
and  receiving  apparatus  is  his  own  discovery ;  while  his  use 

G 


98  SECOND   PERIOD — THE   PRACTICABLE. 

of  condensers  (answering  to  Marconi's  capacity  areas)  and 
gilt  kites  carrying  fine  wire  was  another  step  in  the  right 
direction.  Of  course  he  does  not  use  the  Branly  receiver,  or 
the  Eighi  sparking  arrangement  shown  in  fig.  40  (they  were 
not  known  in  1882),  but  as  regards  the  latter  Marconi  has 
himself  discarded  it  in  recent  times,  using  a  single  spark-gap, 
which  even  is  not  absolutely  necessary  for  the  production  of 
waves,  leaving  the  secondary  coil  "  open  "  alone  sufficing.1 

Prof.  Dolbear's  account  of  the  action  of  his  apparatus  is 
in  places  a  little  puzzling,  which,  perhaps,  can  hardly  be 
wondered  at,  for  Hertz  had  not  yet  come  to  make  clear  the 
way  which  the  American  professor  saw  but  as  in  a  glass 
darkly.  There  can,  however,  be  little  doubt  that  he  was 
using  very  long  electric  waves  in  1882  (that  is,  five  or 
six  years  before  Hertz),  and  in  much  the  same  way  as 
Marconi  does  now.  When,  for  instance,  he  whistled  into 
his  microphonic  transmitter,  making  it  vibrate  say  4000 
times  per  second,  did  he  not  in  effect  start  electric  (now 
called  Hertzian)  waves  4000  =46^  miles  long?  We  can 
easily  see  this  now,  but  in  1882  the  results  were  not  so 
well  understood.  Dolbear  was  inclined  to  attribute  them  to 
some  kind  of  ether  action,  obscure  cases  of  which  were  then 
cropping  up  and  attracting  attention  in  the  electrical  world.2 

Others  thought  that  the  results  were  "  only  extraordinary 
cases  of  electro-static  induction."  Thus  Prof.  Houston,  who 
saw  some  of  Dolbear's  experiments  and  had  himself  re- 
peated them,  says  :  "  The  explanation  of  the  phenomenon  as  I 
understand  it  would  appear  to  be  this — One  of  the  plates  of 
the  receiver  (that  is,  of  the  electro-static  telephone)  being 
connected  through  the  body  of  the  experimenter  to  the 
ground,  partakes  of  the  ground  potential,  while  the  other 

1  Broca,  '  La  Telegraphic  sans  Fils,'  p.  89. 

2  See,  for  example,  '  Telegraphic  Journal,'  February  15,  1876,  p. 
61,  on  The  "  Etheric  "  Force. 


PROFESSOR   A.    E   DOLBEAR.  99 

plate  is  en  rapport  with  the  free  end  of  the  sending  appa- 
ratus by  a  line  of  polarised  air  particles.  The  experiment  is 
simply  an  exceptional  application  of  the  principles  of 
electro-static  induction,  and  I  am  not  at  all  sure  that  it 
is  not  susceptible  of  a  great  increase  in  delicacy,  in  which 
case  it  would  become  of  considerable  commercial  value." 1 

Prof.  Dolbear's  friends  in  America  are  now  claiming  for 
him  the  discovery  of  the  art  of  wireless  telegraphy  a  la 
Marconi.  They  argue  that  Marconi  arranges  and  works  his 
circuits  in  the  way  substantially  shown  in  Dolbear's  patent 
of  1882;  that  he  employs  Dolbear's  transmitting  devices 
(induction  coil,  battery,  and  Morse  key),  as  well  as  his 
aerial  and  ground  connections  on  the  sending  and  receiving 
apparatus.  Dolbear  emitted  electric  waves  of  many  miles 
long,  and  received  them  on  his  electro-static  telephone ; 
Marconi,  by  using  the  same  means,  emits  waves  of  many  feet 
long,  and  receives  them  on  a  Branly  coherer.  Where,  they 
ask,  is  the  difference?  Marconi's  receiver  is  admitted  to 
greatly  extend  the  signalling  range,  but  this  does  not  affect 
the  principle  of  the  art,  only  its  practical  value,  as  to  which 
they  recall  the  fact  that  Graham  Bell's  telephone,  as  patented 
in  1876,  was  practically  inoperative,  yet  the  patent  secured 
to  him  the  honour  and  profit  of  the  invention,  as  it  was 
held  that  the  principle  was  there,  though  in  an  imperfect 
form.  All  this  is  true,  and  I  hope  that  Dolbear's  early  and 
for  the  time  extraordinary  experiments  will  always  be  re- 
membered to  his  credit,  but  this,  I  think,  should  be  done 
without  detracting  from  the  merit  due  to  Marconi  for  his 
successful  and,  as  I  believe,  entirely  independent  application 
of  the  same  principle.  But  of  this  more  anon. 

1  'Scientific  American  Supplement,'  December  6,  1884.  At  first, 
Dolbear's  estimate  of  distance  was  modest — "half  a  mile  at  least," 
but  it  is  said  that  recently  he  has  worked  his  apparatus  up  to  a 
distance  of  thirteen  miles. 


100  SECOND   PERIOD — THE   PRACTICABLE. 


T.  A.  EDISON— 1885. 

Electric  communication  with  trains  in  motion,  like  com- 
munication with  ships  at  sea  and  with  lighthouses,  has 
long  been  a  favourite  problem  with  electrical  engineers  : 
indeed  it  is  much  the  older  of  the  two,  and  dates  back  to 
the  first  days  of  electric  telegraphy. 

In  1838  Edward  Davy,  the  rival  of  Cooke  and  Wheat- 
stone,  proposed  such  a  system.  In  a  lecture  on  "  Electric 
Telegraphy,"  delivered  in  London  during  the  summer  of 
1838,  he  says:— 

"  I  have  a  few  words  to  say  upon  another  application 
of  electricity — namely,  the  purposes  it  will  answer  upon  a 
railway,  for  giving  notices  of  trains,  of  accidents,  and  stop- 
pages. The  numerous  accidents  which  have  occurred  on 
railways  seem  to  xcall  for  some  remedy  of  the  kind ;  and 
when  future  improvements  shall  have  augmented  the  speed 
of  travelling  to  a  velocity  which  cannot  at  present  be 
deemed  safe,  then  every  aid  which  science  can  afford  must 
be  called  in  to  promote  this  object.  Now,  there  is  a  con- 
trivance, secured  by  patent,  by  which,  at  every  station  along 
the  railway  line,  it  may  be  seen  by  mere  inspection  of  a  dial 
what  is  the  exact  situation  of  the  engines  running  either 
towards  or  from  the  station,  and  at  what  speed  they  are 
travelling.  Every  time  the  engine  passes  a  milestone,  the 
pointer  on  the  dial  moves  forward  to  the  next  figure,  a 
sound  or  alarm  accompanying  each  movement. 

"  Not  only  this;  but  if  two  engines  are  approaching  each 
other,  by  any  casualty,  on  the  same  rails,  then,  at  a  distance 
of  a  mile  or  two,  a  timely  notice  can  be  given  in  each 
engine  by  a  sound  or  alarm,  from  which  the  engineer 
would  be  apprised  to  slacken  the  speed ;  or,  if  the  engineer 
be  asleep  or  intoxicated,  the  same  action  might  turn  off  the 


T.   A.   EDISON.  101 

steam,  independently  of  his  attention,  and  thus  prevent  an 
accident." l 

In  1842  William  Fothergill  Cooke  published  his  'Tele- 
graphic Railways,'  descriptive  of  a  crude  system  of  train 
signals,  which  was  tried,  in  1843,  in  the  Queen  Street 
tunnel,  Glasgow,  and  in  the  Clay  Cross  tunnel,  Derby ; 
and,  on  a  more  extensive  scale,  in  1844,  on  the  Great 
Eastern  Railway,  between  Norwich  and  Yarmouth. 

Dujardin  in  1845,  Brett  and  Little  in  1847,  Edwin  Clark 
in  1854,  Bonelli  in  1855,  and  many  others,  proposed  various 
systems  of  train  signalling;  but  as  they  are  all  based  on 
ordinary  telegraphic  principles  and  require  connecting  wires, 
they  do  not  specially  concern  us  in  this  history. 

Mr  A.  C.  Brown,  an  officer  of  the  Eastern  Telegraph 
Company,  claims  to  have  been  the  first  to  suggest,  in  1881, 
the  method  of  induction  for  communicating  with  moving 
trains.  In  a  letter  published  in  the  'Electrician,'  March 
21,  1885,  he  says:— 

"My  object  was  chiefly  to  provide  an  efficient  means  of 
fog-signalling,  by  enabling  the  signalman  to  communicate 
directly  with  the  drivers  or  guards.  I  proposed  to  run  a 
wire  along  the  permanent  way,  parallel  with  the  rails,  and 
to  wind  a  coil  of  wire  round  the  engine,  or  carriage  to  be 
communicated  with,  in  such  a  way  as  to  get  as  long  a  length 
of  wire  parallel  to,  and  as  near  to,  the  line-wire  as  possible, 
so  as  to  be  well  exposed  to  the  inductive  action  thereof.  I 
then  proposed  to  place  in  the  signal-boxes  a  battery,  sig- 
nalling key,  and  rapid  make-and-break  instrument,  or  buzzer, 
and  to  thereby  signal  to  the  train,  using  a  telephone  in 
circuit  with  the  train-coil  as  a  receiver.  By  using  an  ordin- 

1  See  the  writer's  '  History  of  Electric  Telegraphy,'  p.  407.  The 
most  perfect  block  system  of  the  present  day  does  not  do  anything 
like  this.  Davy's  plan  was  actually  patented  by  Henry  Finkus !  See 
his  patent  specification,  No.  8644,  of  September  24,  1840. 


102  SECOND  PEKIOD— THE  PRACTICABLE. 

ary  carbon  transmitter  in  the  line-wire,  I  also  found  it  quite 
practicable  to  speak  verbally  to  the  train,  so  as  to  be  dis- 
tinctly heard  in  the  telephone. 

"  This  design  was  embodied  in  a  paper  which,  in  the  year 

1881,  I  laid  before  the  managing  director  of  the  United 
Telephone   Company,  but  want  of   time  and  opportunity 
prevented  its  being  put  into  practice.    It  was  experimentally 
tried  at  that  time,  using  wire   coils,  properly  proportioned 
in  length,  resistance,  and  distance  apart  to  the  conditions 
that  would   be  obtained  in  practice.      It  has   since  been 
simplified  and  arranged  to  produce  both  visible  and  audible 
signals  on  the  engine  or  car  by  induction  from  a  No.  8  iron 
line-wire  across  a  space  of  6  inches,  with  a  current  of  only 
one  quarter  ampere,  or  such  as  can  easily  be  produced  by 
the  ordinary  Daniell  batteries  used  in  railway  work."  x 

In  1883  Mr  Willoughby  Smith  threw  out  a  similar 
suggestion  towards  the  end  of  his  paper  on  "Voltaic-Electric 
Induction,"  read  before  the  Institution  of  Electrical  En- 
gineers, November  8  of  that  year  :  2 — 

"  Telegraph  engineers,"  he  says,  "  have  done  much 
towards  accomplishing  the  successful  working  of  our  present 
railway  system,  but  still  there  is  much  scope  for  improve- 
ments in  the  signalling  arrangements.  In  foggy  weather 
the  system  now  adopted  is  comparatively  useless,  and 
recourse  has  to  be  had  at  such  times  to  the  dangerous  and 
somewhat  clumsy  method  of  signalling  by  means  of  de- 
tonating charges  placed  upon  the  rails. 

"  Now,  it  has  occurred  to  me  that  Volta- Electric  induction 
might  be  employed  with  advantage  in  various  ways  for 
signalling  purposes.  For  example,  one  or  more  spirals 
could  be  fixed  between  the  rails  at  any  convenient  distance 

*  For  another  proposal  of  Mr  Brown,  see  p.  175,  infra. 

2  Compare  also  his  remarks,  'Jour.  Inst.  Elec.  Engs.,'  March  23, 

1882,  p.  144. 


T.   A.   EDISON.  103 

from  the  signalling  station,  so  that,  when  necessary,  inter- 
mittent currents  could  be  sent  through  the  spirals ;  and 
another  spiral  could  be  fixed  beneath  the  engine,  or  guard's 
van,  and  connected  to  one  or  more  telephones  placed  near 
those  in  charge  of  the  train.  Then,  as  the  train  passed 
over  the  fixed  spiral,  the  sound  given  out  by  the  transmitter 
would  be  loudly  reproduced  by  the  telephone,  and  indicate 
by  its  character  the  signal  intended. 

"  One  of  my  experiments  in  this  direction  will  perhaps 
better  illustrate  my  meaning.  The  large  spiral  was  con- 
nected in  circuit  with  twelve  Leclanche  cells  and  the  two 
make-and-break  transmitters  before  described.  They  were 
so  connected  that  either  transmitter  could  be  switched  into 
circuit  when  required,  and  this  I  considered  the  signalling 
station.  The  small  spiral  was  so  arranged  that  it  passed  in 
front  of  the  large  one  at  the  distance  of  8  inches,  and  at  a 
speed  of  twenty-eight  miles  per  hour.  The  terminals  of  the 
small  spiral  were  connected  to  a  telephone  fixed  in  a  distant 
room,  the  result  being  that  the  sound  produced  from  either 
transmitter  could  be  clearly  heard  and  recognised  every  time 
the  spirals  passed  each  other.  With  a  knowledge  of  this 
fact  I  think  it  will  be  readily  understood  how  a  cheap  and 
efficient  adjunct  to  the  present  system  of  railway  signalling 
could  be  obtained  by  such  means  as  I  have  ventured  to 
bring  to  your  notice  this  evening." 

In  1885  Mr  T.  A.  Edison  had  his  attention  directed  to 
the  subject,  and  with  his  usual  thoroughness  he  soon  pro- 
duced a  very  complete  system,  with  the  assistance  of 
Messrs  Gilliland,  Phelps,  and  W.  Smith  —  to  the  last- 
named  of  whom  the  original  idea  is  said  to  be  due.1 

1  Although  I  have  not  seen  any  acknowledgment  of  their  indebted- 
ness, Mr  Edison  and  his  coadjutors  can  hardly  have  been  ignorant  of 
Mr  Willoughby  Smith's  very  clear  proposal,  of  which  their  contriv- 
ance is  but  the  practical  realisation.  Given  the  idea,  the  rest  was 
easy  enough. 


104      SECOND  PERIOD — THE  PRACTICABLE. 

The  inevitable  avant-c.oureur  appeared  in  the  technical 
journals  of  the  period,  and  as  it  is  delightfully  character- 
istic of  the  great  magician  of  Menlo  Park,  we  venture  to 
reproduce  it  here :  "  Mr  Edison's  latest  invention,  an 
arrangement  to  telegraph  from  moving  trains,  is  thus 
described  by  a  recent  visitor  to  his  laboratory :  Overhead 
was  a  board  eight  inches  wide,  suspended  from  the  ceiling 
by  ropes  fastened  to  one  of  its  edges.  One  side  of  it  was 
covered  with  tinfoil,  and  was  facing  toward  a  wall  20  feet 
distant.  *  That,'  said  Mr  Edison,  '  is  my  railroad  signal ; 
I  make  electricity  jump  35  feet,  and  carry  a  message. 
This  is  something  quite  new ;  no  induction  has  ever  been 
known  that  extended  over  3  or  4  or  5  feet.  This  inven- 
tion uses  what  is  called  static  electricity,  and  it  makes 
every  running  train  of  cars  a  telegraph  station,  accessible  to 
every  other  telegraph  station  on  the  road.  Messages  may 
be  sent  to  and  from  conductors,  and  to  and  from  passengers. 
It  requires  no  extra  wire,  either  under  the  cars  or  at  the 
side  of  the  cars,  but  uses  the  ordinary  telegraph  just  as  it 
is  put  up  at  the  side  of  the  track.  This  white  board  is  a 
receiver  and  transmitter.  A  board  like  it  is  to  be  fastened 
lengthwise  along  the  peak  of  each  car,  where  it  will  be 
out  of  the  way  and  will  not  be  a  blemish.  When  the 
train  is  telegraphed  to,  the  message  jumps  from  the  wire 
on  the  side  of  the  track  and  alights  on  this  board,  and 
is  conveyed  to  the  apparatus  in  the  train  below.  It  works 
beautifully  from  those  wires  strung  yonder.  I  was  as  much 
astonished  as  anybody  at  finding  out  what  could  be  done. 
It  costs  very  little,  moreover,  as  300  miles  of  road  can  be 
equipped  for  1000  dols.'" 

This  contrivance  was  patented  in  England  on  June  22, 
1885,  in  the  joint  names  of  T.  A.  Edison  and  E.  T.  Gilliland, 
and  is  fully  described  in  their  specification,  No.  7583,  of 
which  the  following  is  an  abstract : — 


T.   A.    EDISON. 


105 


The  object  of  the  inven- 
tion is  to  produce  apparatus 
for  telegraphing  between 
moving  trains,  or  between 
trains  and  stations,  by  in- 
duction and  without  the  use 
of  connecting  wires.  The 
accompanying  drawing  (fig. 
9)  represents  a  station  and 
portions  of  two  trains  with 
the  apparatus  for  signal- 
ling. The  carriage  to  be 
used  as  the  signal  office 
has  placed  upon  its  top  or 
side,  or  upon  each  side,  a 
metallic  condensing  surface 
running  the  entire  length  of 
the  car.  This  consists  of  a 
strip  a  of  metal,  say  a  foot 
wide,  well  insulated  by 
blocks  of  glass ;  or  it  may  be 
thin  sheet  metal  or  metallic 
foil  secured  to  canvas,  and 
similarly  insulated  from  the 
body  of  the  car.  To  in- 
crease the  total  condensing 
surface,  all  the  carriages  of 
the  train  are  preferably 
provided  with  such  strips, 
which  are  connected  electri- 
cally by  suitable  couplings  c 
when  the  train  is  made  up. 
A  wire  1  is  connected  with 
this  condensing  surface,  and 


106      SECOND  PERIOD — THE  PRACTICABLE. 

extends  through  the  apparatus  to  the  carriage-truck .  so  as 
to  form  an  earth  connection  through  the  wheels  and  the 
rails  upon  which  they  travel.  The  apparatus  just  men- 
tioned consists  of  an  induction  coil  B,  the  secondary  wire 
of  which  is  of  extremely  high  resistance,  and  is  in  the 
circuit  of  wire  1,  in  which  is  also  connected  a  telephone 
c  of  high  resistance.  This  is  preferably  an  electro-moto- 
graph  telephone,  the  chalk  cylinder  of  which  is  kept  in 
constant  rotation  by  a  suitable  motor,  electrical  or  mechani- 
cal; but  a  magneto-electric  or  other  suitable  form  of  tele- 
phone may  be  employed. 

In  the  primary  circuit  of  the  induction  coil  B  are  a  local 
battery  d  and  a  revolving  circuit -breaker  D.  This  is  a 
wheel  having  its  surface  broken  by  cross  strips  of  insula- 
tion ;  upon  it  rests  a  spring,  the  circuit  being  through  the 
spring  to  the  spindle  of  the  wheel.  This  wheel  is  kept  in 
rapid  motion  by  a  suitable  motor,  electrical  or  mechanical, 
the  current  vibrations  produced  by  it  being  a  great  number 
per  second  and  audible  in  the  telephone  receiver. 

The  circuit -breaker  is  shunted  by  a  back  point  key  B, 
which,  normally,  short-circuits  it  and  prevents  it  from 
affecting  the  induction  coil.  A  switch  p  short-circuits  the 
secondary  wire  of  the  induction  coil  when  receiving,  and  is 
opened  in  transmitting. 

The  ordinary  telegraph  wires  2,  3,  4,  5,  run  on  poles  at 
the  side  of  the  track,  and,  grounded  at  their  ends,  are  util- 
ised collectively  for  conveying  the  signals.  They  form  the 
other  surface  of  the  condenser  (the  strips  on  the  carriages 
forming  one  surface),  while  the  intervening  body  of  air  is 
the  dielectric. 

In  signalling  between  trains,  signals  are  transmitted  by 
working  the  key  E  in  the  office  upon  one  train.  This 
causes  static  impulses  at  the  condensing  surface  upon  the 
carriages  which  affect  the  telegraph  wires.  These  in  turn 


T.  A.   EDISON. 


107 


affect  the  condensing  surface  upon  the  carriages  of  the  other 
train,  and  cause  impulses  which  are  audible  in  the  telephone. 
At  each  signalling  station  I  there  is  erected  between  the 
telegraph  wires  a  large  metallic  condensing  surface  K  (fig. 
10).  This  may  be  attached  to  a  frame  supported  from  the 


Fig.  10. 

telegraph  poles  or  from  separate  poles.     A  wire  6  runs  from 
this  condensing  surface  to  the  station,  where  it  is  connected 
to  ground  through  the  same  character  of  transmitting  and 
receiving  apparatus  already  described  for  the  carriages. 
Instead  of  using  this  condensing  surface  outside  of  the 


108  SECOND   PERIOD — THE   PRACTICABLE. 

station,  a  separate  wire  (7,  8,  9,  10,  fig.  9)  may  be  at- 
tached to  each  telegraph  wire  (or  to  each  of  as  many  as  it  is 
desired  to  utilise)  and  run  into  the  station,  where  it  is  con- 
nected to  one  side  of  a  condenser  L,  of  ordinary  form.  The 
other  sides  of  the  several  condensers  L  are  connected  to- 
gether, and  by  a  common  wire  11  to  ground  through  the 
transmitting  and  receiving  apparatus. 

The  telegraph  wires  are  kept  constantly  closed  for  trans- 
mitting the  induction  impulses  by  shunting  the  regular 
Morse  keys  M  by  condensers  N.  These  condensers  do  not 
interfere  with  the  carrying  on  of  the  ordinary  telegraphing 
over  such  wires,  at  the  same  time  that  they  form  constantly 
closed  paths  for  the  induction  impulses  independent  of  the 
working  of  the  ordinary  Morse  keys.  The  ordinary  Morse 
relay  and  sounder  are  shown  at  o  and  p  respectively. 

The  stations  being  connected  for  railway  signalling  induc- 
tively with  the  line  wires  the  same  as  are  the  trains,  signals 
are  received  and  transmitted  by  a  station  the  same  as  by  a 
train.  The  trains  and  stations  are  connected  inductively 
with  the  line  wires  in  multiple  arc,  so  to  speak,  signals  be- 
ing transmitted  by  keys,  circuit  breakers,  and  induction 
coils,  and  received  by  telephones. 

The  signalling  is  conducted  by  Morse  characters,  or  by 
numerical  signals  in  accordance  with  an  established  code. 

Speaking  of  the  potentialities  of  his  system,  Edison,  early 
in  1886,  said:  "The  outcome  is  easy  to  predict.  Special 
correspondents  may,  in  the  future,  wire  their  despatches 
straight  to  the  offices  of  their  journals.  Railway  business 
will  be  expedited  to  a  degree  undreamt  of  as  things  are, 
and  the  risk  of  accidents  will  be  largely  diminished  by 
knowing  the  position  of  trains  and  the  cause  of  delay  or 
accident,  if  any,  at  every  stage  of  their  route.  Ships  at 
sea,  many  miles  apart,  will  be  able  to  communicate  by 
means  of  balloon-kites,  soaring  several  hundred  feet  above 


T.    A.    EDISON.  109 

their  decks.  Messages  can  be  passed  from  ship  to  ship,  and 
a  casualty  like  that  of  the  Oregon  telegraphed  to  the  nearest 
land.  In  times  of  war  the  applications  of  the  air-telegraph 
system  are  obvious.  Eegions  now  remote  from  telegraphs 
could  be  brought  within  the  civilised  circle  by  means  of 
mountain  or  forest  stations  equipped  with  the  new  apparatus. 
Even  the  man  of  business  of  the  future  may  communicate 
with  his  employes  as  he  journeys  to  and  from  his  office,  and 
save  time  or  make  money  while  he  is  literally  on  the  wing. 
Not  the  least  interesting  feature  of  this  new  departure  in 
telegraphy  is  the  thought  that,  in  its  turn,  it  may  be  the 
harbinger  of  still  more  wondrous  modifications  of  the 
system  which  has  girdled  the  earth  in  a  space  inconceivably 
short  when  compared  with  that  imagined  by  the  fairy 
romancer  who  created  Puck."  l 

The  Edison  system  for  trains  was  first  put  in  operation 
at  Staten  Island,  U.  S. ;  then,  a  few  months  later,  on  the 
Chicago,  Milwaukee,  and  St  Paul  line ;  and  by  October 
1887  it  was  established  on  the  Lehigh  Valley  Eailroad,  as 
related  in  the  following  paragraphs  : — 

"  The  success  of  what  is  called  '  railway  train  telegraphy ' 
is  now  assured,  and  October  6,  1887,  will  be  a  red-letter  day 
in  the  history  of  the  electric  telegraph.  On  that  day  a 
special  train  left  Jersey  City  with  about  230  members  of  the 
Electric  Club  and  guests  of  the  Consolidated  Eailway  Tele- 
graph Company,  in  order  to  witness  the  working  of  the 
system  on  the  Lehigh  Valley  Railroad.  The  system  is  a 
combination  of  the  best  features  of  the  inventions  of  Edison, 
Gilliland,  Phelps,  and  Smith,  and  although  the  speed  often 
reached  the  rate  of  about  sixty  miles  an  hour,  messages  were 
sent  from  and  received  on  the  train  without  difficulty, 
although  the  current  or  the  '  induction '  had  to  jump  from 
the  train  to  the  line  wires,  a  distance  of  25  feet.  About 
1  'Weekly  Irish  Times,'  April  10,  1886. 


110  SECOND   PERIOD — THE   PRACTICABLE. 

four  hundred  messages  were  sent  as  the  train  ran  from  Perth 
Junction  to  Easton,  amongst  them  a  rather  long  one  from 
Colonel  Gouraud  to  Mr  John  Fender  in  London." 1 

"  One  of  the  most  interesting  triumphs  of  invention  has 
been  achieved  on  the  Lehigh  Valley  Eailroad  during  the 
snowstorms  of  the  past  winter  in  the  United  States.  This 
railway  for  some  months  has  been  using  on  its  trains  the 
system  of  communication  known  as  train  telegraphy.  The 
wire,  being  of  steel,  and  stretched  upon  stout  poles  only 
15  or  16  feet  high,  withstood  the  fury  of  the  storm.  The 
consequence  was  that  all  snowed-up  trains  on  the  Lehigh 
Valley  Eailroad  kept  up  constant  communication  with  the 
terminus  of  the  road,  could  define  exactly  their  position,  and, 
in  short,  had  all  the  advantages  of  perfect  telegraphic  com- 
munication."2 

Soon  after  this  the  system  fell  into  desuetude,  and  for  a 
very  simple  reason — nobody  wanted  it.  Whatever  "  special 
correspondents "  and  "  the  man  of  business  "  in  the  future 
may  require,  they,  apparently,  prefer  nowadays  to  be  free 
from  telegrams  of  all  sorts  "while  on  the  wing." 

A  few  years  later  Mr  Edison  took  out  a  fresh  patent  for 
the  application  of  his  method  to  long-distance  communica- 
tions over  sea  and  land.  The  *  Illustrated  London  News ' 
of  February  27,  1892,  gives  an  abstract  of  the  specification 
with  illustrative  drawings. 

If,  says  Mr  Edison,  a  sufficient  elevation  be  obtained  to 
overcome  the  curvature  of  the  earth,  and  to  reduce  as  far 
as  may  be  the  earth's  absorption,  signalling  may  be  carried 
on  by  static  induction  without  the  use  of  connecting  wires. 
For  signalling  across  oceans  the  method  will  be  serviceable, 
while  for  communications  between  vessels  at  sea,  or  between 
vessels  at  sea  and  stations  on  land,  the  invention  would  be 

1  '  Public  Opinion,'  November  4,  1887. 

2  Ibid.,  April  13,  1888. 


W.    F.    MELIIUISH.  Ill 

equally  useful.  There  is  also  no  obstacle  to  its  employ- 
ment between  distant  points  on  land,  but  in  this  case,  he 
says,  "  it  is  necessary  to  increase  the  height  (by  using  very 
high  poles  or  captive  balloons)  from  which  the  signalling 
operations  are  conducted,  because  of  the  induction-absorbing 
effect  of  houses,  trees,  and  hills."  These  poles,  surmounted 
by  "  condensing  surfaces,"  are  of  course  very  like  Marconi's 
— especially  his  earlier  contrivances,  where  "  capacity  areas  " 
in  the  shape  of  square  sheets  or  cylinders  of  zinc  are  shown. 


W.  F.  MELHUISH— 1890. 

We  have  seen  (p.  39  supra)  that  the  want  of  some  form  of 
wireless  telegraph  was  peculiarly  felt  at  a  very  early  date  in 
India,  where  the  rivers  are  many  and  wide,  and  where  for 
various  reasons  cables  are  liable  to  frequent  breakage,  caus- 
ing interruptions  which  are  as  likely  as  not  to  be  of  long 
duration,  owing  to  the  great  rush  of  waters  and  the  flooding 
of  banks. 

I  have  already  given  some  account  of  Dr  O'Shaughnessy's 
experiments  in  this  direction.  It  is  all  too  short,  but, 
unfortunately,  it  is  all  that  I  have  been  able  to  gather. 

About  the  year  1858  Mr  Blissett,  a  superintendent  in 
the  Indian  Telegraph  Department,  resumed  the  inquiry,  and 
obtained  a  fair  measure  of  success  by  employing  land-lines 
of  considerable  length  on  each  bank  of  the  river.  In  1876 
Mr  Schwendler,  then  electrician,  made  some  trials  across  the 
Hooghly  at  Barrackpore,  near  Calcutta,  which  were  continued 
at  intervals  by  his  successor,  the  late  Mr  W.  P.  Johnston. 

On  September  9,  1879,  this  gentleman  tried  the  following 
arrangement  for  signalling  across  the  water  of  a  canal  Fig. 
1 1  shows  the  connections  : — 

B=  10  Bunsen's  cells  joined  in  series ; 


112 


SECOND    PERIOD — THE   PRACTICABLE. 


R,  a  needle  instrument  having  a  resistance  of  1  ohm ;  also 
a  telephone  having  a  resistance  of  4*25  ohms ; 

w  =  a  resistance  of  !}„,. 

,  1ms  arrangement  exactly  balanced 

,,    V     the  natural  current  through  the 
e  =  four  Mmotto  cells 

.  .      ,  receiving  instrument, 

joined  parallel  J 

c 


1 


N) 

o 

o 

<  o 


53   Z 
O  > 


O 
rn 


Fig.  11. 


A,  B,  c,  D  were  copper  plates,  8  feet  8  inches  by  4  feet 
4  inches  by  1-1 6th  inch  thick,  buried  on  the  banks  of  the 
canal.  B  was  buried  15  yards  distant  from  A,  and  i)  the 
same  distance  from  c.  All  the  plates  were  parallel  to  the 
canal.  The  resistance  between  A  and  B  was  7*5  ohms,  and 
that  between  c  and  D  was  the  same.  Under  these  conditions 
both  the  needle  instrument  and  the  telephone  gave  distinct 
and  readable  signals. 

After  several  days  of  experiment  with  another  method 
(fig.  12),  using  a  single  bare  600  Ib.  per  mile  galvanised 
wire,  the  following  results  were  obtained : — 

E  =  15  Bunsen's  cells  in  series ; 

E,  a  polarised  Siemens  relay  of  21  ohms  resistance; 


W.   F.   MELHUISH. 


113 


e  =  4   Minottos  joined   parallel  )  Balanced   the   natural 

w  =  10  ohms  )       current. 

The  signals  received  were  quite  regular  and  safe ;  the 
tongue  of  a  relay  worked  an  ordinary  sounder  in  local 
circuit,  and  no  difficulty  was  experienced  in  balancing  the 
natural  current  through  the  relay. 

A  trial  with  bare  wire  for  a  distance  of  one  and  a  half 
mile  was  not  successful.  Indeed,  as  it  appeared  that  in 
order  to  obtain  signals  the  battery  power  must  be  increased 
as  the  square  of  the  distance,  the  limit  of  signalling  through 
a  bare  wire  under  water  is  very  soon  reached. 

Subsequently,  three  miles  of  the  same  wire,  but  partially 

Bare    trir»  J  Mtle  under  WaUr 


Fig.  12. 

insulated  by  being  passed  through  a  mixture  of  pitch  and 
tar,  answered  perfectly  for  the  hour  that  the  instruments 
were  in  circuit. 

At  various  times  during  the  year  1888  Mr  Johnston 
carried  out  many  experiments  across  canals  and  the  river 
Hooghly,  and  as  the  result  of  these  and  other  careful  in- 
vestigations he  was  led  to  the  following  conclusions  : — 

1.  That  up  to  one  and  a  half  mile  it  is  perfectly  easy  to 

signal  through  a  bare  wire  under  water. 

2.  That  for  greater  distances,  judging  from  experiments, 

practical  signalling  is  not  possible. 
In  April  1889  Mr  Johnston  died,  and  the  duties  of  eleo 


114  SECOND   PERIOD — THE   PRACTICABLE. 

trician  were  entrusted  to  Mr  Melhuish,  who  immediately 
took  up  the  inquiry,  and  in  the  end  produced  some  very 
considerable  results,  for  which,  I  believe,  the  Government  of 
India  gave  him  the  handsome  honorarium  of  5000  rupees. 

The  results  of  his  investigations  are  embodied  in  a 
paper  which  was  read  before  the  Institution  of  Electrical 
Engineers  on  April  10,  1890.  "Having  studied,"  he 
says,  "the  recorded  labours  of  my  predecessor,  and  learnt 
that  by  pursuing  the  same  lines  it  was  hopeless  to  ex- 
pect to  be  able  to  signal  through  a  bare  wire  across  a 
river  that  had  a  greater  breadth  than  one  and  a  half 
mile,  I  resolved  to  change  the  class  of  signalling  appar- 
atus and  to  continue  the  experiment.  Discarding  con- 
tinuous steady  currents  and  polarised  receiving  relays,  I 
adopted  Cardew's  vibrating  sounder,  and  the  sequel  will 
show  how  completely  successful  the  change  of  instru- 
ments proved  to  be.  I  began  from  the  beginning,  and 
tried  to  signal  across  a  water-way  without  a  metallic 
conductor  by  laying  down  two  earth-plates  on  each  of  its 
opposite  banks,  Eeadable  signals  having  been  exchanged, 
the  distance  separating  each  pair  of  plates  was  varied, 
with  the  view  of  ascertaining  how  close  the  plates  might 
be  brought  together,  the  signals  remaining  still  readable. 
Eeadable  signals  were  exchanged  when  the  distance  separ- 
ating the  plates  was  equal  to  the  breadth  of  the  river, 
reading  becoming  more  difficult  as  the  plates  were  made 
to  approach  each  other,  and  clearer  and  more  distinct  as 
the  distance  between  the  plates  was  made  to  exceed  the 
breadth  of  the  river.  I  learnt  from  these  experiments 
that  in  order  to  obtain  signals  of  sufficient  distinctness 
for  the  practical  purpose  of  transmitting  messages,  it  would 
be  necessary  to  construct  a  line  on  each  bank  of  a  river 
much  longer  than  the  breadth  of  the  river;  and  as  the 
rivers  along  the  coasts  in  India  are  extremely  wide,  I 


W.   F.    MELHUISH.  115 

became  impressed  with  the  impracticable  character  of  such 
an  undertaking,  and  decided  to  strike  out  a  new  line. 

"  This  new  line  was  the  laying  of  two  bare  uninsulated 
iron  wires  across  the  water-way  parallel  to  each  other, 
and  separated  by  a  certain  distance,  the  ends  on  each 
bank  being  looped  together  by  means  of  an  insulated 
conductor.  Hence,  though  much  of  the  circuit  was  laid 
under  water,  it  was  nevertheless  a  continuous  metallic 
circuit.  Beginning  first  with  a  complete  square,  by  laying 
the  wires  as  many  yards  apart  as  the  river  was  wide, 
signals  were  instantly  exchanged  that  were  incomparably 
louder  than  those  that  were  exchanged  when  the  same 
area  was  bounded  by  four  earth -plates.  The  length  of 
each  of  the  two  wires  under  water  was  next  gradually 
increased  to  740  yards,  and  the  distance  separating  them 
gradually  diminished  to  35  yards,  the  strength  of  the 
signals  diminishing  proportionately,  and  ceasing  to  be 
readable  when  the  wires  were  further  approached.  The 
conclusion  arrived  at  from  these  experiments  was  that, 
for  the  practical  and  useful  purpose  of  signalling  messages 
across  a  broad  river,  in  the  absence  of  an  insulated  cable, 
a  complete  metallic  circuit  was  at  least  desirable.  Acting 
on  this  conclusion,  it  was  sought  to  apply  it  practically, 
and  the  following  experiment  was  carried  out :  At  a  dis- 
tance of  fifteen  miles  west  of  Calcutta  a  cable  is  laid 
across  the  river  Hooghly,  which  at  this  point  is  900  yards 
wide.  The  iron  guards  of  this  cable  were  employed  to 
form  one  of  the  metallic  conductors,  and  at  a  distance 
of  450  yards  down-stream  a  single  wire,  weighing  900 
Ib.  per  mile,  was  laid  across  the  river  to  form  the  second 
metallic  conductor,  insulated  land-lines  having  been  run 
up  to  loop  the  two  parallel  conductors  together.  The 
experiment  was  quite  a  success,  the  signals  being  readable 
without  difficult/. 


116      SECOND  PERIOD — THE  PRACTICABLE. 

"An  experiment  was  next  made  on  a  defective  cable 
across  Channel  Creek,  at  the  mouth  of  the  river  Hooghly. 
This  creek  is  crossed  by  two  cables  laid  in  the  same  trench ; 
the  length  of  each  is  3000  yards,  and  one  of  them  had 
been  completely  parted  by  a  steamer's  anchor.  Several 
attempts  were  made  to  signal  across  by  using  the  guards 
of  one  of  the  cables  as  a  lead,  and  the  guards  of  the  other 
as  a  return  wire,  but  the  efforts  proved  unsuccessful  owing 
to  the  too  close  proximity  of  the  cables.  For  every  crossing 
there  is  a  certain  minimum  distance  apart  at  which  the 
cables  must  be  laid,  and  if  this  minimum,  which  depends 
on  the  breadth  of  the  river,  be  exceeded,  an  absolute  short- 
circuit  becomes  established.  But  although  it  was  not 
possible  here  to  signal  through  the  iron  guards,  the  most 
perfect  signals  were  passed  through  the  two  conductors 
when  they  were  formed  into  a  loop,  notwithstanding  the 
fact  that  the  two  ends  of  the  broken  conductor  were  ex- 
posed in  the  sea  and  were  lying  at  a  considerable  distance 
apart.  An  experiment  was  now  made  in  order  to  ascertain 
what  chance  there  might  be  in  the  future  of  signalling 
across  the  two  conductors,  should  an  accident  occur  to  the 
good  cable.  Accordingly,  the  conductor  of  the  good  cable 
was  disconnected  in  the  cable-house  from  the  signalling  ap- 
paratus and  placed  upon  the  ground,  when  the  signals, 
though  greatly  diminished  in  volume,  still  continued  to  be 
distinctly  readable.  It  may,  therefore,  be  reasonably  in- 
ferred that  should  the  good  cable  suffer  a  similar  fate  to 
that  of  the  defective  cable,  communication  can,  by  means  of 
Cardew's  sounders,  be  kept  up  by  looping  the  ruptured 
conductors  until  arrangements  can  be  made  for  laying  a  new 
cable  or  repairing  the  defective  ones. 

"  It  will  probably  suffice  if  from  the  succeeding  experi- 
ments that  were  made  to  test  the  efficiency  of  the  vibrating 
sounder  in  the  case  of  conductors  breaking  down  at  river 


W.   F.   MELHUISH.  117 

crossings  I  select  the  following  three,  exhibiting  as  they  do 
progressive  evidence  of  the  value  of  this  signalling  instru- 
ment, and  culminating  in  establishing  it  beyond  dispute  as 
one  that  can  be  relied  on  for  carrying  on  independent  com- 
munication through  the  iron  guards  of  cables  while  the 
insulated  copper  conductors  form  parts  of  other  circuits. 

"Experiment  No.  1. — The  local  line  from  the  Central 
Office,  Calcutta,  to  Garden  Eeach  is  about  four  miles  in 
length,  and  at  about  midway  the  wire  spans  a  small  river. 
Vibrating  sounders  having  been  put  in  circuit  at  each 
end  of  this  line,  the  wire  where  it  crosses  the  river  was 
taken  down  and  laid  along  the  bed  of  the  water-way.  Sig- 
nals were  loud  and  clear  at  both  ends. 

"  From  the  success  of  this  experiment  it  may  be  inferred 
that  on  any  ordinary  line,  should  the  wire  from  accidental 
causes  come  off  the  insulator  and  make  earth  by  touching 
the  bracket,  standard,  or  ground,  or  should  the  wire  break 
and  both  ends  of  it  be  lying  on  the  ground  or  in  a  water- 
course, communication  could  still  be  maintained  by  means 
of  the  vibrating  sounders. 

"  Experiment  No.  2. — The  line  wire  which  connects  the 
town  of  Chandernagore  with  Earrackpore  is  about  ten  and  a 
half  miles  long,  900  yards  of  which  consist  of  a  cable  laid 
across  the  river  Hooghly.  Vibrating  sounders  having  been 
joined  up  in  the  telegraph  offices  at  Barrackpore  and  Chan- 
dernagore, the  insulated  conductor  of  the  cable  was  thrown 
out  of  circuit,  and  the  line  wire  on  each  side  of  the  river 
was  joined  to  the  iron  guards  of  the  cable.  Thus  for  a 
length  of  half  a  mile  out  of  ten  and  a  half  miles  the  con- 
ductor was  wholly  under  water,  yet  it  was  found  quite 
feasible  to  transmit  messages  between  the  two  offices. 

"  From  the  success  of  this  experiment  it  may  be  reason- 
ably inferred  that  in  the  case  of  certain  cable  crossings, 
where  the  rivers  are  not  too  wide,  should  the  copper  con- 


118      SECOND  PERIOD — THE  PRACTICABLE. 

ductor  of  the  cable  make  dead  earth,  or  become  insulated 
by  parting,  communication  could  still  be  kept  up  between 
the  two  offices  on  either  side. 

"  Experiment  No.  3. — The  terminus  of  the  Northern 
Bengal  State  Railway  at  Sara  is  separated  from  that  of  the 
Eastern  Bengal  State  Railway  at  Damukdia  by  the  river 
Ganges.  The  opposite  banks  of  the  river  in  this  locality 
are  connected  by  two  independent  cable  crossings.  The 
length  of  one  of  these  crossings  is  one  mile  610  yards,  and 
of  the  other  four  miles.  The  distance  which  separates  the 
two  cable-houses  on  the  Damukdia  side  is  three  miles  1584 
yards,  and  on  the  Sara  side  the  cable-houses  are  only  one 
mile  211  yards  apart,  giving  a  mean  lateral  distance  in 
alignment  of  two  miles  880  yards.  The  two  cable-houses 
on  each  bank  of  the  river  have  an  insulated  connecting  land- 
line. 

"  The  connecting  land-lines  having  been  joined  to  the  iron 
guards  of  the  cables,  two  vibrating  sounders  were  placed  in 
circuit,  one  on  each  side  of  the  river,  when  signals  so  strong 
were  transmitted  across  that  it  was  not  difficult  to  read  them 
at  a  distance  of  6  feet  away  from  the  receiving  telephone. 

"  From  the  marked  success  of  this  experiment  it  may  be 
inferred  that  at  all  river  cable  crossings  where  the  cables 
are  laid  in  separate  alignments  (and  the  farther  apart  the 
better),  should,  the  cables  become  interrupted,  communica- 
tion may  still  be  maintained  from  bank  to  bank  by  using 
vibrating  sounders,  thus  avoiding  the  delay,  inconvenience, 
and  cost  of  a  boat  service. 

"  It  should  also  be  remembered  in  the  case  of  such  a  par- 
allel cable  crossing  that,  besides  the  circuits  afforded  by  the 
copper  conductors  when  these  are  in  working  order,  there 
is  always  an  additional  local  circuit  available  by  means  of 
the  iron  guards  between  the  opposite  cable-houses,  and  that 
this  circuit  could  be  used  by  means  of  the  vibrating  sounder 


CHAKLES  A.   STEVENSON. 


119 


as  a  talking  circuit,  in  cases  of  necessity,  without  interrupt- 
ing through  working  on  either  of  the  cables. 

"  It  is  desirable  in  circumstances  similar  to  these  to  re- 
duce all  the  resistance  external  to  the  actual  connecting 
lines  to  as  small  a  quantity  as  possible,  and  therefore,  when 
messages  are  being  transmitted,  the  telephone  at  the  sending 


Fig.  13. 

end  should  be  removed  from  the  circuit,  as  also  should  the 
vibrator  from  the  receiving  end.  To  effect  this  twofold 
purpose  a  special  form  of  signalling  key  is  requisite,  and 
should  be  used.  The  action  of  this  key,  together  with  the 
complete  set  of  connections  for  a  parallel  cable  crossing,  is 
shown  in  fig.  13."  1 


CHARLES  A.   STEVENSON— 1892. 

Early  in  1892  Mr  Charles  A.  Stevenson  of  the  Northern 
Lighthouse  Board,  Edinburgh,  threw  out  the  suggestion 
that  telegraphic  communication  could  be  established  between 
ships  at  sea  and  between  ship  and  shore  by  means  of  coils. 2 

1  Melhuish's  plan  is  the  practical  realisation  of  the  early  proposals 
of  Highton  and  Bering.     See  pp.  40,  48,  supra. 

2  '  Engineer,'  March  24,  1892. 


120      SECOND  PERIOD — THE  PRACTICABLE. 

He  tried  many  experiments  in  the  course  of  that  year,  the 
results  of  which  he  reported  to  the  Eoyal  Society  of  Edin- 
burgh on  January  30,  1893.  In  this  paper1  he  describes 
two  methods  of  communicating  between  the  shore  and  a 
ship,  each  of  which  supposes  a  cable  to  be  submerged  along 
the  coast,  and  to  be  earthed  in  the  sea — presumably  (for 
the  account  is  not  clear)  through  an  induction  coil  or 
transformer. 

In  the  first  method  the  ship  has  a  wire,  with  a  telephone 
in  circuit,  stretched  from  bow  to  stern,  and  terminating  in 
coils  which  dip  into  the  water,  and  which  may  or  may  not 
be  insulated.  When  the  ship  approaches  or  crosses  the 
cable  at  a  right  angle,  or  nearly  so,  the  currents  set  up  in 
the  latter  by  a  magneto-electric  machine  at  the  shore  end 
are  rendered  audible  in  the  telephone  on  board.  If  the  coils 
be  in  the  line  of  the  cable,  as  they  will  be  when  the  ship  is 
over  it  lengthways,  or  approaches  it  broadside  on,  no  sound 
is  heard  in  the  telephone,  thus  indicating  the  position  of  the 
vessel  with  respect  to  the  known  direction  of  the  cable. 
An  insulated  wire,  400  feet  long,  was  laid  through  a  small 
lake  (Isle  of  May)  of  brackish  water,  15  feet  deep.  Alter- 
nations of  current  were  set  up  in  this  wire  by  the  bobbins 
of  three-fifths  of  a  De  Meritens'  magneto-electric  machine 
(yielding  80  volts  at  its  terminals).  A  small  boat,  having  a 
wire  with  a  telephone  in  circuit  stretched  from  bow  to  stern 
and  terminating  in  coils  dipping  into  the  water  10  feet  apart, 
was  rowed  about  in  the  vicinity  of  the  submerged  wire,  and 
it  was  found  that  the  currents  in  this  wire  were  distinctly 
audible  in  the  telephone  up  to  a  distance  of  over  300  feet. 

The  second  method  described  by  Mr  Stevenson  con- 
sisted in  dropping  into  the  sea  from  the  deck  of  a  ship 
a  large  electro-magnet  (3  feet  long,  with  2000  turns  of  one- 

1  On  Induction  through  Air  and  Water  at  Great  Distances  without 
the  use  of  Parallel  Wires. 


CHARLES   A.   STEVENSON.  121 

eighth  inch  copper  wire)  with  a  telephone  in  circuit.  Th'e 
interruptions  of  the  current  from  six  dry  cells  through  a 
wire  200  feet  long  could  be  heard  in  the  telephone  at  a 
distance  of  40  feet  in  air,  while  with  twelve  dry  cells  the 
effect  was  audible  through  60  feet  of  salt  water.  Indeed, 
he  says,  there  seemed  to  be  little  difference  whether  the 
medium  was  air,  or  fresh  or  salt  water. 

The  first  described  method  was  practically  tried  in 
America,  early  in  1895,  by  Professor  Lucien  Blake,  and 
was  favourably  spoken  of  in  his  report  to  the  American 
Lighthouse  Board,  September  1895.  A  lightship  is 
moored  in  65  feet  of  water  and  four-and-a-half  miles  off 
Sandy  Hook.  Out  from  the  shore  an  armoured  cable  was 
laid,  terminating  in  a  transformer,  the  core  of  the  cable 
being  earthed  on  the  armour  through  the  high-resistance 
coil  of  the  transformer,  while  the  terminals  of  the  lower- 
resistance  coil  were  earthed  in  the  following  manner.  Three 
insulated  copper  wires,  each  one  quarter  mile  in  length,  were 
laid  parallel  on  the  sea  bottom  and  300  feet  apart.  At  one 
end  they  were  connected  together  and  joined  to  one  terminal 
of  the  transformer,  while  the  other  and  distant  ends  were 
earthed  by  means  of  pieces  of  wire  netting  about  20  feet 
square.  The  other  terminal  of  the  transformer  was  earthed 
by  a  similar  piece  of  netting.  At  the  centre  of  this  "  grid  " 
arrangement  the  ship's  moorings  were  fixed.  The  connec- 
tions on  board  were  as  follows  :  The  two  hawse  pipes  were 
connected  in  the  pipe  by  a  copper  bar,  and  extra  plates 
were  put  between  the  metallic  sheathing  and  the  hawse  pipes 
so  as  to  ensure  good  sea  connection.  From  the  copper  bar 
an  insulated  wire  was  carried  to  a  telephone  in  the  after- 
cabin,  thence  a  wire  from  the  other  telephone  terminal  was 
carried  aft  and  connected  to  a  tail- piece  of  flexible  conductor 
over  the  stern  and  dipping  into  the  water. 

When  intermittent  currents  were  sent  into  the  cable  from 


122      SECOND  PERIOD — THE  PRACTICABLE. 

the  shore,  there  was  set  up  in  the  area  under  the  ship  "  an 
unequal  electrical  distribution,  such  that  the  potentials  were 
of  sufficient  difference  at  the  two  ends  of  the  ship  to  operate 
the  telephone  on  board.  Experiments  showed  that  sufficient 
difference  existed  between  bow  and  rudder  sheathing,  and 
even  between  bow  and  stern  sheathing,  to  operate  the  tele- 
phone, but  the  effect  was  greatest  with  bow  sheathing  and 
stern  tail-rope." 

In  another  experiment  on  board  the  lighthouse  tender 
Gardinia,  the  telephone  circuit  terminated  in  two  plates,  7 
feet  by  3  feet,  submerged  from  bow  and  stern,  a  distance  of 
113  feet.  Here  too,  "  sufficient  difference  of  potential  existed 
between  the  plates  to  make  conversation  with  the  shore 
possible  while  the  tender  was  steaming  about  in  the  neigh- 
bourhood." 

Mr  Stevenson  speaks  of  this  as  an  electro-static  effect,  but 
as  I  understand  it,  and  certainly  as  it  has  been  tried  by 
Prof.  Blake,  the  method  seems  to  belong  more  to  the  con- 
ductive order,  and  to  be  identical  with  that  of  Messrs  Smith 
&  Granville,  to  be  presently  described  (p.  165,  infra). 

Mr  Stevenson  calls  his  second  method  "  electro-magnetic," 
in  contradistinction  to  the  first  or  "  electro-static  "  one,  and 
with  certain  dispositions  of  the  submerged  cable  it  might  be 
available  for  communicating  between  the  shore  and  a  light- 
ship through  a  few  fathoms  of  water.  It  is,  however,  inter- 
esting to  us  as  being  a  step  forward  in  the  evolution  of  Mr 
Stevenson's  ideas  from  conductive  to  inductive  methods. 

In  a  further  paper,  read  before  the  Eoyal  Society  of 
Edinburgh,  March  19,  1894,  he  describes  his  experiments 
with  insulated  coils  of  wire,  or  more  correctly  spirals,  and 
says  that  a  trial  of  his  new  method  on  a  large  scale  had 
recently  been  made  with  a  view  of  ultimately  employing 
it  for  effecting  communication  between  Muckle  Flugga, 
in  the  Shetlands,  and  the  mainland. 


CHARLES   A.   STEVENSON.  123 

As  regards  the  efficacy  of  the  principle,  the  inductive 
effect  of  one  spiral  on  another  at  a  distance  has  long  been 
known  ;  but  hitherto,  even  with  a  very  strong  battery,  it 
was  impossible  to  bridge  a  greater  distance  than  100  yards, 
which  for  practical  purposes  was,  of  course,  useless. 

It  is  evident  that  if  two  coils  are  placed  vertically  so 
that  their  axes  are  coincident,  their  planes  being  parallel, 
or  if  they  be  placed  so  that  their  planes  are  in  the  same 
plane,  they  will  be  in  good  positions  for  electric  currents 
sent  in  one  to  be  apparent  by  induction  in  the  other.  For 
a  small  diameter,  and  where  the  electrical  energy  is  small, 
the  first  position  is  suitable ;  but  where  the  energy  is  great 
and  the  diameter  of  coils  great — in  fact,  when  it  is  wished 
to  carry  the  induction  to  many  times  the  diameter  of  the 
coils — then  it  will  be  found  that  it  is  better  to  let  the  two 
coils  be  in  the  same  plane,  as  it  becomes  impracticable  to 
erect  coils  of  large  diameter  with  their  planes  vertical,  but 
it  is  easy  to  lay  them  on  their  sides. 

Mr  Stevenson  made  a  large  number  of  laboratory 
experiments  on  the  interaction  of  coils,  with  the  view  of 
calculating  the  number  of  wires,  the  diameter  of  coils,  the 
number  of  amperes,  and  the  resistance  of  the  coils  that 
would  be  necessary  to  communicate  with  Muckle  Flugga ; 
and,  after  a  careful  investigation,  it  was  evident  the  gap  of 
800  yards  could,  with  certainty,  be  bridged  by  a  current  of 
one  ampere  with  nine  turns  of  post-office  wire  in  each  coil, 
the  coils  being  200  yards  in  diameter,  and  with  two  good 
telephones  on  the  hearing  coil. 

Two  coils,  on  telegraph-poles  and  insulators,  were  erected 
at  Murray  field,  one  coil  being  on  the  farm  of  Damhead  and 
the  other  on  the  farm  at  Saughton,  and  as  nearly  as  was 
possible  on  a  similar  scale,  and  the  coils  of  similar  shape  to 
what  was  wished  at  Muckle  Flugga.  On  erecting  the  coils, 
communication  was  found  impossible,  owing  to  the  indue- 


124  SECOND   PERIOD— THE  PRACTICABLE. 

tion  currents  from  the  lines  from  Edinburgh  to  Glasgow,  the 
messages  in  those  lines  being  quite  easily  read,  although  the 
coils  were  entirely  insulated  and  were  not  earthed.  The 
phonophore  which  the  North  British  Eailway  Company  have 
on  their  lines  kept  up  nearly  a  constant  musical  sound, 
which  entirely  prevented  observations.  On  getting  the 
phonophore  stopped,  it  was  found  that  100  dry  cells,  with  1*2 
ohms  resistance  each  and  1'4  volts,  gave  good  results,  the 
observations  being  read  with  great  ease  in  the  secondary  by 
means  of  two  telephones.  The  cells  were  reduced  in 
number  down  to  fifteen,  and  messages  could  still  easily  be 
sent,  the  resistance  of  the  primary  being  24  ohms  and  the 
secondary  no  less  than  260  ohms.  If  the  circuit  had  been 
of  good  iron,  with  soldered  joints  and  well  earthed,  the 
resistance  would  have  been  only  60  ohms.  The  induced 
current  generated  in  the  secondary  would  therefore  be  in  the 
ratio  of  480  p  520]  to  210;  or,  allowing  for  the  resistance 
in  the  two  telephones,  we  get  practically  only  half  the 
current  we  would  have  got  if  the  line  had  been  a  permanent 
in  place  of  a  temporary  one. 

A  trial  was  made  of  the  parallel-wire  system : l  with  20 
cells  the  sound  was  not  heard,  and  with  100  cells  it  was 
heard  as  a  mere  scratch  in  comparison  with  the  sound  with 
the  coil  system  with  only  15  cells.  A  trial  was  made  with 
the  phonophore  :  the  coils  worked  with  10  cells  with  perfect 
ease,  and  a  message  was  received  with  only  5  cells.  Speech 
by  means  of  Deckert's  transmitter  was  just  possible,  but  it 
is  believed  that  if  the  hearing  circuit  had  been  of  less  resist- 
ance it  would  have  been  easy  to  hear. 

"It  is  difficult,"  says  Mr  Stevenson,  "to  understand  how 
this  system  of  coils,  in  opposition  to  the  parallel-wire  system, 
has  not  been  recognised  as  the  best ;  for  assume  that,  with 
the  arrangement  we  had,  we  heard  equally  with  100  cells  by 

1  I.e.,  Preece's  method,  to  be  presently  described.  See  p.  144  et 
seq.,  infra. 


CHARLES   A.    STEVENSON.  125 

both  systems,  both  having  the  same  base  (200  yards),  then, 
by  simply  doubling  the  number  of  turns  of  wire  on  the 
primary  and  using  thick  wire,  the  effect  would  have  been 
practically  doubled,  whereas  by  the  parallel-wire  system 
there  is  nothing  for  it  but  to  increase  the  battery  power. 
The  difficulty  of  the  current  is  thus  removed  by  using  a 
number  of  turns  of  wire.  It  must  always  be  borne  in  mind 
that  the  effect  is  the  result  of  simply  increasing  the  diameter, 
keeping  current  and  resistance  the  same.  The  larger  the 
diameter  the  better.  What  is  wanted  is  to  get  induction  at 
a  great  distance  from  a  certain  given  base  with  a  small 
battery  power,  and  the  laboratory  experiments  and  the  trials 
in  the  field  show  that  the  way  to  overcome  the  difficulty  of 
the  current  is  by  using  a  number  of  turns  of  wire.  The 
secret  of  success  is  to  apportion  the  resistance  of  primary 
and  secondary,  and  the  number  of  turns  on  each,  to  a 
practical  battery  power." 

1.  Coil  System. — At  870  yards  from  centre  to  centre  of 
coils,  averaging  each  200  yards  diameter,  with  nine  turns  of 
wire,  it  was  found  that  with  a  phonophore  messages  were  sent 
with  five  dry  cells,  the  resistance  in  primary  being  30  ohms 
and  the  resistance  of  secondary  260  ohms,  the  current  being 
0*23  ampere,  which,  with  nine  turns,  gives  2  ampere  turns. 

2.  With  a  file  as  a  make  and  break,  it  worked  with  10 
cells,  giving  0*4  ampere  or  3 '6  ampere  turns. 

3.  Parallel-Wire  System. — With  a  file  as  a  make  and 
break,  and  with  parallel  lines  earthed,  it  was  heard  with 
100  cells,  giving  1-1  ampere. 

The  primary  coil  circuit  was  entirely  metallic  in  the 
Murrayfield  trials,  as  it  would  have  to  be  if  erected  at 
Muckle  Flugga ;  but  the  secondary  coil  was  earthed. 
AVhen,  however,  the  secondary  was  also  made  a  complete 
insulated  metallic  circuit,  with  eight  turns  of  wire,  there 
seemed  to  be  little  difference  in  the  result. 

The  calculation  of  the  diameter  necessary  to  hear  at  a 


126 


SECOND    PERIOD — THE   PRACTICABLE. 


given  distance  is  simple,  from  the  fact  that  the  hearing 
distance  is  proportional  to  the  square  root  of  the  diameter 
of  one  of  the  coils,  or  directly  as  the  diameter  of  the  two 


Fig.  14. 

coils,  so  that,  with  any  given  number  of  amperes  and 
number  of  turns,  to  hear  double  the  distance  requires 
double  the  diameter  of  coils,  and  so  on.1 

1  Professor  Lodge  has  recently  shown  that  the  law  of  distance  is 
not  the  square  root  of  diameter,  but  the  two-thirds  power,  with  a 


CHARLES   A.    STEVENSON.  127 

In  concluding  his  paper,  Mr  Stevenson  says  : — 
"  It  has  been  attempted  to  be  shown  that  the  coil  system 
is  not  only  theoretically  but  practically  the  best ;  and  I  trust 
that  we  will  soon  hear  of  the  Admiralty,  &c.,  experimenting 
with  it,  and  ultimately  putting  it  in  practice.  Meantime  my 
brother  has  recommended  the  Commissioners  of  Northern 
Lighthouses  to  erect  the  coil  system  at  Muckle  Flugga,  and 
the  Commissioners  have  approved ;  and  I  hope  soon  to  hear 
of  the  erection  of  this  novel  system  of  communication  at  the 
most  northern  point  of  the  British  Isles,  as  well  as  on  our 
warships  to  assist  in  their  manoeuvring,  by  the  establish- 
ment of  instantaneous  communication  unaffected  by  wind 
or  weather. 

"  The  application  of  the  coil  system  to  communication  with 
light  vessels  is  obvious — viz.,  to  moor  the  vessel  in  the 
ordinary  way,  and  lay  out  from  the  shore  a  cable,  and  circle 
the  area  over  which  the  lightship  moorings  will  permit  her 
to  travel  by  a  coil  of  the  cable  of  the  required  diameter, 
which  will  be  twice  the  length  of  her  chain  cable.  On 
board  the  vessel  there  will  be  another  coil  of  a  number  of 
turns  of  thick  wire.  Ten  cells  on  the  lightship  and  ten  on 
the  shore  will  be  sufficient  for  the  installation." l 

given  primary  current ;  and  so  doubling  the  circumference  of  each 
coil  will  permit  signalling  over  more  than  double  the  distance,  if  other 
things  can  be  kept  the  same.  For  such  magnification,  however,  the 
thickness  of  the  wire  must  be  magnified  likewise,  or  else  more  power 
will  be  consumed  in  the  enlarged  coil.  'Jour.  Inst.  Elec.  Engs.,'  No. 
137,  p.  803.  Possibly  Mr  Stevenson  did  not  take  into  account  the 
increase  in  resistance  owing  to  the  increased  length  of  wire,  so  that 
for  practical  purposes  his  formula  may  be  sufficiently  accurate. 

1  On  May  28,  1892,  Mr  Sydney  Evershed  patented  a  similar  method 
of  using  coils  in  connection  with  his  very  delicate  receiving  instru- 
ment or  relay.  The  plan  was  actually  tried  in  August  1896  on  the 
North  Sand  Head  (Goodwin)  lightship.  One  extremity  of  the  cable 
was  coiled  in  a  ring  on  the  bottom  of  the  sea,  embracing  the  whole 
area  over  which  the  lightship  swept  while  swinging  to  the  tide,  and 


128  SECOND   PERIOD — THE   PRACTICABLE. 

In  a  recent  communication1  Mr  Stevenson  gives  some 
additional  particulars.  Eeferring  to  his  proposed  installa- 
tion at  the  North  Unst  lighthouse,  on  Muckle  Flugga,  he 
tells  us  a  gap  of  half  a  mile  had  to  be  bridged.  The  Com- 
missioners of  Northern  Lighthouses,  being  impressed  with 
the  experiments  shown  them  on  a  small  scale — through 
stone  and  mortar — and  on  a  larger  scale  at  Murrayfield, 
decided  on  installing  the  system  on  Muckle  Flugga;  but, 
subsequently,  financial  difficulties  arose,  and  the  project 
was  allowed  to  drop. 

"  It  is  well  to  remember,"  he  says,  "  that  in  the  Murray- 
field  trials  a  small  number  of  cells  was  purposely  used. 
Theory  and  formulae  give  one  the  impression  at  first  sight 
that  a  single  outstretched  wire  is  always  best — the  simple 
fact  of  getting  a  greater  effect  at  a  distance  as  a  coiled  wire 
is  uncoiled  and  made  straight  supporting  this  impression ; 
but  formulae,  if  they  are  to  be  practical,  ought  to  take  into 
account  a  limited  area  and  workable  amounts  of  resistance, 
current,  &c.,  and  then  the  fact  is  disclosed  that  the  coiling 
of  wires  (whether  condensers  be  -used  with  them  or  not)  be- 
comes an  advantage  for  most  work  which  the  engineer  will 
be  called  upon  to  deal  with. 

"It  is  not  necessary,  as  has  been  stated,  that  the  coils 
should  be  identical  in  size  and  shape.  Far  from  it;  each 
case  must  be  treated  for  size  and  configuration  by  itself. 

the  other  end  was  connected  with  the  shore.  The  ship  was  sur- 
rounded above  the  water-line  with  another  coil.  The  two  coils  were 
separated  by  a  mean  distance  of  about  200  fathoms,  but  communica- 
tion was  found  to  be  impracticable.  The  screening  effect  of  the  sea 
water  and  the  effect  of  the  iron  hull  of  the  ship  absorbed  practically 
all  the  energy  of  the  currents  in  the  coiled  cable,  and  the  effects  on 
board,  though  perceptible,  were  very  trifling — too  minute  for  sig- 
nalling. See  Evershed's  paper  on  Telegraphy  by  Magnetic  Induction, 
Jour.  Inst.  Elec.  Engs.,'  No.  137,  p.  852  ;  also  Stevenson  on  Teleg- 
raphy without  Wires,  'Nature,'  December  31,  1896. 

1  '  Jour.  Inst.  Elec.  Engs.,'  No.  137,  p.  951 ;  also  No.  139,  p.  307. 


CHAKLES  A.   STEVENSON.  129 

For  instance,  in  the  case  of  Muckle  Flugga,  my  design  was 
for  a  line  two  miles  in  length  on  the  mainland,  with  a  coil 
at  the  end  enclosing  a  larger  area  than  the  one  on  the  rock, 
which  latter  was  opened  out  to  the  maximum  possible. 
Again,  in  the  case  of  Sule  Skerry  and  the  Flannan  Islands, 
on  the  north-west  of  Scotland,  where  telegraphy  by  induc- 
tion would  be  of  great  value,  it  would  be  impossible  to 
make  the  coils  of  large  diameter,  but  the  coil  on  the  main- 
land should  be  of  large  dimensions;  indeed  a  single  long 
wire  with  the  ends  earthed  would  be,  perhaps,  the  best 
arrangement. 

"  For  guarding  a  dangerous  coast,  a  similar  wire  of  many 
miles  in  length  would  be  suitable  for  communicating  warning 
signals  to  vessels  on  board  of  which  were  detectors,  with 
coils  necessarily  of  small  dimensions.  There  are  two  ways 
of  doing  this,  both  of  which  I  have  tried.  First,  by  means 
of  a  submarine  cable  along  the  line  of  coast.  In  this  case 
the  currents  set  up  in  the  cable  have  to  bridge  only  the 
sheet  of  water  to  the  vessel,  say  twenty  fathoms ;  or,  if  an 
electro-magnet  be  let  down  from  the  ship,  only  four  or  five 
fathoms.  But  here  the  cost  and  maintenance  of  a  cable 
would  be  a  weighty  objection.  The  other  way  is  to  erect  a 
pole  line  on  shore,  either  along  the  coast  or  in  the  form  of 
a  coil  on  a  peninsula.  The  main  difference  from  the  first 
plan  is  that  the  currents  would  have  to  be  stronger  to  bridge 
the  distance  of  several  miles  instead  of  a  few  fathoms ;  but 
the  cost  in  comparison  with  a  cable  would  be  very  small. 
I  have  tried  this  system  with  two  miles  of  pole  line  and  a 
coil  about  a  quarter  of  a  mile  distant  with  perfect  and 
never-failing  success. 

"  I  have  made  numerous  trials  of  the  coil  vwsus  parallel- 
wire  system  since  1891,  and  I  have  found — and  other 
observers  seem  also  to  have  found — that  it  is  not  prac- 
tical to  work  the  latter  more  than  three  or  four  times 


130      SECOND  PERIOD — THE  PRACTICABLE. 

the  length  of  base ;  whereas  by  coils  I  have  found  it  possible 
to  work  many  times  their  diameter.  Thus  in  1892,  at  the 
Isle  of  May  lighthouse,  I  signalled  to  a  distance  360  times 
the  diameter  of  an  electro-magnet  coil  with  currents  from  a 
de  Meritens'  magneto-electric  machine.  Again,  at  Murray- 
field,  I  signalled  four  times  the  base  with  five  dry  cells ; 
and  I  have  in  Edinburgh  a  coil  with  iron  core  17  inches 
diameter,  which  with  one  cell  can  easily  signal  through  a 
space  twenty-five  times  its  diameter." 

PROFESSOR   ERICH    RATHENAU— 1894. 

The  last  example  of  a  wireless  telegraph  with  which  we 
have  to  deal  in  this  part  of  our  history  is  an  arrangement 
devised  by  Prof.  Rathenau  of  Berlin,  with  the  assistance 
of  Drs  Eubens  and  W.  Rathenau,  and  which  was  found 
to  be  practicable  up  to  a  distance  of  three  miles  in  water. 

Reports  of  the  experiments  of  Messrs  Preece,  Stevenson, 
and  others  in  England  having  appeared  in  the  technical 
journals  on  -the  Continent,  Prof.  Rathenau,  at  the  request  of 
the  Berlin  Electrical  Society,  undertook  to  make  a  thorough 
investigation  of  the  subject  de  novo. 

After  a  careful  study  of  the  work  of  these  electricians  he 
felt  convinced  that  the  favourable  results  obtained  in  Eng- 
land, especially  by  Preece,  were  largely  due  to  conduc- 
tion. To  verify  this  opinion  he  commenced  a  course  of 
rigorous  experimentation ;  and  to  prevent  inductive  effects 
entering  into  the  calculation  he  decided  to  use  ordinary 
battery  currents,  and  in  one  direction  only. 

The  outcome  of  the  inquiry  was  published  in  an  article 
which  he  contributed  to  the  Berlin  '  Elektrotechnische 
Zeitschrift,' l  from  which  I  make  a  few  extracts.  When  a 

1  Abstract  in  '  Scientific  American  Supplement,'  January  26,  1895, 
which  I  follow  in  the  text. 


PROFESSOR   ERICH   RATHENAU. 


131 


current  is  sent  through  two  electrodes  immersed  in  a  con- 
ducting liquid,  the  electrical  equilibrium  between  these 
electrodes  is  not  effected  in  a  straight  line,  but  in  lines 
which  spread  out  in  the  manner  shown  in  fig.  15.  Now,  if 
we  place  in  the  liquid  medium  an  independent  conductor  of 
electricity,  it  will  attract  or  condense  upon  its  surface  a 
certain  number  of  these  lines,  which  can  be  utilised  for  the 
excitation  of  a  properly  constructed  receiving  apparatus. 
The  distance  at  which  these  electrical  effects  can  be  produced 
is  found  to  depend  upon  two  factors — the  available  current 
strength  and  the  distance  between  the  electrodes. 


•::*#;# 


It  was  thought  best  to  conduct  the  experiments  on  the 
lake  Wannsee,  near  Potsdam,  on  account  of  the  facilities  in 
the  way  of  apparatus  afforded  by  the  proximity  of  an  electric- 
light  station.  The  arrangement  is  shown  in  fig.  15.  AB  is 
a  battery  of  25  cells,  w  a  set  of  resistance  coils  (0  to  24 
ohrns),  su  an  interrupter  driven  by  a  motor,  AM  an  ampere- 
meter, VM  a  voltmeter,  T  a  Morse  key,  EP  EP  two  zinc  plates 
immersed  in  the  water,  500  yards  apart,  and  connected  by 
cable  as  shown.  The  receiving  circuit  comprises  two  zinc 
plates,  E?!  and  EPI}  suspended  by  cable  x  from  two  boats,  from 


132      SECOND  PERIOD — THE  PRACTICABLE. 

50  to  100  yards  apart,  and  nearly  three  miles  from  the 
sending  station ;  N  N  are  telephones  included  in  the  circuit 
of  x.  For  the  purpose  of  transmitting  signals,  intermittent 
currents  were  sent  from  the  "battery,  which,  by  depressing 
the  key  for  long  and  short  intervals,  could  be  heard  in  the 
telephones  as  dashes  and  dots  of  the  Morse  code. 

The  object  was  to  establish  experimentally  the  best  rela- 
tion between  the  various  factors — i.e.,  the  relation  between 
the  current  strength  in  the  primary  circuit  and  the  hearing 
distance  for  the  telephones  in  the  secondary  circuit ;  the 
effect  of  various  distances  between  the  electrodes  EP  EP  upon 
the  clearness  of  the  signals ;  the  distance  between  EPI  EP.J 
which  gave  the  most  audible  effect ;  and,  finally,  the  effect 
of  altering  the  shape  and  size  of  the  plates. 

On  account  of  the  non-arrival  of  some  apparatus  specially 
designed  for  these  tests,  the  average  current  strength  sent 
through  the  water  did  not  exceed  three  amperes  with  150 
intermissions  or  current  impulses  per  second.  Again,  the 
water  of  the  Wannsee  containing  but  a  very  small  ad- 
mixture of  mineral  salts  offered  a  high  resistance,  so  that 
it  was  found  necessary  to  use  large  plates  of  15  square 
yards  surface. 

With  this  arrangement  no  difficulty  was  encountered 
in  the  transmission  of  signals  from  the  electric-light  station 
to  the  boats  anchored  off  the  village  of  New  Cladow — a 
distance,  as  has  been  said,  of  nearly  three  miles ;  and 
Prof.  Rathenau  was  satisfied  that,  by  a  slight  change  in 
the  construction  of  the  ordinary  telephone,  signals  could 
be  sent  over  much  greater  distances. 

"Lord  Rayleigh,"  he  says,  "has  stated  that  the  sensi- 
tiveness of  the  telephone  for  currents  with  600  reversals 
per  second  is  about  600  times  greater  than  for  currents 
having  but  130  reversals  per  second,  but  in  my  experi- 
ments the  number  of  impulses  did  not  exceed  150  peif 


PROFESSOR   ERICH   RATHENAU. 


133 


second.  To  get  the  best  possible  result  in  this  system  of 
transmission,  a  telephone  should  be  used  having  a  carefully 
tuned  metallic  tongue  in  place  of  the  ordinary  iron  disc. 
Then,  knowing  the  number  of  current-breaks  in  the  primary 
circuit,  the  tongue  should  be  so  tuned  as  to  vibrate  in 
unison  with  that  number,  thereby  producing  much  more 
distinct  signals. 


Fig.  16. 

"  I  may  point  out  that  the  resistance  of  the  receiving 
circuit  should  be  as  small  as  possible.  At  first  I  found 
it  difficult  to  produce  a  call  in  the  distant  receivers,  but 
this  apparently  knotty  problem  may  be  solved  by  attaching 
a  microphone  to  the  membrane  of  the  receiver,  which, 
acting  upon  a  relay  in  a  local  circuit,  produces  the  call. 

"It  does  not  seem  necessary  to  point  out  that  by  the 


134      SECOND  PERIOD — THE  PRACTICABLE. 

use  of  several  current  generators,  each  one  producing  a 
definite  number  of  current  impulses,  a  number  of  non- 
interfering  messages  may  be  sent  through  the  water  to 
distant  telephones,  each  being  constructed  to  respond  to 
but  one  definite  rate  of  vibration ;  or  by  means  of  one 
current  generator  a  message  may  be  sent  (simultaneously) 
to  several  distant  telephone  receivers. 

"The  usefulness  of  this  method  of  transmission  would 
be  much  increased  if  means  can  be  found  to  produce  a 
written  message.  On  the  suggestion  of  Dr  Rubens  an 
apparatus  is  now  being  constructed,  generally  on  the  plan  of 
Dr  Wien's  optical  telephone.  It  is  expected  that  the  use 
of  this  apparatus  will  enable  us  to  transform  the  acoustical 
into  optical  signals,  and  to  register  these  photographically." 

Fig.  16  shows  the  locality  of  these  experiments.  It  will 
be  noticed  that  a  large  sandbank  intervenes  -between  the 
stations,  but  without  any  appreciable  effect  on  the  results. 

Prof.  Rathenau  concludes  a  very  interesting  paper  with 
the  enumeration  of  the  chief  points  to  be  observed  for  in- 
creasing the  effective  signalling  distance  : — 

"1.  Great  current  strength  in  the  primary  circuit. 

"  2.  Increasing  the  distance  between  the  primary 
electrodes. 

"3.  Increasing  the  distance  between  the  receiving 
electrodes. 

"  4.  Replacing  the  metallic  diaphragm  of  the  telephone 
receiver  by  a  light  tongue. 

"  5.  Which  should  be  tuned  to  respond  to  a  definite  rate 
of  vibration." l 

1  Experiments,  based  on  the  same  conductive  principle,  were 
tried  in  Austria  about  the  same  time,  but  with  what  success  I 
cannot  say,  as  the  results,  for  military  reasons,  have  not  been 
published. 


135 


THIED    PERIOD— THE    PEACTICAL. 

SYSTEMS    IN    ACTUAL    USE. 

"  The  invention  all  admired  ;  and  each  how  he 
To  be  the  inventor  missed— so  easy  seemed 
Once  found,  which  yet  unfound  most  would  have  thought 
Impossible." 

SIR  W.  H.  PREECE'S   METHOD. 

SIR  WM.  PREECE,  lately  the  distinguished  engineer-in-chief  of 
our  postal  telegraphs,  has  made  the  subject  of  wireless  teleg- 
raphy a  special  study  for  many  years,  his  first  experiment 
dating  back  to  1882.1  From  that  year  up  to  the  present  he 
has  experimented  largely  in  all  parts  of  the  country,  and 
has  given  us  the  results  in  numerous  papers — so  numerous, 
in  fact,  that  they  offer  a  veritable  embarras  des  richesses  to 
the  historian.  In  what  follows  I  can  only  attempt  a  resume, 
and  that  a  condensed  one ;  but  to  the  reader  greatly 
interested  in  the  subject  I  would  advise  a  careful  study  of 
all  the  papers,  a  list  of  which  I  append : — 

1.  Recent    Progress     in    Telephony :     British     Association 
Report,  1882. 


1  Indeed,  it  so  happens  that  one  of  the  first  experiments  he  ever 
made  in  electricity  was  on  this  very  subject  in  1854.  See  p.  28, 
supra. 


136  THIRD   PERIOD— THE  PRACTICAL. 

2.  On  Electric  Induction  between  "Wires  and  Wires  :  British 

Association  Report,  1886. 

3.  On  Induction  between  Wires  and  Wires  :  British  Associa- 

tion Report,  1887. 

4.  On  the  Transmission  of  Electric  Signals  through  Space  : 

Chicago  Electrical  Congress,  1893. 

5.  Electric  Signalling  without  Wires  :  Journal  of  the  Society 

of  Arts,  February  23,  1894. 

6.  Signalling  through   Space  :    British  Association  Report, 

1894. 

7.  Telegraphy  without  Wires  :  Toynbee  Hall,  December  12, 

1896. 

8.  Signalling  through  Space  without  Wires  :  Royal  Institu- 

tion, June  4,  1897. 

9.  JStheric  Telegraphy :  Institution  of  Electrical  Engineers, 

December  22,  1898. 
10.  Athene  Telegraphy  :  Society  of  Arts,  May  3,  1899.1 

In  his  first-quoted  paper  of  1882,  speaking  of  disturb- 
ances on  telephone  lines,  Sir  William  says  :  "  The  discovery 
of  the  telephone  has  made  us  acquainted  with  many  strange 
phenomena.  It  has  enabled  us,  amongst  other  things,  to 
establish  beyond  a  doubt  the  fact  that  electric  currents 
actually  traverse  the  earth's  crust.  The  theory  that  the 
earth  acts  as  a  great  reservoir  for  electricity  may  be  placed 
in  the  physicist's  waste-paper  basket,  with  phlogiston,  the 
materiality  of  light,  and  other  old-time  hypotheses.  Tele- 
phones have  been  fixed  upon  a  wire  passing  from  the  ground 
floor  to  the  top  of  a  large  building  (the  gas-pipes  being  used 
in  place  of  a  return  wire),  and  Morse  signals,  sent  from  a 
telegraph  office  250  yards  distant,  have  been  distinctly  read. 
There  are  several  cases  on  record  of  telephone  circuits  miles 
away  from  any  telegraph  wires,  but  in  a  line  with  the  earth 
terminals,  picking  up  telegraphic  signals  ;  and  when  an 
electric-light  system  uses  the  earth,  it  is  stoppage  to  all 

1  This  list  does  not  pretend  to  be  complete.  Doubtless  there  are 
other  papers,  which  have  escaped  my  notice. 


SIR  w.  H.  PREECE'S  METHOD.  137 

telephonic  communication  in  its  neighbourhood.  Thus, 
communication  on  the  Manchester  telephones  was  not  long 
ago  broken  down  from  this  cause ;  while  in  London  the 
effect  was  at  one  time  so  strong  as  not  only  to  destroy  all 
correspondence,  but  to  ring  the  telephone  -  call  bells.  A 
telephone  system,  using  the  earth  in  place  of  return  wires, 
acts,  in  fact,  as  a  shunt  to  the  earth,  picking  up  the  currents 
that  are  passing  in  proportion  to  the  relative  resistances  of 
the  earth  and  the  wire." l 

He  then  describes  the  experiment  which  he  had  recently 
(March  1882)  made  of  telegraphing  across  the  Solent, 
from  Southampton  to  Newport  in  the  Isle  of  Wight,  with- 
out connecting  wires.  "The  Isle  of  Wight,"  he  says, 
"is  a  busy  and  important  place,  and  the  cable  across  at 
Hurst  Castle  is  of  consequence.  For  some  cause  the  cable 
broke  down,  and  it  became  of  great  importance  to  know  if 
by  any  means  we  could  communicate  across,  so  I  thought  it 
a  timely  opportunity  to  test  the  ideas  that  had  been  promul- 
gated by  Prof.  Trowbridge.  I  put  a  plate  of  copper,  about 
6  feet  square,  in  the  sea  at  the  end  of  the  pier  at  Eyde  (fig. 
17).  A  wire  (overhead)  passed  from  there  to  Newport,  and 
thence  to  the  sea  at  Sconce  Point,  where  I  placed  another 
copper  plate.  Opposite,  at  Hurst  Castle,  was  a  similar 
plate,  connected  with  a  wire  which  ran  through  Southamp- 
ton to  Portsmouth,  and  terminated  in  another  plate  in  the 
sea  at  Southsea  Pier.  We  have  here  a  complete  circuit,  if 
we  include  the  water,  starting  from  Southampton  to  South- 
sea  Pier,  28  miles ;  across  the  sea,  6  miles  ;  Ryde  through 
Newport  to  Sconce  Point,  20  miles  ;  across  the  water  again, 
1 J  mile ;  and  Hurst  Castle  back  to  Southampton,  24  miles. 

"  We  first  connected  Gower-Bell  loud-speaking  telephones 
in  the  circuit,  but  we  found  conversation  was  impossible. 
Then  we  tried,  at  Southampton  and  Newport,  what  are 
1  For  early  notices  of  the  same  kind,  see  pp.  74-80,  supra. 


138 


THIRD  PERIOD — THE   PRACTICAL. 


called  buzzers  (Theiler's  Sounders) — little  instruments  that 
make  and  break  the  current  very  rapidly  with  a  buzzing 
sound,  and  for  every  vibration  send  a  current  into  the 
circuit.  With  a  buzzer,  a  Morse  key,  and  30  Leclanche 
cells  at  Southampton,  it  was  quite  possible  to  hear  the 


W0<§5=3<? 
Fig.  17. 

Morse  signals  in  a  telephone  at  Newport,  and  vice  versa. 
Next  day  the  cable  was  repaired,  so  that  further  experi- 
ment was  unnecessary."1 

Preece,  however,  kept  the  subject  in  view,  and  in  1884 
he  began  a  systematic  investigation,  theoretically  and  experi- 

1  Captain  (now  Colonel)  Hippisley,  R.E.,  who  conducted  these 
trials,  thought  that  the  presence  of  the  broken  cable  across  the 
Solent  somewhat  vitiated  the  results,  as  its  heavy  iron  sheathing 
may  have  aided  in  conducting  the  current. 


SIR  w.  H.  PREECE'S  METHOD.  139 

mentally,  of  the  laws  and  principles  involved — an  investi- 
gation which  he  has  hardly  yet  completed.  In  his  papers 
read  at  the  International  Electrical  Congress,  Chicago, 
August  23,  1893,  and  at  the  Society  of  Arts,  London, 
February  23,  1894,  he  gives  a  resume  of  his  experiments 
from  1884  to  date. 

He  begins  the  latter  paper  by  asking  the  same  momen- 
tous question  which  a  lady  once  put  to  Faraday,  What 
is  electricity?  Faraday,  with  true  philosophic  caution, 
replied  (I  quote  from  memory)  :  "  Had  you  asked  me  forty 
years  ago,  I  think  I  would  have  answered  the  question ; 
but  now,  the  more  I  know  about  electricity,  the  less  pre- 
pared am  I  to  tell  you  what  it  is."  Sir  William  is  not 
quite  so  epigrammatic,  nor  nearly  so  cautious;  but,  then, 
we  have  learned  a  great  deal  since  Faraday's  time.  "  Few," 
he  says,  "venture  to  reply  boldly  to  this  question— first, 
because  they  do  not  know ;  secondly,  because  they  do 
not  agree  with  their  neighbours,  even  if  they  think  they 
know;  thirdly,  because  their  neighbours  do  not  agree 
among  themselves,  even  as  to  what  to  apply  the  term.1 
The  physicist  applies  it  to  one  thing,  the  engineer  to 
another.  The  former  regards  his  electricity  as  a  form  of 
ether,  the  latter  as  a  form  of  energy.  I  cannot  grasp  the 
concept  of  the  physicist,  but  electricity  as  a  form  of  energy 
is  to  me  a  concrete  fact.  The  electricity  of  the  engineer 
is  something  that  is  generated  and  supplied,  transformed 
and  utilised,  economised  and  wasted,  meted  out  and  paid 
for.  It  produces  motion  of  matter,  heat,  light,  chemical 
decomposition,  and  sound  ;  while  these  effects  are  reversible, 
and  sound,  chemical  decomposition,  light,  heat,  and  motion 
reproduce  those  effects  which  are  called  electricity." 

1  "  Substantialists  "  call  it  a  kind  of  matter.  Others  view  it  as  a 
form  of  energy.  Others,  again,  reject  both  these  views.  Prof. 
Lodge  considers  it  a  form,  or  rather  a  mode  of  manifestation,  of  the 


140  '   THIED   PERIOD — THE  PRACTICAL. 

In  experiments  of  this  kind  it  is  necessary  to  point  out 
that  if  we  have  two  parallel  conductors,  separated  from 
each  other  by  a  finite  space,  and  each  forming  part  of 
a  separate  and  distinct  circuit,  either  wholly  metallic  or 
partly  completed  by  the  earth,  and  called  respectively  the 
primary  and  the  secondary  circuits,  we  may  obtain  currents 
in  the  latter  either  by  conduction  or  by  induction ;  and  we 
may  classify  them  into  those  due  to — 

1.  Earth-currents  or  leakages. 

2.  Electro-static  induction  currents. 

3.  Electro-magnetic  induction  currents. 

It  is  very  important  to  eliminate  (1),  which  is  a  case  of 
conduction,  from  (2)  and  (3),  which  are  cases  of  induction, 
pure  arid  simple. 

1.  Earth-currents  or  Leakages. 

When  a  linear  conductor  dips  at  each  end  into  the  earth, 
and  voltage  is  impressed  upon  it  by  any  means,  the  result- 
ing return  current  would  probably  flow  through  the  earth 
in  a  straight  line  between  these  two  points  if  the  conducti- 
bility  of  the  earth  were  perfect ;  but  as  the  earth,  per  set 
is  a  very  poor  conductor  (and  probably  is  so  only  because 
it  is  moist),  lines  of  current-flow  spread  out  symmetrically 
in  a  way  that  recalls  the  figure  of  a  magnetic  field.  These 
diffused  currents  are  evident  at  great  distances,  and  can 
be  easily  traced  by  means  of  exploring  earth -plates  or 
rods.  The  primary  current  is  best  produced  by  alternating 
currents  of  such  a  frequency  as  to  excite  a  distinct  musical 

ether.  Prof.  Nikola  Tesla  demurs  to  this  view,  but  sees  no  objection 
to  calling  electricity  ether  associated  with  matter,  or  bound  ether. 
High  authorities  cannot  even  yet  agree  whether  we  have  one  elec- 
tricity or  two  opposite  electricities.  —  Sir  W.  Crookes,  'Fortnightly 
Review,'  February  1892. 


sm  w.  ii.  PREECE'S  METHOD.  141 

note  in  a  telephone,  and  if  these  currents  rise  and  fall 
periodically  and  automatically,  they  produce  an  unmistak- 
able wail,  which,  if  made  and  broken  by  a  Morse  key  into 
short  and  long  periods,  can  be  made  to  represent  the  dots 
and  dashes  of  the  Morse  alphabet.  The  secondary  circuit, 
which  contains  the  receiving  telephone,  is  completed  in  the 
case  of  an  earth  area  by  driving  two  rods  into  the  ground, 
and  in  the  case  of  water  by  dipping  plates  therein,  5  to  10 
yards  apart. 

It  is  therefore  necessary  to  be  able  to  distinguish  these 
earth-currents  from  those  due  to  induction,  as  they  are  apt 
to  give  false  effects,  and  to  lead  to  erroneous  conclusions. 
This  is  easily  done,  if  the  instrument  be  sensitive  enough, 
by  making  the  primary  current  continuous  when  the  earth- 
current  also  becomes  continuous,  whereas  the  induction 
currents  will  be  momentary,  and  will  only  be  observed 
at  the  beginning  and  end  of  the  primary  or  inducing 
current. 

2.  Electro-static  Induction  Currents. 

When  a  body,  A,  is  electrified  by  any  means  and  isolated 
in  a  dielectric,  as  air,  it  establishes  an  electric  field  about 
it ;  and  if  in  this  field  a  similar  body,  B,  be  placed,  it  also 
is  electrified  by  induction.  If  B  be  placed  in  connection 
with  the  earth,  or  with  a  condenser,  or  with  any  very  large 
body,  a  charge  of  the  same  sign  as  A  is  conveyed  away,  and 
it  (B)  remains  electrified  in  the  opposite  sense  to  A,  A  and 
B  are  now  seats  of  electric  force  or  stress.  The  dielectric 
between  them  is  displaced  or,  as  we  say,  polarised — that 
is,  it  is  in  a  state  of  electric  strain,  and  remains  so  as  long 
as  A  remains  charged ;  but  if  A  be  discharged,  or  have  its 
charge  reversed  or  varied,  then  similar  changes  occur  in  B, 
and  in  the  dielectric  separating  them.  A  may  be  an  ex- 
tended wire  forming  part  of  a  complete  primary  circuit, 


142  THIRD   PERIOD — THE   PRACTICAL. 

and  its  charge  may  be  due  to  a  battery  or  other  source  of 
electricity;  then,  in  the  equally  extended  secondary  wire 
B  (fig.  18),  the  displaced  charge  in  flowing  to  earth  estab- 
lishes a  momentary  current  whose  direction  and  duration 
depend  on  the  current  in  .A,  and  on  its  rate  of  variation. 


Fig.  18. 

The  strained  (polarised)  state  of  the  dielectric,  and  the 
charges  on  A  and  B,  remain  quiescent  so  long  as  the  current 
flows  steadily ;  but  when  it  ceases  we  have  again,  and  in 
both  circuits,  momentary  currents,  as  shown  by  the  arrows 
(fig.  19),  which  flow  until  equilibrium  is  restored. 


Fig.  19. 

The  secondary  currents  due  to  discharge,  like  those  due 
to  charge,  flow  in  opposite  directions  at  each  end,  and  there 
is  always  some  intermediate  zero  point. 

It  is  thus  easy  in  long  circuits,  by  observing  their  direc- 
tion, to  differentiate  currents  of  induction  due  to  electro- 
static displacement  from  those  due  to  electro  -  magnetic 
disturbance. 

The  effects  of  electro-static  induction  do  not  play  an 
important  part  in  the  inquiry  immediately  before  us,  but 
they  are  of  great  consequence  in  questions  of  speed  of  sig- 


SIR  w.  H.  PREECE'S  METHOD.  143 

nailing  in  submarine  cables  and  long,  well-insulated  land- 
lines,  and  in  clearness  of  speech  in  long-distance  telephony.1 


3.  Electro-magnetic  Induction  Currents. 

Magnetic  force  is  that  which  produces,  or  tends  to  pro- 
duce, polarisation  in  magnetisable  matter  (as  iron,  nickel, 
cobalt),  and  electro-magnetic  disturbance  or  stress  in  non- 
magnetisable  matter  and  the  ether.  An  electric  current  in 
a  conductor  is  a  seat  of  magnetic  force,  and  establishes  in 
its  neighbourhood  a  magnetic  field.  The  lines  of  force  in 
this  field  are  equivalent  to  circles  in  a  plane  perpendicular 
to  the  direction  of  the  current,  which  circles,  during  the  rise 
of  the  current,  flow  outwards  or  expand,  and,  during  the 
fall  of  the  current,  flow  inwards  or  contract,  much  like  the 
waves  on  the  surface  of  smooth  water  when  a  pebble  is 
thrown  in,  but  moving  with  the  speed  of  light  Thus  any 
linear  conductor  placed  in  the  field  of  another  parallel  con- 
ductor carrying  a  current  is  cut  at  right  angles  to  itself  by 
these  lines  of  force — in  one  direction  as  the  current  rises, 
and  in  the  opposite  direction  as  the  current  falls.  This  out- 
ward and  inward  projection  of  magnetic  force  through  such 
linear  conductor  excites  electric  force  in  that  conductor,  and 
if  it  form  part  of  a  circuit  an  electric  current  is  set  up  in 
that  circuit. 

So  far  for  the  theory  of  the  subject.  Now  for  its  experi- 
mental elucidation.  Besides  those  cases  of  interference 
mentioned  on  p.  136,  others  were  of  frequent  occurrence 
in  the  experience  of  the  postal-telegraph  officials,  the  most 
striking  being  that  known  as  the  Gray's  Inn  Road  case.  In 
1884  it  was  there  noticed  that  messages  sent  in  the  ordinary 

For  an  interesting  investigation  of  electro -static  phenomena  on 
telephone  circuits,  see  Mr  Carty's  papers  in  the  *  Electrician,'  Decem- 
ber 6,  1889,  and  April  10,  1891. 


144  THIRD  PERIOD — THE  PRACTICAL. 

way  through  insulated  wires,  buried  in  iron  pipes  along  the 
road,  could  be  read  upon  telephone  circuits  erected  on  poles 
on  the  house-tops  80  feet  high.  To  cure  the  evil  the  tele- 
graph wires  had  to  be  taken  up  and  removed  to  a  more 
distant  route.1 

In  1885  Preece  arranged  an  exhaustive  series  of  experi- 
ments in  the  neighbourhood  of  Newcastle,  which  were 
ably  carried  out  by  Mr  A.  W.  Heaviside,  to  determine 
whether  these  disturbances  were  due  to  electro-magnetic  in- 
duction, and  were  independent  of  earth  conduction  ;  and 
also  to  find  out  how  far  the  distance  between  the  wires 
could  be  extended  before  this  influence  ceased  to  be  evi- 
dent. Insulated  squares  of  wire,  each  side  being  440  yards 
long,  were  laid  out  horizontally  on  the  ground  one  quarter 
of  a  mile  apart,  and  distinct  speech  by  telephones  was 
carried  on  between  them;  while  when  removed  1000  yards 
apart  inductive  effects  were  still  appreciable. 

With  the  parallel  lines  of  telegraph,  ten  and  a  quarter 
miles  apart,  between  Durham  and  Darlington,  the  ordinary 
working  currents  in  the  one  were  clearly  perceptible  in  a 
telephone  on  the  other.  Even  indications  were  obtained  in 
this  way  between  Newcastle  and  Gretna,  on  the  east  and 
west  coasts,  forty  miles  apart ;  but  here  the  observations 
were  doubtless  vitiated  by  conduction  or  leakage  through 

1  The  following  are  more  recent  cases  of  the  same  kind.  Currents 
working  the  City  and  South  London  Electric  Railway  affect  recording 
galvanometers  at  the  Greenwich  Observatory,  four  and  a  half  miles 
distant ;  and  even  a  diagram  of  the  train  service  could  be  made  out 
by  tapping  any  part  of  the  metropolitan  area. 

Some  ten  years  ago  one  of  the  dynamos  at  the  Ferranti  electric- 
light  station  at  Deptford  by  some  accident  got  connected  to  earth, 
with  the  result  that  the  whole  of  the  railway  telegraphs  in  the  signal- 
boxes  of  the  railways  in  South  London  were  temporarily  put  out  of 
order  and  rendered  inoperative,  while  the  currents  flowing  in  the 
earth  were  perceived  in  the  telegraph  instruments  so  far  northwards 
as  Leicester  and  so  far  south  as  Paris. 


SIR  w.  H.  PREECE'S  METHOD.  145 

the  large  network  of  telegraph  wires  between  those  two 
places.1 

The  district  "between  Gloucester  and  Bristol,  along  the 
banks  of  the  Severn,  was  next  (1886)  selected,  where  for  a 
length  of  fourteen  miles,  and  an  average  distance  apart  of 
four  and  a  half  miles,  no  intermediate  disturbing  lines 
existed.  Complete  metallic  circuits  were  employed,  the 
return  wires  passing  far  inland,  in  the  one  case  through 
Monmouth,  and  in  the  other  through  Stroud.  In  one  wire 
currents  of  about  '5  ampere  were  rapidly  made  and  broken 
by  mechanical  means,  producing  on  a  telephone  a  continuous 
note  which  could  be  broken  up  by  a  Morse  key  into  dots 
and  dashes,  as  in  Cardew's  vibrator.  Weak  disturbances 
were  detected  in  the  secondary  circuit,  showing  that  here 
the  range  of  audibility  with  the  apparatus  in  use  was  just 
overstepped.  The  unexpected  fact  was  also  shown  in  these 
experiments  that,  whether  the  circuits  were  entirely  metallic 
or  earthed  at  the  ends,  the  results  were  the  same.2 

Similar  trials  were  made  on  lines  along  the  valley  of  the 
Mersey.  A  new  trunk  line  of  copper  wires  that  was  being 
erected  between  London  and  the  coast  of  North  Wales  was 
then  experimented  upon,  and  some  interesting  results  were 
obtained  in  the  district  between  Shrewsbury  and  Much 
Wenlock,  and  between  Worcester  and  Bewdley. 

In  the  autumn  of  the  same  year  (1886)  some  admirable 
results  were  obtained  by  Mr  Gavey,  another  of  Preece's 
able  assistants,  near  Porthcawl,  in  South  Wales — a  wide 
expanse  of  sand  well  covered  by  the  tide,  thus  giving  the 
opportunity  of  observing  the  effects  in  water  as  well  as  in 
air.  Two  horizontal  squares  of  insulated  wire,  300  yards 
each  side,  were  laid  side  by  side  at  various  distances  apart 

1  British  Association  Report,  1886. 

2  These  experiments  were  repeated  with  more  experience  and 
greater  success  in  1889. 

E 


146  THIRD   PERIOD  —  THE   PRACTICAL. 

up  to  300  yards,  and  the  inductive  effects  of  one  on  the 
other  noted.  Then  one  coil  was  suspended  on  poles  15  feet 
above  the  other,  which  was  covered  with  water  at  high  tide. 
No  difference  was  observable  in  the  strength  of  the  induced 
signals,  whether  the  intervening  space  was  air  or  water  or  a 
combination  of  both,  although  subsequent  experience  (1893) 
showed  that  with  a  space  of  15  feet  the  effect  in  air  was 
distinctly  better  than  through  water. 

The  conclusion  drawn  from  all  these  experiments  was 
that  the  magnetic  field  extends  uninterruptedly  through  the 
earth,  as  it  does  through  the  air  ;  and  that  if  the  secondary 
circuit  had  been  in  a  coal-pit  the  effect  would  be  the  same. 
In  fact,  Mr  Arthur  Heaviside  succeeded  in  1887  in  com- 
municating between  the  surface  and  the  galleries  of  Broom- 
hill  Colliery,  350  feet  deep.  He  arranged  a  circuit  in  a 
triangular  form  along  the  galleries  about  two  and  a  quarter 
miles  in  total  length,  and  at  the  surface  a  similar  circuit  of 
equal  size  over  and  parallel  to  the  underground  line.  Tele- 
phonic speech  was  easily  carried  on  by  induction  from  circuit 
to  circuit.1 

As  the  result  of  all  these  experiments  and  innumerable 
laboratory  investigations,  Preece  deduced  the  following 
formulae.  The  first  shows  the  strength  of  current  C2  in- 
duced in  the  secondary  circuit  by  a  given  current  Cj  in  the 
primary  circuit  — 


D 


1  Subsequent  experiments  showed  that  the  conclusion  arrived  at 
for  earth  and  air  was  only  partially  true  for  water.      Telephonic 
speech  was  carried  on  in  Dover  Harbour  through  36  feet  of  water, 
but  no  practical  signals  could  be  obtained  through  400  feet  at  North 
Sand  Head,  Goodwin  Sands,  showing  that  the  effect  must  diminish 
in  water  with  some  high  power  of  the  distance. 

2  This  formula  does  not  allow  for  the  reverse  effect  of  the  return 
current  through  the  earth,  as  to  which  no  data  exist  at  present. 


sm  w.  H.  PREECE'S  METHOD.  147 

where  R  equals  the  resistance  of  the  secondary  circuit,  D  the 
distance  apart  of  the  two  circuits,  L  the  length  of  the  in- 
ductive system,  and  I  the  inductance  of  the  system.  The 
value  of  I,  obtained  by  experiment  on  two  parallel  squares 
of  wire,  1200  yards  round  and  5  yards  apart,  was  found  to 
be  -003. 

The  second  equation  gives  approximately  the  maximum 
distance  X  which  should  separate  any  two  wires  of  length 
L,  Cx  being  the  primary  current  and  R  the  resistance  of  the 
secondary  circuit. 


The  constant  1*9016  was  obtained  by  experimenting  on  two 
parallel  wires,  each  one  mile  long,  when  the  primary  circuit, 
being  excited  by  one  ampere,  the  limit  of  audibility  in  the 
secondary  was  reached  at  1  '9016  miles.  This  formula  shows 
the  desirability  of  using  copper  wires  of  the  largest  size 
practicable,  so  as  to  reduce  the  value  of  R.  Other  very 
important  elements  of  success  are  (1)  the  rate  at  which  the 
primary  currents  rise  and  fall,  the  faster  the  better,  and  (2) 
the  reduction  to  a  minimum  of  such  retarding  causes  as 
capacity  and  self-induction. 

Having  thus  threshed  out  the  laws  and  conditions  .of 
electro-magnetic  disturbances,  and  determined  the  distance 
at  which  they  could  be  usefully  applied,  it  only  remained 
for  Sir  William  to  put  his  conclusions  to  a  practical  test. 
Accordingly,  when  the  Royal  Commission  on  electric  com- 
munication between  the  shore  and  lighthouses  and  light- 
ships was  appointed  in  June  1892,  he  made  his  proposals  to 
the  Government,  and  on  receiving  sanction  forthwith  pro- 
ceeded to  carry  them  out. 

The  Bristol  Channel  proved  a  very  convenient  locality  to 
test  the  practicability  of  communicating  across  distances  of 


148 


THIRD   PERIOD — THE   PRACTICAL. 


three  and  five  miles  without  any  intermediate  conductors. 
Two  islands,  the  Flat  Holm  and  the  Steep  Holm,  lie  off 
Penarth  and  Lavernock  Point,  near  Cardiff,  the  former 
having  a  lighthouse  upon  it  (fig.  20).  On  the  shore  two 
thick  copper  wires  combined  in  one  circuit  were  suspended 
on  poles  for  a  distance  of  1267  yards,  the  circuit  being 


PENARTH 


Ul 


IAVERNOCK  PI 


\       !•» 


THOLM 


6R&AN    DOWN 


Fig.  20. 

completed  by  the  earth.  On  the  sands  at  low- water  mark, 
600  yards  from  this  primary  circuit  and  parallel  to  it,  two 
gutta-percha  covered  copper  wires  and  one  bare  copper  wire 
were  laid  down,  their  ends  being  buried  in  the  ground  by 
means  of  bars  driven  in  the  sand. 

One  of  the  gutta-percha  wires  was  lashed  to  an  iron  wire 
to  represent  a  cable.     These  wires  were  periodically  covered 


SIK  w.  H.  PREECE'S  METHOD.  149 

by  the  tide,  which  rises  here  at  spring  to  33  feet.  On  the 
Flat  Holm,  3 '3  miles  away,  another  gutta-percha  covered 
copper  wire  was  laid  for  a  length  of  600  yards. 

There  was  also  a  small  steam  launch  having  on  board 
several  lengths  of  gutta-percha  covered  wire.  One  end 
of  such  a  wire,  half  a  mile  long,  was  attached  to  a  small 
buoy,  which  acted  as  a  kind  of  float  to  the  end,  keeping 
the  wire  suspended  near  the  surface  of  the  water  as  it 
was  paid  out  while  the  launch  slowly  steamed  ahead 
against  the  tide.  Such  a  wire  was  paid  out  and  picked 
up  in  several  positions  between  the  primary  circuit  and  the 
islands. 

The  apparatus  used  on  shore  was  a  2-h.p.  portable 
Marshall's  engine,  working  a  Pyke  and  Harris's  alternator, 
sending  192  complete  alternations  per  second  of  any  desir- 
able strength  up  to  a  maximum  of  15  amperes.  These 
alternating  currents  were  broken  up  into  Morse  signals  by  a 
suitable  key.  The  signals  received  on  the  secondary  circuits 
were  read  on  a  pair  of  telephones — the  same  instruments 
being  used  for  all  the  experiments. 

The  object  of  the  experiments  was  not  only  to  test  the 
practicability  of  signalling  between  the  shore  and  the  light- 
house, but  to  differentiate  the  effects  due  to  earth  conduction 
from  those  due  to  electro-magnetic  induction,  and  to  deter- 
mine the  effects  in  water.  It  was  possible  to  trace  without 
any  difficulty  the  region  where  they  ceased  to  be  perceptible 
as  earth-currents  and  where  they  commenced  to  be  solely 
due  to  electro-magnetic  waves.  This  was  found  by  allowing 
the  paid-out  cable,  suspended  near  the  surface  of  the  water, 
to  sink.  Near  the  shore  no  difference  was  perceptible, 
whether  the  cable  was  near  the  surface  or  lying  on  the 
bottom,  but  a  point  was  reached,  just  over  a  mile  away, 
where  all  sounds  ceased  as  the  cable  sank,  but  were  received 
again  when  the  cable  came  to  the  surface.  The  total 


150  THIRD   PERIOD — THE   PRACTICAL. 

absence  of  sound  in  the  submerged  cable  was  rather  sur- 
prising, and  led  to  the  conclusion  either  that  the  electro- 
magnetic waves  of  energy  are  dissipated  in  the  sea-water, 
which  is  a  conductor,  or  else  that  they  are  reflected  away 
from  the  surface  of  the  water,  like  rays  of  light.1 

Experiments  on  the  Conway  Estuary,  showing  the  relative 
transparency  of  air  and  water  to  these  electro-magnetic 
waves,  tend  to  support  the  latter  deduction;  for  if  much 
waste  of  energy  took  place  in  the  water,  the  difference 
would  be  more  marked.  As  it  is,  there  seems  to  be  ample 
evidence  that  the  electro-magnetic  waves  are  transmitted  to 
considerable  distances  through  water,  though  how  far  remains 
to  be  found.2 

There  was  no  difficulty  in  communicating  between  the 
shore  and  Flat  Holm,  3 '3  miles.  The  attempt  to  speak 
between  Lavernock  and  Steep  Holm,  5 '35  miles,  was  not 
so  successful :  though  signals  were  perceptible,  conversation 
was  impossible.  There  was  distinct  evidence  of  sound,  but 
it  was  impossible  to  differentiate  the  sounds  into  Morse 
signals.  If  either  line  had  been  longer,  or  the  primary 
currents  stronger,  signalling  would  probably  have  been 
possible. 

In  1894  Preece  carried  out  some  satisfactory  experi- 
ments near  Frodsham,  on  the  estuary  of  the  Dee,  which 
was  found  to  be  a  more  convenient  locality  than  the 
Conway  sands.  Here,  as  at  Conway  and  other  places, 
squares  and  rectangles  were  formed  of  insulated  wires, 
and  numerous  measurements  were  made  (with  reflecting 
galvanometers  and  telephones)  of  the  effects  due  to  vary- 
ing currents  in  the  primaries,  and  at  varying  distances 
between  them  and  the  secondaries. 

In  Scotland  also  some  very  successful  trials  were  made. 
There  happens  to  be  a  very  convenient  and  accessible  loch 
1  See  note,  p.  167,  infra.  2  See  note,  p.  146,  supra. 


SIR  w.  H.  PREECE'S  METHOD.  151 

in  the  Highlands — Loch  Ness — forming  part  of  the  route 
of  the  Caledonian  Canal  between  Inverness  and  Banavie, 
having  a  line  of  telegraph  on  each  side  of  it.  Five  miles 
on  each  side  of  this  loch  were  taken,  and  so  arranged  that 
any  fractional  length  of  telegraph  wire  on  either  side  could 
be  taken  for  trial.  Ordinary,  and  not  special,  apparatus 
was  employed.  Sending  messages,  as  before,  by  Morse 
signals  and  speaking  by  telephone  across  a  space  of  one 
and  a  quarter  mile  was  found  practical,  and,  in  fact,  easy ; 
indeed,  the  sounds  were  so  loud  that  they  were  found 
sufficient  to  form  a  call  for  attention. 

The  following  apparatus  was  in  use  on  each  side  of 
the  loch :  A  set  of  batteries  consisting  of  100  dry  cells, 
giving  a  maximum  voltage  of  140 ;  a  rapidly  revolving 
rheotome,  which  broke  up  the  current  into  a  musical 
note ;  a  Morse-  key,  by  which  these  musical  notes  could 
be  transformed  into  Morse  signals ;  resistance  coils  and 
ampere  -  meters  to  vary  the  primary  current ;  two  Bell 
telephones  joined  in  multiple  arc  to  act  as  receivers. 
For  the  transmission  of  actual  speech  simple  granular 
carbon  microphones,  known  as  Deckert's,  were  used  as 
transmitters,  and  a  current  of  two  amperes  was  main- 
tained through  these  and  two  Bell  telephones  in  circuit 
with  the  line  wire. 

Any  lingering  fear  that  earth  conduction  had  principally 
to  do  with  these  results  was  removed  by  making  the  earth's 
terminals  on  the  primary  circuit  at  one  end  at  Inverness 
nine  miles  away,  and  at  the  other  end  in  two  directions 
in  a  parallel  glen  about  six  miles  away. 

One  very  interesting  fact  observed  at  Loch  Ness  was 
that  there  was  one  particular  frequency  in  the  primary 
circuit  that  gave  a  decided  maximum  effect  upon  the 
telephones  in  the  secondary  circuit.  This  confirms  the  pres- 
ence of  resonance,  and  is,  of  itself,  a  fact  sufficient  to  prove 


152 


THIRD   PERIOD — THE  PRACTICAL. 


the  effects  as  being  due  to  the  transformation  of  electro- 
magnetic waves  into  electric  currents.1 

During  the  same  year  (1894)  experiments  were  carried 
out  between  the  island  of  Arran  and  Kintyre  across  Kil- 


Ul 


'iste 


/      ARRAN 


Fig.  21. 

brannan  Sound.  Two  parallel  lines  on  opposite  sides,  and 
four  miles  apart,  were  taken  (fig.  21) ;  and,  in  addition, 
two  gutta-percha  covered  wires  were  laid  along  each  coast, 
at  a  height  of  500  feet  above  sea-level  and  five  miles  apart 
horizontally. 

1  This  is  still  a  moot  question,  many  competent  authorities,  as 
Lodge,  Rathenau,  W.  S.  Smith,  and  Stevenson,  being  of  opinion  that 
the  effect  is  partly  inductive  and  partly  conductive.  See  Dr  Lodge's 
contention,  'Jour.  Inst.  Elec.  Engs.,'  No.  137,  p.  814. 


SIR  w.  H.  PREECE'S  METHOD.  153 

Incidentally  some  extremely  interesting  effects  of  electro- 
magnetic resonance  were  observed  during  the  experiments 
in  Arran.  A  metallic  circuit  was  formed  partly  of  the 
insulated  wire  500  feet  above  the  sea -level  and  partly 
of  an  ordinary  line  wire,  the  rectangle  being  two  miles 
long  and  500  feet  high.  Wires  on  neighbouring  poles, 
at  right  angles  to  the  shorter  side  of  the  rectangle,  although 
disconnected  at  both  ends,  took  up  the  vibrations,  and  it 
was  possible  to  read  all  that  was  signalled  on  a  telephone 
placed  midway  in  the  disconnected  circuit  by  the  surgings 
thus  set  up. 

The  general  conclusions  arrived  at  as  the  result  of  these 
numerous  and  long-continued  experiments  may  be  briefly 
summed  up  as  follows:1 — 

The  earth  acts  simply  as  a  conductor,  and  per  se  it  is  a 
very  poor  conductor,  deriving  its  conducting  property  prin- 
cipally, and  often  solely,  from  the  moisture  it  contains.  On 
the  other  hand,  the  resistance  of  the  "  earth  "  between  the 
two  earth  plates  of  a  good  circuit  is  practically  nothing. 
Hence  it  follows  that  the  mass  of  earth  which  forms  the 
return  portion  of  a  circuit  must  be  very  great,  for  we  know 
by  Ohm's  law  that  the  resistance  of  a  circuit  increases  with 
its  specific  resistance  and  length,  and  diminishes  with  its 
sectional  area.  Now,  if  the  material  forming  the  "  earth  " 
portion  of  the  circuit  were,  like  the  sea,  homogeneous,  the 
current-flow  between  the  earth  plates  would  follow  innumer- 
able but  definite  stream  lines,  which,  if  traced  and  plotted 
out,  would  form  a  hemispheroid.  These  lines  of  current 
have  been  traced  and  measured.  A  horizontal  plan  on  the 
surface  of  the  earth  is  of  the  form  illustrated  in  fig.  22, 
while  a  vertical  section  through  the  earth  is  of  the  form 
shown  in  fig.  23. 

With  earth  plates  1200  yards  apart  these  currents  have 
1  British  Association  Report,  1894,  Section  G. 


154 


THIRD   PERIOD — THE   PRACTICAL. 


been  found   on  the  surface  at  a  distance  of  half  a  mile 
behind  each  plate;   and,  in  a  line  joining  the  two  trans- 


Fig.  22. 

versely,   they  are  evident  at   a  similar  distance  at  right 
angles  to  this  line. 

Now  this  hemispheroidal  mass  could  be  replaced  electric- 
ally by  a  resultant  conductor  (R,  fig.  23)  of  a  definite  form 


Fig.  23. 

and  position  ;  and,  in  considering  the  inductive  action  be- 
tween two  circuits  having  earth  returns,  it  is  necessary  to 
estimate  the  position  of  this  imaginary  conductor.  This 
was  the  object  of  the  experiments  at  Frodsham. 

If  the  material  of  the  earth  be  variable  and  dry  the  hemi- 


SIR  w.  H.  PREECE'S  METHOD.  155 

spheroid  must  become  very  much  deformed  and  the  section 
very  irregular :  the  lines  of  current-flow  must  spread  out 
farther,  but  the  principle  is  the  same,  and  there  must  be  a 
resultant  return.  The  general  result  of  the  experiments  at 
Frodsham  indicates  that  the  depth  of  the  resultant  earth 
was  300  feet,  while  those  at  Conway  are  comparable  with  a 
depth  of  350  feet.  In  the  case  of  Frodsham  the  primary 
coil  had  a  length  of  300  feet,  while  at  Conway  the  length 
was  1320  feet.  At  Loch  Ness,  and  between  Arran  and 
Kintyre,  where  the  parallel  lines  varied  from  two  to  four 
miles,  the  calculated  depth  was  found  to  be  about  900  feet. 
The  depth  of  this  resultant  must,  therefore,  increase  with  the 
distance  separating  the  earth  plates,  and  this  renders  it  pos- 
sible to  communicate  by  induction  from  parallel  wires  over 
much  longer  distances  than  would  otherwise  be  possible. 

The  first  and  obvious  mode  of  communicating  across  space 
is  by  means  of  coils  of  wire  opposed  to  each  other  in  the 
way  familiar  to  us  through  the  researches  of  Henry  and 
Faraday.  All  the  methods  here  described  consisted  in 
opposing  two  similar  coils  of  wire  having  many  turns,  the 
one  coil  forming  the  primary  circuit  and  the  other  coil  the 
secondary  circuit. 

Vibratory  or  alternating  currents  of  considerable  fre- 
quency were  sent  through  the  primary  circuit,  and  the 
induced  secondary  currents  were  detected  by  the  sound 
or  note  they  made  on  a  telephone  fixed  in  the  secondary 
circuit. 

The  distance  to  which  the  effective  field  formed  by  a  coil 
extends  increases  with  the  diameter  of  the  coil  more  than 
with  the  number  of  turns  of  wire  upon  it.  A  single  wire 
stretched  across  the  surface  of  the  earth,  forming  part  of  a 
circuit  completed  by  the  earth,  is  a  single  coil,  of  which  the 
lower  part  is  formed  by  the  resultant  earth  return,  and  the 
distance  to  which  its  influence  extends  depends  upon  the 


156  THIRD   PERIOD — THE   PRACTICAL. 

height  of  the  wire  above  the  ground  and  the  depth  of  this 
resultant  earth. 

In  establishing  communication  by  means  of  induction, 
there  are  three  dispositions  of  circuit  available — viz.,  (a) 
single  parallel  wires  to  earth  at  each  extremity ;  (b)  parallel 
coils  of  one  or  more  turns ;  (c)  coils  of  one  or  more  turns 
placed  horizontally  and  in  the  same  plane. 

The  best  practical  results  are  obtained  with  the  first 
arrangement,  more  especially  if  the  conformation  of  the 
earth  admits  of  the  wires  being  carried  to  a  considerable 
height  above  the  sea,  whilst  the  earth  plates  are  at  the  sea- 
level.  By  adopting  this  course  the  size  of  the  coil  is  prac- 
tically enlarged,  and  even  if  it  be  necessary  to  increase  the 
distance  between  the  parallel  wires  in  order  to  get  a  larger 
coil,  the  result  is  still  more  beneficial  In  a  single-wire 
circuit  we  have  the  full  effect  of  electro-static  and  electro- 
magnetic induction,  as  well  as  the  benefit  of  any  earth  con- 
duction, but  in  closed  coils  we  have  only  the  electro-magnetic 
effects  to  utilise. 

In  one  experiment  two  wires  of  a  definite  length  were 
first  made  up  into  two  coils  forming  metallic  circuits,  then 
uncoiled  and  joined  up  as  straight  lines  opposed  to  each 
other,  with  the  circuit  completed  by  earth.  The  effects, 
and  the  distance  between  which  they  were  observable,  were 
very  many  times  greater  with  the  latter  than  with  the  former 
arrangement. 

The  general  law  regulating  the  distance  to  which  we  can 
speak  by  induction  has  not  been  rigorously  determined,  and 
it  is  hardly  possible  that  it  can  be  done,  owing  to  the  many 
disturbing  elements,  geological  as  well  as  electrical.  In 
practice  we  have  to  deal  with  two  complete  circuits  of  un- 
known shape,  and  in  different  planes.  We  have  obtained 
some  remarkably  concordant  and  accurate  results  in  one 
place ;  but,  on  the  other  hand,  we  have  met  with  equally 


SIR  w.  H.  PREECE'S  METHOD.  157 

discordant  results  in  another  place.  Still,  from  the  ap- 
proximate formula  before  given,  we  deduce  the  important 
fact  that  for  parallel  lines  the  limiting  distance  increases 
directly  as  the  square  of  the  length,  which  shows  that  if  we 
can  make  the  length  of  the  two  lines  long  enough  it  would 
be  easy  to  communicate  across  a  river  or  a  channel.  Of 
course,  as  previously  pointed  out,  the  formula  does  not  take 
into  account  the  effects  of  the  reverse  magnetic  waves  gener- 
ated by  the  return  current  through  the  earth,  and  at  present 
no  data  exist  on  which  a  satisfactory  calculation  can  be 
based ;  but,  for  example,  there  is  little  doubt  that  two  wires, 
ten  miles  long,  would  signal  through  a  distance  of  ten  miles 
with  ease. 

"  Although,"  says  Sir  William  in  conclusion,  "  communi- 
cation across  space  has  thus  been  proved  to  be  practical 
in  certain  conditions,  those  conditions  do  not  exist  in  the 
cases  of  isolated  lighthouses  and  light-ships,  cases  which 
it  was  specially  desired  to  provide  for.  The  length  of 
the  secondary  must  be  considerable,  and,  for  good  effects, 
at  least  equal  to  the  distance  separating  the  two  conductors. 
Moreover,  the  apparatus  to  be  used  on  each  circuit  is 
cumbrous  and  costly,  and  it  may  be  more  economical  to 
lay  an  ordinary  submarine  cable. 

"  Still,  communication  is  possible  even  between  England 
and  France,  across  the  Channel,  and  it  may  happen  that 
between  islands  where  the  channels  are  rough  and  rugged, 
the  bottom  rocky,  and  the  tides  fierce,  the  system  may  be 
financially  possible.  It  is,  however,  in  time  of  war  that  it 
may  become  useful.  It  is  possible  to  communicate  with  a 
beleaguered  city  either  from  the  sea  or  on  the  land,  or 
between  armies  separated  by  rivers,  or  even  by  enemies. 

"  As  these  waves  are  transmitted  by  the  ether,  they  are 
independent  of  day  or  night,  of  fog,  or  snow,  or  rain,  and 
therefore,  if  by  any  means  a  lighthouse  can  flash  its  indicat- 


158  THIRD   PERIOD — THE   PRACTICAL. 

ing  signals  by  electro-magnetic  disturbances  through  space, 
ships  could  find  out  their  positions  in  spite  of  darkness  and 
of  weather.  Fog  would  lose  one  of  its  terrors,  and  elec- 
tricity become  a  great  life-saving  agency." 

At  the  Society  of  Arts  (February  23,  1894),  Sir  William 
gave  rein  to  his  imagination,  and,  looking  beyond  these 
mundane  utilities,  concluded  his  address  with  the  following 
magnificent  peroration : — 

"  Although  this  short  paper  is  confined  to  a  description  of 
a  simple  practical  system  of  communicating  across  terrestrial 
space,  one  cannot  help  speculating  as  to  what  may  occur 
through  planetary  space.  Strange  mysterious  sounds  are 
heard  on  all  long  telephone  lines  when  the  earth  is  used  as 
a  return,  especially  in  the  calm  stillness  of  night.  Earth- 
currents  are  found  in  telegraph  circuits  and  the  aurora 
borealis  lights  up  our  northern  sky  when  the  sun's  photo- 
sphere is  disturbed  by  spots.  The  sun's  surface  must  at 
such  times  be  violently  disturbed  by  electrical  storms,  and 
if  oscillations  are  set  up  and  radiated  through  space,  in 
sympathy  with  those  required  to  affect  telephones,  it  is  not 
a  wild  dream  to  say  that  we  may  hear  on  this  earth  a 
thunderstorm  in  the  sun. 

"  If  any  of  the  planets  be  populated  with  beings  like  our- 
selves, having  the  gift  of  language  and  the  knowledge  to 
adapt  the  great  forces  of  nature  to  their  wants,  then,  if  they 
could  oscillate  immense  stores  of  electrical  energy  to  and  fro 
in  telegraphic  order,  it  would  be  possible  for  us  to  hold 
commune  by  telephone  with  the  people  of  Mars." 

The  first  application  of  Preece's  system  to  the  ordinary 
needs  of  the  postal-telegraph  service  was  made  on  March  30, 
1895,  when  the  cable  between  the  Isle  of  Mull  and  Oban, 
in  Scotland,  broke  down.  As  there  was  no  ship  available 
at  the  moment  for  effecting  repairs,  communication  was 
established  by  laying  a  gutta-percha-covered  copper  wire, 
one  and  a  half  mile  long,  along  the  ground  from  Morven, 


SIE  w.  ii.  PREECE'S  METHOD. 


159 


on  the  Argyllshire  coast,  while  on  Mull  the  ordinary  tele- 
graph (iron)  wire  connecting  Craignure  with  Aros  was  used, 
the  mean  distance  separating  the  two  base  lines  being  about 
two  miles.  No  difficulty  was  experienced  in  keeping  up 
communication,  and  many  public  messages  were  transmitted 
for  a  week  until  the  cable  was  repaired.  In  all  about  160 
messages  were  thus  exchanged,  including  a  press  telegram 
of  120  words. 

The  diagram  (fig.  24)  shows  the  apparatus  and  connec- 

CURRENT_8REAKtR 

a 


ADJUSTABLE 
RESISTANCE 


DRIVING  MOTOR 


Fig.  24. 


tions,  as  regards  which  it  is  only  necessary  to  say  that  a  is 
a  rheotome,  or  make-and-break  wheel,  driven  so  as  to  pro- 
duce about  260  interruptions  of  the  current  per  second, 
which  give  a  pleasant  note  in  the  telephone,  and  are  easily 
read  when  broken  up  by  the  key  into  Morse  dots  and 
dashes ;  b  is  a  battery  of  100  Leclanch^  cells,  of  the  so- 
called  dry  and  portable  type ;  c  is  a  switch  to  start  and  stop 
the  rheotome  as  required;  and  d  is  a  telephone  to  act  as 
receiver. 


160  THIRD   PERIOD — THE   PRACTICAL. 

Since  March  1898  this  system  has  been  permanently 
established  for  signalling  between  Lavernock  Point  and 
the  Flat  Holm,  and  has  been  handed  over  to  the  War 
Office.  Permanent  lines  of  heavy  copper  wire  have  been 
erected  parallel  to  each  other,  one  being  on  the  Flat  Holm 
and  the  other  on  the  mainland. 

The  heavy  and  cumbrous  Pyke  and  Harris  alternator  of 
the  earlier  experiment  over  the  same  line  (p.  149,  ante)  has 
been  replaced  by  50  Leclanch6  cells.  The  frequency  has 
been  raised  to  400  makes  and  breaks  per  second,  thus  greatly 
increasing  the  strength  of  the  induced  currents.  By  the 
use  of  heavy  copper  base  lines  the  resistances  have  been 
made  as  low  as  practicable.  There  is  no  measurable 
capacity,  self-induction  is  eliminated,  and  there  is  no  im- 
pedance. Hence  the  signals  are  perfect,  and  the  rate  of 
working  is  only  dependent  on  the  skill  of  the  operator.  It 
is  said  that  as  many  as  40  words  per  minute  have  been 
transmitted  without  the  necessity  for  a  single  repetition — a 
speed  which  few  telegraphists  can  achieve,  and  still  fewer 
can  keep  up. 

A  little  later  Mr  Sydney  Evershed's  relays  were  added  to 
work  a  call-bell,  which  was  the  only  thing  wanted  to  make 
the  system  complete  and  practical.1 

1  During  the  summer  of  1899  Sir  William  began  a  new  series  of 
experiments  on  wireless  telephony  at  the  Menai  Straits,  the  results 
of  which  he  communicated  recently  to  the  British  Association  (Brad- 
ford, September  8,  1900).  After  referring  to  his  Loch  Ness  experi- 
ments (p.  151,  ante),  where  telephonic  signals  were  found  possible 
across  an  average  space  of  1*3  miles  with  parallel  base  lines  of  4  miles 
each,  Sir  William  states  that  his  new  experiments  fully  bore  out  this 
fact,  and  determined  the  further  fact  that  maximum  effects  are 
obtained  when  the  parallel  wires  are  terminated  by  earth-plates  in 
the  sea  itself — showing  that  the  inductive  effects  through  the  air  are 
enhanced  by  conductive  effects  through  the  water,  and  that,  conse- 
quently, shorter  base  lines  are  permissible.  Ordinary  telephone 
transmitters  and  receivers  were  used. 

This  new  method  has  been  successfully  applied  to  establishing 
communication  between  the  Skerries  and  Cemlyn,  Anglesey,  across 
2 '8  miles  average  distance,  and  between  Rathlin  Island  and  the  Irish 
coast,  about  4  miles  across. 


W1LLOUGHBY   SMITH'S   METHOD.  161 


WILLOUGHBY    SMITH'S    METHOD. 

Mr  Smith's  researches  in  wireless  telegraphy  date  back  to 
1883.  His  first  suggestions,  of  the  induction  order,  were 
contained  in  a  paper  on  Voltaic-Electric  Induction,  which 
he  read  before  the  Institution  of  Electrical  Engineers  on 
November  8  of  that  year.  These  have  already  been  noticed 
in  our  account  of  Edison's  invention  (p.  102,  supra). 

Somewhat  later,  early  in  1885,  Mr  Smith  turned  his 
attention  to  conduction  methods,  and  worked  out  a  plan 
which,  in  a  modified  form,  has  been  in  actual  operation  for 
the  last  three  years. 

The  rationale  of  the  system  is  described  by  Mr  Smith  as 
follows : — 

"  Messages  have  been  sent  and  correctly  received  through 
a  submarine  cable  two  thousand  miles  in  length,  the  earth 
being  the  return  half  of  the  circuit,  by  the  aid  of  the  elec- 
tricity generated  by  means  of  an  ordinary  gun-cap  containing 
one  drop  of  water ;  and  small  though  the  current  emanating 
from  such  a  source  naturally  was,  yet  I  believe  it  not  only 
polarised  the  molecules  of  the  copper  conductor,  but  also  in 
the  same  manner  affected  the  whole  earth  through  which  it 
dispersed  on  its  way  from  the  outside  of  the  gun-cap  to  its 
return,  through  the  cable,  to  the  water  it  contained.  I  further 
believe  that  the  time  will  come,  perhaps  sooner  than  may  be 
expected,  when  it  will  be  possible  to  detect  even  such  small 
currents  in  any  part  of  the  world  in  the  same  way  that  it  is 
now  possible  to  do  in  comparatively  small  sections  of  it. 

"  For  researches  of  this  description  it  is  necessary  to  employ 
as  sensitive  an  instrument  as  it  is  possible  to  obtain,  to  pick 
up,  so  to  speak,  such  minute  currents.  Now,  there  is  that 
wonderful  instrument  the  telephone.  I  say  wonderful  ad- 
visedly, for  as  far  as  I  know  it  is  not  to  be  equalled  for  the 

L 


162  THIRD   PERIOD — THE   PRACTICAL. 

simplicity  of  its  mechanical  construction  and  the  ease  with 
which  it  can  be  manipulated,  and  yet  is  so  peculiarly  sensi- 
tive. I  have  used  it  in  most  of  my  experiments  as  the 
receiving  instrument,  although  of  course  there  are  other 
well-known  instruments  that  could  be  employed,  as  all 
depends  upon  the  potential  of  the  current  to  be  detected. 
The  sending  arrangement  was  either  an  ordinary  Morse  key 
so  manipulated  for  a  short  or  long  time  as  to  give  the  neces- 
sary sounds  in  the  telephone  to  represent  dots  and  dashes, 
or  a  double  key  and  two  pieces  of  mechanism  giving  dis- 
similar sounds  were  employed  with  good  results.  I  gave 
much  time  and  thought  to  the  subject,  the  results  of  each 
experiment  giving  me  much  encouragement  to  proceed. 

"  Of  the  many  experiments  made  I  select  the  following, 
as  I  think  it  will  clearly  illustrate  my  system  for  telegraph- 
ing to  a  distant  point  not  in  metallic  connection  with  the 
sending  station.  A  wooden  bathing-hut  on  a  sandy  beach 
made  a  good  shore  station,  from  which  were  laid  two  in- 
sulated copper  wires  115  fathoms  in  length.  The  ends  of 
the  wires,  scraped  clean,  were  twisted  round  anchors,  their 
position  being  marked  by  buoys  about  100  fathoms  apart, 
and  in  about  6  fathoms  of  water.  Midway  between  the  two 
a  boat  was  anchored  with  a  copper  plate  hanging  fore  and 
aft  about  10  fathoms  apart,  and  consequently  about  45 
fathoms  from  either  end  of  the  anchored  shore  wires.  This 
boat  represented  the  sea  station,  and,  owing  to  the  state  of 
the  sea,  a  very  wet  and  lively  one  it  proved ;  therefore, 
taking  this  fact  into  consideration,  together  with  the  crude 
nature  of  the  experiment,  it  was  remarkable  with  what  dis- 
tinctness and  ease  messages  were  passed.  The  last  message 
sent  from  shore  was,  '  Thanks  :  that  will  do  ;  pick  up  anchors 
and  return.'  To  this  the  reply  came  from  the  boat,  '  Under- 
stand,' and  they  then  proceeded  to  carry  out  instructions. 
The  boat  employed  was  a  wooden  one,  but  it  would  have 


WILLOUGHBY   SMITH'S   METHOD.  163 

been  much  better  for  my  purpose  had  it  been  of  metal,  for 
then  I  should  have  used  it  instead  of  one  of  the  collecting 
plates,  as  the  larger  the  surface  of  these  plates  the  better 
the  results  obtained."  l 

This  method  was  secured  by  patent,  June  7,  1887,  from 
the  specification  of  which  (No.  8159)  I  take  the  following 
particulars  :  At  the  present  time  wherever  electric  telegraph 
communication  is  established  between  the  shore  and  a  light- 
house, either  floating  or  on  a  rock,  at  a  distance  from  the 
shore,  it  is  effected  through  an  insulated  conductor  or  cable. 
Much  difficulty  is,  however,  experienced  owing  to  the  rapid 
wearing  of  the  cable,  so  that  it  is  liable  to  break  whenever  a 
storm  comes  on,  and  when,  consequently,  it  is  most  required 
to  be  in  working  order.  By  this  invention  communication 
can  be  effected  between  the  sending  station  and  the  distant 
point  without  the  necessity  of  metallic  connection  between 
them. 

A  in  the  drawing  (fig.  25)  is  a  two-conductor  cable  led 
from  a  signal- station  B  on  shore  towards  the  rock  c.  At  a 
distance  from  the  rock  one  of  the  conductors  is  led  to  a 
metallic  plate  D  submerged  on  one  side  of  the  rock,  and  at 
such  a  distance  from  it  as  to  be  in  water  deep  enough  for  it 
not  to  be  affected  by  waves.  The  other  conductor  is  led  to 
another  metallic  plate  E  similarly  submerged  at  a  distance 
from  the  opposite  side  of  the  rock.  F  F  are  two  submerged 
metallic  plates,  each  opposite  to  the  plates  D  and  E  respec- 
tively. G  G  are  insulated  conductors  leading  from  the  plates 
F  F  to  a  telephone  of  low  resistance  in  the  lighthouse  H. 

To  communicate  from  the  shore,  an  interrupter  or  re- 
verser  i  and  battery  K  are  connected  to  the  shore  ends 
of  the  two-wire  cable.  The  telephone  in  the  lighthouse 
circuit  then  responds  to  the  rapid  makes  and  breaks  or 
reversals  of  the  current,  so  that  signalling  can  readily  be 
1  'Electrician,'  November  2,  1888. 


164 


THIRD   PERIOD — THE   PRACTICAL. 


carried  on  by  the  Morse  alphabet.  If  a  vibrating  inter- 
rupter or  reverser  be  used,  a  short  or  long  sound  in  the 
telephone  can  be  obtained  by  a  contact  key  held  down  for 
short  or  long  intervals. 

A  more  convenient  way  is  to  use  two  finger-keys,  one  of 
which  by  a  series  of  teeth  on  its  stem  produces  a  few  breaks 
or  reversals  of  the  current,  whilst  the  other  key  when 
depressed  produces  a  greater  number  of  breaks  or  reversals. 


Fig.  25. 

For  communicating  from  the  lighthouse  to  the  shore  a 
battery  and  make-and-break  apparatus  are  coupled  to  the 
insulated  conductors  on  the  rock,  and  a  telephone  to  the 
shore  ends. 

In  the  same  way  communication  could  be  carried  on 
from  the  shore  to  a  vessel  at  a  distance  from  it,  if  the 
vessel  were  in  the  vicinity  of  two  submerged  plates  or 
anchors,  each  having  an  insulated  conductor  passing  from 
it  to  the  shore,  and  if  two  metallic  plates  were  let  go  from 


WILLOUGHBY  SMITH'S  METHOD.  165 

the  vessel  so  that  these  plates  might  be  at  a  distance  apart 
from  one  another.  The  position  of  the  two  submerged  plates 
might  be  indicated  by  buoys.  In  this  way  communication 
might  be  effected  between  passing  vessels  and  the  shore,  or 
between  the  shore  and  a  moored  lightship  or  signal-station. 

A  similar  result  might  be  obtained  with  a  single  insulated 
conductor  from  the  shore  by  the  use  of  an  induction  appar- 
atus, the  ends  of  the  secondary  coil  being  connected  by 
insulated  conductors  to  the  submerged  plates. 

An  important  modification  of  this  method  was  subse- 
quently effected  by  Messrs  Willoughby  S.  Smith  &  W. 
P.  Granville,1  based  on  the  following  reasoning : — 

In  fig.  26  A  B  represents  an  insulated  conductor  of  any 
desired  length,  with  ends  to  earth  B  E  as  shown,  c  is  a 


D. 
Fig.  26. 

rock  island  on  which  is  extended  another  insulated  wire 
c  D,  with  its  ends  also  connected  to  earth.  Now,  if  a 
current  is  caused  to  flow  in  A  B,  indications  of  it  will  be 
shown  on  a  galvanometer  in  the  circuit  c  D.  This  is 
Preece's  arrangement  at  Lavernock  and  Flat  Holm. 

1  See  their  patent  specification,  No.  10,706,  of  June  4,  1892. 


166 


THIRD   PERIOD — THE   PRACTICAL. 


Now,  if  we  rotate  the  line  A  B  round  A  until  it  assumes 
the  position  indicated  in  fig.  27,  we  have  Messrs  Smith 
&  Granville's  arrangement,  where,  owing  to  the  proximity 


Fig.  27. 

of  B  to  D,  signalling  is  practicable  with  a  small  battery 
power.  Thus,  where  the  distance  from  B  to  D  was  60 
yards,  one  Leclanche  cell  was  found  to  be  ample.  As 


Fig.  28. 

a  permanent  current  in  A  B  causes  a  permanent  deflection 
on  the  galvanometer  in  c  D,  this  deflection  cannot  be  pro- 
duced otherwise  than  by  conduction. 

Again,  let  A  B  (fig.  28)  represent  an  insulated  conductor 


WILLOUGHBY   SMITH'S   METHOD.  167 

having  its  ends  submerged  in  water  (the  distance  between  A 
and  B  being  immaterial).  Now  cause  a  current  to  flow  con- 
tinuously, and  it  will  be  found  that  the  water  at  each  end 
of  the  conductor  is  charged  either  positively  or  negatively 
(according  to  the  direction  of  the  current)  in  equipotential 
spheroids,  diminishing  in  intensity  as  the  distance  from 
either  A  or  B  is  increased.  To  prove  this,  provide  a  second 
circuit,  connected  with  a  galvanometer,  and  with  its  two 
ends  dipping  into  the  water.  Now,  it  will  be  found  that  a 
current  flows  in  the  c  D  circuit  as  long  as  the  current  in  A  B 
is  flowing ;  the  current  in  c  D  diminishes  as  c  and  D  are 
moved  farther  away  from  B,  and  also  diminishes  to  zero  if 
the  points  c  D  are  turned  until  they  both  lie  in  the  same 
equipotential  curve  as  shown  by  the  dotted  line. 

It  must  be  well  understood  that  although,  for  the  sake  of 
clearness,  the  equipotential  curves  are  shown  as  planes,  yet 
in  a  body  of  water  they  are  more  or  less  spheres  extending 
symmetrically  around  the  submerged  ends  of  the  conductor, 
and  therefore  it  is  evident  from  the  foregoing  that  the 
position  of  c  D,  in  relation  to  B,  must  be  considered  not  only 
horizontally  but  vertically.1 

Early  in  1892  the  Trinity  Board  placed  the  Needles 
Lighthouse  at  the  disposal  of  the  Telegraph  Construction 
and  Maintenance  Company,  so  that  they  might  prove  the 
practicability  of  the  method  here  described.  The  Needles 

1  This  fact,  Mr  Smith  thinks,  fully  explains  Preece's  launch  ex- 
periments (p.  149,  supra).  For  instance,  when  the  launch  towing  the 
half-mile  of  cable  parallel  to  the  wire  on  the  mainland  was  close  to  the 
shore,  the  cable,  although  allowed  to  sink,  could  only  do  so  to  a  very 
limited  extent,  and  therefore  still  remained  in  a  favourable  position 
for  picking  up  the  earth-currents  from  A  B  (fig.  28) ;  but  when  one 
mile  from  the  shore,  and  in  deep  water,  the  cable  was  able  to  assume 
somewhat  of  a  vertical  position  with  the  two  ends  brought  more  or 
less  into  the  same  equipotential  sphere,  it  naturally  resulted  in  a 
diminution  or  cessation  of  the  current  in  the  c  D  or  launch  circuit, 
and  hence  the  absence  of  signals. 


168  THIRD   PERIOD — THE  PRACTICAL. 

Lighthouse  was  chosen  on  account  of  its  easy  access  from 
London. 

In  May  1892  an  ordinary  submarine  cable  was  laid  from 
Alum  Bay  to  within  60  yards  of  the  lighthouse  rock,  where 
it  terminated,  with  its  conductor  attached  to  a  specially  con- 
structed copper  mushroom  anchor.  An  earth  plate  close  to 
the  pier  allowed  a  circuit  to  be  formed  through  the  water. 
On  the  rock  itself  two  strong  copper  conductors  were  placed, 
one  on  either  side,  so  that  they  remained  immersed  in  the 
sea  at  low  water,  thus  allowing  another  circuit  to  be  formed 
through  the  water  in  the  vicinity  of  the  rock. 

The  telephone  was  first  tried  as  the  receiving  instrument, 
with  a  rapid  vibrator  and  Morse  key  in  the  sending  circuit. 
This  arrangement  was  afterwards  abandoned,  as  it  was  not 
nearly  so  satisfactory  as  a  mirror-speaking  galvanometer,  and 
the  men,  being  accustomed  to  flag  work,  preferred  to  watch 
a  light  rather  than  listen  to  a  telephone.  The  speaking 
galvanometer  used  is  a  specially  constructed  one,  and  does 
not  easily  get  out  of  order,  so  that,  everything  being  once 
arranged,  the  men  had  only  to  keep  the  lamp  in  order. 

Messrs  Smith  &  Granville  devised  a  novel  and  strong 
form  of  apparatus  for  a  "  call,"  and  by  its  means  any  number 
of  bells  could  be  rung,  thus  securing  attention.  The  instru- 
ments both  on  rock  and  shore  were  identical,  and,  in  actual 
work,  two  to  three  Leclanche  cells  were  ample. 

By  the  means  above  described,  communication  was  ob- 
tained through  the  gap  of  water  60  yards  in  length.  This  by 
no  means  is  the  limit,  for  it  will  be  apparent  that  the  gap 
distance  is  determined  by  the  volume  of  water  in  the  imme- 
diate neighbourhood  of  the  rock,  as  well  as  by  the  sensitive- 
ness of  the  receiving  instrument  and  the  magnitude  of  the 
sending  current. 

This  method  is  well  suited  for  coast  defences.  For 
instance,  if  a  cable  is  laid  from  the  shore  out  to  sea,  with  its 


WILLOUGHBY   SMITH'S   METHOD.  169 

end  anchored  in  a  known  position,  then  it  would  be  easy  for 
any  ship,  knowing  the  position  of  the  submerged  end,  to 
communicate  with  shore  by  simply  lowering  (within  one  or 
two  hundred  yards  of  the  anchored  end)  an  insulated  wire 
having  the  end  of  its  conductor  attached  to  a  small  mass  of 
metal  to  serve  as  "earth,"  the  circuit  being  completed 
through  the  hull  of  the  ship  and  the  sea.1 

As  this  method  has  been  in  practical  use  at  the  Fastnet 
Lighthouse  for  the  last  three  years,  the  following  account  of 
the  installation,  which  has  been  kindly  supplied  by  Mr  W. 
S.  Smith,  will  be  of  interest : — 

"  The  difficulty  of  maintaining  electrical  communication 
with  outlying  rock  lighthouses  is  so  great  that  it  has  become 
necessary  to  forego  the  advantages  naturally  attendant  upon 
the  use  of  a  submarine  cable  laid  in  the  ordinary  way  con- 
tinuously from  the  shore  to  the  lighthouse,  inasmuch  as  that 
portion  of  the  cable  which  is  carried  up  from  the  sea-bed  to 
the  rock  is  rapidly  worn  or  chafed  through  by  the  combined 
action  of  storm  and  tide.  By  the  use  of  the  Willoughby 
Smith  &  Granville  system  of  communication  this  difficulty 
is  avoided,  for  the  end  of  the  cable  is  not  landed  on  the 
rock  at  all,  but  terminates  in  close  proximity  thereto  and 
in  fairly  deep  undisturbed  water.  This  system,  first  sug- 
gested in  1887  and  practically  demonstrated  at  the  Needles 
Lighthouse  in  1892,  has — on  the  recommendation  of  the 
Koyal  Commission  on  Lighthouse  and  Lightship  Communi- 
cation —  been  applied  to  the  Fastnet,  one  of  the  most 
exposed  and  inaccessible  rock  lighthouses  of  the  United 
Kingdom. 

"  The  Fastnet  Eock,  situated  off  the  extreme  S.  W.  corner 
of  Ireland,  is  80  feet  in  height  and  360  feet  in  length,  with 
a  maximum  width  of  150  feet,  and  is  by  this  system  placed 

1  '  Electrician,'  September  29, 1893.  See  also  the  '  Times,'  Novem- 
ber 24,  1892. 


170  THIRD   PERIOD — THE  PRACTICAL. 

in  electrical  communication  with  the  town  of  Crookhaven, 
eight  miles  distant. 

"  The  shore  end  of  the  main  cable,  which  is  of  ordinary 
construction,  is  landed  at  a  small  bay  called  Galley  Cove, 
about  one  mile  to  the  west  of  the  Crookhaven  Post  Office, 
to  which  it  is  connected  by  means  of  a  subterranean  cable 
of  similar  construction  having  a  copper  conductor  weighing 
107  Ib.  covered  with  150  Ib.  of  gutta-percha  per  nautical 
mile.  The  distant  or  sea  end  of  the  main  cable  terminates 
seven  miles  from  shore,  in  11  fathoms  of  water,  at  a  spot 
about  100  feet  from  the  Fastnet  Rock;  and  the  end  is 
securely  fastened  to  a  copper  mushroom-shaped  anchor 
weighing  about  5  cwt.,  which  has  the  double  duty  of  serving 
electrically  as  an  '  earth '  for  the  conductor,  and  mechanically 
as  a  secure  anchor  for  the  cable  end. 

"The  iron  sheathing  of  the  last  100  feet  of  the  main 
cable  is  dispensed  with,  so  as  to  prevent  the  possibility  of 
any  electrical  disturbance  being  caused  by  the  iron  coming 
in  contact  with  the  copper  of  the  mushroom ;  and,  as  a  sub- 
stitute, the  conductor  has  been  thickly  covered  with  india- 
rubber,  then  sheathed  with  large  copper  wires,  and  again 
covered  with  india-rubber — the  whole  being  further  protected 
by  massive  rings  of  toughened  glass. 

"To  complete  the  main  cable  circuit,  a  short  earth  line, 
about  200  yards  in  length,  is  laid  from  the  post  office  into 
the  haven. 

"  By  reference  to  the  diagram  (fig.  29)  it  will  be  seen 
that  if  a  battery  be  placed  at  the  post  office,  or  anywhere  in 
the  main  cable  circuit,  the  sea  becomes  electrically  charged 
— the  charge  being  at  a  maximum  in  the  immediate  vicinity 
of  the  mushroom,  and  also  at  the  haven  '  earth.'  Under 
these  conditions,  if  one  end  of  a  second  circuit  is  inserted 
in  the  water  anywhere  near  the  submerged  mushroom — for 
instance,  on  the  north  side  of  the  Fastnet — it  partakes, 


WILLOUGHBY  SMITH'S  METHOD. 


•171 


more  or  less,  of  the  charge ;  and  if  the  other  end  of  this 
second  circuit  is  also  connected  to  the  water,  but  at  a  point 
more  remote  from  the  mushroom — for  instance,  at  the  south 
side  of  the  Fastnet — then  a  current  will  flow  in  the  second 
circuit,  due  to  the  difference  in  the  degree  of  charge  at  the 
two  ends  ;  and  accordingly  a  galvanometer  or  other  sensitive 


1 


Fig.  29. 

instrument  placed  in  the  Fastnet  circuit  is  affected  whenever 
the  post  office  battery  is  inserted  in  the  main  cable  circuit, 
or,  vice  versa,  a  battery  placed  in  the  Fastnet  circuit  will 
affect  a  galvanometer  at  the  post  office. 

"  In  practice  ten  large-size  Leclanche  cells  are  used  on 
the  rock,  the  sending  current  being  about  1*5  amperes,  and 


172-  THIRD   PERIOD — THE  PRACTICAL. 

in  this  case  the  current  received  on  shore  is  equal  to  about 
•15  of  a  milliampere.  The  received  current  being  small, 
instruments  of  a  fair  degree  of  sensitiveness  are  required, 
and  such  instruments,  when  used  in  connection  with  cables 
having  both  ends  direct  to  earth,  are  liable  to  be  adversely 
affected  by  what  are  known  as  '  earth '  and  '  polarisation ' 
currents,  consequently  special  means  have  been  devised  to 
prevent  this. 

"  The  receiving  instrument  is  a  D'Arsonval  reflecting 
galvanometer,  which  has  been  modified  to  meet  the  require- 
ments by  mounting  the  apparatus  on  a  vertical  pivot,  so 
that  by  means  of  a  handle  the  galvanometer  can  be  rotated 
through  a  portion  of  a  circle — thus  enabling  the  zero  of  the 
instrument  to  be  rapidly  corrected.  This  facility  of  adjust- 
ment is  necessary  on  account  of  the  varying  'earth'  and 
'  polarisation '  currents  above  mentioned. 

"  An  entirely  novel  and  substantial  '  call '  apparatus  has 
also  been  designed,  which  automatically  adapts  itself  to  any 
variation  in  the  earth  or  polarisation  current.  It  consists 
essentially  of  two  coils  moving  in  a  magnetic  field,  and 
these  coils  are  mounted  one  at  each  end  of  a  balanced  arm 
suspended  at  its  centre  and  free  to  rotate  horizontally  within 
fixed  limits.  The  normal  position  of  the  arm  is  midway 
between  two  fixed  limiting  stops.  Any  current  circulating 
in  the  coils  causes  the  whole  suspended  system  to  rotate 
until  the  arm  is  brought  into  contact  with  one  or  other  of 
the  stops  —  the  direction  of  rotation  depending  upon  the 
direction  of  the  current.  A  local  circuit  is  thus  closed, 
which  releases  a  clockwork  train  connected  to  a  torsion 
head  carrying  the  suspending  wire,  and  thus  a  counter- 
balancing twist  or  torsion  is  put  into  the  wire,  and  this 
torsion  slowly  increases  until  the  arm  leaves  the  stop  and 
again  assumes  its  free  position.  If,  however,  the  current 
is  reversed  within  a  period  of  say  five  or  ten  seconds,  then 


WILLOUGHBY   SMITH'S   METHOD.  173 

the  clockwork  closes  a  second  circuit  and  the  electric  bell  is 
operated.  By  this  arrangement,  whilst  the  relay  automatic- 
ally adjusts  itself  for  all  variations  of  current,  the  call-bell 
will  only  respond  to  definite  reversals  of  small  period  and 
not  to  the  more  sluggish  movements  of  earth-currents.  It 
is  evident  that  one  or  more  bells  can  be  placed  in  any  part 
of  the  building.  The  receiving  galvanometer  and  the  *  call ' 
relay  have  worked  very  satisfactorily,  and  any  man  of  aver- 
age intelligence  can  readily  be  taught  in  two  or  three  weeks 
to  work  the  whole  system. 

"  To  enable  the  two  short  cables  that  connect  the  light- 
house instruments  with  the  water  to  successfully  withstand 
the  heavy  seas  that  at  times  sweep  entirely  over  the  Fastnet, 
it  has  been  found  necessary  to  cut  a  deep  '  chase '  or  groove 
down  the  north  and  south  faces  of  the  rock  from  summit  to 
near  the  water's  edge,  and  to  bed  the  cables  therein  by 
means  of  Portland  cement.  And  since  the  conductors  must 
make  connection  with  the  water  at  all  states  of  sea  and  tide, 
two  slanting  holes  2J  inches  in  diameter  have  been  drilled 
through  the  solid  rock  from  a  little  above  low-water  mark 
to  over  20  feet  below.  Stout  copper  rods  connected  with 
the  short  cables  are  fitted  into  these  holes,  and  serve  to 
maintain  connection  with  the  water  even  in  the  roughest 
weather,  and  yet  are  absolutely  protected  from  damage." 

Mr  Granville  supplies  some  interesting  particulars  as  to 
the  difficulties  of  their  installation  at  the  Fastnet.1  "  The 
rock,"  he  says,  "  is  always  surrounded  with  a  belt  of  foam, 
and  no  landing  can  be  made  except  by  means  of  a  jib  58 
feet  long — not  at  all  a  pleasant  proceeding.  Now,  here  is  a 
case  where  the  Government  desired  to  effect  communication 
telegraphically,  but,  as  had  been  proved  by  very  costly  ex- 
periments, it  was  impossible  to  maintain  a  continuous  cable, 
the  cable  being  repeatedly  broken  in  the  immediate  vicinity 
1  'Jour.  Inst.  Elec.  Engs.,'  No.  137,  p.  941. 


174  THIRD    PERIOD — THE   PRACTICAL. 

of  the  rock.  This,  therefore,  is  a  case  where  some  system 
of  wireless  telegraphy  is  absolutely  necessary,  but  neither  of 
the  systems  described  would  answer  here.1  Dr  Lodge  advises 
us  to  eschew  iron,  and  to  avoid  all  conducting  masses.  But 
the  tower  and  all  the  buildings  are  built  of  boiler-plate,  and 
that  which  is  not  of  iron  is  of  bronze.  In  fact,  the  rock 
itself  is  the  only  bit  of  non-conducting,  and  therefore  non- 
absorbing,  substance  for  miles  around.  It  is  very  clear  in  a 
case  of  this  sort — and  this  is  a  typical  case — that  it  is  abso- 
lutely impracticable  to  employ  here  Dr-  Lodge's  method. 
Now  we  hear  in  regard  to  the  method  used — and  success- 
fully used — at  Lavernock,  that  a  certain  base  is  required,  of 
perhaps  half  a  mile,  a  quarter  of  a  mile,  or  a  mile  in  length  ; 
and  that  base  must  bear  some  proportion  to  the  distance  to 
be  bridged.  But  where  can  you  get  any  such  base  on  the 
rock  ?  You  could  barely  get  a  base  of  20  yards,  so  that 
method  utterly  fails.  Then  we  come  to  the  case  suggested 
by  Mr  Evershed,  of  a  coil  which  would  be  submerged  round 
the  rock.  Well,  where  would  the  coil  be  after  the  first 
summer's  breeze,  let  alone  after  a  winter  gale  1  Why,  prob- 
ably thrown  up,  entangled,  on  the  rock.  A  few  years  ago, 
during  a  severe  gale,  the  glass  of  the  lantern,  150  feet  above 
sea-level,  was  smashed  in ;  and  at  the  top  of  the  rock,  80 
feet  above  the  sea-level,  the  men  dare  not,  during  a  winter's 
gale,  leave  the  shelter  of  the  hut  for  a  moment,  for,  as  they 
said, — and  I  can  well  believe  it, — they  would  be  swept  off 
like  flies.  This  is  a  practical  point,  and  therefore  one  I  am 
glad  to  bring  to  the  notice  of  the  Institution  ;  and,  I  repeat, 
if  wireless  telegraphy  is  to  be  of  use,  it  must  be  of  use  for 
these  exceptional  cases." 

Strange  as  it  may  seem,  we  have  been  using,  on  occasion, 
wireless  telegraphy  of  this  form  for  very  many  years  without 

1  I.e.,  those  advocated  by  Professor  Lodge  and  Mr  Sydney  Ever- 
shed.     See  '  Jour.  Inst.  Elec.  Engs.,'  No.  137,  pp.  799,  852. 


WILLOUGHBY   SMITH'S   METHOD.  175 

recognising  the  fact.  Every  time  in  ordinary  telegraphy 
that  we  "  work  through  a  break,"  as  telegraphists  say,  we 
are  doing  it.  An  early  instance  of  the  kind  is  described  in 
the  old  'Electrician,'  January  9  and  23,  1863.  Many  years 
ago,  in  Persia,  the  author  has  often  worked  with  the  ordinary 
Morse  apparatus  through  breaks  where  the  wire  has  been 
broken  in  one  or  more  places,  with  the  ends  lying  many 
yards  apart  on  damp  ground,  or  buried  in  snow-drifts.  As 
the  result  of  his  experiences  in  such  cases  the  following 
departmental  order  was  issued  by  the  Director,  Persian 
Telegraphs,  as  far  back  as  November  2,  1881  :  "In  cases 
of  total  interruption  of  all  wires,  it  is  believed  that  com- 
munication may  in  most  cases  be  kept  up  by  means  of 
telephones.  Please  issue  following  instructions :  Fifteen 
minutes  after  the  disappearance  of  the  corresponding  station, 
join  all  three  wires  to  one  instrument  at  the  commutator. 
Disconnect  the  relay  wire  from  the  key  of  said  instrument, 
and  in  its  stead  connect  one  side  of  telephone,  other  side  of 
which  is  put  to  earth.  ISTow  call  corresponding  station 
slowly  by  key,  listening  at  telephone  for  reply  after  each 
call.  Should  no  reply  be  received,  or  should  signals  be  too 
weak,  try  each  wire  separately,  and  combined  with  another, 
until  an  arrangement  is  arrived  at  which  will  give  the  best 
signals."  The  Cardew  sounder  or  buzzer  has  in  recent  years 
been  added,  and  with  very  good  results.  It  will  thus  be 
seen  that  Mr  Willoughby  Smith's  plan  is  really  an  old 
friend  in  a  new  guise. 

In  1896  Mr  A.  C.  Brown,  of  whose  work  in  wireless 
telegraphy  we  have  already  spoken  (p.  101,  supra),  revived 
the  early  proposals  of  Gauss  (p.  3),  Lindsay  (p.  20),  Highton 
(p.  40),  and  Dering  (p.  48),  re  the  use  of  bare  wire,  or  badly 
insulated  cables,  in  connection  with  interrupters  and  tele- 
phones. He  also  applied  his  method  to  cases  where  the 
continuity  of  the  cable  is  broken.  "Providing  the  ends 


176  THIRD   PERIOD — THE   PRACTICAL. 

remain  anywhere  in  proximity  under  the  water,  communi- 
cation can  usually  be  kept  up,  the  telephone  receivers  used 
in  this  way  being  so  exceedingly  sensitive  that  they  will 
respond  to  the  very  minute  traces  of  current  picked  up  by 
the  broken  end  on  the  receiving  side  from  that  which  is 
spreading  out  through  the  water  in  all  directions  from  the 
broken  end  on  the  sending  side."  (See  Mr  Brown's  patent 
specification,  No.  30,123,  of  December  31,  1896.) 

Recently  he  has  been  successful  in  bridging  over  in  this 
way  a  gap  in  one  of  the  Atlantic  cables ;  but  in  this  he  has 
done  nothing  more  than  the  present  writer  did  in  1881,  and 
Mr  Willoughby  Smith  in  1887. 


G.  MARCONI'S  METHOD. 

"  Even  the  lightning-elf,  who  rives  the  oak 
And  barbs  the  tempest,  shall  bow  to  that  yoke, 
And  be  its  messenger  to  run." 

— Supple 's  Dampier's  Dream. 

We  now  come  to  the  crowning  work  of  Mr  Marconi  in 
wireless  telegraphy;  but  before  describing  this  method  it 
will  be  desirable  to  make  ourselves  acquainted  with  the 
principles  involved  in  the  special  apparatus  which  he  em- 
ploys, and  which  differentiates  his  system  from  all  those 
that  have  hitherto  occupied  us.  For  this  we  need  only  go 
back  a  few  years,  and  make  a  rapid  survey  of  the  epoch- 
marking  discoveries  of  a  young  German  philosopher,  Hein- 
rich  Hertz.1 

To  properly  appreciate  the  work  of  Hertz  we  must  carry 

1  Hertz  was  born  in  Hamburg,  February  22,  1857,  and  died  in 
Bonn,  January  1,  1894.  For  interesting  notices  of  his  all  too  brief 
life,  see,  inter  alia,  the  'Electrician,'  vol.  xxxiii.  pp.  272,  299,  332, 
and  415. 


G.  MARCONI'S  METHOD.  177 

our  minds  back  two  hundred  years,  to  the  time  when  New- 
ton made  known  to  the  world  the  law  of  universal  gravita- 
tion. Here,  in  the  struggle  between  Newtonianism  and  the 
dying  Cartesian  doctrine,  we  have  the  battle-royal  between 
the  rival  theories  of  action-at-a-distance  and  action-by-contact. 
The  victory  was  to  the  former  for  a  time ;  and  in  the  hands 
of  Bernouilli,  and,  subsequently,  of  Boscovich,  the  doctrines 
of  Newtonianism  were  carried  far  beyond  the  doctrines  of 
the  individual  Newton.  In  fact,  Newton  expressed  himself 
as  being  opposed  to  the  notion  of  matter  acting  where  it  is 
not;  though,  as  we  see  by  his  support  of  the  emission 
theory  of  light,  he  was  not  prepared  to  accept  the  notion 
of  a  luminiferous  ether.  Newton,  however,  suggested  that 
gravitation  might  be  explained  as  being  due  to  a  diminution 
of  pressure  in  a  fluid  filling  space.  Thus  the  doctrine  of 
an  empty  space,  requiring  the  infinitely  rapid  propagation 
of  a  distance-action,  held  the  field,  and  was  recognised  by 
scientists  of  the  eighteenth  century  as  the  only  plausible 
hypothesis. 

History  repeats  itself ;  and  again  the  battle-royal  was 
fought,  this  time,  early  in  the  nineteenth  century,  in  favour 
of  the  ether  hypothesis ;  and  action-at-a-distance  was  mort- 
ally wounded.  Before  the  phenomena  of  interference  of 
light  and  the  magnetic  and  electro-static  researches  of  Fara- 
day, both  the  idea  of  empty  space  action  and  that  of  the 
emission  of  light  failed  ;  and  the  propagation  of  force 
through  the  ether,  and  of  light  by  vibratory  conditions  of 
the  ether,  came  to  be  held  as  necessary  doctrines.  Later 
still,1  Maxwell  assumed  the  existence  of,  and  investigated 
the  state  of,  stress  in  a  medium  through  which  electro- 
magnetic action  is  propagated.  The  mathematical  theory 

1  October  1864,  in  his  paper  on  the  Dynamical  Theory  of  the 
Electro-Magnetic  Field,  'Phil.  Trans.,'  vol.  155.  See  also  his  great 
work,  'Electricity  and  Magnetism,'  published  in  1873. 

M 


178  THIRD   PERIOD — THE   PRACTICAL. 

which  he  deduced  gives  a  set  of  equations  which  are  identi- 
cal in  form  with  the  equations  of  motion  of  an  infinite  elastic 
solid ;  and,  on  this  theory,  the  rate  of  propagation  of  a 
disturbance  is  equal  to  the  ratio  of  the  electro-magnetic 
and  electro-static  units.  The  experimental  determination 
by  Maxwell  and  others,  that  this  ratio  is  a  number  equal  to 
the  velocity  of  light  in  ether  in  centimetres  per  second,  is  a 
fact  which  gave  immense  strength  to  the  Maxwellian  hypo- 
thesis of  identity  of  the  light  and  electro-magnetic  media. 
But,  although  this  is  the  case,  the  Maxwellian  hypothesis, 
even  when  taken  in  conjunction  with  the  experimental 
support  which  he  educed  for  it,  fell  far  short  of  being  a 
complete  demonstration  of  the  identity  of  luminous  and 
electro-magnetic  propagation.1 

To  the  genius  of  Hertz  we  owe  this  demonstration.  One 
of  the  most  important  consequences  of  Maxwell's  theory 
was  that  disturbances  of  electrical  equilibrium  produced  at 
any  place  must  be  propagated  as  waves  through  space,  with 
a  velocity  equal  to  that  of  light.  If  this  propagation  was 
to  be  traced  through  the  small  space  inside  a  laboratory,  the 
disturbances  must  be  rapid,  and  if  a  definite  effect  was  to  be 
observed,  they  must  follow  each  other  at  regular  intervals ; 
in  other  words,  periodical  disturbances  or  oscillations  of 
extreme  rapidity  must  be  set  up,  so  that  the  corresponding 
wave-length,  taking  into  account  the  extraordinarily  high 
velocity  of  propagation  (186,000  miles  per  second),  may  be 
only  a  few  inches,  or  at  most  feet.  Hertz  was  led  to  an  ex- 
periment which  satisfied  these  conditions,  and  thus  supplied 
the  experimental  proof  which  Maxwell  and  his  school  knew 
must  come  sooner  or  later. 

The  oscillatory  nature  of  the  discharge  of  a  Ley  den  jar, 
under  certain  conditions,  was  theoretically  deduced  by  Von 
Helmholtz  in  1847;  its  mathematical  demonstration  was 
1  Lord  Kelvin's  Address,  Royal  Society,  November  30,  1893. 


G.  MARCONI'S  METHOD.  179 

given  by  Lord  Kelvin  in  1853;  and  it  was  experimentally 
verified  by  Feddersen  in  1859.  When  a  Ley  den  jar,  or  a 
condenser,  of  an  inductive  capacity  K,  is  discharged  through 
a  circuit  of  resistance  R  and  self-induction  L,  the  result  is  an 
instantaneous  flow,  or  a  series  of  oscillations,  according  as  R 

is  greater,  or  less,  than  2  /=  ;  and  in  the  latter  case  the 
oscillatory  period  or  amplitude  is  given  in  the  equation  — 


where  TT  is  the  constant  3-1415  ('Phil.  Trans.,'  June  1853).1 
In  his  collected  papers2  Hertz  tells  us  that  his  interest  in 
the  study  of  electrical  oscillations  was  originally  awakened 
by  the  announcement  of  the  Berlin  prize  of  1879,  which 
was  to  be  awarded  for  an  experimental  proof  of  a  relation 
between  electro-dynamic  forces  and  dielectric  polarisation  in 
insulators.  At  the  suggestion  of  his  master  and  friend, 
Von  Helmholtz,  the  young  philosopher  took  up  the  inquiry, 
but  soon  discovered  that  the  then.  known  oscillations  were  too 
slow  to  offer  any  promise  of  success,  and  he  gave  up  the 
immediate  research  •  but  from  that  time  he  was  always  on 
the  look-out  for  phenomena  in  any  way  connected  with  the 
subject.  Consequently,  he  immediately  recognised  the  im- 
portance of  a  casual  observation  which  in  itself  and  at 
another  time  might  have  been  considered  as  too  trivial  for 
further  notice.  In  the  collection  of  physical  apparatus  at 
Karlsruhe  he  found  an  old  pair  of  so-called  Eiess's  or 
Knochenhauer's  spirals  —  short  flat  coils  of  insulated  wire, 

1  In  the  old  'Electrician,'  vol.  iii.  p.  101,  there  is  an  interesting 
paper  on  "  The  Oscillatory  Character  of  Spark  Discharges  shown  by 
Photography."     For  a  concise  exposition  of  the  theory  of  electrical 
oscillations,  see  Prof.  Edser's  paper,  '  Electrical  Engineer,'  June  3, 
1898,  and  following  numbers. 

2  'Electric  Waves,'  London,  1893.     For  an  interesting  account  of 
pre-Hertzian  observations,  see  Lodge's  '  The  Work  of  Hertz,'  p.  61  ; 
also  Appendix  D  of  this  work. 


180  THIED  PERIOD — THE  PRACTICAL. 

with  the  turns  all  in  the  same  plane  C?Prof.  Henry's 
spirals).  While  performing  some  experiments  with  them  at 
a  lecture  he  was  giving,  he  noticed  that  the  discharge  of  a 
very  small  Leyden  jar,  or  of  a  small  induction  coil,  passed 
through  the  one  was  able  to  excite  induced  currents  in  the 
other,  provided  that  a  small  spark-gap  was  made  in  the 
circuit  of  the  first  spiral.  Thus  was  made  the  all-important 
discovery  of  the  "  effective  spark-gap  "  which  started  Hertz 
on  the  road  of  his  marvellous  investigations. 

A  very  little  consideration  of  this  phenomenon  enabled 
him,  even  at  this  early  stage,  to  lay  down  the  following 
propositions  : — 

1.  If  we  allow   a  condenser,  such  as  a  Leyden  jar,  of 
small  capacity,  to  discharge  through  a  short  and  simple 
circuit  with  a  spark-gap  of  suitable  length,  we  obtain  a 
sharply  defined  discharge  of  very  short  duration,  which  is 
the  long-sought-for  sudden  disturbance  of  electrical  equili- 
brium— the  exciter  of  electrical  vibrations. 

2.  Such  vibrations  are  capable  of  exciting   in  another 
circuit  of  like  form  resonance  effects  of  such  intensity  as  to 
be  evident  even  when  the  two  circuits  are  separated  by 
considerable  distances.     In  this  second  circuit  Hertz  had 
found  the  long-sought-for  detector  of  electric  waves. 

With  the  exciter  to  originate  electric  waves  and  the 
detector  to  make  them  evident  at  a  distance,  all  the  pheno- 
mena of  light  were,  one  after  another,  reproduced  in  cor- 
responding electro-magnetic  effects,  and  the  identity  of  light 
and  electricity  was  completely  demonstrated.1 

In  his  paper  "  On  very  Rapid  Electric  Oscillations,"  Hertz 
occupied  himself  with  some  of  these  phenomena.  As  an 
exciter  he  used  wire  rectangles,  or  simple  rods  (fig.  30)  to 
the  ends  of  which  metallic  cylinders  or  spheres  were  con- 

1  See  Appendix  A  for  a  clear  exposition  of  the  views  regarding  the 
relation  of  the  two  before  and  after  Hertz. 


G.  MARCONI'S  METHOD. 


181 


nected,  the  continuity  being  broken  in  the  middle  where 
the  ends  were  provided  with  small  spherical  knobs  between 


Fig.  30. 

which  the  sparks  passed.     The  exciter  was  charged  by  an 
ordinary  Kuhmkorff  induction  coil  of  small  size. 

The  detector  was  mostly  a  simple  rectangle  or  circle  of 
wire  (fig.  31),  also  provided  with  a  spark-gap.  When 
vibrations  are  set  up  in  the  detector 
and  sparks  pass  across  the  gap,  the 
greater  length  of  these  sparks  in- 
dicates the  greater  intensity  of  the 
received  wave  impacts.  When,  there- 
fore, the  dimensions  of  the  detector 
are  so  adjusted  as  to  give  the  maximum 
sparks  with  a  given  exciter  the  two 


Fig.  31. 


circuits  are  said  to  be  in  resonance,  or  to  be  electrically 
tuned.  Fortunately  this  condition  of  resonance  or  syntony 
is  not  essential  to  the  excitement  of  sparks,  else  wireless 
telegraphy  by  Hertzian  waves  would  not  be  so  advanced  as 
it  is  to-day.  Thus,  when  a  good  exciter  is  in  action  it  will 
cause  little  sparks  between  any  conducting  body  in  its 
vicinity  and  a  wire  held  in  the  hand  and  brought  near 
to  the  body,  showing  that  the  influence  of  the  exciter 
extends  to  all  conducting  bodies,  and  not  merely  to  those 
which  are  tuned  to  it.  Of  course  it  still  holds  good  that, 
cceteris  paribus,  the  maximum  effect  is  obtained  with 
resonance. 


182  THIRD   PERIOD — THE  PRACTICAL. 

In  the  course  of  his  experiments  on  electric  resonance, 
Hertz  observed  a  phenomenon  which  for  a  time  was  inex- 
plicable. It  was  seen  that  the  length  and  brightness  of  the 
sparks  at  the  detector  were  greatly  modified  by  the  sparks 
given  off  at  the  exciter.  If  the  latter  were  visible  from  the 
detector  spark-gap  the  sparks  given  off  there  were  small  and 
hardly  perceptible,  but  became  larger  and  brighter  as  soon 
as  a  screen  was  placed  between  the  two  instruments.  By 
carefully  thought-out  experiments  he  showed  that  this 
singular  action  was  due  solely  to  the  presence  of  ultra-violet 
light,  breaking  down  the  insulation  of  the  gap  and  making 
it,  so  to  say,  more  conductive.  This  effect  can  be  shown  in 
another  way,  by  widening  the  spark-gap  of  an  induction 
coil  beyond  the  ordinary  sparking  distance,  when,  by  simply 
directing  a  beam  of  ultra-violet  light  into  the  gap,  sparking 
will  be  resumed.1 

Having  made  himself  familiar  with  the  phenomena  of 
electrical  resonance,  Hertz  went  on  to  study  the  propagation 
of  electric  vibrations  through  space — the  most  difficult,  as 
it  is  probably  the  most  important,  of  all  his  researches. 

1  Prof.  K.  Zickler  has  proposed  to  use  this  property  for  telegraphy. 
At  the  sending  station  an  arc  lamp,  which  is  rich  in  ultra-violet  rays, 
is  provided  with  a  shutter  and  a  lens  for  directing  flashes  towards  the 
receiving  station.  There  they  are  made  to  impinge  on  the  spark- 
gap,  unduly  widened,  of  an  induction  coil  in  action,  and  allow  sparks 
to  pass.  These  give  rise  to  electric  waves  which  act  on  the  coherer, 
which  in  its  turn  operates  a  bell,  a  telephone,  or  a  Morse  instrument 
in  the  way  we  shall  see  later  on  when  we  come  to  speak  of  the  action 
of  the  Marconi  apparatus.  The  reflecting  lens  is  made  of  quartz  and 
not  of  glass,  which  does  not  transmit  the  ultra-violet  rays  ;  but  for 
signalling  or  interrupting  the  rays  in  long  and  short  periods  a  glass 
plate  is  used  as  the  shutter.  The  interruption  of  the  ultra-violet  rays 
is  thus  effected  without  altering  the  light,  which  assures  secrecy  of 
transmission.  Prof.  Zickler  has  in  this  way  signalled  over  a  space 
of  200  metres,  and  thinks  that  with  suitable  lamps  and  reflectors 
the  effect  would  be  possible  over  distances  of  many  kilometres. — 
'Elektrische  Zeitung,'  July  1898. 


G.  MARCONI'S  METHOD.  183 

The  results  he  gave  to  the  world  in  1888,  in  his  paper 
"  On  the  Action  of  a  Eectilinear  Electric  Oscillation  on  a 
Neighbouring  Circuit."  When  sparks  pass  rapidly  at  the 
exciter  electric  surgings  occur,  and  we  have  a  rectilinear 
oscillation  which  radiates  out  into  surrounding  space.  The 
detectors,  whose  spark-gaps  were  adjustable  by  means  of  a 
micrometer  screw,  were  brought  into  all  kinds  of  positions 
with  respect  to  the  exciter,  and  the  effects  were  studied  and 
measured.  These  effects  were  very  different  at  different 
points  and  in  the  different  positions  of  the  detector.  In 
short,  they  were  found  to  obey  a  law  of  radiation  which  was 
none  other  than  the  corresponding  law  in  optics. 

In  his  paper,  "  On  the  Velocity  of  Propagation  of  Electro- 
dynamic  Actions,"  he  gave  experimental  proof  of  the  hitherto 
theoretical  fact  that  the  velocity  of  electric  waves  in  air  was 
the  same  as  that  of  light,  whereas  he  found  the  velocity 
in  wires  to  be  much  smaller — in  the  ratio  of  4  to  7.  For 
the  moment  he  was  puzzled  by  this  result :  he  suspected  an 
error  in  the  calculations,  or  in  the  conditions  of  the  experi- 
ment, but — and  here  he  showed  himself  the  true  philosopher 
— he  did  not  hesitate  to  publish  the  actual  results,  trusting 
to  the  future  to  correct  or  explain  the  discrepancy.  The 
explanation  was  soon  forthcoming.  Messrs  E.  Sarasin  and 
L.  de  la  Rive  of  Geneva  took  up  the  puzzle,  and  ended  by 
showing  that  the  deviations  from  theory  were  caused  simply 
by  the  walls  of  Hertz's  laboratory,  which  reflected  the 
electric  waves  impinging  on  them,  so  causing  interferences 
in  the  observations.  When  these  investigators  repeated 
the  Hertzian  experiment  with  larger  apparatus,  and  on  a 
larger  scale,  as  they  were  able  to  do  in  the  large  turbine 
hall  of  the  Geneva  Waterworks,  they  found  the  rate  of  prop- 
agation to  be  the  same  along  wires  as  in  air.1 

1  'Comptes  Rendus,'  March  31,  1891,  and  December  26,  1892.  See 
also  the  'Electrician,'  vol.  xxvi.  p.  701,  and  vol.  xxx.  p.  270. 


184  THIRD   PERIOD — THE  PRACTICAL. 

In  his  paper,  "  On  Electro-dynamic  Waves  and  their  Ke- 
flection,"  Hertz  further  developed  this  point,  and  showed  the 
existence  of  these  waves  in  free  space.  Opposite  the  exciter 
a  large  screen  of  zinc  plate,  8  feet  square,  was  suspended  on 
the  wall ;  the  electric  waves  emitted  from  the  exciter  were 
reflected  from  the  plate,  and  on  meeting  the  direct  waves 
interference  phenomena  were  produced,  consisting  of  sta- 
tionary waves  with  nodes  and  loops.  When,  therefore, 
Hertz  moved  the  circle  of  wire  which  served  as  a  detector 
to  and  fro  between  the  screen  and  the  exciter,  the  sparks  in 
the  detector  circuit  disappeared  at  certain  points,  reappeared 
at  other  points,  disappeared  again,  and  so  on.  Thus  there 
was  found  a  periodically  alternating  effect  corresponding  to 
nodes  and  loops  of  electric  radiation,  showing  clearly  that  in 
this  case  also  the  radiation  was  of  an  undulatory  character, 
and  the  velocity  of  its  propagation  finite. 

In  a  paper,  "  On  the  Propagation  of  Electric  Waves  along 
Wires,"  March  1889,  Hertz  shows  that  alternating  currents 
or  oscillations  of  very  high  frequencies,  as  one  hundred 
million  per  second,  are  confined  to  the  surface  of  the  con- 
ductor along  which  they  are  propagated,  and  do  not  penetrate 
the  mass.1  This  is  a  very  important  experimental  proof  of 
Poynting's  theory  concerning  electric  currents,  which  he  had 
deduced  from  the  work  of  Faraday  and  Maxwell.  Accord- 
ing to  this  theory,  the  electric  force  which  we  call  the 
current  is  in  nowise  produced  in  the  wire,  but  under  all 
circumstances  enters  from  without,  and  spreads  itself  in  the 
metal  comparatively  slowly,  and  according  to  similar  laws  as 

1  It  should  be  stated  here  that  long  ago  Prof.  Henry,  the  Faraday 
of  America,  held  the  same  views,  and  proved  them,  too,  by  an  experi- 
ment which  is  strangely  like  one  of  Hertz's,  though,  of  course,  he  did 
not  explain  them  as  Hertz  does.  Henry's  views  are  given  clearly  in 
two  letters  addressed  to  Prof.  Kedzie  of  Lansing,  Michigan,  in  1876. 
Being  of  historical  interest,  as  well  as  of  practical  value,  I  give  them 
entire  in  Appendix  B. 


G.  MARCONI'S  METHOD.  185 

govern  changes  of  temperature  in  a  conductor  of  heat.  If 
the  electric  force  outside  the  wire  is  very  rapidly  altering 
in  direction  or  oscillating,  the  effect  will  only  enter  to  a 
small  depth  in  the  wire  ;  the  slower  the  alterations  occur, 
the  deeper  will  the  effect  penetrate,  until  finally,  when 
the  changes  follow  one  another  infinitely  slowly,  the 
electric  effect  occupies  the  whole  mass  of  the  wire  with 
uniform  density,  giving  us  the  phenomenon  of  the  so- 
called  current. 

In  support  of  this  view  Hertz  devised  many  beautiful 
experiments,  one  or  two  of  which  may  be  described  here. 

If  a  primary  conductor  acts  through  space  upon  a  secondary 
conductor,  it  cannot  be  doubted  that  the  effect  reaches 
the  latter  from  without.  For  it  can  be  regarded  as  estab- 
lished that  the  effect  is  propagated  in  space  from  point  to 
point,  therefore  it  will  be  forced  to  meet  first  of  all  the  outer 
boundary  of  the  body  before  it  can  act  upon  the  interior  of 
it.  But  a  closed  metallic  envelope  is  shown  to  be  quite 
opaque  to  this  effect.  If  we  place  the  secondary  conductor 
in  such  a  favourable  position  near  the  primary  one  that  we 
obtain  sparks  5  to  6  millimetres  long,  and  then  surround  it 
with  a  closed  box  made  of  zinc  plate,  the  smallest  trace  of 
sparking  can  no  longer  be  perceived.  The  sparks  similarly 
vanish  if  we  entirely  surround  the  primary  conductor  with 
a  metallic  box.  It  is  well  known  that  with  relatively  slow 
variations  of  current  the  integral  force  of  induction  is  in  no 
way  altered  by  a  metallic  screen.  This  is,  at  the  first  glance, 
contradictory  to  the  present  contention.  However,  the  con- 
tradiction is  only  an  apparent  one,  and  is  explained  by 
considering  the  duration  of  the  effects.  In  a  similar  manner 
a  screen  which  conducts  heat  badly  protects  its  interior  com- 
pletely from  rapid  changes  of  the  outside  temperature,  less 
from  slow  changes,  and  not  at  all  from  a  continuous  rising 
or  lowering  of  the  temperature.  The  thinner  the  screen  is, 


186  THIRD   PERIOD — THE   PRACTICAL. 

the  more  are  the  rapid  variations  of  the  outside  temperature 
felt  in  its  interior. 

In  our  case  also  the  electrical  action  must  plainly 
penetrate  into  the  interior  of  the  closed  box,  if  we  only 
diminish  sufficiently  the  thickness  of  the  metal.  But 
Hertz  did  not  succeed  in  attaining  the  necessary  thinness, 
— a  box  covered  with  tinfoil  protected  completely,  and  even 
a  box  of  gilt  paper,  if  care  was  taken  that  the  edges  of  the 
separate  pieces  of  paper  were  in  metallic  contact.  In  this 
case  the  thickness  of  the  conducting  metal  was  estimated 
to  be  barely  ^V  millimetre.  To  demonstrate  this,  he  fitted 
the  protecting  envelope  as  closely  as  possible  round  the 
secondary  conductor,  and  widened  the  spark-gap  to  about 
20  millimetres,  adding  an  auxiliary  spark  -  gap  exactly 
opposite  to  it.  The  sparks  were  in  this  case  not  so  long 
as  in  the  ordinary  arrangement,  since  the  effect  of  reson- 
ance was  now  wanting,  but  they  were  still  very  brilliant. 
Between  the  ends  of  this  envelope,  then,  brilliant  sparks 
were  produced  ;  but  on  observing  the  auxiliary  spark-gap 
(through  a  wire-gauze  window  in  the  envelope),  not  the 
slightest  electrical  movement  could  be  detected  in  the 
interior. 

The  result  of  the  experiment  is  not  affected  if  the  en- 
velope touches  the  conductor  at  a  few  points  :  the  insulation 
of  the  two  from  each  other  is  not  necessary  in  order  to 
make  the  experiment  succeed,  but  only  to  give  it  the  force 
of  a  proof.  Clearly  we  can  imagine  the  envelope  to  be 
drawn  more  closely  round  the  conductor  than  is  possible 
in  the  experiment ;  indeed,  we  can  imagine  it  to  coin- 
cide with  the  outermost  layer  of  the  conductor.  Although, 
then,  the  electrical  disturbances  on  the  surface  of  our  con- 
ductor are  so  powerful  that  they  give  sparks  5  to  6  milli- 
metres long,  yet  at  -^V  millimetre  beneath  the  surface  there 
exists  such  perfect  freedom  from  disturbance  that  it  is  not 


G.   MAKCONl'S   METHOD.  187 

possible  to  obtain  the  smallest  sparks.  We  are  brought, 
therefore,  to  the  conclusion  that  what  we  call  an  induced 
current  in  the  secondary  conductor  is  a  phenomenon  which 
is  manifested  in  its  neighbourhood,  but  to  which  its  interior 
scarcely  contributes. 

One  might  grant  that  this  is  the  state  of  affairs  when  the 
electric  disturbance  is  conveyed  through  a  dielectric,  but 
maintain  that  it  is  another  thing  if  the  disturbance,  as  one 
usually  says,  has  been  propagated  in  a  conductor.  Let  us 
place  near  one  of  the  end  plates  of  our  primary  conductor  a 
conducting-plate,  and  fasten  to  it  a  long,  straight  wire :  we 
have  already  seen  (in  previous  experiments)  how  the  effect 
of  the  primary  oscillation  can  be  conveyed  to  great  distances 
by  the  help  of  this  wire.  The  usual  theory  is  that  a  wave 
travels  along  the  wire.  But  we  shall  try  to  show  that  all 
the  alterations  are  confined  to  the  space  outside  and  the 
surface  of  the  wire,  and  that  its  interior  knows  nothing 
of  the  wave  passing  over  it. 

Hertz  arranged  experiments  first  of  all  in  the  following 
manner :  A  piece  about  4  metres  long  was  removed  from 
the  wire  conductor  and  replaced  by  two  strips  of  zinc  plate 
4  metres  long  and  10  centimetres  broad,  which  were  laid 
flat  one  above  the  other,  with  their  ends  permanently 
connected  together.  Between  the  strips  along  their  middle 
line,  and  therefore  almost  entirely  surrounded  by  their 
metal,  was  laid  along  the  whole  4  metres'  length  a  copper 
wire  covered  with  gutta-percha.  It  was  immaterial  for 
the  experiments  whether  the  outer  ends  of  this  wire  were 
in  metallic  connection  with,  or  insulated  from,  the  strips : 
however,  the  ends  were  mostly  soldered  to  the  zinc  strips. 
The  copper  wire  was  cut  through  in  the  middle,  and  its  ends 
were  carried,  twisted  round  each  other,  outside  the  space 
between  the  strips  to  a  fine  spark-gap,  which  permitted 
the  detection  of  any  electrical  disturbance  taking  place 


188       THIRD  PERIOD — THE  PRACTICAL. 

in  the  wire.  When  waves  of  the  greatest  possible  intensity 
were  sent  through  the  whole  arrangement  there  was  never- 
theless not  the  slightest  effect  observable  in  the  spark-gap. 
But  if  the  copper  wire  was  displaced  anywhere  a  few  deci- 
metres from  its  position,  so  that  it  projected  just  a  little 
beyond  the  space  between  the  strips,  sparks  immediately 
began  to  pass.  The  sparks  were  the  more  intense  according 
to  the  length  of  copper  wire  extending  beyond  the  edge 
of  the  zinc  strips  and  the  distance  it  projected.  The 
unfavourable  relation  of  the  resistances  was  therefore  not 
the  cause  of  the  previous  absence  of  sparking,  for  this 
relation  had  not  been  changed ;  but  the  wire  being  in 
the  interior  of  the  conducting  mass  was  at  first  deprived 
of  the  influence  coming  from  without.  Moreover,  it  is 
only  necessary  to  surround  the  projecting  part  of  the 
wire  with  a  little  tinfoil  in  metallic  communication  with 
the  zinc  strips,  in  order  to  immediately  stop  the  sparking 
again.  By  this  means  we  bring  the  copper  wire  back 
again  into  the  interior  of  the  conductor. 

We  can  conclude,  then,  that  rapid  electric  oscillations  are 
unable  to  penetrate  metallic  sheets  or  wires  of  any  thick- 
ness, and  that  it  is,  therefore,  impossible  to  produce  sparks 
by  the  aid  of  such  oscillations  in  the  interior  of  closed 
metallic  screens.  If,  then,  we  see  sparks  so  produced  in 
the  interior  of  metallic  envelopes  which  are  nearly,  but  not 
quite,  closed,  we  must  conclude  that  the  electric  disturbance 
has  forced  itself  in  through  the  openings.  Let  us  take  a 
typical  case  of  this  kind. 

In  fig.  S!A  we  have  a  wire  cage  A  just  large  enough  to 
hold  the  spark-gap.  One  of  the  discs  a  is  in  metallic  con- 
nection with  the  central  wire;  the  other  b  is  clear  of  the 
wire  (which  passes  freely  through  the  central  hole),  but  is 
connected  to  the  metallic  tube  c,  which  completely  sur- 
rounds (without  touching  it)  the  central  wire  for  a  length 


G.  MARCONI'S  METHOD.  189 

of  1*5  metre.  On  sending  a  series  of  waves  through  this 
arrangement  in  the  direction  shown  by  the  arrow,  we 
obtain  brilliant  sparks  at  A,  which  do  not  become  materi- 
ally smaller,  if,  without  making  any  other  alteration,  we 
lengthen  the  tube  c  to  as  much  as  4  metres. 

According  to  the  old  theory,  it  would  be  said  that  the 
wave  arriving  at  A  penetrates  easily  the  thin  metallic  disc 
a,  leaps  across  the  spark-gap,  and  travels  on  in  the  central 
wire  ;  but  according  to  the  present  view,  the  explanation  is 
as  follows :  The  wave  arriving  at  A  is  quite  unable  to 
penetrate  the  disc  a ;  it  therefore  glides  over  it,  over  the 
outside  of  the  apparatus,  and  on  to  the  point  d,  4  metres 
distant.  Here  it  divides :  one  part  travels  on  along  the 
wire ;  the  other  bends  into  the  interior  of  the  tube,  and  runs 


d 


Fig.  3lA. 

back  in  the  space  between  the  tube  and  the  wire  to  the 
spark-gap,  where  it  gives  rise  to  the  sparking.  That  this 
view  is  the  correct  one  is  shown  by  the  fact,  amongst 
others,  that  every  trace  of  sparking  disappears  as  soon  as  we 
close  the  opening  at  d  by  a  tinfoil  stopper. 

Reviewing  his  experiments  on  this  subject,  Hertz  says : 
"  A  difference  will  be  noticed  between  the  views  here  put 
forward  and  the  usual  theory.  According  to  the  latter,  con- 
ductors are  represented  as  those  bodies  which  alone  take 
part  in  the  propagation  of  electric  disturbances;  non-con- 
ductors are  the  bodies  which  oppose  this  propagation.  Ac- 
cording to  our  view,  on  the  contrary,  all  transmission  of 
electrical  disturbances  is  brought  about  by  non-conductors ; 
conductors  oppose  a  great  resistance  to  any  rapid  changes  in 


190  THIRD   PERIOD — THE   PRACTICAL. 

this  transmission.  One  might  almost  be  inclined  to  main- 
tain that  conductors  and  non-conductors  should,  on  this 
theory,  have  their  names  interchanged.  However,  such  a 
paradox  only  arises  because  one  does  not  specify  the  kind  of 
conduction  or  non-conduction  considered.  Undoubtedly 
metals  are  non-conductors  of  electric  force,  and  just  for  this 
reason  they  compel  it  under  certain  circumstances  to  remain 
concentrated  instead  of  becoming  dissipated ;  and  thus  they 
become  conductors  of  the  apparent  source  of  these  forces, 
electricity,  to  which  the  usual  terminology  has  reference." * 
In  the  course  of  his  experiments  Hertz  had  succeeded  in 
producing  very  short  electric  waves  of  30  centimetres  in 
length,  the  oscillations  corresponding  to  which  could  be 
collected  by  a  concave  cylindrical  mirror  and  concentrated 
into  a  single  beam  of  electric  radiation.  According  to 
Maxwell's  theory  of  light,  such  a  beam  must  behave  like 
a  beam  of  light,  and  that  this  is  the  case  Hertz  abundantly 
proved  in  his  next  paper,  "On  Electric  Eadiation."  He 
showed  how  such  radiation  was  propagated  in  straight  lines 
like  light ;  that  it  could  not  pass  through  metals,  but  was 
reflected  by  them ;  that,  on  the  other  hand,  it  was  able  to 
penetrate  wooden  doors  and  stone  walls.  He  also  proved, 
by  setting  up  metallic  screens,  that  a  space  existed  behind 
them  in  which  no  electric  action  could  be  detected,  thus 
producing  electric  shadows  ;  and,  by  passing  the  electric 
rays  through  a  wire  grating,  he  was  able  to  polarise  them, 
just  as  light  is  polarised  by  passage  through  a  Nicol  prism. 

1  As  this  is  a  matter  of  some  complexity  to  all  who,  like  myself 
belong  to  the  old  way  of  thinking — the  ancien  regime — and  as,  more- 
over, it  is  of  great  practical  importance,  especially  as  regards  the 
proper  construction  of  lightning  protectors,  and  the  supply  mains  of 
electric  light  and  power,  I  have  thought  it  useful  to  give  in  Appendix 
B  some  extracts,  which  I  hope  will  make  the  new  views  intelligible  to 
the  ordinary  reader.  Lodge's  '  Modern  Views  of  Electricity '  should 
also  be  consulted. 


G.  MARCONI'S  METHOD.  191 

Perhaps  the  most  striking  experiment  of  all  in  this  field  was 
his  last  one,  in  which  he  directed  the  ray  on  to  a  large  pitch 
prism  weighing  12  cwts.  :  the  ray  was  deflected,  being,  in 
fact,  refracted  like  a  ray  of  light  in  a  glass  prism. 

Thus  he  gave  to  the  experimental  demonstration  of  Max- 
well's electro-magnetic  theory  of  light  its  finishing  touch, 
and  the  edifice  was  now  complete.  Hertz's  marvellous 
researches  were  presented  in  succession,  as  rapid  and  sur- 
prising almost  as  the  sparks  with  which  he  dealt,  to  the 
Berlin  Academy  of  Sciences,  between  November  10,  1887, 
and  December  13,  1889.  They  were  collected  and  pub- 
lished in  book  form,  in  1893,  under  the  title  of  'Electric 
Waves '  (English  translation  edited  by  Prof.  D.  E.  Jones), 
to  which  the  reader  is  referred  for  further  information.1 

Here  it  will  suffice,  in  conclusion,  to  briefly  sum  up  the 
chief  results  of  these  epoch-making  investigations.  In  the 
first  place,  Hertz  has  freed  us  from  the  bondage  of  the  old 
theory  of  action-at-a-distance ;  and  as  regards  electric  and 
magnetic  effects,  he  has  shown  that  they  are  propagated 
through  the  ether  which  fills  all  space  and  with  finite  veloc- 
ity. The  mysterious  darkness  which  surrounded  those  strange 
distance-actions — that  something  can  act  where  it  is  not — 
has  now  been  cleared  away.  Further,  the  identity  of  the 
form  of  energy  in  the  case  of  two  powerful  agents  in  nature 
has  been  conclusively  established ;  light  and  electrical  radia- 
tion are  essentially  the  same,  different  manifestations  of  the 
same  processes,  and  so  the  old  elastic-solid  theory  of  optics 
is  resolved  into  an  electro-magnetic  theory.  The  velocity  of 
propagation  of  light  is  the  same  as  that  of  electro-magnetic 
waves,  and  these  in  turn  obey  all  the  laws  of  optics.  The 
scope  of  optics  is  thus  enormously  widened  ;  to  the  ultra- 
violet, visible,  and  infra-red  rays,  with  their  wave-lengths 

1  Our  account  of  Hertz's  investigations  is  chiefly  drawn  from  Prof. 
Ebert's  paper  in  the  'Electrician,'  vol.  xxxiii.  pp.  333-335. 


192  THIRD   PERIOD — THE   PRACTICAL. 

of  thousandths  of  a  millimetre,  are  now  to  be  added, 
lower  down  the  scale,  electro-magnetic  waves,  producible 
in  any  length  from  fractions  of  an  inch  to  thousands  of 
miles. 

Hertz's  ordinary  waves  were  many  metres  long,  and  he 
does  not  appear  to  have  ever  worked  with  waves  of  less 
than  30  centimetres.  Righi,  however,  by  employing  ex- 
citers with  small  spheres,  obtained  waves  of  2 '5  centimetres; 
while  Prof.  Chunder  Bose  of  Calcutta,  using  little  pellets  of 
platinum,  was  able  to  produce  them  of  only  6  millimetres ! 
The  smaller  the  exciter  and  its  pellets  the  shorter  the 
waves,  until  we  come  in  imagination  to  the  exciter — the 
ultimate  molecule,  whose  waves  should  approximate  to  light. 

The  following  table  compares  approximately  some  of  the 
known  vibrations  in  ether  and  air  : — 

Ether  vibrations  per  second — 

billions  (?)  =  Rontgen  rays. 

10,000        ,.        (?)  =  Actinic       .. 

8,000        „  =  Violet         „ 

5,500        ii  =  Green         n 

4,000        it  =  Red  it 

2,800        it  =  Infra  red    .. 

1,000  to  2,000        it  =  Radiant  heat. 

50  thousands  to  2,000  billions     =  Hertzian  waves. 

Air  vibrations  per  second — 

33,000  =  Highest  audible  note. 

4,000  =  Highest  musical  note. 

2,000  =  Highest  soprano. 

150  to  500  =  Ordinary  voice. 

32  =  Lowest  musical  note. 

16  =          n       audible      n 

The  work  of  Hertz  was  immediately  taken  up,  and  is  now 
being  carried  on  (doubtless  towards  fresh  conquests,  for 
there  is  no  finality  in  science)  by  a  whole  army  of  investi- 


G.  MARCONI'S  METHOD.  193 

gators,  of  whom  we  need  only  mention  a  few — as  Lodge, 
Righi,  Branly,  Sarasin,  and  de  la  Rive — whose  discoveries, 
especially  as  regards  the  exciter  and  detector,  more  imme- 
diately concern  us  in  this  history. 

The  exciter  of  Hertz,  although  sufficing  for  his  special 
purposes,  had  the  disadvantage  that  the  sparks  in  a  short 
time  oxidised  the  little  knobs  and  roughened  their  surfaces, 
which  made  their  action  irregular  and  necessitated  their 
frequent  polishing.  Messrs  Sarasin  and  de  la  Rive  of  Geneva 
obviated  this  difficulty  by  placing  the  knobs  in  a  vessel  con- 
taining olive-oil.  The  effect  of  this  arrangement  was  at 
once  to  augment  the  sparks  at  the  detector,  so  that  when  it 
was  placed  close  to  the  exciter  the  sparks  were  a  perfect 
blaze ;  and  at  10  metres*  distance,  with  detectors  of  large 
diameter  (*75  to  1  metre),  they  were  still  very  bright  and 
visible  from  afar.  It  is  true  that  here,  too,  the  oil  carbon- 
ises in  time  and  loses  its  transparency ;  but  if  a  considerable 
quantity,  as  two  or  three  litres,  be  employed,  there  is  no 
perceptible  heating,  and  the  intensity  of  the  sparks  is  hardly 
altered,  even  after  half  an  hour's  continuous  working.  Prof. 
Righi  substituted  vaseline-oil,  made  suitably  thick  by  the  ad- 
dition of  solid  vaseline.  His  exciter  is  composed  of  two  metal 
balls,  each  set  in  an  ebonite  frame ;  a  parchment  envelope 
connects  these  frames  and  contains  the  oil  which  thus  fills 
the  spark-gap.  Righi  attributes  the  increased  efficiency  of 
his  exciter  (1)  to  the  heightening  effect  which  a  cushion  of 
(insulating)  liquid  seems  to  have  on  the  electric  potential 
which  gives  rise  to  the  sparks — a  sort  of  (to  adopt  an  ex- 
pressive French  phrase)  reculant  pour  mieux  sauter;  and 
(2)  to  some  sort  of  regularising  effect  making  their  produc- 
tion more  uniform.  Like  Sarasin  and  de  la  Rive,  he  found 
that  the  use  of  vaseline  obviated  the  necessity  of  frequent 
cleaning  of  the  knobs,  for  even  after  long  usage,  when  the 
liquid  had  become  black  and  a  deposit  of  carbon  had  formed 


194  THIRD   PERIOD — THE   PRACTICAL. 

on  the  opposing  surfaces,  the  apparatus  continued  to  work 
satisfactorily.  Eighi  also  found  that  solid  knobs  gave 
better  results  than  hollow  ones,  the  oscillations  in  the  former 
case  being  perceptible  in  the  detector  at  nearly  double  the 
distance  attained  in  the  latter  case. 

The  detector  usually  employed  by  Hertz  consisted  of  a 
metal  wire  bent  into  a  rectangle  or  a  circle  (see  fig.  31),  and 
terminated  by  two  little  knobs  between  which  the  sparks 
played.  But  this  form  is  not  obligatory  :  any  two  distinct 
conducting  surfaces  separated  by  a  spark-gap  will  serve 
equally  well.  Many  kinds  of  detectors  have  been  em- 
ployed, but  in  this  place  we  need  only  concern  ourselves 
with  those  of  the  microphonic  order,  which  alone  enter  into 
the  construction  of  the  Marconi  system  of  telegraphy.1 

Just  mentioning  the  well-known  electrical  behaviour  of 
selenium  under  the  action  of  light ;  the  fact  observed  by 
^Prof.  Minchin  that  his  delicate  "  impulsion-cells "  were 
affected  by  Hertzian  waves  ;  the  Eighi  detector,  consisting 
of  thin  bands  of  quicksilver  (as  used  for  mirrors)  rendered 
discontinuous  by  cross-lines  lightly  traced  with  a  diamond ; 
and  the  original  Lodge  "  coherer,"  consisting  of  a  metallic 
point  lightly  resting  on  a  metal  plate,2 — we  come  to  the 
special  form  known  as  Branly's  detector,  or,  as  he  prefers  to 
call  it,  the  radio-conductor. 

The  observance  of  the  phenomena  underlying  Branly's 
detector  goes  back  further  than  is  usually  supposed.  Thus, 
Mr  S.  A.  Yarley,  as  long  ago  as  1866,  noticed  some  of  them, 

1  For  other  forms  of  detectors,  based  on  physiological,  chemical, 
electrical,  thermal,  and  mechanical  principles,  see  Lodge's  '  The  Work 
of  Hertz  and  his  Successors,'  pp.  25,  56. 

2  For  the  first  suggestions  of  Lodge's  detector  see  his  paper,  "  On 
Lightning  -  Guards   for   Telegraphic   Purposes,"    '  Jour.    Inst.   Elec. 
Engs.,'  vol.  xix.  pp.  352-354.     Even  before  this  the  learned  professor 
succeeded  in  detecting  electric  waves  by  means  of  a  telephone,  '  Jour. 
Inst.  Elec.  Engs.,'  vol.  xviii.  p.  405. 


G.    MARCONI'S   METHOD.  195 

and  applied  them  in  the  construction  of  a  lightning  pro- 
tector for  telegraph  apparatus. 

In  his  paper  read  before  the  British  Association  (Liverpool 
meeting,  1870),  he  says  : — 

"  The  author,  when  experimenting  with  electric  currents 
of  varying  degrees  of  tension,  had  observed  the  very  great 
resistance  which  a  loose  mass  of  dust  composed  even  of 
conducting  matter  will  oppose  to  electric  currents  of 
moderate  tension. 

"  With  a  tension  of,  say,  fifty  Daniell  cells,  no  appreciable 
quantity  will  pass  across  the  dust  of  blacklead  or  fine  char- 
coal powder  loosely  arranged,  even  when  the  battery  poles 
are  approached  very  near  to  one  another. 

"  If  the  tension  be  increased  to,  say,  two  or  three  hundred 
cells,  the  particles  arrange  themselves  by  electrical  attraction 
close  to  one  another,  making  good  electrical  contact,  and 
forming  a  channel  or  bridge  through  which  the  electric  cur- 
rent freely  passes. 

"  When  the  tension  was  still  further  increased  to  six  or 
seven  hundred  cells  the  author  found  the  electricity  would 
pass  from  one  pole  to  the  other  through  a  considerable  in- 
terval of  the  ordinary  dust  which  we  get  in  our  rooms,  and 
which  is  chiefly  composed  of  minute  particles  of  silica  and 
alumina  mixed  with  more  or  less  carbonaceous  and  earthy 
matters. 

"Incandescent  matter  offers  a  very  free  passage  to  electrical 
discharge,  as  is  indicated  by  the  following  experiments.  The 
author  placed  masses  of  powdered  blacklead  and  powdered 
wood  charcoal  in  two  small  crucibles  ;  no  current  would  pass 
through  these  masses  whilst  they  were  cold,  however  close 
the  poles  were  approached,  without  actually  touching.  The 
battery  employed  in  this  experiment  was  only  twelve  cells. 
"  The  crucibles  were  then  heated  to  a  red  heat,  and  elec- 
tricity freely  passed  through  the  heated  powder;  and  on 


196  THIRD   PERIOD — THE  PRACTICAL. 

testing  the  resistance  opposed  by  the  heated  particles,  placing 
the  poles  1  inch  apart,  and  employing  only  six  cells,  the 
average  resistance  opposed  by  the  blacklead  was  only  four 
British  Association  units,  and  that  opposed  by  the  wood 
charcoal  five  units.  The  average  resistance  of  a  needle 
telegraph  coil  may  be  taken  at  300  units,  or  ohms  as  they 
are  now  termed. 

"  These  observations  go  to  show  that  an  interval  of  dust 
separating  two  metallic  conductors  opposes  practically  a  de- 
creasing resistance  to  an  increasing  electrical  tension,  and 
that  incandescent  particles  of  carbon  oppose  about  -^th 
part  of  the  resistance  opposed  by  a  needle  telegraph  coil. 
Reasoning  upon  these  data,  the  author  was  led  to  construct 
what  he  terms  a  'lightning-bridge,'  which  he  constructs  in 
the  following  way  : — 

"  Two  thick  metal  conductors  terminating  in  points  are 
inserted  usually  in  a  piece  of  wood.  These  points 

approach  one  another  within 
about  -rVth  of  an  inch  in  a 
chamber  cut  in  the  middle  of 
the  wood. 

"This  bridge  is  placed  in 
the  electric  circuit  in  the  most 
direct  course  which  the  light- 
ning can  take,  as  shown  in 
the  diagram  (fig.  32),  and  the 
space  separating  the  two  points 
Fig.  32.  is  filled  loosely  with  powder, 

which  is  placed  in  the  chamber, 

and  surrounds  and  covers  the  extremities  of  the  pointed 
conductors. 

"  The  powder  employed  consists  of  carbon  (a  conductor) 
and  a  non-conducting  substance  in  a  minute  state  of  division. 
The  lightning  finds  in  its  direct  path  a  bridge  of  powder, 


G.   MARCONI'S   METHOD.  197 

consisting  of  particles  of  conducting  matter  in  close  proximity 
to  one  another ;  it  connects  these  under  the  influence  of  the 
discharge,  and  throws  the  particles  into  a  highly  incandescent 
state.  Incandescent  matter,  as  has  been  already  demon- 
strated, offers  a  very  free  passage  to  electricity,  and  so  the 
lightning  discharge  finds  an  easier  passage  across  the  heated 
matter  than  through  the  coils. 

"  The  reason  a  powder  consisting  entirely  or  chiefly  of 
conducting  matter  cannot  be  safely  employed  is  that, 
although  in  the  ordinary  conditions  of  things  it  would  be 
found  to  oppose  a  practically  infinite  resistance  to  the 
passage  of  electricity  of  the  tension  of  ordinary  working 
currents,  when  a  high  tension  discharge  occurs  the  particles 
under  the  influence  of  the  discharge  will  generally  be  found 
to  arrange  themselves  so  closely  as  to  make  a  conducting 
connection  between  the  two  points  of  the  lightning-bridge. 
This  can  be  experimentally  demonstrated  by  allowing  the 
secondary  currents  developed  by  a  Buhmkorff's  coil  to  spark 
through  a  loose  mass  of  blacklead.1 

"These  lightning-bridges  have  been  in  use  since  January 
1866.  At  the  present  time  there  are  upwards  of  one 
thousand  doing  duty  in  this  country  alone,  and  not  a  single 
case  has  occurred  of  a  coil  being  fused  when  protected  by 
them. 

"  It  is  only  right,  however,  to  mention  that  three  cases, 
but  three  cases  only,  have  occurred  where  connection  was 
made  under  the  influence  of  electrical  discharge  between 
the  two  metallic  points  in  the  bridge. 

"The  protectors  in  which  this  occurred  were  amongst 
those  first  constructed,  in  which  a  larger  proportion  of  con- 
ducting matter  was  employed  than  the  inventor  now  adopts. 
The  points  also  in  those  first  constructed  were  approached 
to  -styth  of  an  inch  from  one  another ;  and  the  author  has  no 
1  See  pp.  292,  293  infra. 


198 


THIRD   PERIOD — THE   PRACTICAL. 


doubt,  from  an  examination  of  the  bridges  afterwards,  that 
under  the  influence  of  a  high  tension  discharge  connection 
was  made  between  the  two  metallic  points  by  a  bridge  of 
conducting  matter,  arranged  closely  together,  and  if  the 
instruments  had  been  shaken  to  loosen  the  powder,  all  would 
have  been  put  right." 1 

In  the  little-known  researches  of  the  Italian  professor, 
Calzecchi-Onesti,  we   find  this  curious  phenomenon  again 


Fig.  33. 

cropping  up,  and  in  a  form  more  apposite  from  our  present 
point  of  view.  In  1884-85  Prof.  Calzecchi-Onesti  found 
that  copper  filings  heaped  between  two  plates  of  brass  were 
conductors  or  non-conductors  according  to  the  degree  of  heap- 
ing and  pressure,  and  that  in  the  latter  case  they  could  be 
made  conductors  under  the  influence  of  induction.  Fig.  33 
illustrates  his  experiment.  In  the  circuit  of  a  small  battery 
A  is  placed  a  telephone  B,  a  galvanometer  o,  and  two  brass 
plates  D  E,  separated  by  the  copper  filings.  So  long  as  the 
short-circuit  arrangement  F  (a  wire  dipping  into  mercury)  is 

1  Sir  "Win.  Preece  tells  us  the  arrangement  acted  well,  but  was  sub- 
ject to  what  we  now  call  coherence,  which  rendered  the  cure  more 
troublesome  than  the  disease,  and  its  use  had  to  be  abandoned. 


G.  MARCONI'S  METHOD.  199 

open,  the  galvanometer  shows  traces  of  a  very  feeble  current 
across  the  filings ;  but,  on  dipping  the  wire  for  a  moment 
into  the  mercury  and  then  withdrawing  it,  a  sharp  click  is 
heard  in  the  telephone,  and  the  galvanometer  indicates  the 
passing  of  a  strong  current,  showing  that  the  filings  must 
now  be  conductors.  This  change  he  traced  to  the  induced 
current  of  the  telephone  coil  (the  extra-current  direct)  at  the 
moment  of  opening  the  short-circuit.  He  repeated  this 
experiment  with  various  powders  or  filings  of  metal,  and 
ended  by  showing  that  rapid  interruptions  of  a  circuit  con- 
taining an  inductance  coil,  or  contact  with  an  electrified 
body,  or  electro-static  discharges  were  sufficient  to  make  the 
filings  conductive. 

For  these  experiments  Calzecchi-Onesti  had  actually  con- 
structed a  glass  tube  (35  millimetres  long  and  10  milli- 
metres internal  diameter)  only  differing  from  that  shown 
in  fig.  34  in  that  it  was  revolvable  on  its  axis,  for  the 
purpose  of,  as  we  now  say,  decohering  the  particles,  one 
revolution  or  less  of  the  tube  sufficing  for  this  purpose. 

These  observations  were  published  in  *  II  Nuovo  Cimento/ 
October  15,  1884,  and  March  2,  1885,1  but  attracted  no 
attention ;  and  it  was  only  after  Prof.  E.  Branly,  of  the 
Catholic  University  of  Paris,  had  published  his  results  in 
1890  that  the  earlier  discoveries  of  Varley  and  Onesti  came 
to  be  remembered  and  appreciated  at  their  proper  value. 

Prof.  Branly's  investigations  are  very  clearly  described  in 
'La  Lumiere  Electrique,  May  and  June  1891. '2  As  this 
now  classic  paper  deals  with  facts  which  are  at  the  very 

1  See  also  'Jour.  Inst.  Elec.  Engs.,'  vol.  xvi.  p.  156.     In  March 
1886  Calzecchi-Ouesti  suggested  the  use  of  his  tube  as  a  detector  of 
seismical  movements,  thinking  that  the  conductivity  of  the  filings, 
imparted  by  one  or  other  of  the  above  means,  would  be  destroyed  by 
even  the  smallest  earth  movement. 

2  See  also  an  abstract  in  the  '  Electrician,'  vol.  xxvii.  pp.  221,  448. 


200  THIRD   PERIOD — THE  PRACTICAL. 

foundation  of  the  Marconi  system,  I  give  some  extracts 
from  it  in  Appendix  C.  Here,  therefore,  I  need  only  say 
that  Branly  verified  and  extended  Calzecchi-Onesti's  obser- 
vations, and  made  the  further  (and  for  our  purpose  vital) 
discovery  that  conducting  power  was  imparted  to  filings  by 
electric  discharges  in  their  vicinity,  and  that  this  power  can 
be  destroyed  by  simply  shaking  or  tapping  them. 

The  Branly  detector,  as  constructed  by  Prof.  Lodge,  is 
shown  in  fig.  34.  It  consists  of  an  ebonite  or  glass  tube 
about  7  inches  long,  half-an-inch  outer  diameter,  and  fitted 
at  the  ends  with  copper  pistons,  which  can  be  regulated  to 
press  on  the  filings  with  any  required  degree  of  pressure. 


Fig.  34. 

To  bring  back  the  filings  to  their  normal  non-conducting 
state,  Lodge  applied  to  the  tube  a  mechanical  tapper,  worked 
either  by  clockwork  or  by  a  trembling  electrical  mechanism. 
These,  then,  the  exciters  and  the  detectors  of  Hertzian 
waves,  are  the  bricks  and  mortar,  so  to  speak,  of  the  Marconi 
system,  and  it  now  only  remains  to  see  how  they  have  been 
shaped  and  put  together  to  produce  a  telegraph  without 
connecting  wires,  which  is  the  realisation  of  the  dream  of 
Steinheil  in  1838.  And,  first,  we  must  notice  two  or  three 
applications,  or  suggested  applications,  which  preceded  the 
announcement  of  Marconi's  invention.  We  do  so  without 
in  the  least  meaning  to  detract  one  iota  from  the  merit  due 
to  the  young  Irish-Italian  inventor,1  for  we  believe  the  idea 

1  Guglielmo  Marconi  was  born  in  Bologna,  25th  April  1874,  and 
was  educated  at  Leghorn,  and  at  the  Bologna  University,  where  he 
was  a  sedulous  attendant  at  the  lectures  of  Prof.  A.  Righi. 


G.  MARCONI'S  METHOD.  201 

was  entirely  original  with  him,  and  was  unprompted  by  any 
suggestions  from  outside.  The  history  of  the  applications 
of  science  to  art  shows  us  that  these  applications  often  occur 
simultaneously  to  several  persons,  and  it  is,  therefore,  not 
strange  that  such  is  the  case  in  the  present  instance. 

Sir  William  Crookes,  the  eminent  chemist  and  elec- 
trician, was,  I  believe,  the  first  to  distinctly  foresee  the 
applicability  of  Hertzian  waves  to  practical  telegraphy.  In. 
a  very  interesting  paper  on  "Some  Possibilities  of  Elec- 
tricity," x  he  gives  us  the  following  marvellous  forecast  of 
the  Marconi  system: — 

"  Eays  of  light  will  not  pierce  through  a  wall,  nor,  as  we 
know  only  too  well,  through  a  London  fog;  but  electrical 
vibrations  of  a  yard  or  more  in  wave-length  will  easily 
pierce  such  media,  which  to  them  will  be  transparent.  Here 
is  revealed  the  bewildering  possibility  of  telegraphy  without 
wires,  posts,  cables,  or  any  of  our  present  costly  appliances. 
Granted  a  few  reasonable  postulates,  the  whole  thing  comes 
well  within  the  realms  of  possible  fulfilment.  At  present 
experimentalists  are  able  to  generate  electric  waves  of  any 
desired  length,  and  to  keep  up  a  succession  of  such  waves 
radiating  into  space  in  all  directions.  It  is  possible,  too, 
with  some  of  these  rays,  if  not  with  all,  to  refract  them 
through  suitably  shaped  bodies  acting  as  lenses,  and  so  to 
direct  a  sheaf  of  rays  in  any  given  direction.  Also  an  ex- 
perimentalist at  a  distance  can  receive  some,  if  not  all,  of 
these  rays  on  a  properly  constituted  instrument,  and  by  con- 
certed signals  messages  in  the  Morse  code  can  thus  pass 
from  one  operator  to  another. 

"  What  remains  to  be  discovered  is — firstly,  simpler  and 
more  certain  means  of  generating  electrical  rays  of  any 

1  '  Fortnightly  Keview,'  February  1892,  p.  173.  Prof.  Lodge  has  since 
kindly  pointed  out  to  me  that  about  1890  Prof.  E.  Threlfall  of  Sydney, 
N.S.  Wales,  threw  out  a  suggestion  of  the  same  kind  at  a  meeting  of 
the  Australasian  Association  for  the  Advancement  of  Science. 


202        THIRD  PERIOD — THE  PRACTICAL. 

desired  wave-length,  from  the  shortest,  say  a  few  feet,  which 
will  easily  pass  through  buildings  and  fogs,  to  those  long 
waves  whose  lengths  are  measured  by  tens,  hundreds,  and 
thousands  of  miles ;  secondly,  more  delicate  receivers  which 
will  respond  to  wave-lengths  between  certain  defined  limits 
and  be  silent  to  all  others ;  and  thirdly,  means  of  darting 
the  sheaf  of  rays  in  any  desired  direction,  whether  by  lenses 
or  reflectors,  by  the  help  of  which  the  sensitiveness  of  the 
receiver  (apparently  the  most  difficult  of  the  problems  to  be 
solved)  would  not  need  to  be  so  delicate  as  when  the  rays 
to  be  picked  up  are  simply  radiating  into  space,  and  fading 
away  according  to  the  law  of  inverse  squares.  .  .  . 

"At  first  sight  an  objection  to  this  plan  would  be  its 
want  of  secrecy.  Assuming  that  the  correspondents  were  a 
mile  apart,  the  transmitter  would  send  out  the  waves  in  all 
directions,  and  it  would  therefore  be  possible  for  any  one 
living  within  a  mile  of  the  sender  to  receive  the  communica- 
tion. This  could  be  got  over  in  two  ways.  If  the  exact 
position  of  both  sending  and  receiving  instruments  were 
known,  the  rays  could  be  concentrated  with  more  or  less 
exactness  on  the  receiver.  If,  however,  the  sender  and 
receiver  were  moving  about,  so  that  the  lens  device  could 
not  be  adopted,  the  correspondents  must  attune  their  instru- 
ments to  a  definite  wave-length,  say,  for  example,  50  yards. 
I  assume  here  that  the  progress  of  discovery  would  give 
instruments  capable  of  adjustment  by  turning  a  screw,  or 
altering  the  length  of  a  wire,  so  as  to  become  receptive  of 
waves  of  any  preconcerted  length.  Thus,  when  adjusted  to 
50-yard  waves,  the  transmitter  might  emit,  and  the  receiver 
respond  to,  rays  varying  between  45  and  55  yards,  and  be 
silent  to  all  others.  Considering  that  there  would  be  the 
whole  range  of  waves  to  choose  from,  varying  from  a  few 
feet  to  several  thousand  miles,  there  would  be  sufficient 
secrecy,  for  the  most  inveterate  curiosity  would  surely  recoil 


G.  MARCONI'S  METHOD.  203 

from  the  task  of  passing  in  review  all  the  millions  of  pos- 
sible wave-lengths  on  the  remote  chance  of  ultimately  hitting 
on  the  particular  wave-length  employed  by  those  whose 
correspondence  it  was  wished  to  tap.  By  coding  the 
message  even  this  remote  chance  of  surreptitious  tapping 
could  be  rendered  useless. 

"  This  is  no  mere  dream  of  a  visionary  philosopher.  All 
the  requisites  needed  to  bring  it  within  the  grasp  of  daily 
life  are  well  within  the  possibilities  of  discovery,  and  are  so 
reasonable  and  so  clearly  in  the  path  of  researches  which 
are  now  being  actively  prosecuted  in  every  capital  of  Europe, 
that  we  may  any  day  expect  to  hear  that  they  have  emerged 
from  the  realms  of  speculation  into  those  of  sober  fact. 
Even  now,  indeed,  telegraphing  without  wires  is  possible 
within  a  restricted  radius  of  A  few  hundred  yards,  and  some 
years  ago  I  assisted  at  experiments  where  messages  were 
transmitted  from  one  part  of  a  house  to  another  without  an 
intervening  wire  by  almost  the  identical  means  here  de- 
scribed."1 

In  1893  Nikola  Tesla,  the  lightning-juggler,  proposed  to 
transmit  electrical  oscillations  to  any  distance  through  space, 
by  erecting  at  each  end  a  vertical  conductor,  connected  at 
its  lower  end  to  earth  and  at  its  upper  end  to  a  conducting 
body  of  large  surface.  Owing  to  press  of  other  work  this 
experiment  was  never  tried,  and  so  has  remained  a  bare 
suggestion.2 

At  the  Eoyal  Institution,  June  1,  1894,  and  later  in  the 

1  The  experiments  here  referred  to  were  made  in  1879  by  Prof. 
Hughes,  who  has  kindly  supplied  the  author  with  an  account  of 
them.     As  this  interesting  and  important  document  was  received 
too  late  for  embodiment  in  the  text,   I  must  ask  my  readers  to 
refer  to  Appendix  D. 

2  See   a  full  account   of  Tesla's   marvellous  researches  in  '  Jour. 
Inst.  Elec.  Engs.'  for  1892,  No.  97,  p.  51  ;  also  'Pearson's  Magazine,' 
May  1899,  for  some  of  his  latest  wonders. 


204  THIRD  PERIOD — THE  PRACTICAL. 

same  year  at  the  Oxford  meeting  of  the  British  Association, 
Prof.  Lodge  showed  how  his  form  of  Branly  detector  could 
be  made  to  indicate  signals  at  a  distance  of  about  150  yards 
from  the  exciter,  but  •  at  this  time  the  applicability  of  his 
experiment  to  practical  long-distance  telegraphy  was  hardly 
grasped  by  him.  Kef  erring  to  this  in  his  *  Work  of  Hertz ' 
(p.  67,  1897  edition),  he  says  : — 

"  Signalling  was  easily  carried  on  from  a  distance  through 
walls  and  other  obstacles,  an  emitter  being  outside  and  a 
galvanometer  and  detector  inside  the  room.  Distance  with- 
out obstacle  was  no  difficulty,  only  free  distance  is  not  very 
easy  to  get  in  a  town,  and  stupidly  enough  no  attempt  was 
made  to  apply  any  but  the  feeblest  power  so  as  to  test  how 
far  the  disturbance  could  really  be  detected. 

"Mr  Rutherford,  however,  with  a  magnetic  detector  of 
his  own  invention,  constructed  on  a  totally  different  prin- 
ciple, and  probably  much  less  sensitive  than  a  coherer,  did 
make  the  attempt  (June  1896),  and  succeeded  in  signalling 
across  half  a  mile  full  of  intervening  streets  and  houses  at 
Cambridge." 

Between  1895  and  1896  Messrs  Popoff,  Minchin, 
Rutherford,  and  others  applied  the  Hertzian  method  to 
the  study  of  atmospheric  electricity ;  and  their  mode  of 
procedure,  in  the  use  of  detectors  in  connection  with  vertical 
exploring  rods,  was  much  the  same  as  that  of  Marconi. 

Popoff's  arrangement  especially  is  so  like  Marconi's  that 
we  are  tempted  to  reproduce  it  from  the  '  Elektritchestvo ' 
of  St  Petersburg  for  July  1896.  Fig.  35  shows  the 
apparatus,  the  action  of  which  is  easily  understood.  The 
relay  actuates  another  circuit,  not  shown,  containing  a 
Richard's  register,  which  plots  graphically  the  atmospheric 
perturbations. 

Prof.  Popoff's  plans  were  communicated  to  the  Physico- 
Chemical  Society  of  St  Petersburg  in  April  1895  ;  and  in  a 


G.  MARCONI'S  METHOD. 


205 


further  note,  dated  December  1895,  he  adds  :  "  I  entertain 
the  hope  that  when  my  apparatus  is  perfected  it  will  be 
applicable  to  the  transmission  of  signals  to  a  distance  by 
means  of  rapid  electric  vibrations — when,  in  fact,  a  suffi- 
ciently powerful  generator  of  these  vibrations  is  discovered." 
We  shall  see  presently  that  Popoff  was  looking  in  the  wrong 


LARTH 


Pile 


Fig.  35. 


Relay 


direction.  It  was  not  so  much  a  more  powerful  generator 
(which  is  easily  obtained)  that  was  wanted,  as  a  detector 
more  suitable  for  signalling  purposes  than  the  Branly-Lodge 
arrangement  which  he  used.  Mr  Marconi,  we  shall  see, 
supplied  this,  and  in  doing  so  did  the  main  thing  necessary 
to  make  Popoff  s  apparatus  a  practical  telegraph.1 

1  On  hearing  of  Marconi's  success  in  England,  Prof.  Popoff  tried  his 
apparatus  quasi  telegraph  (presumably  using  more  sensitive  detectors), 
and  in  April  1897  succeeded  in  signalling  through  a  space  of  1  kilo- 
metre, then  through  1£,  and  finally  through  5  kilometres,  with  vertical 
wires,  18  metres  high. 


206  THIRD   PERIOD — THE   PRACTICAL. 

Sir  Wm.  Preece  tells  us  that  in  December  1895  Captain 
Jackson,  K.N.,  commenced  working  in  the  same  direction, 
and  succeeded  in  getting  Morse  signals  through  space  before 
be  heard  of  Marconi.  His  experiments,  however,  were 
treated  as  confidential  at  the  time,  and  have  not  been 
published. 

In  1896  the  Eev.  F.  Jervis-Smith  had  a  detector  made 
of  finely-powdered  carbon,  such  as  is  used  in  incandescent 
electric  lamps  (in  fact,  a  kind  of  carbon-powder  telephone), 
for  observing  atmospheric  electricity ;  and  a  little  later  (in 
the  spring  of  1897)  he  actually  applied  it  to  telegraphic 
purposes  over  a  distance  of  more  than  a  mile.  This  form 
of  detector  was  to  a  certain  extent  self-restoring  and  did 
'•"''not  require  any  tapping  device.1 

Finally,  in  1896,  Mr  Charles  A.  Stevenson,  of  whose 
work  in  wireless  telegraphy  we  have  already  spoken  (p. 
119,  supra),  had  the  idea  of  utilising  the  coherer  principle 
in  the  construction  of  a  relay  of  great  delicacy.2  He 
does  not,  however,  enter  into  details,  merely  referring 
to  his  "relay  with  metallic  powder  between  two  electro- 
magnets "  in  the  course  of  some  remarks  on  Prof.  Blake's 
experiments  in  America  (p.  121,  supra). 

I  now  come  to  Mr  Marconi,  whose  special  application  of 
Hertzian  waves  to  practical  telegraphy  will  be  easily  under- 
stood if  my  readers  have  carefully  followed  me  in  the 
preceding  pages. 

His  apparatus  for  short  distances,  with  clear  open  spaces, 
consists  of  the  parts  which  are  shown  in  diagrammatic  form 

1  Recently,  October  1898,  I  have  seen  it  stated  that  Signer  Rovelli 
has  found  that  a  detector  made  of  iron  filings  acts  well,  and  requires 
no  tapping.     See  also  Prof.  Chunder  Bose's  important  researches  en 
potassium  as  a  self -restoring  detector — 'Proceedings  Royal  Society/ 
July  1899. 

2  'Electrical  Review,'  August  1896. 


G.  MARCONI'S  METHOD. 


207 


in  figs.  36,  37,  38,  and  39.     The  apparatus  at  the  sending 
station  consists  of  a  modified  Rigid  exciter  A  (fig.  36),  a 
Kuhmkorff  coil  B,  a  battery 
of   a   few  cells   o,   and   a 
Morse  key  K. 

The  exciter  consists  of 
two  solid  brass  spheres  A 
B  (fig.  37),  11  centimetres 
in  diameter  and  1  milli- 
metre apart.  The  spheres  /\J. 
are  fixed  in  an  oil -tight 
case  of  parchment  or 
ebonite,  so  that  an  outside 
hemisphere  of  each  is  ex- 
the  other  hemi- 


Fig.  36. 


spheres  being  immersed  in  vaseline-oil  thickened  by  the 
addition  of  a  little  vaseline.  As  already  explained,  the 
use  of  oil  has  several  advantages,  all  of  which  combine  to 


Fig.  37. 

increase  the  effectiveness  of  the  arrangement,  and  therefore 
the  distance  at  which  the  effect  can  be  detected.  It  keeps 
the  opposing  surfaces  of  the  spheres  clean  and  bright,  and 
gives  to  the  electric  sparks  a  more  uniform  and  regular 


208  THIRD   PERIOD — THE   PRACTICAL. 

character,  which  is  best  adapted  for  signalling.1  Two  small 
balls,  also  of  solid  brass,  a  I,  are  fixed  in  a  line  with  the 
large  ones,  usually  about  2*5  centimetres  apart,  and  are 
capable  of  adjustment.  The  larger  the  spheres  and  balls, 
and  the  greater  the  distances  separating  them  (compatible 
with  the  power  of  the  induction  coil),  the  higher  is  the 
potential  of  the  sparks  and  the  greater  the  oscillations 
to  which  they  give  rise,  and  consequently  the  greater  the 
distance  at  which  they  are  perceptible.  The  balls  a  b  are 
connected  each  to  one  end  of  the  secondary  coil  of  the 
Buhmkorff  apparatus  B.  The  primary  wire  of  the  induction 
coil  is  excited  by  the  battery  c,  thrown  in  and  out  of 
circuit  by  the  key  K.  The  efficiency  of  the  sending 
apparatus  depends  greatly  on  the  power  and  constancy  of 
the  induction  coil :  thus  a  coil  yielding  a  6-inch  spark  will 
be  effective  up  to  three  or  four  miles ;  but  for  greater 
distances  than  this  more  powerful  coils,  as  one  emitting 
10-inch  sparks,  must  be  used.2 

The  various  parts  of  the  sending  apparatus  are  generally 
so  constructed  and  adjusted  as  to  emit  per  second  about  250 
million  waves  of  about  1*3  metres  long. 

At  the  receiving  station  N  (fig.  38)  is  Marconi's  special 
form  of  the  Eranly-Lodge  detector,  shown  full  size  in  fig.  39. 
This  is  the  part  which  gave  him  the  most  trouble.  While 

1  Mr  Marconi's  later  experience  has  led  him  to  doubt  these  advan- 
tages, and  to  discard  the  use  of  oil.     He  now  uses  simply  a  single 
spark-gap  between  two  balls,  as  a  6  in  fig.  37.    See  '  Jour.  Inst.  Elec. 
Engs.,'  No.  139,  p.  311,  or  p.  232  infra. 

2  But  there  is  a  limit :  powerful  induction  coils  of  the  Kuhmkorff 
kind  are  difficult  to  make  and  keep  in  order,  and  do  not  by  reason  of 
their  residual  magnetism  admit  of  the  very  rapid  make-and-break 
action  required.     Doubtless  other  and  more  effective  means  of  excite- 
ment will  soon  be  discovered,  as  Tesla's  oscillators,  or  by  the  use  of 
Wehnelt's  electrolytic  contact-breaker,  which  can  be  made  to  inter- 
rupt a  current  one  thousand  times  and  more  per  second.     See  '  Jour. 
Inst.  Elec.  Engs.,'  No.  131,  p.  317. 


G.  MARCONI'S  METHOD. 


209 


for  laboratory  experiments  any  detector  sufficed  to  give  in- 
dications on  a  sensitive  mirror  galvanometer  at  a  distance  of 
a  few  yards,  Mr  Marconi  had  to  seek  a  thoroughly  practical 
and  reliable  arrangement  which  could  stand  the  compara- 
tively rough  usage  of  everyday  work,  be  restorable  to  its 


Fig.  38. 

normal  condition  (after  every  wave)  with  the  utmost  cer- 
tainty, and,  at  the  same  time,  be  sufficiently  responsive  to  the 
very  feeble  waves  which  are  found  at  a  great  distance  from 
the  source,  so  as  to  allow  of  the  passage  of  a  current  strong 
enough  to  actuate  a  telegraph  relay.  His  detector  consists 


Fig.  39. 

of  a  glass  tube,  4  centimetres  long  and  2 '5  millimetres 
interior  diameter,  into  which  two  silver  pole-pieces,  1  milli- 
metre apart,  are  tightly  fitted,  so  as  to  prevent  any  scat- 
tering of  the  powder.  The  small  intervening  space  is 
filled  with  a  mixture  of  96  parts  of  nickel  and  4  of  silver, 
not  too  finely  powdered,  and  worked  up  with  a  trace  of 
mercury. 

o 


210  THIRD   PERIOD — THE   PRACTICAL. 

By  increasing  the  proportion  of  silver  powder  the  sensi- 
tiveness of  the  detector  is  increased  pro  raid;  but  it  is 
better  for  ordinary  work  not  to  have  too  great  sensitiveness, 
as  the  detector  then  too  readily  responds  to  atmospheric 
electricity  and  other  stray  currents.  Similarly,  the  smaller 
the  powder  space  the  more  sensitive  is  the  instrument ;  but 
if  too  small,  the  action  is  capricious.  The  quantity  of 
powder  required  is,  of  course,  very  small,  but  it  must  be 
treated  with  care  :  it  must  neither  be  too  compressed  nor 
too  loose.  If  too  tight  the  action  is  irregular,  and  often  the 
particles  will  not  return  to  their  normal  condition,  or  "  deco- 
here," as  Lodge  expresses  it ;  if  too  loose  coherence  is  slight, 
and  the  instrument  is  not  sufficiently  sensitive.  The  best 
adjustment  is  obtained  when  the  detector  works  well  under 
the  action  of  the  sparks  from  a  small  electric  trembler  at 
one  metre's  distance.  The  tube  is  then  hermetically  sealed, 
having  been  previously  exhausted  of  air  to  about  ^  ^Q  0  th 
of  an  atmosphere.  This,  though  not  essential,  is  desirable, 
as  it  prevents  the  oxidation  of  the  powder. 

In  its  normal  condition  the  metallic  powder,  as  already 
stated,  is  practically  a  non-conductor,  offering  many  meg- 
ohms resistance.  The  particles  (to  use  Preece's  expressive 
words)  lie  higgledy-piggledy,  anyhow,  in  disorder.  They 
lightly  touch  each  other  in  a  chaotic  manner;  but  when 
electric  waves  fall  upon  them  they  are  polarised — order  is 
installed — they  are  marshalled  in  serried  ranks  and  press  on 
each  other, — in  a  word,  they  cohere,  electrical  continuity  is 
established,  and  a  current  passes,  the  resistance  falling  from 
practical  insulation  to  a  few  ohms  or  a  few  hundred  ohms 
according  to  the  energy  of  the  received  impacts.  Usually  it 
ranges  from  100  to  500  ohms.1 

1  The  action  of  the  detector  is  hardly  yet  understood,  but  recent 
investigations  of  Arons  (Broca,  '  Te'le'graphie  sans  Fils,'  Paris,  1899, 
p.  117),  of  Sundorph  ('Science  Abstracts,'  No.  23,  p.  757),  and  of 


G.  MARCONI'S  METHOD.  211 

The  detector  is  included  in  the  circuit  of  two  electro- 
magnetic impedance  or  choking  coils  n  n',  a  local  battery  of 
one  or  two  Leclanche  cells  P,  and  a  fairly  sensitive  polarised 
relay  as  ordinarily  used  in  telegraphy  E.  The  impedance  or 
choking  coils,  consisting  of  a  few  turns  of  insulated  copper 
wire  on  a  glass  tube,  containing  an  iron  bar  5  or  6  centi- 
metres long,  are  intended  to  prevent  the  electric  energy 
escaping  through  the  relay  circuit.  Prof.  Silvanus  Thomp- 
son doubts  the  efficacy  of  this  contrivance,  but  Mr 
Marconi's  experience  shows  its  great  utility.  Thus,  when 
the  coils  are  removed,  all  other  things  remaining  the  same, 
the  signalling  distance  is  reduced  by  nearly  one-half. 

A  A'  are  resonance  plates  or  wings  (copper  strips)  whose 
dimensions  must  be  adjusted  so  as  to  bring  the  detector 
into  tune  electrically  with  the  exciter. 

The  relay  actuates  two  local  circuits  on  the  parallel  or 
shunt  system,  one  containing  an  ordinary  Morse  instrument 
M,  and  the  other  the  tapper  s.  The  relay  and  tapper  are 
provided  with  small  shunt  coils  s1  and  s2  to  prevent  sparking 
at  the  contacts,  which  would  otherwise  impair  the  good 
working  of  the  detector.  The  Morse  instrument  and  the 
tapper  may  also  be  connected  in  series  in  one  circuit,  in 
which  case  the  former  may  be  made  to  act  as  a  buzzer,  the 
signals  being  read  by  sound.  Indeed,  the  Morse  machine 
may  be  left  out  altogether  and  the  signals  be  read  from  the 
sound  of  the  tapper  alone.  The  printing  lever  of  the  Morse 
is  so  adjusted — an  easy  matter — as  not  to  follow  the  rapid 
makes  and  breaks  of  the  local  current  caused  by  the  action 
of  the  tapper.  Consequently,  although  the  current  in  the 


Tommasina  ('Electrician,'  vol.  xliv.  p.  213)  seem  to  bear  out  the  view 
adopted  in  the  text.  Compare  Prof.  Lodge's  views  re  coherence  in 
his  'Work  of  Hertz/  pp.  22,  70.  Also  Lamotte's  excellent  article  on 
"Cohe'reurs  ou  Radioconducteurs,"  'L'^lclairage  ihectrique,'  Paris, 
March  31,  1900. 


212  THIRD   PERIOD — THE  PRACTICAL. 

coils  of  the  Morse  is  rapidly  discontinuous,  the  lever  remains 
down  (and  prints)  so  long  as  the  detector  is  influenced  by 
the  waves  sent  out  by  the  exciter.  In  this  way  the  lever 
gives  an  exact  reproduction  of  the  movements  of  the  distant 
sending  key,  dots  and  dashes  at  the  key  coming  out  as  dots 
and  dashes  in  the  Morse.  The  speed  at  which  signalling 
can  be  carried  on  is  but  little  slower  than  that  in  ordinary 
(Morse)  telegraphy,  fifteen  words  a  minute  being  easily 
attained. 

In  practice,  the  sending  part  of  the  apparatus  should  be 
screened  as  much  as  possible  by  interposed  metal  plates  from 
the  receiving  instruments,  so  as  to  prevent  local  inductive 
interferences ;  or  better,  the  detector  may  be  shut  up  in  a 
metal  box. 

This  arrangement  is  effective  for  short  distances,  up  to 
two  miles,  with  clear  open  spaces,  especially  if  metallic 
reflectors  are  erected  behind  the  exciter  and  detector,  and 
carefully  focussed  so  as  to  throw  the  electric  rays  in  the 
right  direction.  But  for  long  distances,  and  where  obstacles 
intervene,  as  trees,  houses,  hills  —  in  fact,  for  practical 
purposes  —  certain  modifications  are  necessary  which  are 
shown  in  fig.  40.  Eeflectors  are  discarded  which  are 
troublesome  and  expensive  to  make  and  difficult  to  adjust 
One  knob  of  the  exciter  is  connected  to  a  stout  insulated 
copper  wire,  led  to  the  top  of  a  mast  and  terminating  in  a 
square  sheet  or  a  cylinder  of  zinc,  which  Marconi  calls  a 
"  capacity  area."  For  still  greater  distances  the  wire  may 
be  flown  from  a  kite  or  balloon1  covered  with  tinfoil. 

1  In  a  recent  popular  lecture  it  is  seriously  stated  that,  when  kites 
are  used  to  carry  the  conductors,  "  the  electricity  obtained  from  the 
air,  when  they  were  flown  high  enough,  was  sufficient  to  enable  the 
operator  to  do  away  with  a  primary  battery"  !  ('  Electrical  Engineer,' 
October  1,  1897).  This  is  the  Mahlon  Loomis  idea  redivivus  (see 
p.  68  supra),  and  is  as  true  as  another  "  vulgar  error  " — to  wit,  that 
Marconi,  and  now  Tesla,  can  explode  torpedoes  and  powder-magazines 


G.  MARCONI'S  METHOD. 


213 


The  other  knob  of  the   exciter   is   connected   to   a  good 
earth. 

The  exciting  apparatus  is  adapted  and  adjusted  for  the 
emission  into  space  of  much  longer  waves  than  those  men- 
tioned on  page  208.  The  wave-length  is  determined  by  the 
height  of  the  vertical  wire,  being  approximately  equal  to 


Fig.  40. 

four  times  the  height,  so  that  in  long-distance  signalling  the 
Marconi  waves  may  be  many  hundreds  of  feet  long. 

At  the  receiving  station  the  resonance  wings  of  the 
detector  are  discarded,  and  one  side  is  connected  to  a  vertical 
wire  and  the  other  side  to  earth,  as  in  the  case  of  the  exciter. 
Of  course,  in  practice  only  one  vertical  wire  is  required  at 

at  their  own  sweet  will.  This,  of  course,  might  be  done,  if  they 
could  plant  a  properly  adjusted  exploding  apparatus  near  the  powder ; 
but  if  they  could  do  this,  they  could,  as  Preece  says,  do  many  other 
funny  things. 


214  THIRD   PERIOD — THE  PRACTICAL. 

each  station,  as  by  means  of  a  switch  it  can  be  connected 
with  the  exciter  for  sending,  or  with  the  detector  for  re- 
ceiving, as  may  be  necessary.  The  parallelism  of  the  wires 
and  plates,  x  and  y,  should  be  preserved  as  much  as  possible 
in  order  to  obtain  the  best  effects. 

The  raison  d'etre  of  the  earth  connections  is  not  yet 
clearly  understood.  An  earth  wire  on  the  exciter  for  long 
distances  is  essential,  but  at  the  detector  it  may  apparently 
be  dispensed  with  without  any  (appreciable)  effect.1 

However  this  may  be,  an  earth  wire  (and  a  good  one  too) 
should  be  used  on  the  detector  as  well  as  on  the  exciter,  if 
only  as  a  protection  from  lightning.  The  vertical  wire  is 
practically  a  lightning  -  catcher,  and  the  detector  is  an 
excellent  lightning-guard  when  connected  to  earth.  But  if 
disconnected  from  earth,  and  lightning  strikes  the  wire, 
then  we  may  expect  all  the  disastrous  results  which  follow 
from  a  badly  constructed  or  defective  lightning-protector. 
The  fear,  then,  that  the  Marconi  apparatus  is  especially 
dangerous  may  be  put  aside.  Being  an  excellent  lightning- 
conductor  and  lightning-guard  in  one,  it  may,  in  my  opinion, 
be  safely  used,  even  in  a  powder-magazine. 

From  a  long  series  of  experiments  in  Italy  in  1895  Mr 
Marconi  worked  out  a  law  of  distance  which  all  his  later 
experience  seems  to  verify.  "  The  results,"  he  says,  "  showed 
that  the  distance  at  which  signals  could  be  obtained  varied 
approximately  as  the  square  of  the  height  of  the  capacity 
areas  from  earth,  or,  perhaps,  as  the  square  of  the  length  of 
the  vertical  conductors.  This  law  furnishes  us  with  a  safe 
means  of  calculating  what  length  the  vertical  wire  should 
be  in  order  to  obtain  results  at  a  given  distance.  The  law 
has  never  failed  to  give  the  expected  results  across  dear 
space  in  any  installation  I  have  carried  out,  although  it 
usually  seems  that  the  distance  actually  obtained  is  slightly 

1  'Jour.  Inst.  Elec.  Engs.,'  No.  137,  pp.  801,  802,  900,  918,  946,  962. 


G.  MARCONI'S  METHOD.  215 

in  excess.  I  find  that,  with  parity  of  other  conditions, 
vertical  wires  20  feet  long  are  sufficient  for  communicating 
one  mile,  40  feet  four  miles,  80  feet  sixteen  miles,  and  so  on. 

"Professor  Ascoli  has  confirmed  this  law,  and  demon- 
strated mathematically,  using  Neumann's  formula,  that  the 
action  is  directly  proportional  to  the  square  of  the  length 
of  one  of  the  two  conductors  if  the  two  are  vertical  and 
of  equal  length,1  and  in  simple  inverse  proportion  to  the 
distance  between  them.  Therefore  the  intensity  of  the  re- 
ceived oscillation  does  not  diminish  with  the  increase  of 
distance  if  the  length  of  the  vertical  conductors  is  increased 
in  proportion,  or  as  the  square  root  of  the  distance."  2 

Delicate  as  the  apparatus  undoubtedly  is,  and  complicated 
as  it  may  seem,  its  action  is  simplicity  itself  to  the  telegraph- 
ist, differing  only  in  the  kind  of  electricity  and  the  medium 
of  communication  from  that  of  the  everyday  telegraph.  On 
depressing  the  key  k  (fig.  40)  to  make,  say,  a  dash,  induced 
currents  are  set  up  in  the  secondary  coil  of  the  Euhmkorff 
machine ;  the  vertical  wire  is  thereby  "  charged "  up  to 
such  a  point  that  it  "  discharges  "  itself  in  sparks  across  the 
gaps  1,  2,  and  3,  and  this  charging  and  discharging  goes  on 
with  extreme  rapidity.  The  wire  thus  becomes  the  seat  of  a 
rapidly  alternating  or  oscillating  current,  which  gives  rise  to  an 
equally  rapid  oscillatory  disturbance  of  the  ether  all  round  the 
wire.  These  ether  oscillations  are  the  Hertzian  waves,  and 

1  If  of  unequal  lengths  then  the  action  is  proportional  to  the  pro- 
duct of  the  two  lengths,  which,  however,  must  not  be  too  dissimilar. 
Thus,  in  the  recent  American  Navy  trials,  signals  from  a  torpedo- 
boat  with  45  feet  of  vertical  wire  to  a  warship  with  140  feet  of  wire 
were  read  at  a  distance  of  eighty-five  miles  ;  but  vice  versd,  from  the 
higher  sending  to  the  lower  receiving  wire,  signalling  was  only  prac- 
ticable over  seven  miles.     See  p.  243  infra. 

2  Recent  experience  goes  to  show  that  there  is  no  such  simple  law. 
Greater  distances  are   now   worked  over   with  shorter  wires   than 
formerly. 


216  THIRD   PERIOD — THE  PRACTICAL. 

they  spread  out  into  space,  much  as  water  waves  do  when  a 
stone  is  thrown  into  a  pond,  or  as  air  waves  do  when  a  sound 
or  a  musical  note  is  struck.  On  arriving  at  the  receiving 
station  these  Hertzian,  or,  as  they  are  also  called,  electro- 
magnetic waves,  enfeebled  more  or  less  as  the  distance  is 
great  or  small,  strike  the  wire  y,  and  generate  along  it  an 
oscillatory  current  of  the  same  kind  (though,  of  course, 
weaker)  as  that  along  the  wire  x.  This  results  in  what  I 
may  call  invisible  sparks  across  the  detector  gap,  which 
break  down  the  insulation  resistance  of  the  contained 
powder  and  make  it  conductive,  thus  allowing  the  local 
battery  to  act ;  the  relay  thereupon  closes,  and  the  Morse 
instrument  sounds,  or  prints  the  signal  as  may  be  required, 
the  tapper  all  the  while  doing  its  work  of  decohering. 

This  account  of  what  occurs  on  depressing  the  key  must 
be  considered  as  popular  rather  than  as  scientifically  accu- 
rate, for  I  do  not  think  we  yet  know  what  actually  takes 
place,  or  precisely  how  it  takes  place.  It  must  also  be 
confessed  that  the  Marconi  apparatus  itself  is  still  in  the 
empirical  stage,  and  many  questions  connected  with  its 
distinctive  features  and  their  interdependence  have  yet 
to  be  solved.  For  instance,  is  the  Marconi  effect  under 
all  circumstances  truly  Hertzian  and  oscillatory?  Some 
authorities  seem  to  think  that  it  is  one  of  electro-static, 
others  of  electro-magnetic,  induction.  Again,  do  the  waves 
radiating  from  the  sending  station  always  travel  in  rectilinear 
lines,  or  are  they  susceptible  of  deflection  by  intervening 
masses  of  earth  and  water  1  To  obtain  the  best  effects,  the 
elevated  wires  must  be  vertical  as  regards  the  earth,  and 
parallel  to  each  other ;  but  hbw  can  they  |be  both  in  the 
case  of  great  distances  where  the  curvature  of  the  earth 
comes  into  play?  Are  the  capacity  areas  x  and  ?/  necessary? 
Some  say  no ;  others,  and  amongst  them  Mr  Marconi,  say 
yes,  but  only  for  short  distances.  Then  again,  assuming 


G.   MABCONl'S  METHOD.  217 

that  true  Hertzian  waves  are  radiated  from  x  and  arrive 
at  y,  how  do  the  feeble  invisible  sparks  (so  to  speak) 
which  they  evoke  at  the  detector  gap  act  upon  the  filings 
so  as  to  make  them  conductive?  Why  is  it  that  trans- 
mission is  practicable  to  greater  distances  over  sea  than 
over  land?  Why  is  a  thick  vertical  wire  better  for 
use  with  the  exciter,  and  a  thin  wire  for  use  with  the 
detector?  Finally,  why  is  it  (apparently)  immaterial 
whether  or  not  we  use  an  earth  connection  on  the  de- 
tector ?  These  are  some  of  the  questions  awaiting  solu- 
tion; but  if  I  may  hazard  an  opinion,  I  would  say  that 
when  solved  we  shall  find  that  after  all  the  Marconi  effect 
is  but  on  a  large  scale  a  Leyden  jar  effect,  complicated 
no  doubt,  but  still  such  as  every  schoolboy  is  familiar 
with  in  principle,  and  that  it  conforms  to  the  same  laws 
/and  conditions. 

Marconi's  first  trials  on  a  small  scale  were  made  at 
Bologna,  and  these  proving  successful  he  came  to  England 
and  applied  for  a  patent,  June  2,  1896.1  Soon  after,  in 
July,  he  submitted  his  plans  to  the  postal-telegraph  authori- 
ties, and,  to  his  honour  be  it  said,  they  were  unhesitatingly 
— even  eagerly — taken  up  by  Preece,  although,  as  we  have 
already  seen,  he  was  introducing  a  method  of  his  own. 

The  first  experiments  in  England  were  from  a  room  in 
the  General  Post  Office,  London,  to  an  impromptu  station 
on  the  roof,  over  100  yards  distant,  with  several  walls,  &c., 
intervening.  Then,  a  little  later,  trials  were  made  over 
Salisbury  Plain  for  a  clear  open  distance  of  nearly  two  miles. 
In  these  experiments  roughly-made  copper  parabolic  reflec- 
tors were  employed,  with  resonance  plates  on  each  side  of 
the  detector  (see  figs.  36,  38). 

1  This  being  the  first  patent  of  the  New  Telegraphy  order,  is  his- 
torically interesting.  I  have  therefore  thought  it  convenient  to 
reproduce  it  in  Appendix  E,  with  the  original  rough  drawings. 


218  THIRD  PERIOD — THE  PRACTICAL. 

In  May  1897  still  more  extensive  trials  were  made  across 
the  Bristol  Channel  between  Lavernock  and  Flat  Holm,  3 '3 
miles,  and  between  Lavernock  and  Brean  Down,  near 
Weston-super-Mare,  8 '7  miles  (see  fig.  20,  supra).  Here  the 
reflectors  and  resonance  plates  were  discarded.  Earth  and 
vertical  air  wires  were  employed,  as  in  fig.  40,  the  vertical 
wires  being  in  the  first  case  50  yards  high,  while  in  the 
second  case  kites  carrying  the  wires  were  had  recourse  to. 

The  receiving  apparatus  was  at  first  set  up  on  the  cliff 
at  Lavernock  Point,  about  20  yards  above  sea-level.  Here 
was  erected  a  pole,  30  yards  high,  on  the  top  of  which  was 
a  cylindrical  cap  of  zinc,  2  yards  long  and  1  yard  diameter. 
Connected  with  this  cap  was  an  insulated  copper  wire 
leading  to  one  side  of  the  detector,  the  other  side  of  which 
was  connected  to  a  wire  led  down  the  cliff  and  dipping  into 
the  sea.  At  Flat  Holm  the  sending  apparatus  was  arranged, 
the  Euhmkorff  coil  used  giving  20-inch  sparks  with  an  eight- 
cell  battery. 

On  the  10th  May  experiments  on  Preece's  electro-mag- 
netic method  (already  fully  described)  were  repeated,  and 
with  perfect  success. 

The  next  few  days  were  eventful  ones  in  the  history  of 
Mr  Marconi.  On  the  llth  and  12th  his  experiments  were 
unsatisfactory — worse,  they  were  failures — and  the  fate  of 
the  new  system  trembled  in  the  balance.  An  inspiration 
saved  it.  On  the  13th  the  receiving  apparatus  was  carried 
down  to  the  beach  at  the  foot  of  the  cliff,  and  connected  by 
another  20  yards  of  wire  to  the  pole  above,  thus  making  a 
height  of  50  yards  in  all.  Eesult,  magic !  The  instru- 
ments, which  for  two  days  failed  to  record  anything  intelli- 
gible, now  rang  out  the  signals  clear  and  unmistakable,  and 
all  by  the  addition  of  a  few  yards  of  wire  !  Thus  often,  as 
Carlyle  says,  do  mighty  events  turn  on  a  straw. 

Prof.  Slaby  of  Charlottenberg,  who  assisted  at  these  ex- 


G.   MAECONI'S   METHOD.  219 

periments,  has  told  us  in  a  few  graphic  words  the  feelings 
of  those  engaged.  "It  will  be  for  me,"  he  says,  "an 
ineffaceable  recollection.  Five  of  us  stood  round  the  ap- 
paratus in  a  wooden  shed  as  a  shelter  from  the  gale,  with 
eyes  and  ears  directed  towards  the  instruments  with  an 
attention  which  was  almost  painful,  and  waited  for  the 
hoisting  of  a  flag,  which  was  the  signal  that  all  was  ready. 
Instantaneously  we  heard  the  first  tic  tac,  tic  tac,  and  saw 
the  Morse  instrument  print  the  signals  which  came  to  us 
silently  and  invisibly  from  the  island  rock,  whose  contour 
was  scarcely  visible  to  the  naked  eye — came  to  us  dancing 
on  that  unknown  and  mysterious  agent  the  ether!" 

After  this  the  further  experiments  passed  off  with  scarcely 
a  hitch,  and  on  the  following  day  communication  was  estab- 
lished between  Lavernock  and  Brean  Down. 

The  next  important  trials  were  carried  out  at  Spezia,  by 
request  of  the  Italian  Government,  between  July  10  and  18, 
1897.  The  first  three  days  were  taken  up  with  experiments 
between  two  land  stations  3*6  kilometres  apart,  which  were 
perfectly  successful.  On  the  14th,  the  sending  apparatus 
being  at  the  arsenal  of  San  Bartolomeo,  the  receiving  instru- 
ments were  placed  on  board  a  tug  vessel,  moored  at  various 
distances  from  the  shore.  The  shore  wire  was  26  metres 
high,  and  could  be  increased  to  34  if  necessary;  the  tug  wire 
was  carried  to  the  top  of  the  mast,  and  was  16  metres  high. 
The  results  were  unsatisfactory :  signals  came,  but  they  were 
jumbled  up  with  other  weird  signals,  which  came  from  the 
atmosphere  (the  weather  was  stormy)  in  the  way  which 
telegraph  and  telephone  operators  know  so  well.  On  the 
15th  and  16th  (the  weather  having  moderated)  better  results 
were  obtained,  and  communication  was  kept  up  at  distances 
up  to  7'5  kilometres. 

On  the  17th  and  18th  the  receiving  apparatus  was  trans- 
ferred to  a  warship  (ironclad),  and,  with  a  shore  elevation  of 


220        THIRD  PERIOD — THE  PRACTICAL. 

34  metres  and  a  ship  elevation  of  22  metres,  signals  were 
good  at  all  distances  up  to  12  kilometres,  and  fairly  so  at 
16  kilometres. 

During  these  experiments  it  was  observed  that  whenever 
the  funnels,  iron  masts,  and  wire  ropes  of  the  vessels  were 
in  line  with  the  shore  apparatus  the  detector  did  not  work 
properly,  which  was  to  be  expected  from  the  screening  pro- 
perty of  metals ;  but  another  and  more  serious  difficulty 
was  also  encountered.  When  the  vessel  got  behind  a  point 
of  the  land  which  cut  off  the  view  of  the  shore  station,  the 
signals  came  capriciously,  and  good  working  was  not  estab- 
lished until  the  shore  was  again  in  full  view.  Here  was  a 
difficulty  which  must  be  surmounted  if  the  new  system  was 
to  be  of  any  practical  utility.  "We  have  seen  in  our  account 
of  the  work  of  Hertz  that  electric  waves  pass  without  ap- 
preciable hindrance  through  doors  and  walls  and,  generally, 
non-conducting  bodies,  being  only  arrested  by  metals  and 
other  conductors ;  but  in  practice,  when  we  come  to  deal 
with  doors  and  walls  in  large  masses — as  trees,  buildings, 
hills — they  seem  to  partake  of  the  nature  of  metals,  and 
largely  absorb  the  waves,  just  as  light  passes  through  a  thin 
sheet  of  glass  but  is  arrested  by  a  thick  sheet. 

This  is  one  of  the  vexed  questions  connected  with 
the  theory  of  the  Marconi  telegraph.  In  the  early  days 
intervening  obstacles  certainly  did  interfere  with  correct 
signalling,  and  in  some  cases  they  do  so  still.1  Yet  in 
many  of  Marconi's  later  trials  he  appears  to  have  found  no 
difficulty.  At  the  Isle  of  Wight  a  hill  300  feet  higher  than 
his  vertical  wires  has  proved  no  obstacle. 

In  the  experiments  at  Dover  during  the  last  British 
Association  meeting  (August  1899)  the  great  mass  of  the 

1  'Jour.  Inst.  Elec.  Engs.,'  No.  139,  pp.  295,  305,  315;  'Science 
Abstracts,' No.  15,  p.  214,  and  No.  24,  p.  878;  'Electrician,'  vol. 
xliv.  pp.  140,  212. 


a  MARCONI'S  METHOD.  221 

Castle  Rock,  400  feet  high,  did  not  seem  to  interfere  with 
the  signalling  between  Dover  Town  Hall  and  the  South 
Foreland  lighthouse,  four  miles  distant,  or  the  Goodwin 
lightship,  twelve  miles  farther  off.  Again,  between  the 
Town  Hall  and  Wimereux,  across  Channel,  a  mass  of 
houses,  tall  buildings,  and  overhead  tramway  wires  appeared 
to  have  no  bad  effect.1 

Better  proof  still,  we  learn  that  during  the  same  experi- 
ments the  Wimereux  signals  intended  for  Dover  were  re- 
ceived at  the  Marconi  factory  at  Chelmsford,  eighty-five 
miles  distant  from  the  French  station,  and  that,  in  fact, 
signalling  was  carried  on  between  those  two  places.2 

During  the  naval  manoeuvres  last  summer  (1899)  off 
Bantry,  messages  were  correctly  exchanged  between  ships 
when  a  hill  over  800  feet  high  intervened ;  and,  again, 
between  the  Europa  and  Juno,  when  eighty -five  miles 
apart,  and  with  thirty  ironclads,  &c.  (with  all  their  masses 
of  metal,  funnels,  iron  masts,  and  wire  rigging),  manoeuvring 
in  between.  The  vertical  wire  on  each  ship  was  170  feet 
high,  so  that,  owing  to  the  curvature  of  the  earth,  a  hill  of 
water  must  have  intervened,  through  or  round  which  the 
electric  waves  must  have  travelled — but  which  1 

According  to  the  observations  of  Le  Bon,3  they  must 
have  gone  round  it.  The  length,  he  says,  of  the  Hertzian 
waves  enables  them  to  turn  round  obstacles  with  facility, 
even  metallic  bodies  in  certain  circumstances — a  fact  which 
accounts  for  the,  apparently,  partial  transparence  of  metallic 
mirrors.  "  Non-metallic  bodies,"  he  goes  on  to  say,  "  have 
been  considered  to  be  perfectly  transparent  to  Hertzian 
waves,  but  do  these  waves  go  through  a  hill  or  round  it  1 
12  centimetres  of  Portland  cement  are  only  partially 

1  '  Electrician/  vol.  xliii.  pp.  737,  768. 

8  '  Electrician,'  vol.  xliii.  p.  816. 

8  '  Science  Abstracts,'  No.  22,  p.  671. 


222 


THIRD   PERIOD — THE   PRACTICAL. 


transparent,  while  30  centimetres  are  non  -  transparent  or 
wholly  opaque.  Dry  sand  is  almost  entirely  transparent, 
but  wet  sand  much  less  so — that  is,  is  partially  opaque. 
Freestone  is  more  transparent  than  cement,  but  increases 
in  opacity  as  it  becomes  wet.  Generally  speaking,  the 
transparency  of  non-metallic  bodies  varies  for  each  substance 
and  decreases  as  the  thickness  and  humidity  of  the  body 
increase."  If  this  be  so,  the  Hertzian  waves  which  act  upon 
a  detector  on  the  other  side  of  a  hill  must  go  over  and 
round  the  hill,  not  through  it,  just  as  they  go  round  the 
edges  of  metallic  mirrors,  or  travel  over  the  bent  or  looped 
wire  in  some  experiments  of  Hertz  and  Lodge. 


Fig.  41. 

This  is  also  the  conclusion  at  which  Sir  William  Preece,1 
Mr  Marconi  himself,2  and  other  authorities  have  arrived. 
When,  says  the  former,  the  ether  is  entangled  in  matter 
of  different  degrees  of  inductivity,  the  lines  of  force  are 
curved,  as  in  fact  they  are  in  light.  Fig.  41,  which  I 
borrow  from  Preece,  shows  how,  according  to  his  view, 
hills  are  bridged  over. 

On  the  other  hand,  Prof.  Branly,  while  maintaining  the 
theory  that  electric  waves  travel  in  straight  lines  only, 
has  thrown  out  the  suggestion  that  the  opacity  or  otherwise 

1  Lecture,  Royal  Institution,  June  4,  1897. 

2  Lecture,  Royal  Institution,  February  2, 1900.     Compare  his  view 
in  'Jour.  Inst.  Elec.  Engs.,'  March  2,  1899. 


G.  MARCONI'S  METHOD.  223 

of  intervening  bodies  may  be  only  a  question  of  wave- 
lengths— that  such  bodies  may  be  opaque  to  some  waves, 
and  transparent  or  partially  so  to  others.  Referring  to  the 
proposal  for  firing  submarine  mines  from  a  distance  by 
means  of  electric  waves,  he  says,  "  The  thing  can  only  be 
done  if  water  is  transparent  to  the  waves  used.  The  fact 
that  a  sheet  of  tinfoil  is  capable  of  completely  intercepting 
electric  waves,  would  make  us  think  that  the  opacity  of 
water,  and  especially  of  salt  water,  is  very  probable.  He 
tested  various  liquids  and  solutions  experimentally,  and 
found  that  a  layer  of  tap  water,  20  centimetres  thick, 
suffices  to  reduce  the  signalling  distance  to  one -fifth  of 
its  value  in  open  air.  The  same  thickness  of  salt  water 
intercepts  the  waves  completely.  Mineral  oil  is  no  more 
absorptive  than  air  itself.  Sea  salt  is  particularly  absorptive 
— more  so  than  the  sulphates  of  zinc,  sodium,  and  copper. 
The  result  is  therefore  fatal  to  the  use  of  electric  waves 
across  intervening  water ;  but  it  is  just  possible  that  the 
wave-length  used  may  make  some  difference.  Waves  from 
a  2-cm.  spark  are  completely  intercepted,  while  those  from 
a  20-cm.  Righi  spark  are  transmitted  to  the  extent  of 
about  |  per  cent  by  sea  water  20  cm.  thick.  It  should 
be  remembered  that  sea  water  is  largely  transparent  to 
electric  waves  of  the  length  of  light  waves  [Rontgen 
waves],  and  it  is  just  possible  that  there  are  other  regions 
of  non-absorption  in  the  electric  spectrum."  l 

Whatever  the  explanation  may  be,  the  fact  remains  that 
intervening  masses  do  reduce  the  distance  over  which  a 
given  power  and  adjustment  of  apparatus  can  work,  and 
that  their  effect  is  greater  over  land  than  over  sea — by 
about  one -third.  When  therefore  it  is  said  that  inter- 
posed bodies  offer  no  difficulty,  it  should  be  understood 
that  they  offer  no  difficulty  that  is  not  surmountable,  and 

1  'Comptes  Rendus,'  October  1899,  quoted  in  the  *  Electrician,' 
vol.  xliv.  p.  140. 


224  THIRD   PERIOD — THE   PRACTICAL. 

we  may  suppose  that  the  loss  is  in  practice  compensated  for 
in  one  or  both  of  the  following  ways  :  (1)  by  increasing  the 
height  of  the  vertical  wires,  and  so  increasing  the  length  of 
the  wave  and  the  volume  of  the  ether  disturbed  at  the 
sending  station ;  and  (2)  by  increasing  the  power  of  the 
sending  and  the  sensitiveness  of  the  receiving  apparatus. 
But  we  speedily  reach  a  limit  in  these  directions,  so  that  as 
far  as  one  can  see  at  present  the  effective  distance  of  the 
Marconi  system  must  be  small  compared  with  the  older 
methods  of  telegraphy  by  wire. 

Of  course,  if  ever  required,  means  of  automatically  re- 
peating the  signals  could  be  devised,  although  there  would 
be  great  practical  difficulties  attending  the  use  of  the 
metallic  screens  which  would  have  to  be  employed.  An- 
other young  Italian,  Mr  Guarini-Eoresio,  is  now  working 
in  this  direction.1 

On  his  return  to  Germany  after  witnessing  the  Marconi 
trials  in  England,  Prof.  Slaby  in  September  1897  engaged 
in  some  very  instructive  experiments  in  the  vicinity  of 
Potsdam,  first  between  Matrosenstation  and  the  church  at 
Sacrow,  1-6  kilometre,  and  then  between  the  former  place 
and  the  castle  of  Pfaueninsel,  3'1  kilometres.  I  take  the 
following  particulars  from  the  '  Electrical  Engineer,'  De- 
cember 3,  1897  : — 

Prof.  Slaby  recently,  at  a  technical  college  in  Berlin,  gave 
an  interesting  report  of  his  experiments  on  telegraphy  with- 
out wires,  or,  as  he  wants  it  to  be  called,  "  spark  telegraphy." 
He  mentioned  an  experiment  made  by  himself  by  which  he 
was  able  to  send  by  means  of  one  wire  two  different  messages 
simultaneously  without  interfering  with  each  other.  He 
explained  that  the  continuous  current  used  in  ordinary  teleg- 
raphy is  conducted  along  the  middle  of  the  wire,  and  he 

1  See  his  brochure,  'Transmission  de  L'iElecfricite'  sans  Fil,'  2nd 
edition,  p.  29  et  seq.;  or  'Electrical  Review,'  November  10,  1899. 


G.  MARCONI'S  METHOD.  225 

proved  that  electric  waves  on  their  way  through  the  ether 
are  attracted  by  wires  which  come  in  their  way,  and  that 
they  travel  along  the  outside  of  those  wires  without  in- 
fluencing the  interior.  In  making  use  of  these  observations 
lie  succeeded  in  sending  a  wave  message  along  the  outside 
of  the  wire  while  another  message  was  proceeding  through 
the  centre  by  the  continuous  current. 

Prof.  Slaby  says  that,  in  conjunction  with  Dr  Dietz,  he 
made  many  experiments  with  "  spark  telegraphy "  before 
Marconi's  inventions  became  known,  but  did  not  achieve 
any  important  results.1 

After  his  return,  however,  from  England  lie  experi- 
mented still  further.  The  Emperor  of  Germany  was  present 
at  some  of  these  experiments,  and  put  a  number  of  sailors 
and  the  large  royal  gardens  at  Potsdam  at  his  disposal. 
The  receiver  was  erected  at  the  naval  station  and  the 
transmitter  on  Peacock  Island.  The  first  experiments  gave 
no  result,  because  the  coherers  used  were  a  great  deal  too 
sensitive,  and  contained,  among  other  things,  too  much 
silver,  and  were  affected  by  the  electricity  in  the  atmo- 
sphere, and  in  consequence  were  constantly  affected  even 
when  no  signals  were  sent  from  the  sending  station. 

1  Referring  to  these  experiments  in  his  book,  '  Die  Fuukentele- 
gniphie,'  Berlin,  1897,  Prof.  Slaby  handsomely  acknowledges  Marconi's 
merits  in  the  following  words  :  "  Like  many  others,  I  also  had  taken, 
up  this  study,  but  never  got  beyond  the  limits  of  our  High  School. 
Even  with  the  aid  of  parabolic  reflectors  and  great  capacity  of 
apparatus  I  could  not  attain  any  further.  Marconi  has  made  a  dis- 
covery. He  worked  with  means  the  full  importance  of  which  had  not 
been  recognised,  and  which  alone  explain  the  secret  of  his  success.  I 
ought  to  have  said  this  at  the  commencement  of  my  subject,  as  latterly, 
especially  in  the  English  technical  press,  the  novelty  of  Marconi's 
process  was  denied.  The  production  of  the  Hertzian  waves,  their 
radiation  through  space,  the  sensitiveness  of  the  electric  eye,  all  were 
known.  Very  good  ;  but  with  these  means  50  metres  were  attained, 
but  no  mure." 

P 


226  THIRD   PERIOD — THE  PRACTICAL. 

Further  experiments  showed  that  the  results  increased  in 
the  same  measure  as  the  sensitiveness  of  the  coherer  de- 
creased. Prof.  Slaby  uses  now  very  rough  and  jagged 
nickel  filings  which  have  been  carefully  cleaned  and 
dried.  As  the  receiving  station  could  not  be  seen  from  the 
island,  the  sending  station  was  removed  to  a  church  a  little 
farther  away,  and  the  exciter  was  put  between  the  columns 
of  the  portico,  while  the  mast  which  carried  the  wire  was 
erected  on  the  spire.  The  experiments  then  went  very  well. 

When  the  sending  apparatus  was  put  back  a  little  farther 
into  the  church,  and  the  wire  was  put  for  about  a  length  of 
2  yards  parallel  with  the  stone  slabs  of  the  floor  and  a  yard 
and  a  half  above  it,  it  ceased  to  work  properly,  because  the 
waves  seek  the  earth.  Hence  one  must  not  bring  the  wire 
too  near  to  the  earth,  or  lay  it  parallel  when  near  the  earth. 
"When  the  sending  apparatus  was  moved  back  to  the  island, 
it  was  found  that  trees  near  the  wire  proved  an  obstacle 
because  they  received  the  waves.  Therefore  the  Professor 
says  that  it  is  best  to  so  arrange  that  the  wires  on  the 
receiver  and  on  the  transmitter  can  be  seen  from  each 
other.  Even  the  sail  of  a  little  boat  or  the  smoke  from 
a  steamer  cause  small  interruptions,  which  make  the  signals 
more  or  less  indistinct.  The  waves  get  through  impedi- 
menta, and  even  through  buildings,  but  there  is  always 
much  loss.  In  order  to  make  the  wire  which  wras  placed 
on  the  island  more  visible  from  the  mainland,  it  was 
lengthened  from  25  to  65  yards,  and  placed  upon  a  boat 
on  the  river.  That  did  not  remedy  matters ;  but  when  the 
wire  on  the  receiver  was  also  lengthened  to  65  yards  very 
good  results  followed,  showing  that  the  length  of  the  wire 
is  of  great  importance. 

Prof.  Slaby  next  proceeded,  early  in  October,  to  experi- 
ment over  an  open  stretch  of  country,  free  from  all  inter- 
vening obstacles,  between  Eangsdorf  (sending  station)  and 


G.   MARCONI'S  METHOD.  227 

Schb'neberg  (receiving  station),  a  distance  of  21  kilometres. 
Captive  balloons  raised  to  a  height  of  300  metres  were 
employed.  On  the  first  t\vo  days  the  results  were  dis- 
appointing, and  the  fault  was  found  to  be  in  the  vertical 
conductors,  which  consisted  of  the  wire  cables  holding  the 
balloons.  A\rith  a  double  telephone  wire  there  was  a  slight 
improvement ;  and  eventually,  on  the  7th  October,  "  fine 
insulated  copper  wire  of  *46  millimetres  diameter  was  sub- 
stituted with  excellent  results." 

Correspondence  was  now  always  good,  except  when  dis- 
turbed by  atmospheric  discharges  (the  weather  being 
stormy).  At  such  times  the  signals  were  distorted  and  con- 
fused, and  often  the  discharges  were  so  strong  as  to  un- 
pleasantly shock  the  operators,  making  it  necessary  to 
handle  the  apparatus  with  the  greatest  care.1  Here  is 
another  serious  difficulty  with  which  Mr  Marconi  has  to 
contend,  and  from  which  we  see  no  escape  short  of  total 
suspension  of  operations  during  stormy  weather — namely, 
the  great  liability  to  accident  and  derangement,  not  merely 
from  lightning  flashes,  to  which  all  telegraph  systems  are 
subject,  but  from  all  those  other  electrical  disturbances  of 
the  atmosphere  which  have  hitherto  been  of  little  account. 
The  greater  the  distance  worked  over,  the  higher  must  be 
the  conductors,  and,  consequently,  the  greater  must  be  the 
danger. 

The  apparatus  used  by  Prof.  Slaby  differed  somewhat 
from  Marconi's,  the  following  being  the  more  important 
points : — 

1.  A  AVeston  galvanometer  relay,  which,  it  is  curious  to 
note,  is  our  old  friend  in  modern  guise,  the  Wilkins' 
relay,  used  by  Mr  Wilkins  in  his  wireless  telegraph 
experiments  in  1845  (see  p.  39,  supra). 

1  See  also  Brett's  remarks,  '  Jour.  Inst.  Elec.  Engs.,'  No.  137,  p 
915  ;  and  Freece,  '  Jour.  Soc.  Arts,'  vol.  xlvii.  p.  522. 


228       THIRD  PERIOD — THE  PRACTICAL. 

2.  An  ordinary  Branly- Lodge  detector  with  hard  nickel 

powder  only. 

3.  Ko  impedance  or  "choking"  coils.1 

The  further  course  of  Marconi's  experiments  is  so  suc- 
cinctly given  by  the  chairman  of  the  Wireless  Telegraph 
Company  in  a  recent  address,  October  7,  1898,  that  wo 
cannot  do  better  than  follow  him.2 

"A  year  ago,"  he  says,  "when  this  company  Avas  started 
(July  1897),  Mr  Marconi  happened  to  be  in  Italy  making 
experiments  for  the  Italian  Government,  and  for  the  King 
and  Queen  at  the  Quit-in al.  On  his  return  to  this  country, 
the  first  long-distance  trial  was  made  between  Bath  and 
Salisbury.  The  receiver  in  this  case  was  given  to  a  post- 
office  official,  who  went  to  Bath  and  by  himself  rigged  up  a 
station,  at  which  he  received  signals  thirty-four  miles  distant 
from  where  they  were  sent  at  Salisbury.  After  this  we  put 
a  permanent  station  at  Alum  Bay,  Isle  of  Wight.  This 
station  at  first  was  used  in  connection  with  a  small  steamer 
that  cruised  about  in  the  neighbourhood  of  Bournemouth, 
Boscombe,  Poole  Bay,  and  Swanage,  a  distance  of  eighteen 
miles  from  the  Needles  Hotel  station,  with  which  it  was  in 
constant  telegraphic  communication. 

"  Various  exhibitions  were  given  later — one  at  the  House 
of  Commons,  where  a  station  was  erected,  and  another  sta- 
tion at  St  Thomas's  Hospital  opposite  (May  1898).  Within 
an  hour  of  the  time  our  assistants  arrived  to  put  up  the 
installation,  the  system  was  at  work.  We  had  many 
exhibitions  at  our  offices,  at  which  a  number  of  people 

1  About  this  time  Dr  Tuma  of  Vicuna  was  engaged  on  similar  ex- 
periments, using,  however,  instead  of  a  Ruhmkorff  coil  a  Tesla  oscil- 
lator or  exciter,  with  nickel  powder  only  in  the  detector.     I  have  nofc 
seen  any  detailed  account  of  these  experiments. 

2  I  have  incorporated  a  few  passages  from  Mr  Marconi's  recent  paper 
(Institution  of  Electrical  Engineers,  March  2, 1899),  so  as  to  make  the 
account  more  complete.     These  are  shown  in  brackets  thus  [  J. 


G.  MARCONI'S  METHOD.  229 

attended;  amongst  others  Mr  Brinton,  a  director  of  the 
Donald  Currie  line  of  steamers,  who  asked  if  we  could 
report  a  ship  passing  our  station.  This  was  done.  The 
ship  was  the  Carisbrooke  Castle,  on  her  first  voyage  out, 
and  as  she  passed  the  Needles  a  message  reporting  the 
fact  was  wirelessly  telegraphed  to  Bournemouth,  and  there 
put  on  the  ordinary  telegraph  wires  for  transmission  to 
Mr  Brinton. 

"After  this  Lord  Kelvin  visited  our  station  at  Alum  Bay, 
and  expressed  himself  highly  pleased  with  all  he  saw.  He 
sent  several  telegrams,  via  Bournemouth,  to  his  friends,  for 
each  of  which  he  insisted  on  paying  one  shilling  royalty, 
wishing  in  this  way  to  show  his  appreciation  of  the  system 
and  to  illustrate  its  fitness  for  commercial  uses.  The  follow- 
ing day  the  Italian  Ambassador  visited  the  station.  Among 
other  messages,  he  sent  a  long  telegram  addressed  to  the 
Aide-de-camp  to  the  King  of  Italy.  As  it  was  in  Italian, 
and  as  Mr  Marconi's  assistant  at  Bournemouth  had  no  know- 
ledge of  that  language,  it  may  be  taken  as  a  severe  test — as, 
in  fact,  a  code  message.  The  telegram  was  received  exactly 
as  it  was  sent.  Previously,  we  had  a  display  for  the 
*  Electrical  Eeview '  and  the  '  Times,'  both  of  which  papers 
sent  representatives.  They  put  the  system  to  every  possible 
test,  and,  among  others,  sent  a  long  code  message,  which 
had  to  be  repeated  back.  In  their  reports  they  stated  that 
this  was  done  exactly  as  sent. 

[In  May  Lloyd's  desired  to  have  an  illustration  of  the. 
possibility  of  signalling  between  Bally  castle  and  Bathlin 
Island  in  the  north  of  Ireland.  The  distance  between  the 
two  positions  is  seven  and  a  half  miles,  of  which  about  four 
are  overland  and  the  remainder  across  the  sea,  a  high  cliff 
also  intervening  between  the  two  positions.  At  Ballycastle 
a  pole  70  feet  high  was  used  to  support  the  wire,  and  at 
liathlin  a  vertical  conductor  was  supported  by  the  light- 


230  THIRD  PERIOD — THE  PRACTICAL. 

house  80  feet  high.  Signalling  was  found  quite  possible 
between  the  two  points,  but  it  was  thought  desirable  to 
bring  the  height  of  the  pole  at  Ballycastle  to  100  feet,  as 
the  proximity  of  the  lighthouse  to  the  wire  at  Eathlin 
seemed  to  diminish  the  effectiveness  of  that  station.  At 
Ilathlin  we  found  that  the  lighthouse-keepers  were  not  long 
in  learning  how  to  work  the  instruments,  and  after  the  sad 
accident  which  happened  to  poor  Mr  Glanville,  that  installa- 
tion was  worked  by  them  alone,  there  being  no  expert  on 
the  island  at  the  time.1] 

"Following  this,  in  July  last  (1898)  we  were  requested 
by  a  Dublin  paper,  the  'Daily  Express,'  to  report  the 
Kingstown  regatta.  In  order  to  do  this  we  erected  a  [land] 
station  at  Kingstown,  and  another  on  board  a  steamer  which 
followed  the  yachts.  A  telephone  wire  connected  the 
Kingstown  station  with  the  'Daily  Express'  offices,  and  as 
the  messages  came  from  the  ship  they  were  telephoned  to 
Dublin  and  published  in  successive  editions  of  the  evening 
papers.2 

[After  the  races  longer  distances  were  tried,  and  it  was 
found  that  with  a  height  of  80  feet  on  the  ship  and  110  feet 
on  land  it  was  possible  to  communicate  up  to  a  distance  of 
twenty-five  miles ;  and  it  is  worthy  of  note  in  this  case  that 
the  curvature  of  the  earth  intervened  very  considerably  at 
such  a  distance  between  the  two  positions.] 

"  After  this,  Mr  Marconi  was  requested  to  put  up  a  sta- 
tion at  Osborne  to  connect  with  the  Prince  of  Wales'  yacht 
Osborne.  Bulletins  of  the  Prince's  health  (his  Royal  High- 
ness, as  we  all  know,  met  with  a  lamentable  accident  just 

1  Mr  Glanville,  a  promising  young  electrician  (only  twenty-five 
years  old),  was  missing  from  Saturday  to  the  Tuesday  evening  fol- 
lowing, when  his  body,  terribly  mutilated,  was  found  at  the  foot  of 
a  cliff  300  feet  high  in  Ilathlin  Island. 

-  Very  full  illustrated  accounts  of  this  remarkable  experiment  are 
given  in  the  Dublin  *  Mail,'  July  20,  21,  and  22,  1898. 


a  MARCONI'S  METHOD.  231; 

"before  then)  were  reported  to  her  Majesty :  not  only  that, 
but  the  royalties  made  great  use  of  our  system  during  the 
Cowes  week. 

[In  this  installation  incluction-coils  capable  of  giving  a 
10-inch  spark  were  used  at  both  stations.  The  height  of 
the  pole  supporting  the  vertical  conductor  was  100  feet  at 
Osborne  Houso,  On  the  yacht  the  top  of  the  conductor  was 
attached  to  the  mainmast  at  a  height  of  83  feet  from  the 
deck,  thus  being  very  near  one  of  the  funnels,  and  in  the 
proximity  of  a  great  number  of  wire  stays.  The  vertical 
conductor  consisted  of  a  YV  stranded  wire  at  each  station. 
The  yacht  was  usually  moored  in  Cowes  Bay  at  a  distance 
of  nearly  two  miles  from  Osborne  House,  the  two  positions 
not  being  in  sight  of  each  other,  the  hills  behind  East 
Cowes  intervening. 

[On  August  12  the  Osborne  steamed  to  the  Needles  and 
communication  was  kept  up  with  Osborne  House  until  off 
Newton  Ba}r,  a  distance  of  seven  miles,  the  two  positions 
being  completely  screened  from  each  other  by  the  hills  lying 
between.  From  the  same  position  we  found  it  quite  pos- 
sible to  speak  with  our  station  at  Alum  Bay,  although 
Headon  Hill,  Golden  Hill,  and  over  five  miles  of  land  lay 
directly  between.  Headon  Hill  was  45  feet  higher  than  the 
top  of  our  wire  at  Alum  Bay,  and  314  feet  higher  than  the 
wire  on  the  yacht.] 

"  Within  the  last  few  days  we  have  had  to  move 
our  station  at  Bournemouth  four  miles  farther  west, 
where  we  have  put  up  the  same  instruments,  the  same 
pole,  and  everything  at  the  Haven  Hotel,  Poole,  which 
is  eighteen  miles  from  Alum  Bay.  This  increase  of 
distance  has  no  detrimental  effect  on  our  work ;  in  fact 
it  seems  rather  easier,  if  anything,  to  receive  signals  at 
the  Haven  Hotel  than  at  our  former  station:  thus,  the 
height  of  the  conductor  at  Bournemouth  was  150  feet, 


232  THIRD  PERIOD— THE  PRACTICAL. 

but  tliis  is  now  reduced  to  100  feet,  which  is  a  very 
great  improvement.1 

[The  vertical  conductors  are  stranded  ^  copper  wire  in- 
sulated with  india-rubber  and  tape.  A  10-inch  spark  induc- 
tion coil  is  used  at  each  station,  worked  by  a  battery  of  100 
Obach  cells  M  size,  the  current  taken  by  the  coil  being  14 
volts  of  from  6  to  9  amperes.  The  sparks  take  place  be- 
tween two  small  spheres  about  1  inch  diameter,  this  form 
of  transmitter  having  been  found  more  simple  and  more 
effective  than  the  Eighi  exciter  previously  used.  The 
length  of  spark  is  adjusted  to  about  1  centimetre,  which, 
being  much  shorter  than  the  coil  can  give,  allows  a  large 
margin  for  any  irregularity  that  may  occur.  No  care  is 
now  taken  to  polish  the  spheres  at  the  place  where  the 
sparks  occur,  as  working  seems  better  with  dull  spheres 
than  with  polished  ones.] 

"  The  Marconi  invention  is  the  only  (electric)  telegraph 
by  means  of  which  a  moving  object  can  be  kept  in  commu- 
nication with  any  other  moving  object,  or  a  fixed  station, 
and  therefore  any  one  can  see  the  great  use  of  the  invention, 
not  only  to  the  Royal  K"aval  authorities,  but  also  to  the 
mercantile  marine.  A  ship  fitted  with  Mr  Marconi's 
apparatus  can  not  only  keep  in  telegraphic  communi- 
cation with  the  shore  up  to  any  reasonable  distance — it 
has  been  thoroughly  tested  up  to  twenty -live  miles  off 
the  shore  —  but  ships  can  also,  if  properly  equipped, 
be  warned  of  approaching  danger  or  their  proximity 
to  dangerous  coasts  which  are  fitted  with  the  wireless 
apparatus. 

[If  we  imagine  a  lighthouse  provided  with  a  transmitter 

constantly  giving  an  intermittent  series  of  electric  waves, 

and  a  ship  provided  with  a  receiving  apparatus  placed  in 

the  focal  line  of  a  reflector,   it  is  plain  that  when   the 

1  The  height  has  since  been  gradually  reduced  to  75  feet. 


233 

receiver  comes  within  the  range  of  the  transmitter  the  bell 
will  be  rung  only  when  the  reflector  is  directed  towards  the 
transmitter.  If,  then,  the  reflector  is  caused  to  revolve  by 
clockwork  or  by  hand,  it  will  give  warning  only  when  occu- 
pying a  certain  sector  of  the  circle  in  which  it  revolves.  It 
is  therefore  eas3r  for  a  ship  in  a  fog  to  make  out  the  exact 
direction  of  the  lighthouse,  and,  by  the  conventional  number 
of  taps  or  rings  corresponding  to  the  waves  emitted,  she 
will  be  able  to  discern,  either  a  dangerous  point  to  be 
avoided,  or  the  port  for  which  she  is  endeavouring  to 
steer.1] 

[In  December  of  last  year  the  Company  thought  it  desir- 
able to  demonstrate  that  the  system  was  available  for  tele- 
graphic communication  between  lightships  and  the  shore. 
This,  as  you  are  aware,  is  a  matter  of  much  importance,  as 
all  other  systems  tried  so  far  have  failed,  and  the  cables  by 
which  ships  are  connected  are  exceedingly  expensive,  and 
require  special  moorings  and  fittings,  which  are  troublesome 
to  maintain  and  liable  to  break  in  storms.  The  officials  of 
Trinity  House  offered  us  the  opportunity  of  demonstrating 
to  them  the  utility  of  the  system  between  the  South  Fore- 

1  Theoretically  this  is  possible,  but  practically  I  fear  the  size  and 
management  of  the  reflector  would  make  it  very  difficult.  A  simpler 
way  might  be  by  reverting  to  the  original  form  of  the  apparatus 
(p.  206  supra),  and  by  revolving  a  cylindrical  metallic  screen  (with 
a  longitudinal  slit  or  opening  not  too  wide)  around  the  detector 
until  the  position  is  found  in  which  the  bell  rings  under  the  influ- 
ence of  the  electric  rays  entering  at  the  opening.  Even  here  I  foresee 
difficulties.  However,  the  thing  is  easily  put  to  actual  test,  and,  con- 
sidering its  great  importance,  I  am  surprised  that  this  has  not  been 
done. 

Bela  Schiifer  in  Austria,  and  Russo  d'Asar  in  Italy,  are  said  to 
be  able  to  determine  the  presence  and  course  of  a  ship  at  60  to 
80  kilometres  distant.  If  this  has  been  done,  then,  vice  versd,  a 
ship  should  be  able  to  determine  the  presence  and  direction  of  a 
lighthouse. 


234  THIRD   PEPJOD— THE  PRACTICAL. 

land  Lighthouse  and  one  of  the  following  light-vessels-— 
viz.,  the  Gull,  the  South  Goodwin,  and  the  East  Goodwin. 
"VVe  naturally  chose  the  one  farthest  away — the  East  Good- 
win— which  is  just  tAvelve  miles  from  the  South  Foreland 
Lighthouse. 

[The  apparatus  was  taken  on  board  in  an  open  boat  and 
rigged  up  in  one  afternoon.  The  installation  started  working 
from  the  very  first,  December  24,  without  the  slightest 
difficulty.  The  system  has  continued  to  work  admirably 
through  all  the  storms,  which  during  this  year  have  been 
remarkable  for  their  continuance  and  severity.  On  one 
occasion,  during  a  big  gale  in  January  last,  a  very  heavy  sea 
struck  the  ship,  carrying  part  of  her  bulwarks  away.  The 
report  of  this  mishap  was  promptly  telegraphed  to  the 
superintendent  of  Trinity  House,  with  all  details  of  the 
damage  sustained. 

[The  height  of  the  wire  on  board  the  ship  is  80  feet,  the 
mast  being  for  GO  feet  of  its  length  of  iron,  and  the  re- 
mainder of  wood.  The  aerial  wire  is  led  down  among  a 
great  number  of  metal  stays  and  chains,  which  do  not 
appear  to  have  any  detrimental  effect  on  the  strength  of  the 
signals.  The  instruments  are  placed  in  the  aft-cabin,  and 
the  aerial  wire  comes  through  the  framework  of  a  skylight, 
from  which  it  is  insulated  by  means  of  a  rubber  pipe.  As 
usual,  a  10-inch  coil  is  used,  worked  by  a  battery  of  dry 
cells,  the  current  taken  being  about  6  to  8  amperes  at  14 
volts. 

[The  instruments  at  the  South  Eoreland  Lighthouse  are 
similar  to  those  used  on  the  ship ;  but  as  we  contemplate 
making  some  long-distance  tests  from  the  South  Foreland 
to  the  coast  of  France,  the  height;  of  the  pole  is  much 
greater  than  would  be  necessary  foi?  the  lightship  installa- 
tion alone.] 

These  tests  were  duly  carried  out,  and  on  March  27, 


G.   MARCONI'S  METHOD.  235 

1899,  communication  was  successfully  established  between 
England  and  France.1 

"  On  this  side  ol  th«  Channel,"  says  the  '  Daily  Graphic ' 
(March  30,  1899),  "the  operations  took  place,  by  per- 
mission of  the  Trinity  House,  in  a  little  room  in  the  front 
part  of  the  engine-house  from  which  the  power  is  derived  for 
the  South  Foreland  lighthouses.  The  house  is  on  the  top 
of  the  cliffs  overlooking  the  Channel.  The  demonstrations 
are  being  conducted  for  the  benefit  of  the  French  Govern- 
ment, who  have  the  system  under  observation,  and  besides 
Signer  Marconi  there  were  present  at  the  Foreland  yesterday 
Colonel  Comte  du  Eontavice  de  Heussey,  French  Military 
Attache  in  England ;  Captain  Ferric,  representing  the 
French  Government;  and  Captain  Fieron,  French  Xaval 
Attache  in  England.  During  the  afternoon  a  great  number 
of  messages  in  French  and  English  crossed  and  rccrossed 
between  the  little  room  at  the  South  Foreland  and  the  Chalet 
D'Artois,  at  "Wimereux,  near  Boulogne. 

"The  whole  of  the  apparatus  stood  upon  a  small  table  about 
3  feet  square,  in  the  centre  of  the  room.  Underneath  the 
table  the  space  was  fitted  with  about  fifty  primary  cells ;  a 
10 -inch  induction  coil  occupied  the  centre  of  the  table. 
The  spark  is  1 J  centimetre  long,  or  about  three-quarters  of 
an  inch ;  the  pole  off  the  top  of  which  the  current  went  into 
space  is  150  feet  high.  The  length  of  spark  and  power  of 
current  were  the  same  as  used  for  communication  with  the 
East  Goodwin  lightship,  a  fact  which  seems  remarkable 
when  it  is  considered  that  the  distance  over  which  the 
messages  were  sent  yesterday  was  nearly  three  times  as 
great.  The  greater  distance  is  compensated  for  by  the 
increased  height  of  the  pole. 

"  Throughout  the  whole  of  the  messages  sent  yesterday 

1  All  the  London  daily  papers  of  March  29  and  30  contain  full  and 
glowing  accounts  of  this  installation. 


236  THIRD   PERIOD — THE  PRACTICAL. 

there  was  not  once  a  fault  to  be  detected — everything  was 
clearly  and  easily  recorded.  The  rate  of  transmission  was 
about  fifteen  words  a  minute." 

The  first  international  press  message  sent  by  the  new 
system  was  secured  by  the  '  Times,'  and  is  as  follows  : — 


"  (From  our  Boulogne  Correspondent.) 

' '  WIMEREUX,  March  28. 

"Communication  between  England  and  the  Continent 
was  set  up  yesterday  morning  by  the  Marconi  system  of 
wireless  telegraphy.  The  points  between  which  the  experi- 
ments are  being  conducted  are  South  Foreland  and 
Wimereux,  a  village  on  the  French  coast  two  miles  north  of 
Boulogne,  where  a  vertical  standard  wire,  150  feet  high,  has 
been  set  up.  The  distance  is  thirty-two  miles.  The  experi- 
ments are  being  carried  on  in  the  Morse  code.  Signor 
.Marconi  is  here  conducting  the  trials,  and  is  very  well 
satisfied  with  the  results  obtained. 

"This  message  has  been  transmitted  by  the  Marconi 
system  from  Wimereux  to  the  Foreland." 

Amongst  the  experts  in  electrical  science  who  witnessed 
these  experiments  was  Prof.  Fleming,  F.E.S.,  of  University 
College,  London,  who  has  given  us  his  impressions  in  a  long 
letter  to  the  'Times'  (April  3,  1899).  He  tells  us  that 
throughout  the  period  of  his  visit  messages,  signals,  con- 
gratulations, and  jokes  were  freely  exchanged  between  the 
operators  sitting  on  either  side  of  the  Channel,  and  auto- 
matically printed  down  in  telegraphic  code  signals  on  the 
ordinary  paper  slip  at  the  rate  of  twelve  to  eighteen  words 
a  minute.  !Not  once  was  there  the  slightest  difficulty  or 
delay  in  obtaining  an  instant  reply  to  a  signal  sent.  Ko 
familiarity  with  the  subject  removes  the  feeling  of  vague 
wonder  with  which  one  sees  a  telegraphic  instrument  merely 


G.   MARCONI S   METHOD. 


237 


connected  with  a  length  of  150  feet  of  copper  wire  run  up 
the  side  of  a  flagstaff  begin  to  draw  its  message  out  of 
space  and  print  down  in  dot  and  dash  on  the  paper  tape 
the  intelligence  ferried  across  thirty  miles  of  water  by  the 
mysterious  ether. 

An  extensive  trial  of  the  system  between  ships  at  sea 
was  next  made  during  the  British  naval  mano3uvres  in 
July  1899.  Three  ships  of  the  B  fleet  were  fitted  up 
— the  flagship,  Alexandra,  and  the  cruisers,  Juno  and 
Europa.  The  greatest  distance  to  which  signals  were  sent 


Fig.  41A. 

was  sixty  nautical  miles  between  the  Juno  and  Europa,  and 
forty  nautical  miles  between  the  Juno  and  Alexandra. 
These  were  not  the  maximum  ranges  attained,  but  the  dis- 
tances at  which,  under  all  circumstances,  the  system  could 
be  relied  on  for  certain  and  accurate  transmission.  Test 
signals  were  obtainable  up  to  a  distance  of  seventy-four 
nautical  miles  (eighty-five  miles). 

These  important  results  were  obtained  by  the  use  of 
Marconi's  peculiar  form  of  induction  coil  or  transformer.1 

1  Then  just  patented.  See  his  specification,  No.  12,326,  of  June 
1,  1898  (accepted  July  1,  1899);  or  abstract  iu  'Electrician,'  vol. 
xliii.  p.  847. 


238 


THIRD   PERIOD — THE  PRACTICAL. 


Fig.  4lA  shows  the  arrangement,  where  a  is  the  vertical 
wire,  b  the  earth  connection,  c  the  primary  and  d  the 
secondary  wires  of  the  transformer,  and  e  a  condenser. 
"The  object  of  this  arrangement,"  says  Mr  Marconi,  "is 
to  increase  the  electromotive  force  of  the  oscillations  at  the 
terminals  of  the  detector  /,  and  therefore  to  cause  its  state 
of  insulation  to  break  down  with  weaker  oscillations,  and 
so  be  affected  at  a  much  greater  distance  than  is  possible 
when  the  detector  is  connected  directly  with  the  vertical 
wire."  The  primary  coil  is  wound  with  fine  wire  (contrary  to 
the  usual  practice),  and  the  secondary  with  still  finer  wire. 
In  his  first  experiments  with  transformer  coils  of  various 


kinds,  Marconi  found  that  if  the  secondary  wire  be  wound 
in  more  than  one  layer,  little  if  any  advantage  is  obtained. 
He  was  led  to  try  a  mode  of  winding  in  which  the  centre 
of  the  coil  still  consisted  of  a  single  layer,  but  with  the 
number  of  turns  increased  at  the  ends.  This  gave  much 
better  results,  and  led,  finally,  to  the  arrangement  shown  in 
fig.  41fi,  which  "represents  an  enlarged  half  -  longitudinal 
section  of  the  coil,  but  is  not  drawn  strictly  to  scale.  Also, 
instead  of  showing  the  section  of  each  layer  of  wire  as  a 
longitudinal  row  of  dots  or  small  circles,  as  it  should  appear, 
it  is  for  simplicity  drawn  as  a  single  continuous  line."  It 
will  thus  be  seen  that  the  secondary  wire  is  wound  curi- 
ously in  four  sections ;  and  another  peculiarity  is  that  these 


G.  MARCONI'S  METHOD.  239 

sections  must  be  connected  together  in  the  way  shown, 
and,  as  the  distance  from  the  primary  wire  increases,  the 
number  of  turns  in  each  section  must  decrease. 

The  use  of  these  small  coils  during  the  naval  manoeuvres 
had  a  very  marked  effect  on  the  detector,  enabling  it  to 
respond  to  waves  from  greater  distances.  Thus,  when 
working  between  the  Juno  and  Europa  with  a  given  power 
in  the  transmitter  and  height  of  vertical  wires,  the  effective 
signalling  distance  was  seven  nautical  miles  without  the  coil, 
and  sixty  nautical  miles  with  it.1 

After '  the  naval  manoeuvres  Marconi  stations  were 
opened  at  Chelmsford  and  Harwich,  forty  miles  apart ;  and 
in  August  (1899),  during  the  meetings  of  the  British  Associa- 
tion at  Dover  and  the  French  Association  at  Boulogne, 
messages  were  freely  exchanged  between  the  two  places,  the 
distance  across  Channel  being  about  thirty  miles.  Corre- 
spondence was  also  kept  up  between  Dover  and  the 
South  Foreland  (four  miles)  and  the  Goodwin  (sixteen  miles) 
stations  across  the  great  masses  of  the  Castle  Rock  (400 
feet  high)  and  the  South  Foreland  cliffs.  Communication 
was  also  found  possible  between  Wimereux  and  Chelmsford 
or  Harwich.  The  distance  in  each  of  these  cases  is  about 
eighty- five  miles,  of  which  thirty  are  over  sea  and  fifty-five 
over  land.  The  height  of  the  vertical  wires  at  each  end 
was  150  feet,  thus  showing,  and  confirming  the  results  of 
many  previous  experiments,  that  considerable  masses  of  in- 
tervening rock,  earth,  and  water  do  not  offer  an  insur- 
mountable obstacle  to  the  transmission  of  signals.  If  they 
did,  and  if  it  had  been  necessary  for  a  line  drawn  between 
the  tops  of  the  wires  to  clear  the  curvature  of  the  earth, 

1  '  Electrician,'  vol.  xliv.  p.  555.  Prof.  Fessenden,  in  America,  uses 
in  the  same  way  a  specially  constructed  transformer  which  is  reported 
to  be  many  times  more  effective  than  Marconi's  ('Electrician,'  vol. 
xliii.  p.  807),  and  with  which  "it  should  be  possible  to  signal  across 
the  Atlantic  with  200  feet  vertical  wires  "!  ('  Globe/  January  1, 1900.) 


240  THIRD   PERIOD — THE  PRACTICAL. 

they  would  have  had  to  be  in  this  case  over  1000  feet 
high. 

In  America,  October  1899,  the  Marconi  apparatus  was 
employed  to  report  from  sea  the  progress  of  the  yachts 
in  the  international  contest  between  the  Columbia  and  the 
Shamrock.  The  working  was  (of  course)  perfectly  satis- 
factory, and  as  many  as  4000  words  are  said  to  have  been 
transmitted  in  one  day  from  the  (two)  ship  stations  to  the 
shore  station.2 

Immediately  after  the  races  the  instruments  were  placed, 
by  request,  at  the  service  of  the  American  Navy  Board, 
who  put  them  to  some  severe  and  interesting  tests.  The 
cruiser,  New  York,  and  the  battleship,  [Massachusetts,  were 
equipped  under  Mr  Marconi's  personal  supervision.  The 
two  vessels  lay  at  anchor  in  the  North  Itiver,  480  yards 
apart,  or  about  the  distance  that  would  separate  ships 
steaming  in  squadron  formation.  The  signalling  operations 
on  the  New  York  were  performed  by  Mr  Marconi  himself, 
aided  by  an  assistant,  and  under  the  directions  of  two 
members  of  the  Navy  Board ;  while  the  signalling  on  the 
Massachusetts  was  done  by  one  of  Marconi's  assistants,  under 
the  inspection  of  another  navy  official.  The  object  of  the 
first  experiments  was  to  determine  the  practicability  of  the 
system  for  short-distance  signalling  between  squadrons  at 
sea.  The  first  test  was  the  sending  and  receiving  of  a 
newspaper  article  of  about  1500  words,  which  was  done 
without  error,  and  at  a  speed  of  eleven  words  per  minute. 
The  second  test  was  the  transmission  of  a  series  of  numbers 
of  various  lengths,  which  was  also  done  correctly,  and  with 
a  little  more  rapidity.  The  third  test  dealt  with  a  series  of 
letters  written  down  at  random ;  the  fourth,  a  series  of 
short  messages ;  and  the  fifth  and  sixth,  series  of  code-word 

1  'Electrician,'  vol.  xliii.  pp.  737,  768,  793,  816 ;  vol.  xliv.  p.  557. 
•  'New  York  Herald'  (Paris  edition),  October  6,  1899. 


G.  MARCONI'S  METHOD.  241 

messages.  These  latter  naturally  taxed  the  skill  of  the 
operators,  the  "  words  "  having  a  weird  look,  unpronounc- 
able,  and  with  absolutely  no  sense  or  meaning.  It  is  there- 
fore not  surprising  that  in  these  tests  one  or  two  errors 
were  detected ;  but  they  were  probably  as  much  the  fault 
of  the  operator  as  of  the  apparatus.  Indeed,  as  Mr 
Marconi  has  pointed  out,  all  these  experiments  were  more 
tests  of  the  operators  for  correctness  and  speed  of  signalling 
than  of  the  utility  of  the  apparatus,  which  for  such  short 
distances  was  incontestable. 

The  vessels  then  left  for  the  open  sea.  At  a  point  about 
five  miles  off  the  Highlands  the  New  York  anchored,  while 
the  Massachusetts  continued  on  her  course,  exchanging 
signals  with  her  consort  at  intervals  of  ten  minutes.  Up  to 
some  distance  short  of  thirty-six  miles  the  signals  were 
good,  but  what  that  distance  was  the  report  from  which 
we  are  quoting  does  not  specify ;  it  merely  says,  "  At  a 
distance  of  thirty-six  miles  the  messages  failed  to  carry,  and 
the  battleship  came  back  and  anchored  a  few  hundred  yards 
from  the  New  York." l 

In  order  to  test  the  possibility  of  interference  with  tho 
signals,  a  Marconi  apparatus  was  established  at  the  High- 
lands, with  a  vertical  wire  of  150  feet.  At  intervals  during 
the  time  that  messages  were  being  exchanged  between  the 
two  warships  the  Highlands  station  sent  out  other  signals, 
with  the  invariable  result  that  the  correspondence  between 
the  ships  was  rendered  unintelligible.2 

The  official  report  of  such  an  independent  authority  as 
the  American  Navy  Board  must  always  be  valuable ;  and 
as,  moreover,  it  contains  precise  information  on  other  points 

1  Iu  an  article  in  the  'Times,'  November  16,  1899,  the  effective 
distance  is  said  to  have  been  thirty-five  miles,  and  that  the  apparatus 
was  only  designed  to  carry  thirty  miles,  that  being  considered  the 
outside  raiigfe  requisite  for  the  yacht-reporting  operation*. 

2  'Electrician,'  vol.  xliv.  p.  106. 

Q 


242  TIIIHD   PERIOD — THE  PRACTICAL. 

not  referred  to  in  the  preceding  paragraphs,  I  think  it  use- 
ful to  reproduce  it  as  follows  : — 

"We  respectfully  submit  the  following  findings  as  the 
result  of  our  investigation  of  the  Marconi  system  of  wire- 
less telegraphy :  It  is  well  adapted  for  use  in  squadron 
signalling  under  conditions  of  rain,  fog,  and  darkness. 
Wind,  rain,  fog,  and  other  conditions  of  weather  do  not 
affect  the  transmission ;  but  dampness  may  reduce  the  range, 
rapidity,  and  accuracy  by  impairing  the  insulation  of  tho 
aerial  wire  and  the  instruments.  Darkness  has  no  effect. 
We  have  no  data  as  to  the  effects  of  rolling  and  pitching ; 
but  excessive  vibration  at  high  speed  apparently  produced 
no  bad  effect,  on  the  instruments,  and  we  believe  the.  work- 
ing of  tho  system  would  be  very  little  affected  by  the 
motion  of  the  ship.  The  accuracy  is  good  within  the 
working  ranges.  Cipher  and  important'  signals  may  bo 
repeated  back  to  the  sending  station/  if  necessary,  to 
ensure  absolute  accuracy.  When  'ships  are  close  together 
(less  than  400  yards)  adjustments,  easily  made,  of  the 
instruments  are  necessary.  The  greatest  distance  that 
messages  were  exchanged  with  the  station  at  ^N"avesink 
was  16 J  miles.  This  distance  was  exceeded  consider- 
ably during  the  yacht  races,  when  a  more  efficient  set 
of  instruments  was  installed  there.1  The  best  location 
of  instruments  would  be  below,  well  protected,  in  easy 
communication  with  the  commanding  officer.  The  spark 
of  the  sending  coil,  or  of  a  considerable  leak,  due  to 
faulty  insulation  of  the  sending  wire,  would  be  sufficient 
to  ignite  an  inflammable  mixture  of  gas  or  other  easily 
lighted  matter,  but  with  direct  lead  (through  air  space, 
if  possible)  and  the  high  insulation  necessary  for  good 
work  no  danger  of  fire  need  be  apprehended.  When  two 

1  This  is  a  mistake.  The  instruments  were  the  same  iu  both  cases. 
See  'Times'  article,  November  16,  1899. 


G.  MARCONI'S  METHOD.  243 

transmitters  arc  sending  at  the  same  time,  all  the  receiving 
wires  within  range  receive  the  impulses,  and  the  tapes, 
although  unreadable,  show  unmistakably  that  such  double 
sending  is  taking  place.  In  every  case,  under  a  great 
number  of  varied  conditions,  the  interference  was  com- 
plete. Mr  Marconi,  although  he  stated  to  the  Board 
before  these  attempts  were  made  that  he  could  prevent 
interference,  never  explained  how,  nor  made  any  attempt 
to  demonstrate  that  it  could  be  done.  Between  large  ships 
(heights  of  masts  130  feet  and  140  feet)  and  a  torpedo- 
boat  (height  of  mast  45  feet),  across  open  water,  signals 
can  be  read  up  to  seven  miles  on  the  torpedo-boat  and 
eighty-five  miles  on  the  ship.  Communication  might  be 
interrupted  altogether  when  tali  buildings  of  iron  framing 
intervene.  The  rapidity  is  not  greater  than  twelve  words 
per  minute  for  skilled  operators.  The  shock  from  the 
sending  coil  of  wire  may  be  quite  severe,  and  even  dan- 
gerous to  a  person  with  a  weak  heart.  Ko  fatal  accidents 
have  been  recorded.  The  liability  to  accident  from  light- 
ning has  not  been  ascertained.  The  sending  apparatus  and 
wire  would  injuriously  affect  the  compass  if  placed  near  it. 
The  exact  distance  is  not  known,  and  should  be  determined 
by  experiment.  The  system  is  adapted  for  use  on  all 
vessels  of  the  navy,  including  torpedo-boats  and  small 
vessels,  as  patrols,  scouts,  and  despatch  boats,  but  it  is 
impracticable  in  a  small  boat.  For  landing  -  parties  the 
only  feasible  method  of  use  would  be  to  erect  a  pole  on 
shore  and  thence  communicate  with  the  ship.  The  system 
could  be  adapted  to  the  telegraphic  determination  of  differ- 
ences of  longitude  in  surveying.  The  Eoard  respectfully 
recommends  that  the  system  be  given  a  trial  in  the  navy."  l 
On  Mr  Marconi's  return  voyage  from  America  he  gave 
an  interesting  demonstration  of  the  value  of  his  system  for 
1  'Electrician,'  vol.  xliv.  p.  212. 


244  THIRD   PERIOD— THE  PRACTICAL. 

«hips  at  sea.  " A  few  days  previous,"  he  says,  "to  my 
departure,  the  war  in  South  Africa  broke  out.  Some  of  the 
officials  of  the  American  liner  suggested  that,  as  a  per- 
manent installation  existed  at  the  Needles,  Isle  of  AVight, 
it  would  be  a  great  thing,  if  possible,  to  obtain  the  latest 
war  news  before  our  arrival  at  Southampton.  I  readily 
consented  to  fit  up  my  instruments  on  the  St  Paul,  and 
succeeded  in  calling  up  the  Needles  station  at  a  distance  of 
sixty-six  nautical  miles,  when  all  the  important  news  was 
received  on  board,  the  ship  the  while  steaming  her  twenty 
knots  per  hour.  The  news  was  collected  and  printed  in 
a  small  paper,  called  the  *  Transatlantic  Times,'  several 
hours  before  our  arrival  at  Southampton."1 

In  October  1899  the  War  Office  sent  out  some  Marconi 
instruments  to  South  Africa,  for  use  at  the  base  and  on  the 
railways ;  but  the  military  authorities  on  the  spot  realised 
that  the  system  could  only  be  of  value  at  the  front,  and 
the  apparatus  was  moved  up  to  the  camp  at  De  Aar.  The 
results  at  first  were  not  altogether  satisfactory,  a  fact  which 
is  accounted  for  by  the  absence  of  suitable  poles  or  kites ; 
and  afterwards,  when  kites  were  improvised,  the  wind 
was  so  variable  that  it  often  happened  that  when  the  kite 
was  flying  at  one  station  there  was  a  calm  at  the  other 
station.  However,  when  suitable  kites  were  obtained,  and 
the  wind  was  favourable,  communication  was  possible 
from  De  Aar  to  the  Orange  Kiver,  or  about  seventy  miles. 
Stations  were  subsequently  established  at  Belmont,  Enslin, 
and  Modder  river  on  the  west,  and  in  Xatal  on  the  east. 
Ko  reliable  reports  of  the  work  of  these  installations 

'  *  *  Electrician,'  vol.  xliv.  p.  557.  Also  the  '  Times,'  November 
16  and  18,  1899.  This  unique  production  was  printed  by  the  ehip'a 
compositor,  and  published  at  a  dollar  per  copy,  the  proceeds  going  to 
the  Seamen's  Fund.  The  'Times'  of  November  16  reproduces  the 
conteuU. 


c.  MARCONI'S  METHOD,  245 

amongst  the  South -African  kopjes  have  yet  reached  us^ 
but  \ve  hope,  with  Mr  Marconi,  that  "  before  the  campaign 
is  ended  wireless  telegraphy  will  have  proved  its  utility  in 
actual  warfare."  l 

Having  now  brought  my  account  of  the  more  important 
of  Marconi's  public  demonstrations  up  to  date,2  I  -propose 
to  occupy  a  few  final  pages  with  some  further  remarks  on 
the  theory  and  practice  of  Hertzian-wave  telegraphy. 

It  has  been  objected  to  the  Marconi  system  that,  with 
the  removal  of  the  reflectors  and  the  resonance  wings,  the 
condition  of  privacy  in  telegrams  is  no  longer  possible,  since 
any  one  provided  with  the  necessary  apparatus  can  receive 
the  signals  at  any  point  within  the  circle  of  which  the 
sending  station  is  the  centre  and  the  receiving  station  the 
radius.  Another,  and  in  some  cases  more  serious,  objection 
is  that  any  one  by  erecting  a  wire  or  wires  in  the  vicinity  of 
a  Marconi  station  can  propagate  therefrom  Hertzian  waves, 
which  by  interference  will  so  confuse  the  effects  in  the 
detector  as  to  make  correct  signalling  impracticable.  It 
may  not  even  be  necessary  to  propagate  counter- waves :  a 
large  sheet  of  metal  (or  several  such  sheets)  erected  high 
in  air,  in  line  with  the  stations,  at  right  angles  to  the  direc- 
tion of  the  waves,  and  connected  by  a  wire  to  the  earth, 
will  intercept  much  of  the  energy,. and  the  more  so  as  it 
is  near  to  either  of  the  stations.  Thus,  if  used  for  naval  or 

1  'Electrician,'  vol.  xliv.  p.  557.     Up  to  date  (January  1901)  we 
have  no  authentic  accounts  of  the  results  obtained,  although  the 
Marconi  staff  have  long  ago  returned  to  England.     Rumour  says  the 
kopjes  have  proved  too  difficult.     See,  however,  Major  Flood  Page's 
remarks,  'Electrician,'  March  2,  1900. 

2  Of  course  I  do  not  pretend  that  these  are  the  only  demonstrations 
of  value  that  have  been  made.     In  America,  France,  Germany,  and 
Italy,  and  doubtless  in  other  countries,  important  experiments  have 
been  and  are  being  made  ;  but  beyond  occasional  brief  notices  of  them 
in  the  newspapers,  and  still  fewer  notices  in  the  technical  journals, 
few  clear  and  veracious  accounts  have  come  under  mv  notice. 


246  THIRD   PERIOD— THE  PRACTICAL. 

military  purposes,  an  enemy  could  either  tap  the  dispatches 
or  render  them  unintelligible  at  pleasure.  The  latter  ob- 
jection is  from  the  nature  of  things  unavoidable,  and  in 
practice  must  limit  the  application  of  the  system  to  lines  of 
communication  sufficiently  apart  as  not  to  interfere  with  one 
another.  The  first  objection,  however,  can  be  obviated  to 
some  extent  by  reverting  to  the  condition  of  syntony  or 
resonance  with  reflectors,  and  it  is  in  this  direction  that 
improvements  may  soon  be  expected. 
s  Dr  Oliver  Lodge,  F.luS.,  the  distinguished  Professor  of 
Physics,  University  College,  Liverpool,  and  the  coadjutor 
and  expounder  of  Hertz  in  England,  has  long  been  engaged 
on  the  problem  of  a  Hertzian-wave  telegraph — especially 
with  a  view  of  securing  syntony  in  the  sending  and  re- 
ceiving apparatus,  and  thereby  limiting  the  communications 
to  similarly  attuned  instruments,  the  absence  of  which  selec- 
tive character  is  at  present  one  of  the  great  drawbacks  of 
the  Marconi  system. 

We  have  seen  (p.  204,  supra)  that  as  early  as  June  1, 1894, 
Prof.  Lodge  had  exhibited  apparatus  which  was  effective 
for  signalling  on  a  small  scale,  but,  as  he  says,  "stupidly 
enough  no  attempt  was  then  made  to  apply  any  but  the 
feeblest  power,  so  as  to  test  how  far  the  disturbance  could 
really  be  detected.  .  .  .  There  remained,  no  doubt,  a 
number  of  points  of  detail,  and  considerable  improvements 
in  construction,  if  the  method  was  ever  to  become  practic- 
ally useful."  l  These  he  has  since  worked  out,  and  some  of 
them  are  embodied  in  his  patent,  ISTo.  11,575,  of  May  10, 
1897,  "  Improvements  in  Syntonised  Telegraphy  without 
Line  Wires." 

As  capacity  areas,  spheres  or  square  plates  of  metal  may 
be  employed ;  but  for  the  purpose  of  combining  low  resist- 
ance with  large  electro-static  capacity,  cones  or  triangles  are 
l  'The  Work  of  Hertz,'  pp.  67,  68. 


G.  MARCONI'S  METHOD. 


247 


preferred,  with  the  vertices  adjoining  and  their  larger  areas 
spreading  out  into  space.  Or  a  single  insulated  surface  may 
be  used  in  conjunction  with  the  earth — the  earth,  or  con- 
ductors embedded  in  it,  constituting  the  other  capacity  area. 
As  radiation  from  these  surfaces  is  greater  in  the  equatorial 
than  in  the  axial  direction,  so,  when  signalling  in  all  direc- 
tions is  desired,  the  axis  of  the  emitter  should  be  vertical. 
Moreover,  radiation  in  a  horizontal  plane  is  less  likely  to 


Fig.  42. 

be  absorbed  during  its  passage  over  partially  conducting 
earth  or  water. 

Fig.  42  shows  the  arrangement  for  long-distance  signalling. 
n  H l  are  large  triangular  sheets  of  metal,  which  by  means 
of  suitable  switches  (not  shown)  can  be  connected  to  the 
sending  or  the  receiving  apparatus  as  desired.  Those  on 
the  left-hand  side  of  the  figure  are  shown  in  connection 
with  polished  knobs  H  2  H  3  (protected  by  glass  from,  ultra- 
violet light),  which  form  the  adjustable  spark-gap  of  the 


248  THIRD  PERIOD— THE  PRACTICAL. 

exciter.  Between  each  capacity  area  and  its  knob  is 
inserted  a  self-inductance  coil  of  thick  wire  or  metallic 
ribbon  (see  H  \  fig.  43)  suitably  insulated,  the  object  of 
which  is  to  prolong  the  electrical  oscillations  in  a  succession 
of  waves,  and  thereby  obtain  a  definite  frequency  or  pitch, 
rendering  syntony  possible,  since  exactitude  of  working 
depends  on  the  fact  that  with  the  emission  of  a  mimber  of 
successive  waves  the  feeble  impulse  at  the  receiving  statiqn 
is  gradually  strengthened  till  it  causes  a  perceptible  effect, 
on  the  well-known  principle  of  sympathetic  resonance. 

The  capacity  areas  and  inductance  coils  are  exactly  alike 
at  the  two  communicating  stations,  so  as  to  have  the  same 
frequency  of  electrical  vibration.  This  frequency  can  be 
altered  either  by  varying  the  capacity  of  the  Leyden  jars 
used  in  the  exciting  circuit,  or  by  varying  the  number  and 
position  of  the  inductance  coils,  or  by  varying  both  in  the 
proper  degree,  thus  permitting  only  those  stations  whose 
rate  of  oscillation  is  the  same  to  correspond. 

To  actuate  the  exciter  a  HuhmkoriF  coil  may  be  used,  or 
a  Tesla  coil,  a  Wimshurst  machine,  or  any  other  high 
tension  apparatus. 

Fig.  43  shows  the  details  of  the  arrangement  for  exciting 
and  detecting  the  electric  waves.  When  used  as  a  trans- 
mitter the  receiving  circuit  is  disconnected  from  the  capacity 
areas  by  a  suitable  switch  (not  shown).  Let  us  first  con- 
sider the  arrangement  as  a  transmitter.  Putting  the  Euhm- 
korff  coil  A  in  action,  it  charges  the  Leyden  jars  J  J,  whose 
outer  coatings  are  connected,  first,  through  a  self-inductance 
coil  H  5  of  fairly  thin  wire,  so  as  to  permit  of  thorough 
charging  of  the  jars;  and,  second,  to  the  "supply  gaps" 
H  6  H  7.  When  the  jars  are  fully  charged  to  sparking- point, 
sparks  occur  at  the  "  starting-gap  "  H  8.  These  precipitate 
sparks  at  the  "  supply  gaps,"  which  evoke  electrical  charges 
iu  the  capacity  areas  unl.  These  charges  surge  through 
the  inductance  coils  H4,  and  spark  into  each  other  across 


c.  MALCONL'S  METHOD, 


249 


the  "  discharge  gap  "  between  the  knobs  H  2  H  3.  This  last 
discharge,  according  to  Prof.  Lodge,  is  the  chief  agent  in 
starting  the  oscillations  which  are  the  cause  of  the  emitted 
waves ;  but  it  is  permissible  to  close  the  "  discharge  gap," 
and  so  leave  the  oscillations  to  be  started  by  the  sparks 
at  the  "  supply  gaps "  only,  whose  knobs  must  then  be 
polished  and  protectecl  from  ultra-violet  light,  "so  as 
to  supply  the  electric  charge  in  as  sudden  a  manner  as 
possible." 


Fig.  43. 

When  used  as  a  receiver  the  "  discharge-gap  "  is  bridged 
over  by  a  suitable  cut-out,  and  connection  is  made  with  the 
receiving  circuit,  as  shown  on  the  top  of  fig.  43.  As 
detector,  Lodge  uses — 

1.  His  own  original  form  of  coherer,  fig.  44,  wherein 
a  metallic  point  N  rests  lightly  on  a  flat  metallic  surface 
o  (for  instance,  a  needle  point  of  steel  or  platinum  making 
light  contact  with  a  steel  or  aluminium  bar  like  a  watch 
spring),  fixed  at  one  end  P,  and  delicately  adjustable  by  a 


250 


THIRD  PERIOD— THE  PRACTICAL. 


micrometer  screw  Q,  so  as  to  regulate  the  pressure  at  tlio 
point  N.     Or — 

2.  A  Branly  tube   filled  with   selected  iron  filings  of 
uniform  size,  sealed  up  in  a  good  vacuum,  and  with  the 


^ 


_u 

o" 


-? 


electrodes,  which  are  of  platinum,  reduced  to  points  a  short 
distance  apart. 

Ilis  latest  form  of  the  Branly  coherer  is  shown  full  size 
in  fig.  45,  and  is  said  to  be  exceedingly  sensitive  and 
certain  in  its  action,  especially  in  a  very  high  vacuum. 
A  A  is  a  glass  tube  held  tightly  by  ebonite  supports  B  B  ; 
o  is  a  pocket  or  reservoir  for  spare  filings,  which  can  be 
added  to,  or  taken  from,  the  effective  portion  as  required 
by  inverting  the  tube ;  D  D  are  the  silver  electrodes 
immersed  in  the  filings,  which  are,  as  before,  of  carefully 
selected  iron  of  uniform  size  as  nearly  as  possible ;  E  is 
one  of  the  terminals  of  the  silver  electrodes,  the  other 
of  which  is  hidden  from  view. 

The  instrument  is  secured  by  the  clamp  screw  F  to  any 
convenient  support,  to  which  the  tapping  or  decohering 
apparatus  is  applied.1 

1  It  appears  that  to  Professor  Blondel  is  due  the  credit  of  first 
constructing  a  coherer  of  this  kind  in  August  1898.  See  the  '  Elec- 
trician,' vol.  xliii.  p.  277. 


c.  MARCONI'S  METHOD. 


251 


When  an  electric  wave  from  a  distant  exciter  arrives  and 
stimulates  electric  vibrations  in  the  syntonised  capacity 
areas,  the  electrical  resistance  of  the  coherer  suddenly  and 
greatly  falls  and  permits  the  small  battery  F,  fig.  43,  to 
actuate  a  relay  G,  or  a 
telephone,  or  other  tele- 
graphic instrument. 

To  break  contact,  or  to 
restore  the  original  great 
resistance  of  the  coherer, 
any  form  of  mechanical 
vibration  suffices,  as  a 
clock,  or  a  tuning-fork,  or 
a  cog-wheel  (as  in  fig.  44), 
or  other  device  for  caus- 
ing a  shake  or  tremor, 
and  kept  in  motion  by 
a  spring,  or  weight,  or 
by  electrical  means.  In- 
deed, the  mere  motion 
of  any  clockwork  at- 
tached to  the  coherer 
stand  will  suffice,  an  ex- 
ceedingly slight,  almost 
imperceptible,  tremor 
being  all  that  is  usually 
required. 

Usually  the  coherer  is 
arranged  in  simple  series 
with  the  battery  and  tele- 


Fig.  45. 


graphic  instrument,  and  is  so  joined  to  the  capacity  areas  as 
to  include  in  its  circuit  the  self -inductance  coils — an  arrange- 
ment which  Prof.  Lodge  considers  of  great  advantage,  or,  as 
lie  says,  "  an  improvement  on  any  mode  of  connection  that 
had  previously  been  possible  without  these  coils." 


232  THIRD  PEErOD— THE  PRACTICAL. 

The  patent  specification  figures  and  describes  another 
way — viz.,  enclosing  the  inductance  coils  in  an  outer  ot 
secondary  coil  (constituting  a  species  of  transformer),  and 
making  this  coil  part  of  the  coherer  circuit.  In  this  case 
the  coherer  is  stimulated  by  the  waves  in  the  secondary  coil 
instead  of,  as  before,  by  those  in  the  inductance  coils,  which 
with  their  capacity  areas  are  thus  left  free  to  vibrate  without 
disturbance  from  attached  wires. 

In  all  cases  it  is  permissible,  and  sometimes  desirable,  to 
shunt  the  coils  of  the  telegraphic  instrument  G  by  means  of 
a  fino  wire  or  other  non-inductive  resistance  coil  w,  "in 
order  to  connect  the  coherer  more  effectively  and  closely  to 
the  capacity  areas." 

At  the  Royal  Society  Conversazione  on  May  11,  1898,  a 
complete  set  of  Lodge's  apparatus  was  shown  in  action,  in 
which  certain  modifications  in  the  signalling  and  recording 
parts  were  introduced  at  the  suggestion  of  Dr  Alexander 
Muirhead.  Instead  of  the  ordinary  Morse  key,  Muirhead's 
well-known  automatic  transmitter  with  punched  tape  was 
employed  at  one  end  of  the  suite  of  rooms,  and  a  siphon- 
recorder  as  the  receiving  instrument  at  the  other  end.  The 
recorder  was  so  arranged  as  to  print,  not  as  usually  zigzag 
traces,  but  (the  needle  working  between  stops)  a  momentary 
deflection  mark  for  a  dot  and  a  longer  continued  mark  for 
a  dash. 

The  siphon-recorder  is  so  quick  in  its  responses  that  it 
indicates  each  one  of  the  group  of  sparks  emitted  from  the 
sending  apparatus  :  hence  a  dash  is  not  merely  a  deflection 
held  over,  but  is  made  up  of  a  series  of  minute  vibrations ; 
and  even  a  dot  is  seen  to  consist  of  similar  vibrations,  though 
of  course  of  a  lesser  number.  If  the  speed  of  signalling  is 
slow  and  the  recorder  tape  moves  slowly,  these  vibrations 
appear  as  actual  dots  and  dashes ;  but  each  signal,  when 
examined  with  a  microscope,  is  seen  to  consist  of  a  short  or 
long  series  of  lines  representing  the  constituent  vibrations. 


G.   MARCONI'S  METHOD.  253 

At  a  slow  rate  of  working  the  signals  can  thus  be  got 
with  exceeding  clearness ;  but  for  actual  signalling  this  is 
not  at  all  necessary,  and  it  is  possible  to  attain  a  high  speed, 
making  such  brief  contacts  that  a  single  deflection  of  the 
recorder  needle  indicates  a  dot,  and  three  consecutive  deflec- 
tions a  dash.  The  paper  thus  marked  docs  not  look  like 
the  ordinary  record,  but  more  resembles  the  original  Morse 
characters  as  depicted  on  pp.  404  and  409  of  Shaffner's 
'  Telegraph  Manual'  (New  York,  1859),  and  is  easily  legible 
with  a  little  practice. 

An  ordinary  telephone  was  also  available  as  a  receiver 
(connected  through  a  transformer  coil)  in  which  the  dots 
and  dashes  were  heard  very  clearly  and  distinctly. 

The  apparatus  is  reported  to  have  worked  well  (except  at 
the  high  speeds,  when  it  occasionally  missed  fire),  and  did 
not  seem  to  be  in  the  least  affected  by  any  of  the  numerous 
electrical  exhibits  in  the  neighbourhood,  although  some  of 
them  must  have  set  up  considerable  radiation  of  Hertzian 
waves. 

Based  on  the  same  principles  —  viz.,  the  emission  of 
electric  waves  at  one  place  and  their  detection  by  some 
form  of  coherer  at  another  place — there  is  naturally  a 
similarity  in  the  outlines  of  the  Lodge  system  and  that  of 
Marconi  for  short  distances  (where  vertical  wires  are  not 
used),  as  depicted  in  fig,  38,  supra.  The  differences  are 
differences  of  arrangement  and  detail  only,  but  they  appear 
to  be  fraught  with  some  important  consequences. 

In  the  first  place,  Prof.  Lodge  claims  that  his  arrange- 
ment of  the  sending  apparatus  is  a  more  persistent  exciter, 
in  that  it  emits  a  longer  train  of  longer  waves,1  which  by 
acting  cumulatively  on  the  detector  breaks  down  its  in- 
sulation, when  more  powerful  but  fewer  trains  of  shorter 
waves  might  be  inoperative.  Then  in  the  next  place,  this 

1  For  some  important  observations  on  this  point  see  Mr  A.  Camp- 
bell Swintoii,  'Jour.  Inst.  Elec.  Engs.,'  No.  139,  p.  317* 


254  THIRD  PERIOD — THE  PRACTICAL. 

element  of  persistency  permits  of  the  use  of  syntonising 
contrivances,  by  means  of  which  the  rate  of  oscillation  of 
any  desired  set  of  instruments  can  be  accurately  attuned  so 
that  only  those  instruments  can  correspond,  without  affect- 
ing or  being  affected  by  other  sets  tuned  to  a  different 
frequency,  thus  securing  to  some  extent  the  advantage  of 
privacy  in  the  communications. 

Lodge's  arrangement  has  worked  well  in  the  laboratory 
and  lecture-room,  but  lie  does  not  appear  to  have  tried  it 
(which  is  a  pity)  over  any  considerable  distance,  so  that  it  re- 
mains to  be  seen  how  far  he  can  go  without  having  recourse 
to  vertical  wires,  which  Marconi  finds  so  essential  for  prac- 
tical work  over  distances  of  more  than  two  or  three  miles.1 

Speaking  of  the  waste  of  energy  all  round  a  Marconi 
transmitter  as  now  constructed,  and  of  the  desirability  of 
preventing  it  if  possible,  a  writer  in  a  recent  volume  of  the 
'Electrician'  (vol.  xli.  p.  83)  has  some  remarks  which  may  ap- 
propriately be  given  here.  "  Unless,"  he  says,  "  some  means 
are  adopted  for  converging  the  radiation  along  a  definite 
path,  the  practical  and  commercial  efficiency  of  Hertzian- 
wave  telegraphy  will  be  small,  and  the  enormous  quan- 
tities of  wasted  radiation  spreading  away  from  the  line  of 
signalling  will  have  to  be  prevented  from  interfering  with 
other  receiving  stations.  Prof.  Lodge  has  proposed  the 
syntonising  of  instruments  as  a  means  of  preventing  this 
interference,  and  it  is  undoubtedly  possible  to  tune  the 
receiver  so  that  it  will  respond  only  to  waves  of  a  par- 
ticular pitch  ;  but  should  wireless  telegraphy  by  Hertzian 
waves  ever  become  extensively  practised  over  considerable 
distances,  the  number  of  possible  non-interfering  tones  of 
wave-lengths  will  be  found  insufficient  for  the  number  of 
receiving  stations.  Besides,  the  syntonising  method  of 
confining  the  message  to  its  proper  path  has  the  disadvan- 

1  For  Professor  Lodge's  newest  developments  see  his  paper,  'Jour. 
Insfc.  Elec.  Engs.,'  No.  137,  p.  799,  which  deserves  careful  study. 


G.   MARCONI'S   METHOD.  255 

tage  that  it  docs  not  confine  the  energy  to  that  path ;  it  is 
therefore  very  wasteful. 

"  Hertzian  waves,  like  their  natural  relatives  light  waves, 
have  the  property  that  they  can  be  reflected  and  refracted ; 
though,  from  the  fact  of  their  much  greater  wave-length, 
the  apparatus  requisite  for  converging  them  in  a  parallel 
beam  is  more  difficult  to  construct  and  more  costly  than 
is,  for  example,  the  parabolic  reflector  of  a  search  light  or 
the  compound  lens  of  a  lighthouse.  Nevertheless  there 
are  well-known  substances,  of  which  pitch  is  an  example, 
which,  when  formed  into  a  lens  or  prism,  have  the  power 
of  acting  upon  Hertzian  waves  precisely  as  lenses  or  prisms 
of  glass  act  upon  rays  of  ordinary  light.  As  a  scientific  fact 
this  has  been  known  since  Hertz's  time,  but  there  would 
appear  to  be  considerable  difficulty  in  its  application. 

"  We  are  inclined  to  think,  however,  that  it  will  ultimately 
be  found  necessary  to  employ,  in  wireless  telegraphy,  some 
such  means  as  a  huge  pitch  lens  would  afford  for  collecting 
the  scattering  rays  from  the  Hertzian  wave  generator  or 
oscillator,  and  refracting  them  into  a  beam  of  almost,  if  not 
quite,  parallel  rays;  thus  improving,  both  in  efficiency  and 
in  penetrative  power,  this  interesting  method  of  propagating 
signals  through  space." 

Mr  Marconi  has  been  steadily  working  at  these  problems 
of  syntony  and  reflection.  The  latter  is,  I  fear,  only  possible 
for  short  distances,  up  to  a  few  miles,  and  with  apparatus 
as  originally  constructed  (p.  206,  ante).  For  greater  dis- 
tances necessitating  considerable  lengths  of  vertical  wire 
such  huge  reflectors  would  be  required,  and  their  adjust- 
ment would  be  so  difficult  as  to  make  the  plan  practically 
impossible. 

From  syntonising  methods  some  promising  results  have 
been  obtained.  In  a  recent  letter  to  the  *  Times '  (October 
4,  1900)  Prof.  Fleming  has  some  startling  revelations. 
"For  the  last  two  years,"  he  says,  "Mr  Marconi  has  not 


256  THIRD   PEKIOD — THE  PRACTICAL. 

ceased  to  grapple  with  the  problem  of  isolating  the  lines  of 
communication,  and  success  has  now  rewarded  his  skill  and 
industry.  Technical  details  must  be  left  to  be  described  by 
him  later  on,  but  meanwhile  I  may  say  that  he  has  modified 
his  receiving  and  transmitting  appliances  so  that  they 
will  only  respond  to  each  other  when  properly  tuned  to 
sympathy. 

"These  experiments  have  been  conducted  between  two 
stations  30  miles  apart — one  near  Poole  in  Dorset  and  the 
other  near  St  Catherine's  in  the  Isle  of  Wight.  At  the 
present  moment  there  are  established  at  these  places  Mr 
Marconi's  latest  appliances,  so  adjusted  that  each  receiver  at 
one  station  responds  only  to  its  corresponding  transmitter  at 
the  other.  During  a  three  days'  visit  to  Poole,  Mr  Marconi 
invited  me  to  apply  any  test  I  pleased  to  satisfy  myself  of 
the  complete  independence  of  the  circuits,  and  the  following 
are  two  out  of  many  such  tests :  Two  operators  at  St 
Catherine's  were  instructed  to  send  simultaneously  two 
different  wireless  messages  to  Poole,  and  without  delay  or 
mistake  the  two  were  correctly  recorded  and  printed  down 
at  the  same  time  in  Morse  signals  on  the  tapes  of  the  two 
corresponding  receivers  at  Poole. 

"  In  this  first  demonstration  eacli  receiver  was  connected 
to  its  own  independent  aerial  wire  hung  from  the  same 
mast.  But  greater  wonders  followed.  Mr  Marconi  placed 
the  receivers  at  Poole  one  on  the  top  of  the  other,  and  con- 
nected them  both  to  one  and  the  same  wire,  about  40  feet 
in  length,  attached  to  a  mast.  I  then  asked  to  have  two 
messages  sent  at  the  same  moment  by  the  operators  at  St 
Catherine's,  one  in  English  and  the  other  in  French.  With- 
out failure  each  receiver  a.t  Poole  rolled  out  its  paper  tape, 
the  message  in  English  perfect  on  one  and  that  in  French 
on  the  other.  When  it  is  realised  that  these  visible  dots 
and  dashes  are  the  results  of  trains  of  intermingled  electric 


G.   MARCONI'S   METHOD.  257 

waves  rushing  with  the  speed  of  light  across  the  intervening 
30  miles,  caught  on  one  and  the  same  short  aerial  wire, 
and  disentangled  and  sorted  out  automatically  by  the  two 
machines  into  intelligible  messages  in  different  languages, 
the  wonder  of  it  all  cannot  but  strike  the  mind. 

"  Your  space  is  too  valuable  to  be  encroached  upon  by 
further  details,  or  else  I  might  mention  some  marvellous 
results,  exhibited  by  Mr  Marconi  during  the  same  demon- 
strations, of  messages  received  from  a  transmitter  30  miles 
away  and  recorded  by  an  instrument  in  a  closed  room  merely 
by  the  aid  of  a  zinc  cylinder,  4  feet  high,  placed  on  a  chair. 
More  surprising  is  it  to  learn  that,  whilst  these  experiments 
have  been  proceeding  between  Poole  and  St  Catherine's, 
others  have  been  taking  place  for  the  Admiralty  between 
Portsmouth  and  Portland,  these  lines  of  communication 
intersecting  each  other ;  yet  so  perfect  is  the  independence 
that  nothing  done  on  one  circuit  now  affects  the  other,  unless 
desired.  A  corollary  of  these  latest  improvements  is  that 
the  necessity  for  very  high  masts  is  abolished.  Mr  Marconi 
now  has  established  perfect  independent  wireless  telegraphic 
communication  between  Poole  and  St  Catherine's,  a  distance 
of  30  miles,  by  means  of  a  pair  of  metal  cylinders  elevated 
25  feet  or  30  feet  above  the  ground  at  each  place." 

If  these  latest  improvements  yield  only  one-half  of  the 
results  indicated  by  Prof.  Fleming,  the  value  of  Marconi's 
system  will  be  enormously  enhanced  and  its  sphere  of  utility 
correspondingly  extended.1  We  therefore  await  with  im- 
patience the  promised  disclosures  as  to  how  all  these  won- 
derful things  can  be  done. 

Even  should  the  improvements  turn  out  to  be  of  no  great 
practical  value,  or  to  be  not  susceptible  of  extensive  applica- 


1  In  which  case  we  shall  have,  in  future  editions,  to  withdraw  or 
at  least  to  modify  some  of  our  remarks  as  to  its  present  limitations. 


258  THIRD  PERIOD — THE  PRACTICAL. 

tion,  we  can  well  be  content  with  the  system  as  described 
in  these  pages.  It  has  proved  to  be  practical  up  to  sixty 
or  seventy  miles,  and  within  this  limit  there  ought  to  be 
a  wide  and  useful  field  for  activity.  Thus,  many  outlying 
islands  are  within  this  distance  from  each  other  and  from 
the  continents,  with  which  communication  at  all  times  has 
hitherto  been  practicable  only  by  the  use  of  cables,  which 
are  always  costly  to  make  and  lay,  and  often  costly  to  keep 
in  repair.  Here,  especially  between  places  where  the  traffic 
is  not  great,  is  a  large  field  to  be  occupied  as  cables  grow 
old  and  fail. 

Then,  we  have  seen  from  the  address  of  the  chairman 
of  the  Wireless  Telegraph  Company  that  negotiations  are 
going  on  with  Lloyd's  which,  if  carried  into  practical  effect, 
will  result  in  an  extensive  application  for  signalling  between 
Lloyd's  stations  and  outward  and  inward  bound  vessels 
passing  in  their  vicinity.  Indeed  it  is  not  rash  to  predict 
that  the  lighthouses  and  lightships  around  the  coasts,  not 
only  of  the  British  Isles  but  of  all  countries,  will  in  time 
be  supplied  with  wireless  telegraphs,  keeping  up  constant 
correspondence  with  all  who  go  down  to  the  sea  in  ships. 
Then,  again,  there  is  the  application  to  intercommunication 
between  ships  at  sea.  Ships  carrying  the  Marconi  ap- 
paratus can  carry  on  a  definite  conversation  with  the  occu- 
pants of  lighthouses  and  lightships  and  with  each  other. 
It  will  readily  be  seen  that  this  might,  in  many  cases,  be 
far  more  serviceable  than  the  few  light  signals  now  obtain- 
able, or  the  signalling  by  flags,  horns,  &c. — a  tedious  process 
at  best,  and  one  that  is  often  full  of  uncertainty,  if  not  of 
positive  error.1 

1  The  English,  American,  German,  and  French  naval  authorities 
are  now  making  independent  experiments  with  the  Marconi  system, 
and  it  is  probable  we  may  soon  hear  of  its  adoption,  or  of  some  modi- 
fication of  it,  as  part  of  the  equipment  of  not  only  warships  but  of 
all  large  vessels. 


G.   MARCONI'S   METHOD.  259 

Turning  from  sea  to  land,  we  find,  for  the  reasons  we 
have  already  indicated,  a  more  circumscribed  field  of  ap- 
plication— at  all  events,  until  means  are  devised  for  focus- 
sing the  electric  rays  and  rendering  the  apparatus  syntonic. 
But  even  then,  although  by  these  means  we  will  be  able  to 
record  messages  only  where  intended,  there  still  remain 
cross  interferences  of  which  I  fear  we  can  never  be  rid, 
and  therefore  we  can  never  use  the  system  in  a  network 
of  lines  as  now,  where  wires  cross,  recross,  and  overlap  each 
other  in  all  ways  and  directions.  The  various  waves  of 
electricity  would  so  interfere  with  each  other  in  their 
effects  on  the  detectors  that  the  result  would  be  chaos. 
Therefore  wireless  telegraphy  can  only  be  used  in  lines 
removed  from  each  other's  disturbing  influences,  as  in 
sparsely  populated  countries  and  undeveloped  regions. 

However,  many  cases  of  impromptu  means  of  communi- 
cation arise  where,  as  Prof.  Lodge  says,  it  might  be  advan- 
tageous to  "shout"  the  message,  spreading  it  broadcast 
to  receivers  in  all  directions,  and  for  which  the  wireless 
system  is  well  adapted,  seeing  that  it  is  so  inexpensive  and 
so  easily  and  rapidly  installed, — such  as  for  army  manoeu- 
vres, for  reporting  races  and  other  sporting  events,  and, 
generally,  for  all  important  matters  occurring  beyond  the 
range  of  the  permanent  lines. 

But  for  the  regular  daily  correspondence  of  a  nation 
with  its  lines  ramifying  in  all  directions  and  carrying 
enormous  traffics,  the  Marconi  system  is  not  adapted, 
no  more  than  any  other  wireless  method  that  has  been 
proposed,  or  is  likely  to  be  invented  in  our  day.  So,  for  a 
long  time  to  come  we  must  keep  to  our  present  telegraphic 
and  telephonic  wires,  using  the  wireless  telegraph  as  an 
adjunct  for  special  cases  and  contingencies  such  as  I  have 
mentioned. 

A  few  words  as  to  the  future,  by  way  of  conclusion,  and 


2 GO  THIRD   PERIOD — THE   PRACTICAL. 

our  task  is  completed.  On  tins  point  we  find  some  recent 
remarks  of  Prof.  Silvanus  Thompson  so  appropriate  that  we 
quote  them  in  full,  as  being  more  authoritative  than  anything 
we  could  ourselves  say.  Prof.  Thompson  has  thoroughly 
studied  the  subject,  and  therefore  "  speaks  by  the  card." 

"It  has  been  shown,"  he  says,  "that  there  are  three 
general  methods  of  transmitting  electric  signals  across  space. 
All  of  them  require  base  lines  or  base  areas.  The  first — 
conduction — requires  moist  earth  or  water  as  a  medium,  and 
is  for  distances  under  three  miles  the  most  effective  of  the 
three.  The  second — induction — is  not  dependent  upon 
earth  or  water,  but  will  equally  well  cross  air  or  dry  rock. 
The  third — electric  wave  propagation — requires  no  medium 
beyond  that  of  the  ether  of  space,  but  is  interfered  with  by 
interposed  things  such  as  masts  or  trees.  Given  proper  base 
lines  or  base  areas,  given  adequate  methods  of  throwing 
electric  energy  into  the  transmitting  system,  and  sufficiently 
sensitive  instruments  to  pick  up  and  translate  the  signals,  it 
is  possible,  in  my  opinion,  so  to  develop  each  of  the  three 
methods  that  by  any  one  of  them  it  will  be  possible  to 
establish  electric  communication  between  England  and 
America  across  the  intervening  space.  It  is  certainly  pos- 
sible, either  by  conduction  or  by  induction ;  whether  by 
waves  I  am  somewhat  less  certain.  Conduction  might  very 
seriously  interfere  with  other  electric  agencies,  since  the 
waste  currents  in  the  neighbourhood  of  the  primary  base 
line  would  be  very  great.  It  is  certainly  possible  either  by 
conduction  or  induction  to  establish  direct  communication 
across  space  with  either  the  Cape,  or  India,  or  Australia 
(under  the  same  assumptions  as  before),  and  at  a  far  less  cost 
than  that  of  a  connecting  submarine  cable. 

"  Instruments  which  operate  by  means  of  alternating  cur- 
rents of  high  frequency,  like  Mr  Langdon-Davies's  phono- 
phore,  are  peculiarly  liable  to  set  up  disturbance  in  other 


G.  MARCONI'S  METHOD.  2G1 

circuits.  A  single  plionopliore  circuit  can  be  heard  in  lines 
a  hundred  miles  away.  When  this  first  came  to  my  notice 
it  impressed  me  greatly,  and  coupled  in  my  mind  with  the 
Ferranti  incident  mentioned  above  "  (see  note,  p.  1 44,  supra), 
"caused  me  to  offer  to  one  of  my  financial  friends  in  the  City, 
some  eight  years  ago,  to  undertake  seriously  to  establish 
telegraphic  communication  with  the  Cape,  provided  £10,000 
were  forthcoming  to  establish  the  necessary  basal  circuits  in 
the  two  countries,  and  the  instruments  for  creating  the  cur- 
rents. My  offer  was  deemed  too  visionary  for  acceptance. 
The  thing,  however,  is  quite  feasible.  The  one  necessary 
thing  is  the  adequate  base  line  or  area.  All  the  rest  is 
detail."  l 

One  word  more.  A  press  telegram  of  April  12,  1899, 
says  :  "  The  Wireless  Telegraph  Company  have  been 
approached  by  the  representative  of  a  proposed  syndicate 
which  desires  to  acquire  the  sole  rights  of  establishing 
wireless  telegraphic  communication  between  England  and 
America.  The  directors  of  the  Company  will  consider 
the  matter  at  their  first  meeting,  which  is  fixed  for  an 
early  date."2 

Thus  I  end  my  task  as  I  began  it,  with  a  dream — the 
self-same  dream  !  As  to  its  realisation  in  the  distant  future 
who  can  say  nay  ? 

"  There  are  more  things  in  heaven  and  earth,  Horatio, 
Than  are  dreamt  of  in  our  philosophy." 


1  'Journal,  Society  of  Arts,'  April  1,  1898. 

2  The  syndicate  must  hurry  up,  as  Mr  Nikola  Tesla  is  now  on  their 
track  with  a  wireless  telegraph  that  will  "stagger  humanity."     We 
read  ('Electrician,'  January  19,  1900)  that  he  is  convinced  he  will 
soon  be  able  to  communicate,  not  only  with  Paris,  but  with  every 
city  in  the  world,  and  that  at  a  speed  of  from  1500  to  2000  words  per 
minute  J     See  also  p.  239,  supra,  for  Prof.  Fessenden's  great  hopes. 


2G2 


APPENDIX  A. 

THE  KELATION  BETWEEN  ELECTRICITY  AND  LIGHT 
— BEFORE  AXD  AFTER  HERTZ. 

Before  Hertz. 

SUBSTANCE  of  a  lecture  by  Prof.  Oliver  Lodge,  London  In- 
stitution, December  16,  1880.1 

Ever  since  the  subject  on  which  I  have  to  speak  to-night 
•was  arranged,  I  have  been  astonished  at  my  own  audacity 
in  proposing  to  deal,  in  the  course  of  sixty  minutes,  with 
a  subject  so  gigantic  and  so  profound  that  a  course  of  sixty 
lectures  would  be  inadequate  for  its  thorough  and  exhaustive 
treatment.  I  must,  therefore,  confine  myself  to  some  few  of 
the  most  salient  points  in  the  relation  between  electricity  and 
light,  and  I  must  economise  time  by  plunging  at  once  into  the 
middle  of  the  matter  without  further  preliminary. 

What  is  electricity  1  We  do  not  know.  We  cannot  assert 
that  it  is  a  form  of  matter  ;  neither  can  we  deny  it.  On  the 
other  hand,  we  cannot  certainly  assert  that  it  is  a  form  of 
energy  ;  and  I  should  be  disposed  to  deny  it.  It  may  be 
that  electricity  is  an  entity  per  se,  just  as  matter  is  an 
entity  per  se.  Nevertheless,  I  can  tell  you  what  I  mean 
by  electricity  by  appealing  to  its  known  behaviour. 

Here  is  a  voltaic  battery.  I  want  you  to  regard  it,  and 
all  electrical  machines  and  batteries,  as  kinds  of  electricity- 
pumps,  which  drive  the  electricity  along  through  the  wire 
very  much  as  a  water-pump  can  drive  water  along  pipes. 

1  Based  on  a  report  in  '  Design  and  Work,'  February  5,  1881. 


RELATION   BETWEEN  ELECTRICITY  AND   LIGHT.      2G3 

While  this  is  going  on,  the  wire  manifests  a  whole  series  of 
properties,  which  are  called  the  properties  of  the  current. 

[Here  were  shown  an  ignited  platinum  wire,  the  electric 
arc  between  two  carbons,  an  electric  machine  spark,  an  in- 
duction coil  spark,  and  a  vacuum  tube  glow.  Also  a  large 
nail  was  magnetised  by  being  wrapped  in  the  current,  and 
two  helices  were  suspended  and  seen  to  direct  and  attract 
each  other.] 

To  make  a  magnet,  then,  we  only  need  a  current  of  elec- 
tricity flowing  round  and  round  in  a  whirl.  A  vortex  or 
whirlpool  of  electricity  is  in  fact  a  magnet,  and  vice  versa. 
And  these  whirls  have  the  power  of  directing  and  attracting 
other  previously  existing  whirls  according  to  certain  laws, 
called  the  laws  of  magnetism.  And,  moreover,  they  have 
the  power  of  exciting  fresh  whirls  in  neighbouring  con- 
ductors, and  of  repelling  them  according  to  the  laws  of 
diamagnetism.  The  theory  of  the  actions  is  known,  though 
the  nature  of  the  whirls,  as  of  the  simple  streams  of  elec- 
tricity, is  at  present  unknown. 

[Here  was  shown  a  large  electro-magnet  and  an  induction- 
coil  vacuum  discharge  spinning  round  and  round  when  placed 
in  its  field.] 

So  much  for  what  happens  when  electricity  is  made  to 
travel  along  conductors — i.e.,  when  it  travels  along  like  a 
stream  of  water  in  a  pipe,  or  spins  round  and  round  like 
a  whirlpool. 

But  there  is  another  set  of  phenomena,  usually  regarded 
as  distinct  and  of  another  order,  but  which  are  not  so 
distinct  as  they  appear,  which  manifest  themselves  when 
you  join  the  pump  to  a  piece  of  glass  or  any  non-conductor 
and  try  to  force  the  electricity  through  that.  You  succeed 
in  driving  some  through,  but  the  flow  is  no  longer  like  that 
of  water  in  an  open  pipe  ;  it  is  as  if  the  pipe  were  com- 
pletely obstructed  by  a  number  of  elastic  partitions  or  dia- 
phragms. The  water  cannot  move  without  straining  and 
bending  these  diaphragms,  and  if  you  allow  it,  these  strained 
partitions  will  recover  themselves  and  drive  the  water  back 
again.  [Here  was  explained  the  process  of  charging  a  Ley  den 
jar.]  The  essential  thing  to  remember  is  that  we  may  have 
electrical  energy  in  two  forms,  the  static  and  the  kinetic ; 


264  APPENDIX  A. 

and  it  is  therefore  also  possible  to  have  the  rapid  alternation 
from  one  of  these  forms  to  the  other,  called  vibration. 

Now  we  will  pass  to  the  second  question  :  What  do  you 
mean  by  light  ?  And  the  first  and  obvious  answer  is,  Every- 
body knows.  And  everybody  that  is  not  blind  does  know  to 
a  certain  extent.  We  have  a  special  sense-organ  for  appreci- 
ating light,  whereas  we  have  none  for  electricity.  Neverthe- 
less, we  must  admit  that  we  really  know  very  little  about  the 
intimate  nature  of  light — very  little  more  than  about  elec- 
tricity. But  we  do  know  this,  that  light  is  a  form  of  energy  ; 
and,  moreover,  that  it  is  energy  rapidly  alternating  between 
the  static  and  the  kinetic  forms — that  it  is,  in  fact,  a  special 
kind  of  energy  of  vibration.  We  are  absolutely  certain  that 
light  is  a  periodic  disturbance  in  some  medium,  periodic  both 
in  space  and  time — that  is  to  say,  the  same  appearances  regu- 
larly recur  at  certain  equal  intervals  of  distance  at  the  same 
time,  and  also  present  themselves  at  equal  intervals  of  time 
at  the  same  place ;  that,  in  fact,  it  belongs  to  the  class 
of  motions  called  by  mathematicians  undulatory  or  wave 
motions. 

Now  how  much  connection  between  electricity  and  light 
have  we  perceived  in  this  glance  into  their  natures  1  Not 
much  truly.  It  amounts  to  about  this :  That  on  the  one 
hand  electrical  energy  may  exist  in  either  of  two  forms — 
the  static  form,  when  insulators  are  electrically  strained  by 
having  had  electricity  driven  partially  through  them  (as  in 
the  Leyden  jar),  which  strain  is  a  form  of  energy,  because 
of  the  tendency  to  discharge  and  do  work  ;  and  the  kinetic 
form,  where  electricity  is  moving  bodily  along  through  con- 
ductors, or  whirling  round  and  round  inside  them,  which 
motion  of  electricity  is  a  form  of  energy,  because  the  con- 
ductors and  whirls  can  attract  or  repel  each  other  and  thereby 
do  work. 

On  the  other  hand,  light  is  the  rapid  alternation  of  energy 
from  one  of  these  forms  to  the  other — the  static  form  where 
the  medium  is  strained,  to  the  kinetic  form  when  it  moves. 
It  is  just  conceivable  then  that  the  static  form  of  the  energy 
of  light  is  electro- static — that  is,  that  the  medium  is  electrically 
strained — and  that  the  kinetic  form  of  the  energy  of  light  is 
efectfro-kinetic — that  is,  that  the  motion  is  not  ordinary  motion, 


RELATION   BETWEEN   ELECTUICITY  AND   LIGHT.      265 

but  electrical  motion — in  fact,  that  light  is  an  electrical  vibra- 
tion, not  a  material  one. 

On  November  5  last  year  there  died  at  Cambridge  a  man  in 
the  full  vigour  of  his  faculties — such  faculties  as  do  not  appear 
many  times  in  a  century — whose  chief  work  had  been  the 
establishment  of  this  very  fact,  the  discovery  of  the  link  con- 
necting light  and  electricity,  and  the  proof — for  I  believe  that  it 
amounts  to  a  proof— that  they  are  different  manifestations  of 
one  and  the  same  class  of  phenomena, — that  light  is,  in  fact,  an 
electro-magnetic  disturbance.  The  premature  death  of  James 
Clerk -Maxwell  is  a  loss  to  science  which  appears  at  present 
utterly  irreparable,  for  he  was  engaged  in  researches  that  no 
other  man  can  hope  as  yet  adequately  to  grasp  and  follow  out ; 
but  fortunately  it  did  not  occur  till  he  had  published  his  book 
on  'Electricity  and  Magnetism,'  one  of  those  immortal  pro- 
ductions which  exalt  one's  idea  of  the  mind  of  man,  and  which 
has  been  mentioned  by  competent  critics  in  the  same  breath 
as  the  Trincipia'  itself. 

The  main  proof  of  the  electro-magnetic  theory  of  light  is 
this  :  The  rate  at  which  light  travels  has  been  measured 
many  times,  and  is  pretty  well  known.  The  rate  at  which 
an  electro-magnetic  wave  disturbance  would  travel,  if  such 
could  be  generated  (and  Mr  Fitzgerald,  of  Dublin,  thinks 
he  has  proved  that  it  cannot  be  generated  directly  by  any 
known  electrical  means),  can  be  also  determined  by  calcula- 
tion from  electrical  measurements.  The  two  velocities  agree 
exactly. 

The  first  glimpse  of  this  splendid  generalisation  was  caught 
in  1845,  five-and -thirty  years  ago,  by  that  prince  of  pure  ex- 
perimentalists, Michael  Faraday.  His  reasons  for  suspecting 
some  connection  between  electricity  and  light  are  not  clear  to 
us — in  fact,  they  could  not  have  been  clear  to  him  ;  but  he 
seems  to  have  felt  a  conviction  that  if  he  only  tried  long 
enough,  and  sent  all  kinds  of  rays  of  light  in  all  possible  direc- 
tions across  electric  and  magnetic  fields  in  all  sorts  of  media, 
he  must  ultimately  hit  upon  something.  Well,  this  is  very 
nearly  what  he  did.  With  a  sublime  patience  and  persever- 
ance which  remind  one  of  the  way  Kepler  hunted  down  guess 
after  guess  in  a  different  field  of  research,  Faraday  combined 
electricity,  or  magnetism,  and  light  in  all  manner  of  ways,  and 


266  APPENDIX  A. 

at  last  he  was  rewarded  with  a  result— and  a  most  out-of-the- 
way  result  it  seemed.  First,  you  have  to  get  a  most  powerful 
magnet,  and  very  strongly  excite  it ;  then  you  have  to  pierce 
its  two  poles  with  holes,  in  order  that  a  beam  of  light  may 
travel  from  one  to  the  other  along  the  lines  of  force  ;  then,  as 
ordinary  light  is  no  good,  you  must  get  a  beam  of  plane 
polarised  light  and  send  it  between  the  poles.  But  still  no 
result  is  obtained  until,  finally,  you  interpose  a  piece  of  a  rare 
and  out-of-the-way  material  which  Faraday  had  himself  dis- 
covered and  made,  a  kind  of  glass  which  contains  borate  of 
lead,  and  which  is  very  heavy  or  dense,  and  which  must  be 
perfectly  annealed. 

And  now,  when  all  these  arrangements  are  completed,  what 
is  seen  is  simply  this,  that  if  an  analyser  is  arranged  to  stop 
the  light  and  make  the  field  quite  dark  before  the  magnet  is 
excited,  then  directly  the  battery  is  connected  and  the  magnet 
called  into  action  a  faint  and  barely  perceptible  brightening 
of  the  field  occurs,  which  will  disappear  if  the  analyser  be 
slightly  rotated.  [The  experiment  was  shown.]  Now,  no 
wonder  that  no  one  understood  this  result.  Faraday  himself 
did  not  understand  it  at  all.  He  seems  to  have  thought  that 
the  magnetic  lines  of  force  were  rendered  luminous,  or  that  the 
light  was  magnetised  ;  in  fact  he  was  in  a  fog,  and  had  no  idea 
of  its  real  significance.  Nor  had  any  one.  Continental  phil- 
osophers experienced  some  difficulty  and  several  failures 
before  they  were  able  to  repeat  the  experiment.  It  was,  in 
fact,  discovered  too  soon,  and  before  the  scientific  world  was 
ready  to  receive  it,  and  it  was  reserved  for  Sir  William 
Thomson  briefly,  but  very  clearly,  to  point  out,  and  for  Clerk- 
Maxwell  more  fully  to  develop,  its  most  important  conse- 
quences. 

This  is  the  fundamental  experiment  on  which  Clerk-Max- 
well's theory  of  light  is  based  ;  but  of  late  years  many  fresh 
facts  and  relations  between  electricity  and  light  have  been 
discovered,  and  at  the  present  time  they  are  tumbling  in  in 
great  numbers. 

It  was  found  by  Faraday  that  many  other  transparent 
media  besides  heavy  glass  would  show  the  phenomenon  if 
placed  between  the  poles,  only  in  a  less  degree  ;  and  the  very 
important  observation  that  air  itself  exhibits  the  same  phenorn- 


RELATION   BETWEEN   ELECTRICITY  AND  LIGHT.       267 

enon,  though  to  an  exceedingly  small  extent,  has  just  been 
made  by  Kundt  and  Eontgen  in  Germany. 

Dr  Kerr,  of  Glasgow,  has  extended  the  result  to  opaque 
bodies,  and  has  shown  that  if  light  be  passed  through  mag- 
netised iron  its  plane  is  rotated.  The  film  of  iron  must  be 
exceedingly  thin,  because  of  its  opacity  ;  and  hence,  though 
the  intrinsic  rotating  power  of  iron  is  undoubtedly  very  great, 
the  observed  rotation  is  exceedingly  small  and  difficult  to 
observe  ;  and  it  is  only  by  very  remarkable  patience  and  care 
and  ingenuity  that  Dr  Kerr  has  obtained  his  result.  Mr 
Fitzgerald,  of  Dublin,  has  examined  the  question  mathemati- 
cally, and  has  shown  that  Maxwell's  theory  would  have 
enabled  Dr  Kerr's  result  to  be  predicted. 

Another  requirement  of  the  theory  is  that  bodies  which  are 
transparent  to  light  must  be  insulators  or  non-conductors  of 
electricity,  and  that  conductors  of  electricity  are  necessarily 
opaque  to  light.  Simple  observation  amply  confirms  this. 
Metals  are  the  best  conductors,  and  are  the  most  opaque  bodies 
known.  Insulators  such  as  glass  and  crystals  are  transparent 
whenever  they  are  sufficiently  homogeneous,  and  the  very 
remarkable  researches  of  Professor  Graham  Bell  in  the  last  few 
months  have  shown  that  even  ebonite,  one  of  the  most  opaque 
insulators  to  ordinary  vision,  is  certainly  transparent  to  some 
kinds  of  radiation,  and  transparent  to  no  small  degree. 

[The  reason  why  transparent  bodies  must  insulate,  and  why 
conductors  must  be  opaque,  was  here  illustrated  by  mechanical 
models.] 

A  further  consequence  of  the  theory  is  that  the  velocity  of 
light  in  a  transparent  medium  will  be  affected  by  its  electrical 
strain  constant ;  in  other  words,  that  its  refractive  index  will 
bear  some  close  but  not  yet  quite  ascertained  relation  to  its 
specific  inductive  capacity.  Experiment  has  partially  con- 
firmed this,  but  the  confirmation  is  as  yet  very  incomplete. 

But  there  are  a  number  of  results  not  predicted  by  theory, 
and  whose  connection  with  the  theory  is  not  clearly  made  out. 
"VVe  have  the  fact  that  light  falling  on  the  platinum  electrode 
of  a  voltameter  generates  a  current,  first  observed,  I  think,  by 
Sir  W.  E.  Grove  ;  at  any  rate  it  is  mentioned  in  his  *  Correla- 
tion of  Forces ' — extended  by  Becquerel  and  Eobert  Sabine  to 
other  substances,  and  now  being  extended  to  fluorescent  and 


268  APPENDIX  A. 

other  bodies  by  Professor  Minchin.  And  finally — for  I  must 
be  brief — we  have  the  remarkable  action  of  light  on  selenium. 
This  fact  was  discovered  accidentally  by  an  assistant  in  the 
laboratory  of  Mr  Willoughby  Smith,  who  noticed  that  a  piece 
of  selenium  conducted  electricity  very  much  better  when  light 
was  falling  upon  it  than  when  it  was  in  the  dark.  The  light 
of  a  candle  is  sufficient,  and  instantaneously  brings  down  the 
resistance  to  something  like  one-fifth  of  its  original  value. 

This  is  the  phenomenon  which,  as  you  know,  has  been 
utilised  by  Professor  Graham  Bell  in  that  most  ingenious  and 
striking  invention,  the  photophone.  • 

I  have  now  trespassed  long  enough  upon  your  patience,  but 
I  must  just  allude  to  what  may  very  likely  be  the  next  strik- 
ing popular  discovery,  and  that  is  the  transmission  of  light  by 
electricity.  I  mean  the  transmission  of  such  things  as  views 
and  pictures  by  means  of  the  electric  wire.  It  has  not  yet 
been  done,  but  it  seems  already  theoretically  possible,  and  it 
may  very  soon  be  practically  accomplished. 


THE  RELATION  BETWEEN  ELECTRICITY  AND  LIGHT. 
After  Hertz. 

Substance  of  a  lecture  by  Prof.  Oliver  Lodge,  Ashmolean 
Society,  Oxford,  June  3,  1889.1 

For  now  wellnigh  a  century  we  have  had  a  wave-theory  of 
light ;  and  a  wave-theory  of  light  is  certainly  true.  It  is 
directly  demonstrable  that  lignt  consists  of  waves  of  some 
kind  or  other,  and  that  these  waves  travel  at  a  certain  well- 
known  velocity,  seven  times  the  circumference  of  the  earth 
per  second,  taking  eight  minutes  011  the  journey  from  the  sun 
to  the  earth.  This  propagation  in  time  of  an  undulatory  dis- 
turbance necessarily  involves  a  medium.  If  waves  setting  out 
from  the  sun  exist  in  space  eight  minutes  before  striking  our 
eyes,  there  must  necessarily  be  in  space  some  medium  in  which 
they  exist  and  which  conveys  them.  Waves  we  cannot  have 
unless  they  be  waves  in  something. 

*  Based  on  a  report  in  the  (London)  '  Electrician/  September  6,  1889. 


RELATION   BETWEEN   ELECTRICITY  AND  LIGHT.      2G9 

No  ordinary  medium  is  competent  to  transmit  waves  at 
anything  like  the  speed  of  light ;  hence  the  luminiferous 
medium  must  be  a  special  kind  of  substance,  and  it  is  called 
the  ether.  The  luminiferous  ether  it  used  to  be  called,  because 
the  conveyance  of  light  was  all  it  was  then  known  to  be  capable 
of ;  but  now  that  it  is  known  to  do  a  variety  of  other  things 
also,  the  qualifying  adjective  may  be  dropped. 

Wave  motion  in  ether  light  certainly  is  ;  but  what  does  one 
mean  by  the  term  wave  ?  The  popular  notion  is,  I  suppose, 
of  something  heaving  up  and  down,  or  perhaps  of  something 
breaking  on  the  shore  in  which  it  is  possible  to  bathe.  But 
if  you  ask  a  mathematician  what  he  means  by  a  wave,  he  will 
probably  reply  that  the  simplest  wave  is 
y  =  a  sin  (p  t-n  x\ 

and  he  might  possibly  refuse  to  give  any  other  answer.  And 
in  refusing  to  give  any  other  answer  than  this,  or  its  equivalent 
in  ordinary  words,  he  is  entirely  justified  ;  that  is  what  is 
meant  by  the  term  wave,  and  nothing  less  general  wonld  be 
all-inclusive. 

Translated  into  ordinary  English,  the  phrase  signifies  "a  dis- 
turbance periodic  both  in  space  and  time."  Anything  thus 
doubly  periodic  is  a  wave  ;  and  all  waves — whether  in  air  as 
sound  waves,  or  in  ether  as  light  waves,  or  on  the  surface  of 
water  as  ocean  waves— are  comprehended  in  the  definition. 

What  properties  are  essential  to  a  medium  capable  of  trans- 
mitting wave  motion  ?  Roughly  we  may  say  two — elasticity 
and  inertia.  Elasticity  in  some  form,  or  some  equivalent  of 
it,  in  order  to  be  able  to  store  up  energy  and  effect  recoil ; 
inertia,  in  order  to  enable  the  disturbed  substance  to  overshoot 
the  mark  and  oscillate  beyond  its  place  of  equilibrium  to  and 
fro.  Any  medium  possessing  these  two  properties  can  transmit 
waves,  and  unless  a  medium  possesses  these  properties  in  some 
form  or  other,  or  some  equivalent  for  them,  it  may  be  said 
with  moderate  security  to  be  incompetent  to  transmit  waves. 
But  if  we  make  this  latter  statement  one  must  be  prepared 
to  extend  to  the  terms  elasticity  and  inertia  their  very  largest 
and  broadest  signification,  so  as  to  include  any  possible  kind 
of  restoring  force  and  any  possible  kind  of  persistence  of 
motion  respectively. 

These  matters  may  be  illustrated  in  many  ways,  but  perhaps 


270  APPENDIX  A. 

a  simple  loaded  lath  or  spring  in  a  vice  will  serve  well  enough. 
Pull  aside  one  end,  and  its  elasticity  tends  to  make  it  recoil ; 
let  it  go,  and  its  inertia  causes  it  to  overshoot  its  normal 
position  :  both  causes  together  cause  it  to  swing  to  and  fro 
till  its  energy  is  exhausted.  A  regular  series  of  such  springs 
at  equal  intervals  in  space,  set  going  at  regular  intervals  of 
time  one  after  the  other,  gives  you  at  once  a  wave  motion  and 
appearance  which  the  most  casual  observer  must  recognise 
as  such.  A  series  of  pendulums  will  do  just  as  well.  Any 
wave-transmitting  medium  must  similarly  possess  some  form 
of  elasticity  and  of  inertia. 

But  now  proceed  to  ask  what  is  this  ether  which  in  the 
case  of  light  is  thus  vibrating?  What  corresponds  to  the 
elastic  displacement  and  recoil  of  tbe  spring  or  pendulum? 
What  corresponds  to  the  inertia  whereby  it  overshoots  its 
mark  ?  Do  we  know  these  properties  in  the  ether  in  any 
other  way  ? 

The  answer,  given  first  by  Clerk-Maxwell,  and  now  reiter- 
ated and  insisted  on  by  experiments  performed  in  every  im- 
portant laboratory  in  the  world,  is — 

The  elastic  displacement  corresponds  to  electro- static  charge 
(roughly  speaking,  to  electricity). 

The  inertia  corresponds  to  magnetism. 

This  is  the  basis  of  the  modern  electro-magnetic  theory  of 
light.  Now  let  me  illustrate  electrically  how  this  can  be. 

The  old  and  familiar  operation  of  charging  a  Leyden  jar — 
the  storing  up  of  energy  in  a  strained  dielectric — any  electro- 
static charging  whatever — is  quite  analogous  to  the  drawing 
aside  of  our  flexible  spring.  It  is  making  use  of  the  elasticity 
of  the  ether  to  produce  a  tendency  to  recoil.  Letting  go  the 
spring  is  analogous  to  permitting  a  discharge  of  the  jar — per- 
mitting the  strained  dielectric  to  recover  itself,  the  electro- 
static disturbance  to  subside. 

In  nearly  all  the  experiments  of  electro  -  statics  ethereal 
elasticity  is  manifest. 

Next  consider  inertia.  How  would  one  illustrate  the  fact 
that  water,  for  instance,  possesses  inertia — the  power  of  per- 
sisting in  motion  against  obstacles — the  power  of  possessing 
kinetic  energy  ?  The  most  direct  way  would  be  to  take  a 
stream  of  water  and  try  suddenly  to  stop  it.  Open  a  water- 


RELATION   BETWEEN   ELECTRICITY  AND   LIGHT.       271 

tap  freely  and  then  suddenly  shut  it.  The  impetus  or 
momentum  of  the  stopped  water  makes  itself  manifest  by  a 
violent  shock  to  the  pipe,  with  which  everybody  must  be 
familiar.  The  momentum  of  water  is  utilised  by  engineers  in 
the  "  water-ram." 

A  precisely  analogous  experiment  in  electricity  is  what 
Faraday  called  "  the  extra  current."  Send  a  current  through 
a  coil  of  wire  round  a  piece  of  iron,  or  take  any  other  arrange- 
ment for  developing  powerful  magnetism,  and  then  suddenly 
stop  the  current  by  breaking  the  circuit.  A  violent  flash 
occurs  if  the  stoppage  is  sudden  enough,  a  flash  which  means 
the  bursting  of  the  insulating  air  partition  by  the  accumulated 
electro-magnetic  momentum. 

Briefly,  we  may  say  that  nearly  all  electro-magnetic  experi- 
ments illustrate  the  fact  of  ethereal  inertia. 

Now  return  to  consider  what  happens  when  a  charged  con- 
ductor (say  a  Leyden  jar)  is  discharged.  The  recoil  of  the 
strained  dielectric  causes  a  current,  the  inertia  of  this  current 
causes  it  to  overshoot  the  mark,  and  for  an  instant  the  charge 
of  the  jar  is  reversed  :  the  current  now  flows  backwards  and 
charges  the  jar  up  as  at  first ;  again  flows  the  current,  and  so 
on,  discharging  and  charging  the  jar  with  rapid  oscillations 
until  the  energy  is  all  dissipated  into  heat.  The  operation  is 
precisely  analogous  to  the  release  of  a  strained  spring,  or  to 
the  plucking  of  a  stretched  string. 

But  the  discharging  body  thus  thrown  into  strong  electrical 
vibration  is  embedded  in  the  all-pervading  ether,  and  we  have 
just  seen  that  the  ether  possesses  the  two  properties  requisite 
for  the  generation  and  transmission  of  waves — viz.,  elasticity, 
and  inertia  or  density  ;  hence,  just  as  a  tuning-fork  vibrating 
it  air  excites  aerial  waves  or  sound,  so  a  discharging  Leyden 
jar  in  ether  excites  ethereal  waves  or  light. 

Ethereal  waves  can  therefore  be  actually  produced  by  direct 
electrical  means.  I  discharge  here  a  jar,  and  the  room  is  for 
an  instant  filled  with  light.  With  light,  I  say,  though  you 
can  see  nothing.  You  can  see  and  hear  the  spark  indeed, — 
but  that  is  a  mere  secondary  disturbance  we  can  for  the 
present  ignore — I  do  not  mean  any  secondary  disturbance.  I 
mean  the  true  ethereal  waves  emitted  by  the  electric  oscilla- 
tion going  on  in  the  neighbourhood  of  this  recoiling  dielectric. 


APPENDIX  A. 

You  pull  aside  the  prong  of  a  tuning-fork  and  let  it  go  :  vibra- 
tion follows  and  sound  is  produced.  You  charge  a  Leyden  jar 
and  let  it  discharge  :  vibration  follows  and  light  is  excited. 

It  is  light  just  as  good  as  any  other  light.  It  travels  at  the 
same  pace,  it  is  reflected  and  refracted  according  to  the  same 
laws  ;  every  experiment  known  to  optics  can  be  performed 
with  this  ethereal  radiation  electrically  produced,  and  yet  you 
cannot  see  it.  Why  not  ?  For  no  fault  of  the  light ;  the  fault 
(if  there  be  a  fault)  is  in  the  eye.  The  retina  is  incompetent 
to  respond  to  these  vibrations — they  are  too  slow.  The  vibra- 
tions set  up  when  this  large  jar  is  discharged  are  from  a  hun- 
dred thousand  to  a  million  per  second,  but  that  is  too  slow  for 
the  retina.  It  responds  only  to  vibrations  between  4000  bil- 
lions and  7000  billions  per  second.  The  vibrations  are  too 
quick  for  the  ear,  which  responds  only  to  vibrations  between 
40  and  40,000  per  second.  Between  the  highest  audible  and 
the  lowest  visible  vibrations  there  has  been  hitherto  a  great 
gap,  which  these  electric  oscillations  go  far  to  fill  up.  There 
has  been  a  great  gap  simply  because  we  have  no  intermediate 
sense-organ  to  detect  rates  of  vibration  between  40,000  and 
4,000,000,000,000,000  per  second.  It  was,  therefore,  an  un- 
explored territory.  Waves  have  been  there  all  the  time  in 
any  quantity,  but  we  have  not  thought  about  them  nor  at- 
tended to  them. 

It  happens  that  I  have  myself  succeeded  in  getting  electric 
oscillations  so  slow  as  to  be  audible.  The  lowest  I  have  got 
at  present  are  125  per  second,  and  for  some  way  above  this 
the  sparks  emit  a  musical  note  ;  but  no  one  has  yet  succeeded 
in  directly  making  electric  oscillations  which  are  visible,  though 
indirectly  every  one  does  it  by  lighting  a  candle. 

Here,  however,  is  an  electric  oscillator  which  vibrates  300 
million  times  a  second,  and  emits  ethereal  waves  a  yard  long. 
The  whole  range  of  vibrations  between  musical  tones  and  some 
thousand  millions  per  second  is  now  filled  up. 

These  electro-magnetic  waves  have  long  been  known  on  the 
side  of  theory,  but  interest  in  them  has  been  immensely  quick- 
ened by  the  discovery  of  a  receiver  or  detector  for  them.  The 
great  though  simple  discovery  by  Hertz  of  an  "  electric  eye,' 
as  Sir  W.  Thomson  calls  it,  makes  experiments  on  these  waves 
for  the  first  time  possible,  or  even  easy.  We  have  now  a  sort 


RELATION   BETWEEN   ELECTPJCITY  AND   LIGHT.      273 

of  artificial  sense  -  organ  for  their  appreciation  —  an  electric 
arrangement  which  can  virtually  "see"  these,  intermediate 
rates  of  vibration. 

The  Hertz  receiver  is  the  simplest  thing  in  the  world — 
nothing  but  a  bit  of  wire,  or  a  pair  of  bits  of  wire,  adjusted 
so  that  when  immersed  in  strong  electric  radiation  they  give 
minute  sparks  across  a  microscopic  air-gap. 

The  receiver  I  have  here  is  adapted  for  the  yard-long  waves 
emitted  from  this  small  oscillator  ;  but  for  the  far  longer  waves 
emitted  by  a  discharging  Leyden  jar  an  excellent  receiver  is 
a  gilt  wall-paper  or  other  interrupted  metallic  surface.  The 
waves  falling  upon  the  metallic  surface  are  reflected,  and  in 
the  act  of  reflection  excite  electric  currents,  which  cause  sparks. 
Similarly,  gigantic  solar  waves  may  produce  aurorse ;  and 
minute  waves  from  a  candle  do  electrically  disturb  the  retina. 

The  smaller  waves  are,  however,  far  the  most  interesting 
and  the  most  tractable  to  ordinary  optical  experiments.  From 
a  small  oscillator,  which  may  be  a  couple  of  small  cylinders 
kept  sparking  into  each  other  end  to  end  by  an  induction  coil, 
waves  are  emitted  on  which  all  manner  of  optical  experiments 
can  be  performed. 

They  can  be  reflected  by  plain  sheets  of  metal,  concentrated 
by  parabolic  reflectors,  refracted  by  prisms,  concentrated  by 
lenses.  I  have  at  the  College  a  large  lens  of  pitch,  weighing 
over  3  cwt.,  for  concentrating  them  to  a  focus.  They  can  be 
made  to  show  the  phenomenon  of  interference,  and  thus  have 
their  wave  lengths  accurately  measured.  They  are  stopped  by 
all  conductors,  and  transmitted  by  all  insulators.  Metals  are 
opaque,  but  even  imperfect  insulators,  such  as  wood  or  stone, 
are  strikingly  transparent,  and  waves  may  be  received  in  one 
room  from  a  source  in  another,  the  door  between  the  two  being 
shut. 

The  real  nature  of  metallic  opacity  and  of  transparency  has 
long  been  clear  in  Maxwell's  theory  of  light,  and  these  elec- 
trically produced  waves  only  illustrate  and  bring  home  the 
well-known  facts.  The  experiments  of  Hertz  are  in  fact  the 
apotheosis  of  that  theory. 

Thus,  then,  in  every  way  Maxwell's  brilliant  perception  of 
the  real  nature  of  light  is  abundantly  justified  ;  and  for  the 
first  time  we  have  a  true  theory  of  light,  no  longer  based  upon 

S 


274  APPENDIX  A. 

analogy  with  sound,  nor  upon  a  hypothetical  jelly  or  elastic 
solid. 

Light  is  an  electro-magnetic  disturbance  of  the  ether.  Optics 
is  a  branch  of  electricity.  Outstanding  problems  in  optics  are 
being  rapidly  solved  now  that  we  have  the  means  of  definitely 
exciting  light  with  a  full  perception  of  what  we  are  doing,  and 
of  the  precise  mode  of  its  vibration. 

It  remains  to  find  out  how  to  shorten  down  the  waves — to 
hurry  up  the  vibration  until  the  light  becomes  visible.  No- 
thing is  wanted  but  quicker  modes  of  vibration.  Smaller  oscil- 
lators must  be  used — very  much  smaller — oscillators  not  much 
bigger  than  molecules.  In  all  probability — one  may  almost 
say  certainly — ordinary  light  is  the  result  of  electric  oscillation 
in  the  molecules  of  hot  bodies,  or  sometimes  of  bodies  not  hot 
— as  in  the  phenomenon  of  phosphorescence. 

The  direct  generation  of  visible  light  by  electric  means,  so 
soon  as  we  have  learnt  how  to  attain  the  necessary  frequenc} 
of  vibration,  will  have  most  important  practical  consequences. 

For  consider  our  present  methods  of  making  artificial  light : 
they  are  both  wasteful  and  ineffective. 

We  want  a  certain  range  of  oscillation,  between  7000  and 
4000  billion  vibrations  per  second, — no  other  is  useful  to  us, 
because  110  other  has  any  effect  upon  our  retina  ;  but  we  do 
not  know  how  to  produce  vibrations  of  this  rate.  We  can 
produce  a  definite  vibration  of  one  or  two  hundred  or  thousand 
per  second — in  other  words,  we  can  excite  a  pure  tone  of 
definite  pitch  ;  and  we  can  command  any  desired  range  of 
such  tones  continuously  by  means  of  bellows  and  a  keyboard. 
We  can  also  (though  the  fact  is  less  well  known)  excite 
momentarily  definite  ethereal  vibrations  of  some  millions  per 
second,  as  1  have  explained  ;  but  we  do  not  at  present  seem  to 
know  how  to  maintain  this  rate  quite  continuously.  To  get 
much  faster  rates  of  vibration  than  this,  we  have  to  fall  back 
upon  atoms.  We  know  how  to  make  atoms  vibrate, — it  is 
done  by  what  we  call  "heating"  the  substance;  and  if  we 
could  deal  with  individual  atoms  unhampered  by  others,  it  ia 
possible  that  we  might  get  a  pure  and  simple  mode  of  vibra- 
tion from  them.  It  is  possible,  but  unlikely  ;  for  atoms,  even 
when  isolated,  have  a  multitude  of  modes  of  vibration  special 
to  themselves,  of  which  only  a  few  are  of  practical  use  to  ua, 


RELATION   BETWEEN   ELECTRICITY  AND   LIGHT.      275 

and  we  do  not  know  how  to  excite  some  without  also  the 
others.  However,  we  do  not  at  present  even  deal  with  indi- 
vidual atoms  ;  we  treat  them  crowded  together  in  a  compact 
mass,  so  that  their  modes  of  vibration  are  really  infinite. 

We  take  a  lump  of  matter,  say  a  carbon  filament  or  a  piece 
of  quicklime,  and  by  raising  its  temperature  we  impress  upon 
its  atoms  higher  and  higher  modes  of  vibration,  not  transmut- 
ing the  lower  into  the  higher,  but  superposing  the  higher  upon 
the  lower,  until  at  length  we  get  such  rates  of  vibration  as  our 
retina  is  constructed  for,  and  we  are  satisfied.  But  how  waste- 
ful and  indirect  and  empirical  is  the  process  !  We  want  a  small 
range  of  rapid  vibrations,  and  we  know  no  better  than  to  make 
the  whole  series  leading  up  to  them.  It  is  as  though,  in  order 
to  sound  some  little  shrill  octave  of  pipes  in  an  organ,  we  are 
obliged  to  depress  every  key  and  every  pedal,  and  to  blow  a 
young  hurricane. 

I  have  purposely  selected  as  examples  the  more  perfect 
methods  of  obtaining  artificial  light,  wherein  the  waste  radia- 
tion is  only  useless,  and  not  noxious.  But  the  old-fashioned 
plan  was  cruder  even  than  this  :  it  consisted  simply  in  setting 
something  burning,  whereby  not  the  fuel  but  the  air  was 
consumed  ;  whereby  also  a  most  powerful  radiation  was  pro- 
duced, in  the  waste  waves  of  which  we  were  content  to  sit 
stewing,  for  the  sake  of  the  minute — almost  infinitesimal — 
fraction  of  it  which  enabled  us  to  see. 

Every  one  knows  now,  however,  that  combustion  is  not  a 
pleasant  or  healthy  mode  of  obtaining  light ;  but  everybody 
does  not  realise  that  neither  is  incandescence  a  satisfactory 
and  unwasteful  method,  which  is  likely  to  be  practised  for 
more  than  a  few  decades,  or  perhaps  a  century. 

Look  at  the  furnaces  and  boilers  of  a  great  steam-engine 
driving  a  group  of  dynamos,  and  estimate  the  energy  ex- 
pended ;  and  then  look  at  the  incandescent  filaments  of  the 
lamps  excited  by  them,  and  estimate  how  much  of  their 
radiated  energy  is  of  real  service  to  the  eye.  It  will  be  as 
the  energy  of  a  pitch-pipe  to  an  entire  orchestra. 

It  is  not  too  much  to  say  that  a  boy  turning  a  handle  could, 
if  his  energy  were  properly  directed,  produce  quite  as  much 
real  light  as  is  produced  by  all  this  mass  of  mechanism  and 
consumption  of  material.  There  might,  perhaps,  be  something 


270  APPENDIX  A. 

contrary  to  the  laws  of  nature  in  thus  hoping  to  get  and  util- 
ise some  specific  kind  of  radiation  without  the  rest ;  but  Lord 
Rayleigh  has  shown  in  a  short  communication  to  the  British 
Association  at  York  that  it  is  not  so,  and  that  therefore  we 
have  a  right  to  try  to  do  it. 

We  do  not  yet  know  how,  it  is  true,  but  it  is  one  of  the 
things  we  have  got  to  learn. 

Any  one  looking  at  a  common  glowworm  must  be  struck 
with  the  fact  that  not  by  ordinary  combustion,  nor  yet  on  the 
steam-engine  and  dynamo  principle,  is  that  easy  light  pro- 
duced. Very  little  waste  radiation  is  there  from  phosphor- 
escent things  in  general.  Light  of  the  kind  able  to  affect  the 
retina  is  directly  emitted  ;  and  for  this,  for  even  a  large  supply 
of  this,  a  modicum  of  energy  suffices. 

Solar  radiation  consists  of  waves  of  all  sizes,  it  is  true  ;  but 
then  solar  radiation  has  innumerable  things  to  do  besides 
making  things  visible.  The  whole  of  its  energy  is  useful.  In 
artificial  lighting  nothing  but  light  is  desired  ;  when  heat  is 
wanted  it  is  best  obtained  separately  by  combustion.  And  so 
soon  as  we  clearly  recognise  that  light  is  an  electrical  vibra- 
tion, so  soon  shall  we  begin  to  beat  about  for  some  mode  of 
exciting  and  maintaining  an  electrical  vibration  of  any  required 
degree  of  rapidity.  When  this  has  been  accomplished,  the 
problem  of  artificial  lighting  will  have  been  solved. 


PROF.   HENilY   UN   HIGH  TENSION   ELECTiilCl'JX       277 


APPENDIX  B. 
PROF.  HENRY  ON  HIGH  TENSION  ELECTRICITY  BEING  CONFINED 

TO     THE     SURFACE    OF    CONDUCTING     BODIES,     WITH     SPECIAL 
REFERENCE    TO    THE   PROPER   CONSTRUCTION   OF    LlGIITNING- 

EODS. 

(Extracted  from  the  l  Journal  of  the  Telegraph?  New  York, 
Sept.  1,  1877.) 

WASHINGTON,  March  11,  1876. 

DEAR  SIR, — In  answer  to  your  letter  of  the  7th  inst.,  I  have 
to  say  that  the  discrepancy  which  exists  as  to  the  question 
whether  electricity  passes  at  the  surface  or  through  the  whole 
capacity  of  the  rod  has  arisen  principally  from  experiments  on 
galvanic  electricity,  which,  having  little  or  no  repulsive  energy, 
passes  through  the  whole  substance  of  the  rod,  and  also  from 
experiments  in  which  a  very  large  quantity  of  frictional  elec- 
tricity is  transmitted  through  a  small  wire  :  in  this  case  the 
metal  is  resolved  into  its  elements  and  reduced  to  an 
impalpable  powder. 

In  the  case,  however,  of  the  transmission  of  atmospheric 
electricity  through  a  rod  of  sufficient  size  to  transmit  the  dis- 
charge freely,  there  can  be  no  doubt  that  it  tends  to  pass  at 
the  surface,  the  thickness  of  the  stratum  of  electricity  varying 
with  the  diameter  of  the  rod  and  the  amount  and  the  intensity 
of  the  charge. 

To  test  this  by  actual  experiment  I  made  the  following  ar- 
rangement :  through  a  gun-barrel  about  2  feet  in  length  a 
copper  wire  was  passed,  the  ends  projecting.  The  middle  of 
the  wire  in  the  barrel  was  coiled  into  the  form  of  a  magnetis- 
ing spiral,  and  the  ends  of  the  gun-barrel  were  closed  with 
plugs  of  tinfoil,  so  as  to  make  a  perfect  metallic  connection 
between  the  wire  and  the  barrel.  On  the  outside  of  the  barrel 
another  magnetising  spiral  was  placed,  the  whole  arrangement 
being  shown  in  the  sketch. 


278  APPENDIX  B. 

A  powerful  charge  was  now  sent  through  the  copper  wire 
from  a  Leyden  jar  of  about  two  gallons'  capacity.  The  needle 
within  the  barrel  showed  not  the  least  sign  of  magnetism, 
while  the  one  on  the  outside  was  strongly  magnetic. 


From  this  experiment  I  conclude  that  a  gas-pipe  can  convey 
an  ordinary  charge  of  electricity  from  the  clouds  as  well  as  a 
solid  rod  of  the  same  diameter. 

The  repulsive  energy  of  the  electrical  discharge  at  right 
angles  to  the  axis  remains  of  the  same  intensity  as  in  the  case 
of  a  statical  charge.  This  I  have  shown  to  be  the  case  by 
drawing  sparks  of  considerable  intensity  from  a  conductor,  one 
end  of  which  was  connected  with  the  ground  while  sparks 
were  thrown  on  the  other  end  from  a  large  prime  conductor. 
This  spark  is  of  a  peculiar  character,  for  though  it  gives  a 
pungent  shock  and  sets  fire  to  combustible  substances,  such  as 
an  electrical  pistol,  it  does  not  affect  a  sensitive  gold-leaf  elec- 
trometer. The  fact  is,  it  consists  of  two  sparks,  the  one 
negative  and  the  other  positive.  The  rod  during  the  trans- 
mission of  the  electricity  through  it  is  charged  +  at  the  upper 
end,  and  immediately  in  advance  of  this  point  it  is  charged  - 
by  induction,  and  the  electricity  passes  through  it  in  the  dis- 
charge in  the  form  of  a  series  of  +  and  —  waves. — Yours  very 
truly,  JOSEPH  HENRY,  Sec.  Smithsonian  Inst. 

Prof.  R.  C.  KEDZIE,  Lansing,  Michigan. 

WASHINGTON,  April  15,  1876. 

DEAR  SIR, — Your  letter  was  received  by  due  course  of  mail, 
but  a  press  of  business  connected  with  the  preparation  of  the 
Annual  Report  for  1875  and  the  Lighthouse  Board  has  pre- 
vented an  earlier  reply. 

I  have  now  to  say  that,  as  far  as  I  know,  I  am  the  only  person 
who  has  made  a  special  study  of  the  conduction  of  frictional 
electricity  in  regard  to  lightning-rods.  It  has  long  been  estab- 
lished by  Coulomb  and  others  that  the  electricity  of  a  charged 
conductor  exists  in  a  thin  stratum  at  the  surface,  and  this  is  a 


PROF.   HENRY   ON  HIGH  TENSION   ELECTRICITY.      27 y 

necessary  consequence  of  the  repulsion  of  electricity  for  itself, 
every  particle  being  repelled  from  every  other  as  far  as  possible. 
From  this  it  was  hastily  assumed  that  electricity  in  motion 
also  moves  at  the  surface  ;  but  this  was  an  inference  without 
physical  proof  until  I  commenced  the  investigation.  I  found 
from  a  series  of  experiments  that  frictional  electricity — that  is, 
electricity  of  repulsive  energy,  such  as  that  from  the  clouds — 
does  pass  at  the  surface,  but  that  galvanic  electricity,  the  kind 
to  which  Faraday,  Daniell,  De  La  Rive,  and  others  refer, 
passes  through  the  whole  capacity  of  the  conductor.  This 
latter  fact,  however,  was  previously  established  by  others.  I 
further  found  that  whenever  a  charge  of  electricity  was  thrown 
on  a  rod  explosively,  however  well  connected  the  rod  was  with 
the  earth,  it  gave  off  sparks  in  the  course  of  its  length  sufficient 
to  fire  an  electric  pistol  and  light  flocculent  substances.  I  also 
found  that,  in  sending  a  powerful  discharge  from  a  battery  of 
nine  jars  through  a  wide  plate,  no  electricity  passed  along  the 
middle  of  the  plate,  but  that  it  was  accumulated  in  its  passage 
at  the  edges. 

From  all  my  study  of  this  subject  I  do  not  hesitate  to  say 
that  the  plan  I  have  given  of  lightning-rods  is  the  true  one, 
and  that  a  tube  of  a  sufficient  degree  of  thickness  serves  to 
conduct  the  electricity  as  well  as  a  solid  mass,  provided  the 
thickness  is  sufficient  to  give  free  conduction.  A  very  heavy 
charge  sent  through  a  wire  frequently  deflagrates  it,  but  no 
discharge  from  the  clouds,  of  which  I  have  any  knowledge,  has 
ever  sufficed  to  deflagrate  a  gas-pipe  of  an  inch  in  diameter. 

The  plan  of  increasing  the  surface  of  a  rod  by  converting  the 
metal  into  a  ribbon  is  objectionable.  It  tends  to  increase  the 
power  of  the  lateral  discharge,  and  gives  no  increase  of  con- 
ducting power. 

Another  fallacy  is  much  insisted  on — viz.,  the  better  conduc- 
tion of  copper  than  iron.  It  is  true  that  copper  is  a  better 
conductor  of  galvanic  electricity,  which  pervades  the  whole 
mass,  but  in  regard  to  frictional  electricity  the  difference  in 
conducting  capacity  is  too  small  to  be  of  any  importance.  Iron 
is  sufficiently  good  in  regard  to  conduction,  and  withstands 
deflagration  better  than  copper :  besides  this,  it  is  much 
cheaper.— Yours  truly,  JosEm  HENRY-. 

Prof.  R.  C.  KEDZIK. 


280  APPENDIX  B. 


ON  MODERN  VIEWS  WITH  EESPECT  TO  THE  NATURE  OP 
ELECTRIC  CURRENTS. 

Substance  of  a  lecture  by  Prof.  H.  A.  Rowland,  American 
Institute  of  Electrical  Engineers,  May  22,  1889. l 

How  great,  then,  the  difference  between  a  current  of  water 
and  a  current  of  electricity  !  The  action  of  the  former  is  con- 
fined to  the  interior  of  the  tube,  while  that  of  the  latter  ex- 
tends to  great  distances  on  all  sides,  the  whole  of  the  space  being 
agitated  by  the  formation  of  an  electric  current  in  any  part. 
To  show  this  agitation,  I  have  here  two  large  frames  with  coils 
of  wire  around  them.  They  hang  face  to  face  about  6  feet 
apart.  Through  one  I  discharge  this  Leyden  jar,  and  imme- 
diately you  see  a  spark  at  a  break  in  the  wire  of  the  other  coil, 
and  yet  there  is  no  apparent  connection  between  the  two.  I 
can  carry  the  coils  50  feet  or  more  apart,  and  yet,  by  suitable 
means,  I  can  observe  the  disturbances  due  to  the  current  in 
the  first  coil. 

The  question  is  forced  upon  us  as  to  how  this  action  takes 
place.  How  is  it  possible  to  transmit  so  much  power  to  such  a 
distance  across  apparently  unoccupied  space?  According  to 
our  modern  theories  of  physics,  there  must  be  some  medium 
engaged  in  this  transmission.  We  know  that  it  is  not  the  air, 
because  the  same  effects  take  place  in  a  vacuum,  and  therefore 
we  must  fall  back  on  that  medium  which  transmits  light,  and 
•which  we  have  named  the  ether — that  medium  which  is  sup- 
posed to  extend  unaltered  throughout  the  whole  of  space, 
whose  existence  is  very  certain,  but  whose  properties  we  have 
yet  but  vaguely  conceived. 

I  cannot  in  the  course  of  one  short  hour  give  even  an  idea 
of  the  process  by  which  the  minds  of  physicists  have  been  led 
to  this  conclusion,  or  the  means  by  which  we  have  finally 
completely  identified  the  ether  which  transmits  light  with  the 
medium  which  transmits  electrical  and  magnetic  disturbances. 
The  great  genius  who  first  identified  the  two  is  Maxwell, 
whose  electro-magnetic  theory  of  light  is  the  centre  around 

1  Based  on  reports  in  the  (London)  '  Electrician,'  June  21  and  28 

1889. 


NATURE  OF  ELECTRIC   CURRENTS.  281 

•which  much  scientific  thought  is  to-day  revolving,  and  which  we 
regard  as  one  of  the  greatest  steps  by  which  we  advance  nearer 
to  the  understanding  of  matter  and  its  laws.  It  is  this  great 
discovery  of  Maxwell  which  allows  me  to  attempt  to  explain 
to  you  the  wonderful  events  which  happen  everywhere  in 
space  when  one  establishes  an  electric  current  in  any  other 
portion. 

In  the  first  place,  we  discover  that  the  disturbance  does  not 
take  place  in  all  portions  of  space  at  once,  but  proceeds  out- 
ward from  the  centre  of  the  disturbance  with  a  velocity  exactly 
equal  to  the  velocity  of  light ;  so  that  when  I  touch  these 
wires  together  so  as  to  complete  the  circuit  of  yonder  battery, 
I  start  a  wave  of  ethereal  disturbance  which  passes  outward 
with  a  velocity  of  185,000  miles  per  second,  and  continues  to 
pass  outwards  for  ever,  or  until  it  reaches  the  bounds  of  the 
universe.  And  yet  none  of  our  senses  informs  us  of  what  has 
taken  place  unless  sharpened  by  the  use  of  suitable  instru- 
ments. Thus,  in  the  case  of  these  two  coils  of  wire,  suspended 
near  each  other,  when  the  wave  from  the  primary  disturbance 
reaches  the  second  coil  we  perceive  the  disturbance  by  means 
of  the  spark  formed  at  the  break  in  the  coil.  Should  I  move 
the  coils  farther  apart,  the  spark  in  the  second  coil  would  be 
somewhat  delayed,  but  the  distance  of  185,000  miles  would  be 
necessary  before  this  delay  could  amount  to  as  much  as  one 
second.  Hence  the  effects  we  observe  on  the  earth  take  place 
so  nearly  instantaneously  that  the  interval  of  time  is  very 
difficult  to  measure,  amounting  in  the  present  case  to  only 
T5Uoo<yTnratn  of  a  second. 

It  is  impossible  for  me  to  prove  the  existence  of  this  interval, 
so  infinitesimal  is  it,  but  I  can  at  least  show  you  that  waves 
have  something  to  do  with  the  action  observed.  For  instance, 
I  have  here  two  tuning-forks  mounted  on  sounding-boxes  and 
tuned  to  exact  unison.  I  sound  one  and  then  stop  its  vibra- 
tions with  my  hand  ;  instantly  you  hear  that  the  other  is  in 
vibration,  caused  by  the  waves  of  sound  in  the  air  between  the 
two.  When,  however,  I  destroy  the  unison  by  fixing  this  piece 
of  wax  on  one  of  the  forks,  the  action  ceases. 

Now,  this  combination  of  a  coil  of  wire  and  a  Leyden  jar 
forms  a  vibrating  system  of  electricity,  and  its  time  of  vibra- 
tion is  about  lOjOOOjOOO  times  a  second.  Here  is  another 


282  APPENDIX  B. 

combination  of  coil  and  jar,  the  same  as  the  first,  and  therefore 
its  time  of  vibration  is  the  same.  You  see  how  well  the 
experiment  works,  because  the  two  are  in  unison.  But  let  me 
take  away  this  second  Leyden  jar,  thus  destroying  the  unison, 
and  you  see  that  the  sparks  instantly  cease.  Replacing  it,  the 
sparks  reappear.  Adding  another  on  one  side,  they  disappear 
again,  only  to  reappear  when  the  system  is  made  symmetrical 
by  placing  two  on  each  side. 

This  experiment  and  that  of  the  tuning-forks  have  an  exact 
analogy  to  one  another.  In  each  we  have  two  vibrating 
systems  connected  by  a  medium  capable  of  transmitting 
vibrations,  and  they  both  come  under  the  head  of  what  we 
know  as  sympathetic  vibrations.  In  the  one  case,  we  have 
two  mechanical  tuning-forks  connected  by  the  air  ;  in  the 
other,  two  pieces  of  apparatus,  which  we  might  call  electrical 
tuning-forks,  connected  by  the  ether.  The  vibrations  in  one 
case  can  be  seen  by  the  eye  or  heard  by  the  ear,  but  in  the 
other  case  they  can  only  be  perceived  when  we  destroy  them 
by  making  them  produce  a  spark.  The  fact  that  we  are  able 
to  increase  the  effect  by  proper  tuning  demonstrates  that 
vibrations  are  concerned  in  the  phenomenon.  This  can,  how- 
ever, be  separately  demonstrated  by  examining  the  spark  by 
means  of  a  revolving  mirror,  when  we  find  that  it  is  made  up 
of  many  successive  sparks  corresponding  to  the  successive 
backward  and  forward  movements  of  the  current. 

Thus,  in  the  case  of  a  charged  Leyden  jar  whose  inner  and 
outer  coatings  have  been  suddenly  joined  by  a  wire,  the  elec- 
tricity flows  back  and  forth  along  the  wire  until  all  the  energy 
originally  stored  up  in  the  jar  has  expended  itself  in.  heating 
the  wire  or  the  air  where  the  spark  takes  place,  and  in  gener- 
ating waves  of  disturbance  in  the  ether  which  move  outward 
into  space  with  the  velocity  of  light.  These  ethereal  waves  we 
have  demonstrated  by  letting  them  fall  on  this  coil  of  wire, 
causing  the  electrical  disturbance  to  manifest  itself  by  electric 
sparks. 

I  have  here  another  more  powerful  arrangement  for  produc- 
ing electro-magnetic  waves  of  very  long  wave  length,  each  one 
being  about  500  miles  long.  It  consists  of  a  coil  within  which 
is  a  bundle  of  iron  wires.  On  passing  a  powerful  alternating 
current  through  the  coil  the  iron  wires  are  rapidly  magnetised 


NATURE  OF   ELECTRIC   CURRENTS.  283 

and  demagnetised,  and  send  forth  into  space  a  system  of  electro- 
magnetic waves  at  the  rate  of  SCO  in  a  second. 

Here  also  I  have  another  piece  of  apparatus  for  sending  out 
the  same  kind  of  electro-magnetic  waves,  and  on  applying  a 
match  we  start  it  also  into  action.  But  the  last  apparatus  is 
tuned  to  so  high  a  pitch  that  the  waves  are  only  -gnoun  ^nc^ 
long,  and  55,000,000,000,000  are  given  out  in  one  second.  These 
short  waves  are  known  by  the  name  of  light  and  radiant  heat, 
though  the  name  radiation  is  more  exact.  Placing  any  body 
near  the  lamp  so  that  the  radiation  can  fall  on  it,  we  observe 
that  when  the  body  absorbs  the  rays  it  is  heated  by  them.  Is 
it  not  possible  for  us  to  get  some  substance  to  absorb  the  long 
(or  electro-magnetic)  waves  of  disturbance,  and  so  obtain  a 
heating  effect '?  I  have  here  such  a  substance  in  the  shape  of  a 
sheet  of  copper,  which  I  fasten  on  the  face  of  a  thermopile, 
and  I  hold  it  where  these  waves  are  strongest.  As  I  have 
anticipated,  great  heat  is  generated  by  their  absorption,  and 
BOOH  the  plate  of  copper  becomes  very  warm,  as  we  see  by  this 
thermometer,  by  feeling  it  with  the  hand,  or  even  by  the  steam 
from  water  thrown  upon  it.  In  this  experiment  the  copper 
had  not  touched  the  coil  or  the  iron  wire  core,  although  if  it 
did  they  are  very  much  cooler  than  itself.  The  heat  has  been 
produced  by  the  absorption  of  the  waves  in  the  same  way  as  a 
blackened  body  absorbs  the  rays  of  shorter  wave  length  from 
the  lamp. 

In  these  experiments,  so  far,  the  wave-like  nature  of  the 
disturbance  has  not  been  proved.  We  have  caused  electric 
sparks,  and  have  heated  the  copper  plate  across  an  interval  of 
space,  but  have  not  in  either  of  these  cases  proved  experi- 
mentally the  progressive  nature  of  the  disturbance. 

A  ready  means  of  experimenting  on  the  waves,  obtaining 
their  wave  length  and  showing  their  interferences,  has  hitherto 
been  wanting.  This  deficiency  has  been  recently  supplied  by 
Prof.  Hertz,  of  Carlsruhe. 

I  scarcely  know  how  to  present  this  subject  to  a  non-technical 
audience  and  make  it  clear  how  a  coil  of  wire  with  a  break  in 
it  can  be  used  to  measure  the  velocity  and  length  of  ethereal 
waves.  However,  I  can  but  try.  If  the  waves  moved  very 
slowly,  we  could  readily  measure  the  time  the  first  coil  took  to 
affect  the  second,  and  show  that  this  time  was  longer  as  the 


284  APPENDIX  B. 

distance  was  greater.  But  it  is  absolutely  inappreciable  by  any 
of  our  instruments,  and  another  method  must  be  found.  To 
obtain  the  wave  length  Prof.  Hertz  used  several  methods,  but 
that  by  the  formation  of  stationary  waves  is  the  most  easily 
grasped.  I  hold  in  my  hand  one  end  of  a  spiral  spring,  which 
makes  a  heavy  and  flexible  rope.  As  I  send  a  wave  down  it, 
you  see  that  it  is  reflected  at  the  farther  end,  and  returns  again 
to  my  hand.  If,  however,  I  send  a  succession  of  waves  down 
the  rope,  the  reflected  waves  interfere  with  the  direct  ones,  and 
divide  the  rope  into  a  succession  of  nodes  and  loops  which  you 
now  observe.  So,  a  series  of  sound  waves,  striking  on  a  wall, 
forms  a  system  of  stationary  waves  in  front  of  the  wall. 
Indeed  we  can  use  any  waves  for  this  purpose,  even  ethereal 
waves.  With  this  in  view  Prof.  Hertz  established  his  apparatus 
in  front  of  a  reflecting  wall,  and  observed  the  nodes  and  loops 
by  the  sparks  produced  in  a  ring  of  wire,  somewhat  resembling 
the  coil  I  have  been  using,  but  much  smaller.  It  is  impossible 
for  me  to  repeat  this  experiment  before  you,  as  it  is  a  very 
delicate  one,  and  the  sparks  produced  are  almost  microscopic. 
Indeed  I  should  have  to  erect  an  entirely  different  apparatus, 
as  the  waves  from  the  one  before  me  are  nearly  a  quarter-mile 
long.  To  produce  shorter  waves  we  must  use  apparatus  very 
much  smaller — tuned,  as  it  were,  to  a  higher  pitch,  so  that 
several  stationary  waves,  or  nodes  and  loops,  of  a  few  yards 
long  could  be  obtained  in  the  space  of  this  room. 

The  testing  coil  would  then  be  moved  to  different  parts  of  the 
room,  and  the  nodes  would  be  indicated  by  the  disappearance 
of  the  sparks,  and  the  loops  by  the  greater  brightness  of  them. 
The  presence  of  stationary  waves  would  thus  be  proved,  and 
their  half -wave  length  found  from  the  distance  from  node 
to  node,  for  stationary  waves  can  always  be  considered  as 
produced  by  the  interference  of  two  waves  advancing  in  op- 
posite directions. 

The  closing  of  a  battery  circuit,  then,  and  the  establishment 
of  a  current  of  electricity  in  a  wire,  is  a  very  different  process 
from  the  formation  of  a  current  of  water  in  a  pipe,  though 
after  the  first  shock  the  laws  of  the  flow  of  the  two  are  very 
much  alike.  Furthermore,  the  medium  around  the  current  of 
electricity  has  very  strange  properties,  showing  that  it  is  ac- 
companied by  a  disturbance  throughout  space.  The  wire  is 


NATURE   OF  ELECTRIC   CURRENTS.  285 

but  the  core  of  the  disturbance,  which  latter  extends  indefin- 
itely in  all  directions. 

One  of  the  strangest  things  about  it  is  that  we  can  calculate 
with  perfect  exactness  the  velocity  of  the  wave  propagation 
and  the  amount  of  the  disturbance  at  every  point  and  at  any 
instant  of  time  ;  but  as  yet  we  cannot  conceive  of  the  details  of 
the  mechanism  which  is  concerned  in  the  propagation  of  an 
electric  current.  In  this  respect  our  subject  resembles  all 
other  branches  of  physics  in  the  partial  knowledge  we  have  of 
it.  We  know  that  light  is  the  undulation  of  the  luminiferous 
ether,  and  yet  the  constitution  of  the  latter  is  unknown.  We 
know  that  the  atoms  of  matter  can  vibrate  with  purer  tones 
than  the  most  perfect  piano,  and  yet  we  cannot  even  conceive 
of  their  constitution.  We  know  that  the  sun  attracts  the 
planets  with  a  force  whose  law  is  known,  and  yet  we  fail  to 
picture  to  ourselves  the  process  by  which  it  takes  our  earth 
within  its  grasp  at  the  distance  of  many  millions  of  miles  and 
prevents  it  from  departing  for  ever  from  its  life-giving  rays. 
Science  is  full  of  this  half-knowledge. 

So  far  we  have  considered  the  case  of  alternating  electric 
currents  in  a  wire  connecting  the  inner  and  outer  coatings  of  a 
Leyden  jar.  The  invention  of  the  telephone,  by  which  sound 
is  carried  from  one  point  to  another  by  means  of  electrical 
waves,  has  forced  into  prominence  the  subject  of  these  waves. 
Furthermore,  the  use  of  alternating  currents  for  electric  light- 
ing brings  into  play  the  same  phenomenon.  Here,  again,  the 
difference  between  a  current  of  water  and  a  current  of  elec- 
tricity is  very  marked.  A  sound  wave,  traversing  the  water 
in  the  tube,  produces  a  to-and-fro  current  of  water  at  any 
given  point.  So,  in  the  electrical  vibration  along  a  wire,  the 
electricity  moves  to  and  fro  along  it  in  a  manner  somewhat 
similar  to  the  water,  but  with  this  difference  :  the  disturbance 
from  the  water-motion  is  confined  to  the  tube,  and  the  oscilla- 
tion of  the  water  is  greatest  in  the  centre  of  the  tube  ;  while  in 
the  case  of  the  electric  current  the  ether  around  the  wire  is  dis- 
turbed, and  the  oscillation  of  the  current  is  greatest  at  the 
surface  of  the  wire  and  least  in  its  centre.  The  oscillations  in 
the  water  take  place  in  the  tube  without  reference  to  the 
matter  outside  the  tube,  whereas  the  electric  oscillations  in  the 
\vire  are  entirely  dependent  on  the  surrounding  space,  and  thd 


286  APPENDIX  B. 

velocity  of  the  propagation  is  nearly  independent  of  the  nature 
of  the  wire,  provided  it  is  a  good  conductor. 

We  have  then  in  the  case  of  electrical  waves  along  a  wire  a 
disturbance  outside  the  wire  arid  a  current  within  it,  and  the 
equations  of  Maxwell  allow  us  to  calculate  these  with  perfect 
accuracy  and  give  all  the  laws  with  respect  to  them. 

We  thus  find  that  the  velocity  of  propagation  of  the  waves 
along  a  wire,  hung  far  away  from  other  bodies  and  made  of 
good  conducting  material,  is  that  of  light,  or  185,000  miles  per 
second  ;  but  when  it  is  hung  near  any  conducting  matter,  like 
the  earth,  or  enclosed  in  a  cable  and  sunk  into  the  sea,  the 
velocity  becomes  much  less.  When  hung  in  space,  away  from 
other  bodies,  it  forms,  as  it  were,  the  core  of  a  system  of  waves 
in  the  ether,  the  amplitude  of  the  disturbance  becoming  less 
and  less  as  we  move  away  from  the  wire.  But  the  most 
curious  fact  is  that  the  electric  current  penetrates  only  a 
short  distance  into  the  wire,  being  mostly  confined  to  the 
surface,  especially  where  the  number  of  oscillations  per  second 
is  very  great. 

The  electrical  waves  at  the  surface  of  a  conductor  are  thus, 
in  some  respects,  very  similar  to  the  waves  on  the  surface  of 
water.  The  greatest  motion  in  the  latter  case  is  at  the  surface, 
while  it  diminishes  as  we  pass  downwards  and  soon  becomes 
inappreciable.  Furthermore,  the  depth  to  which  the  disturb- 
ance penetrates  into  the  water  increases  with  increase  of  the 
length  of  the  wave,  being  confined  to  very  near  the  surface  for 
very  short  waves.  So  the  disturbance  in  the  copper  penetrates 
deeper  as  the  waves  and  the  time  of  oscillation  are  longer,  and 
the  disturbance  is  more  nearly  confined  to  the  surface  as  the 
waves  become  shorter.1 

There  are  very  many  practical  applications  of  these  theor- 
etical results  for  electric  currents.  The  most  obvious  one  is 
to  the  case  of  conductors  for  the  alternating  currents  used 

1  A  striking  illustration  of  this  skin-deep  penetration  of  high-voltage 
electricity  was  communicated  by  Lord  Armstrong  to  Sir  William  Thom- 
son (now  Lord  Kelvin)  at  the  Newcastle  meeting  of  the  British  Associa- 
tion in  1889.  A  bar  of  steel  about  a  foot  long,  which  Lord  Armstrong 
was  holding  in  his  hand,  was  allowed  accidentally  to  short  circuit  tie 
two  terminals  of  a  dynamo  giving  an  alternate  current  of  85  amperes,  at 
&  difference  of  potential  of  103  volts.  He  instantly  felt  a  sensation  of 


NATURE  OF  ELECTRIC   CURRENTS.  287 

in  producing  the  electric  light.  We  find  that  when  these  are 
larger  than  about  half  an  inch  diameter  they  should  be  re- 
placed by  a  number  of  conductors  less  than  half  an  inch  dia- 
meter, or  by  strips  about  a  quarter  of  an  inch  thick,  and  of 
any  convenient  width. 

Prof.  Oliver  Lodge  has  recently  drawn  attention  to  another 
application  of  these  results — that  is,  to  lightning-rods.  Al- 
most since  the  time  of  Franklin  there  have  been  those  who 
advocated  the  making  of  lightning-rods  hollow  in  order  to  in- 
crease the  surface  for  a  given  amount  of  copper.  We  now 
know  that  these  persons  had  no  reason  for  their  belief,  as  they 
simply  drew  the  inference  that  electricity  at  rest  is  on  the 
surface.  Neither  were  the  advocates  of  the  solid  rods  quite 
correct,  for  they  reasoned  that  electricity  in  a  state  of  steady 
flow  occupies  the  whole  area  of  the  conductor  equally.  The 
true  theory,  we  now  know,  indicates  that  neither  party  was 
entirely  correct,  and  that  the  surface  is  a  very  important  factor 
in  the  case  of  a  current  of  electricity  so  sudden  as  that  from  a 
lightning  discharge.  But  increase  of  surface  can  best  be  ob- 
tained by  multiplying  the  number  of  conductors,  rather  than 
making  them  flat  or  hollow.  Theory  indicates  that  the  current 
penetrates  only  one-tenth  the  distance  into  iron  that  it  does 
into  copper.  As  the  iron  has  seven  times  the  resistance  of 
copper,  we  should  need  seventy  times  the  surface  of  iron  that 
we  should  of  copper.  Hence  I  prefer  copper  wire  about 
a  quarter  of  an  inch  diameter  and  nailed  directly  to  the  house 
without  insulators,  and  passing  down  the  four  corners,  around 
the  eaves,  and  over  the  roof,  for  giving  protection  from  light- 
ning in  all  cases  where  a  metal  roof  and  metal  down-spouts  do 
not  accomplish  the  same  purpose. 

Whether  the  discharge  of  lightning  is  oscillatory  or  not  does 
not  enter  into  the  question,  provided  it  is  only  sufficiently 
sudden.  I  have  recently  solved  the  mathematical  problem  of 
the  electric  oscillations  along  a  perfectly  conducting  wire  join- 
burning  and  dropped  the  bar.  His  fingers  were  badly  blistered,  though 
on  examining  the  bar  a  few  seconds  afterwards  it  was  found  to  be  quite 
cold.  This  proved  that  the  action  lay  at  the  surface,  and  had  not  time  to 
sensibly  penetrate  the  substance  of  the  bar.  There  were  two  little 
hollows  burned  out  of  the  metal  at  the  points  where  it  touched  tbe 
dynamo  terminals. — J,  J.  F. 


288  APPENDIX  B. 

ing  two  infinite  and  perfectly  conducting  planes  parallel  to 
each  other,  and  find  that  there  is  no  definite  time  of  oscillation, 
but  that  the  system  is  capable  of  vibrating  in  any  time  in 
which  it  is  originally  started.  The  case  of  lightning  between 
a  cloud  of  limited  extent  and  the  earth  along  a  path  through 
the  air  of  great  resistance  is  a  very  different  problem.  Both 
the  cloud  and  the  path  of  the  electricity  are  poor  conductors, 
which  tends  to  lengthen  the  time.  If  I  were  called  on  to 
estimate  as  nearly  as  possible  what  took  place  in  a  flash  of 
lightning,  I  would  say  that  I  did  not  believe  that  the  discharge 
was  always  oscillating,  but  more  often  consisted  of  one  or  more 
streams  of  electricity  at  intervals  of  a  small  fraction  of  a  sec- 
ond, each  one  continuing  for  not  less  than  ynoWo  second.  An 
oscillating  current  with  100,000  reversals  per  second  would 
penetrate  about  ^j  inch  into  copper  and  ^^  inch  into  iron. 
The  depth  for  copper  would  constitute  a  considerable  propor- 
tion of  a  wire  5-  inch  diameter,  and  as  there  are  other  con- 
siderations to  be  taken  into  account,  I  believe  it  is  scarcely 
worth  while  making  tubes,  or  flat  strips,  for  such  small 
sizes. 

It  is  almost  impossible  to  draw  proper  conclusions  from  ex- 
periments on  this  subject  in  the  laboratory,  such  as  those  of 
Prof.  Oliver  Lodge.1  The  time  of  oscillation  of  the  current  in 
most  pieces  of  laboratory  apparatus  is  so  very  small,  being 
often  the  TTiOUuffoW  °f  a  second,  that  entirely  wrong  inferences 
may  be  drawn  from  them.  As  the  size  of  the  apparatus  in- 
creases, the  time  of  oscillation  increases  in  the  same  propor- 
tion, and  changes  the  whole  aspect  of  the  case.  I  have  given 
TooWir  °f  a  second  as  the  shortest  time  a  lightning-flash  could 
probably  occupy.  I  strongly  suspect  it  is  often  much  greater, 
and  thus  departs  even  further  from  the  laboratory  experiments 
of  Prof.  Lodge,  who  has,  however,  done  very  much  towards 
drawing  attention  to  this  matter  and  showing  the  importance 
of  surface  in  this  case.  All  shapes  of  the  rod  with  equal  sur- 
face are  not,  however,  equally  efficient.  Thus,  the  inside 
surface  of  a  tube  does  not  count  at  all.  Neither  do  the  corru- 
gations on  a  rod  count  for  the  full  value  of  the  surface  they 

1  For  Prof.  Lodge's  views  see  his  paper,  'Jour.  Inst.  Elec.  Engs./ 
vol.    xix.    p. 
J.  J.  F. 


NATURE  OF  ELECTRIC  CURRENTS.  269 

expose,  for  the  current  is  not  distributed  uniformly  over  the 
surface  ;  but  I  have  recently  proved  that  rapidly  alternating 
currents  are  distributed  over  the  surface  of  very  good  conduc- 
tors in  the  same  manner  as  electricity  at  rest  would  be  dis- 
tributed over  them,  so  that  the  exterior  angles  and  corners 
possess  much  more  than  their  share  of  the  current,  and  corru- 
gations on  the  wire  concentrate  the  current  on  the  outer 
angles  and  diminish  it  in  the  hollows.  Even  a  flat  strip  has 
more  current  on  the  edges  than  in  the  centre. 

For  these  reasons,  shape,  as  well  as  extent  of  surface,  must 
be  taken  into  account,  and  strips  have  not  always  an  advan- 
tage over  wires  for  quick  discharges. 

The  fact  that  the  lightning-rod  is  not  melted  on  being  struck 
by  lightning  is  not  now  considered  as  any  proof  that  it  has  done 
its  work  properly.  It  must,  as  it  were,  seize  upon  the  discharge, 
and  offer  it  an  easier  passage  to  the  earth  than  any  other.  Such 
sudden  currents  of  electricity  we  have  seen  to  obey  very  dif- 
ferent laws  from  continuous  ones,  and  their  tendency  to  stick 
to  a  conductor  and  not  fly  off  to  other  objects  depends  not  only 
on  having  them  of  small  resistance,  but  also  on  having  what  we 
call  the  self-induction  as  small  as  possible.  This  latter  can  be 
diminished  by  having  the  lightning-rod  spread  sideways  as 
much  as  possible,  either  by  rolling  it  into  strips,  or  better,  by 
making  a  network  of  rods  over  the  roof  with  several  connections 
to  the  earth  at  the  corners,  as  I  have  before  described. 

Thus  we  see  that  the  theory  of  lightning-rods,  which  appeared 
so  simple  in  the  time  of  Franklin,  is  to-day  a  very  complicated 
one,  and  requires  for  its  solution  a  very  complete  knowledge  o£ 
the  dynamics  of  electric  currents.  In  the  light  of  our  present 
knowledge  the  frequent  failure  of  the  old  system  of  rods  is  no 
mystery,  for  I  doubt  if  there  are  a  hundred  buildings  in  the 
country  properly  protected  from  lightning.  "With  our  modern 
advances,  perfect  protection  might  be  guaranteed  in  all  cases, 
if  expense  were  no  object. 

We  have  now  considered  the  case  of  oscillations  of  electricity 
in  a  few  cases,  and  can  turn  to  that  of  steady  currents.  The 
closing  of  an  electric  circuit  sends  ethereal  waves  throughout 
space,  but  after  the  first  shock  the  current  flows  steadily  with- 
out producing  any  more  waves.  However,  the  properties  of 
the  space  around  the  wire  have  been  permanently  altered,  aa 

,T 


APPENDIX  B. 


we  have  already  seen.  Let  us  now  study  these  properties  more 
in  detail.  I  have  before  me  a  wire  in  which  I  can  produce  a 
powerful  current  of  electricity,  and  we  have  seen  that  the 
space  around  it  has  been  so  altered  that  a  delicately  suspended 
magnetic  needle  cannot  remain  quiet  in  all  positions,  but 
stretches  itself  at  right  angles  to  the  wire,  the  north  pole 
tending  to  revolve  around  it  in  one  direction  and  the  south 
pole  in  the  other.  This  is  a  very  old  experiment,  but  we  now 
regard  it  as  evidence  that  the  properties  of  the  space  around 
the  wire  have  been  altered  rather  than  that  the  wire  acts  on 
the  magnet  from  a  distance. 

Put,  now,  a  plate  of  glass  around  the  wire,  the  latter  being 
vertical  and  the  former  with  its  plane  horizontal,  and  pass  a 
powerful  current  through  the  wire.  On  now  sprinkling  iron 
tilings  on  the  plate  they  arrange  themselves  in  circles  around 
the  wire,  and  thus  point  out  to  us  the  celebrated  lines  of  mag- 
netic force  of  Faraday.  Using  two  wires  with  currents  in  the 
same  direction  we  get  these  other  curves,  and,  testing  the  forces 
acting  on  the  wire,  we  find  that  they  are  trying  to  move  towards 
each  other. 

Again,  pass  the  currents  in  the  opposite  directions  and  we 
get  these  other  curves,  and  the  currents  repel  each  other.  If 
we  assume  that  the  lines  of  force  are  like  rubber  bands  which 
tend  to  shorten  in  the  direction  of  their  length  and  repel  each 
other  sideways,  Faraday  and  Maxwell  have  shown  that  all  mag- 
netic attractions  arid  repulsions  are  explained.  The  property 
which  the  presence  of  the  electric  current  has  conferred  on  the 
ether  is  then  one  by  which  it  tends  to  shorten  in  one  direction 
and  spread  out  in  the  other  two  directions. 

We  have  thus  done  away  with  action  at  a  distance,  and  have 
accounted  for  magnetic  attraction  by  a  change  in  the  inter- 
vening medium,  as  Faraday  partly  did  almost  fifty  years  ago. 
For  this  change  in  the  surrounding  medium  is  as  much  a 
part  of  the  electric  current  as  anything  that  goes  on  within 
the  wire. 

To  illustrate  this  tension  along  the  lines  of  force,  1  have  con- 
structed this  model,  which  represents  the  section  of  a  coil  of 
wire  with  a  bar  of  iron  within  it.  The  rubber  bands  represent 
the  lines  of  force  which  pass  around  the  coil  and  through  the 
iron  bar,  as  they  have  an  easier  passage  through  the  iron  than 


NATURE   OF  ELECTKIC   CURRENTS.  291 

the  air.  As  we  draw  the  bar  down  and  let  it  go,  you  see  that 
it  is  drawn  upward  and  oscillates  around  its  position  of  equili- 
brium until  friction  brings  it  to  rest.  Here,  again,  I  have  a 
coil  of  wire  with  an  iron  bar  within  it  with  one  end  resting  on 
the  floor.  As  we  pass  the  current,  and  the  lines  of  magnetic 
force  form  around  the  coil  and  pass  through  the  iron,  it  is  lifted 
upwards,  although  it  weighs  24  lb.,  and  oscillates  around  i^s 
position  of  equilibrium  exactly  the  same  as  though  it  were 
sustained  by  rubber  bands  as  in  the  model.  The  rubber  bands 
in  this  case  are  invisible  to  our  eye,  but  our  mental  vision 
pictures  them  as  lines  of  magnetic  force  in  the  ether  drawing 
the  bar  upward  by  their  contractile  force.  This  contractile 
force  is  no  small  quantity,  as  it  may  amount,  in  some  cases,  to 
one  or  even  two  hundred  pounds  to  the  square  inch,  and 
thus  rivals  the  greatest  pressure  which  we  use  in  our  steam- 
engines. 

Thus  the  ether  is,  to-day,  a  much  more  important  factor  in 
science  than  the  air  we  breathe.  We  are  constantly  surrounded 
by  the  two,  and  the  presence  of  the  air  is  manifest  to  us  all  ; 
we  feel  it,  we  hear  by  its  aid,  arid  we  even  see  it  under  favour- 
able circumstances,  and  the  velocity  of  its  motion  as  well  as  the 
amount  of  moisture  it  carries  is  a  constant  topic  of  conversation. 
The  ether,  on  the  other  hand,  eludes  all  our  senses,  and  it  ia 
only  with  imagination,  the  eye  of  the  mind,  that  its  presence 
can  be  perceived.  By  its  aid  in  conveying  the  vibrations  we 
call  light  we  are  enabled  to  see  the  world  around  us  ;  and  by  ita 
other  motions,  which  cause  magnetism,  the  mariner  steers  his 
ship  through  the  darkest  night  when  the  heavenly  bodies  are 
hid  from  view.  When  we  speak  in  a  telephone,  the  vibrations 
of  the  voice  are  carried  forward  to  the  distant  point  by  waves 
in  the  ether,  there  again  to  be  resolved  into  the  sound  waves 
of  the  air.  When  we  use  the  electric  light  to  illuminate  our 
streets,  it  is  the  ether  which  conveys  the  energy  along  the 
wires  as  well  as  transmits  it  to  our  eye  after  it  has  assumed  the 
form  of  light.  We  step  upon  an  electric  street-car  and  feel  it 
driven  forward  with  the  power  of  many  horses,  and  again  it  is 
the  ether  whose  immense  force  we  have  brought  under  our 
control  and  made  to  serve  our  purpose — no  longer  a  feeble,  un- 
certain sort  of  medium,  but  a  mighty  power,  extending  through- 
out all  space,  and  binding  the  whole  universe  together. 


292  APPENDIX  C. 


APPENDIX  C. 

VARIATIONS  OF  CONDUCTIVITY  UNDER  ELECTRICAL 
INFLUENCE. 

Substance  of  a  paper  by  Prof.  E.  Branly,  of  the  Catholic 
University  of  Paris.1 

The  object  of  this  article  is  to  describe  the  first  results 
obtained  in  an  investigation  of  the  variation  or  resistance  of  a 
large  number  of  conductors  under  various  electrical  influences. 
The  substances  which  up  to  the  present  have  presented  the 
greatest  variations  in  conductivity  are  the  powders  or  filings 
of  metals.  The  enormous  resistance  offered  by  metal  in  a 
state  of  powder  is  well  known  ;  indeed,  if  we  take  a  somewhat 
long  column  of  very  fine  metallic  powder,  the  passage  of  the 
current  is  completely  stopped.  The  increase  in  the  electrical 
conductivity  by  pressure  of  powdered  conducting  substances  is 
also  well  known,  and  has  had  various  practical  applications. 
The  variations  of  conductivity,  however,  which  occur  on  sub- 
jecting such  bodies  to  various  electrical  influences  have  not 
been  previously  investigated. 

The  Effect  of  Electric  Sparks. — Let  us  take  a  circuit  compris- 
ing a  single  cell,  a  galvanometer,  and  some  powdered  metal 
enclosed  in  an  ebonite  tube  of  one  square  centimetre  cross  section 
ami  a  few  centimetres  long.  Close  the  extremities  of  the  tube 
with  two  cylindrical  copper  tubes  pressing  against  the  powdered 
metal  and  connected  to  the  rest  of  the  circuit.  If  the  powder 
is  sufficiently  fine,  even  a  very  sensitive  galvanometer  does 
not  show  any  evidence  of  a  current  passing.  The  resistance  is 
of  the  order  of  millions  of  ohms,  although  the  same  metal 
melted  or  under  pressure  would  only  offer  (the  dimensions 
being  the  same)  a  resistance  equal  to  a  fraction  of  an  ohm. 
There  being,  therefore,  no  current  in  the  circuit,  a  Leyden 

i  Based  on  reports  in  the  (London)  'Electrician,'  June  26  and  August 
21,  1891. 


VARIATIONS  OF  CONDUCTIVITY.  293 

jar  is  discharged  at  some  little  distance  off,  when  the  abrupt 
and  permanent  deflection  of  the  galvanometer  needle  shows 
that  an  immediate  and  a  permanent  reduction  of  the  resistance 
has  been  caused.  The  resistance  of  the  inetal  is  no  longer  to 
be  measured  in  millions  of  ohms,  but  in  hundreds.  Its  con- 
ductivity increases  with  the  number  and  intensity  of  the 
sparks. 

Some  20  or  30  centimetres  from  a  circuit  comprising  some 
metallic  filings  contained  in  an  ebonite  cup,  let  us  place  a 
hollow  brass  sphere,  15  to  20  centimetres  in  diameter,  insu- 
lated by  a  vertical  glass  support.  The  filings  offer  an  enormous 
resistance  and  the  galvanometer  needle  remains  at  zero.  But 
if  we  bring  an  electrified  stick  of  resin  near  the  sphere,  a  little 
spark  will  pass  between  the  stick  and  the  sphere,  and  imme- 
diately the  needle  of  the  galvanometer  is  violently  jerked  and 
then  remains  permanently  deflected.  On  some  fresh  filings 
being  placed  in  the  ebonite  cup,  the  resistance  of  the  circuit 
will  again  keep  the  needle  at  zero.  If  now  the  charged  brass 
sphere  is  touched  with  the  finger,  there  is  a  minute  discharge 
and  the  galvanometer  needle  is  again  deflected.  With  a  few 
accumulators  the  experiment  can  easily  be  made  without  a 
galvanometer.  The  circuit  consists  of  the  battery,  some 
metallic  powder,  a  platinum  wire,  and  a  mercury  cup.  The  re- 
sistance of  the  powder  is  so  high  that  the  interruption  of  the 
circuit  takes  place  without  any  sparking  of  the  mercury  cup. 
If  now  a  Leyden  jar  is  discharged  in  the  neighbourhood  of  the 
circuit  the  powder  is  rendered  conducting,  the  platinum  wiie 
immediately  becomes  red  hot,  and  a  violent  spark  occurs  on 
breaking  the  circuit. 

The  influence  of  the  spark  decreases  as  the  distance  increases, 
but  its  influence  is  observable  several  metres  away  from  the 
powder,  even  with  a  small  Wimshurst  machine.  Repeating 
the  spark  increases  the  conductivity  ;  in  fact,  with  certain 
substances  successive  sparks  produce  successive  jerks,  and  a 
gradually  increasing  and  persistent  deflection  of  the  galvan- 
ometer needle. 

Influence  of  a  Conductor  traversed  by  Condenser  Discharges. — 
While  using  the  Wimshurst  machine  it  was  noticed  that  the 
reduction  in  the  resistance  of  the  filings  frequently  took  place 
before  discharge.  This  led  me  to  the  following  experiment : 


294  APPENDIX  C. 

Take  a  long  brass  tube,  one  end  of  which  is  close  to  the  circuit 
containing  the  metallic  powder  ;  its  other  end,  several  metres 
distant  from  the  circuit,  is  fairly  close  to  a  charged  Leyden 
jar.  A  spark  takes  place  and  the  conductor  is  charged.  At 
the  same  instant,  the  conductivity  of  the  metallic  powder  is 
greatly  increased. 

The  following  arrangement,  owing  to  its  efficacy,  conven- 
ience, and  regularity  of  action,  was  used  by  me  in  most  of 
my  researches,  and  I  shall  briefly  call  it  the  A  arrangement 

(fig-  I)- 

The  source  of  electricity  is  a  two-plate  Holtz  machine  driven 
at  from  100  to  400  revolutions.    A  sensitive  substance  is  intro- 
duced into  one  of  the  arms  of  a  Wheatstone  bridge,  or  into  the 
circuit  of  a  single  Daniell   cell  at  a  dis- 

mimj  LJimU        tan(Je    of   gome    ]()    metreg    from    the    Holtz 

1  ,00,  '  T  machine.  Between  the  discharge  knobs  of 
the  machine  and  the  Wheatstone  bridge, 
and  connected  to  the  former,  there  are 
two  insulated  brass  tubes,  A  A',  running 
parallel  to  one  another  40  centimetres 
apart.  The  Leyden  jars  usually  attached 
to  a  Holtz  machine  may  be  dispensed 
K  with,  the  capacity  of  the  long  brass  tubes 

Fig.  1.  being  in  sojne  measure  equivalent  to  them. 

The  knobs  s  were  1  mm.,  '5  mm.,  or  -1  mm. 
apart.  When  the  plates  were  rotated,  sparks  rapidly  succeeded 
each  other.  Experiments  showed  that  these  sparks  had  no  di- 
rect effect  at  a  distance  of  10  metres.  The  two  tubes  A  A'  are  not 
absolutely  necessary  ;  the  diminution  of  resistance  is  easily  pro- 
duced if  only  one  is  employed,  and  in  some  cases,  indeed,  a 
single  conductor  is  more  efficacious.  An  increase  in  the  speed 
of  the  machine  increases  its  action  to  a  marked  extent.  The 
sparks  at  s  may  be  suppressed  by  drawing  the  knobs  apart, 
but  the  conductor  A  will  still  continue  to  exert  its  influence, 
especially  if  there  is  a  spark-gap  anywhere  about. 

Effects  of  Induced  Currents. — The  passage  of  induced  currents 
through  a  sensitive  substance  produces  similar  effects  to  those 
described  above.  In  one  instance  an  induction  coil  was  taken, 
having  two  similar  wires.  The  circuit  of  the  secondary  wire 
was  closed  through  a  tube  containing  filings,  the  galvanometer 


VARIATIONS   OF  CONDUCTIVITY.  295 

being  also  in  circuit.  Care  was  taken  to  ascertain  before  intro- 
ducing  the  filings  into  the  circuit  that  the  currents  on  make 
and  break  gave  equal  and  opposite  deflections.  Filings  were 
then  introduced  into  the  circuit,  the  primary  being  made  and 
broken  at  regular  intervals.  The  following  table  gives  the 
results  obtained  in  the  case  of  zinc  filings  : — 

ZINC  FILINGS. 

Galvanometer  throws.  Galvanometer  throws. 

1st  closing      .        .        1°  1st  opening    .        .       18° 

2nd     „           .        .       04°  2nd      „          .        .     100° 

3rd      „           .        .     Mt>°  3rd      ,,          .        .140° 

Effects  of  passing  Continuous  Currents  of  High  E.M.F. — If  a 
continuous  current  of  high  E.M.F.  is  employed,  it  renders 
a  sensitive  substance  conducting.  The  phenomenon  may  be 
shown  in  the  following  manner.  A  circuit  is  made  up  con- 
sisting of  a  battery,  a  sensitive  substance,  and  a  galvanometer. 
The  E.M.F.  of  the  battery  is  first  1  volt,  then  100  volts,  then  1 
volt.  Below  I  give  the  galvanometer  deflections  obtained 
with  an  E.M.F.  of  1  volt  for  three  different  substances  before 
and  after  the  application  of  the  E.M.F.  of  100  volts  : — 

Before  application  After  application 
of  current.  of  current. 

16  100 

0  15 

1  500 

In  the  case  of  some  measurements  taken  on  a  Wheatstone 
bridge,  a  prism  of  aluminium  filings  interposed  between  two 
copper  electrodes  offered  a  resistance  of  several  million  ohms 
before  a  high  E.M.F.  was  applied,  but  only  offered  a  resistance 
of  350  ohms  after  the  application  of  this  pressure  for  one 
minute.  The  time  during  which  the  powder  should  be  inter- 
posed in  the  battery  circuit  should  not  be  too  short.  Thus,  in 
one  instance  the  application  for  10  seconds  of  75  mercury 
sulphate  cells  produced  no  effect,  but  their  application  for  60 
seconds  resulted  in  the  resistance  being  reduced  from  several 
megohms  to  2500  ohms. 

It  should  be  observed  that  the  phenomenon  of  suddenly  in- 
creased conductivity  occurs  even  if  the  sensitive  substance  ia 


296 


APPENDIX  C. 


not  in  circuit  with  a  battery  at  the  time  it  is  influenced. 
Thus,  the  metallic  filings,  after  having  been  placed  in  circuit 
with  a  Daniell  cell,  and  their  high  resistance  observed,  may  then 
be  completely  insulated  and  submitted  in  this  condition  to  the 
action  of  a  distant  spark,  or  of  a  charged  rod,  or  of  induced 
currents.  If,  after  this,  the  filings  are  replaced  in  their 
original  circuit,  the  enormous  increase  in  their  conductivity 
is  immediately  apparent. 

The  conductivity  produced  by  these  various  methods  takes 
place  throughout  the  Avhole  mass  of  the 
metallic  filings,  and  in  every  direction, 
as  the  following  experiment  will  show. 
A  vertical  ebonite  cup  containing  alu- 
minium powder  (fig.  2)  is  placed  between 
two  metal  plates  A,  B  ;  laterally  the  pow- 

n  ^J^-^':~-"^¥(  ^  ^er  *s  *11  con^ac^  with  two  short  rods 
|fC2|  r^^rr-*,  ££^J  c,  D,  which  pass  through  the  sides  of 
the  ebonite  cylinder.  A  and  B  can  be 
connected  to  two  terminals  of  one  of 
the  arms  of  the  Wheatstone  bridge, 
c  and  D  being  free,  and  vice  versa. 
Whatever  arrangement  is  adopted,  if  a 
battery  of  100  cells  is  joined  up  for  a 
few  seconds  with  one  or  the  other  of 
the  pairs  of  terminals,  the  increase  in 

the  conductivity  is  immediately  visible  in  that  direction,  and 
is  found  to  exist  also  in  the  direction  at  right  angles. 

Substances  in  which  Diminution  of  Resistance  lias  been  ob- 
served.— The  substances  in  which  the  phenomenon  of  the  sudden 
increase  of  conductivity  is  most  easily  observed  are  filings  of 
iron,  aluminium,  copper,  brass,  antimony,  tellurium,  cadmium, 
zinc,  bismuth,  &c.  The  size  of  the  grains  and  their  nature  are 
not  the  only  elements  to  be  considered,  for  grains  of  lead  of 
the  same  size,  but  coming  from  different  quarters,  offer  at  the 
same  temperature  great  differences  in  resistance  (20,000  to 
500,000  ohms).  Extremely  fine  metallic  powder,  as  a  rule, 
offers  almost  perfect  resistance  to  the  passage  of  a  current. 
But  if  we  take  a  sufficiently  short  column  and  exert  a  suffi- 
ciently great  pressure,  a  point  is  soon  reached  when  the  elec- 
trical influence  will  effect  a  sudden  increase  in  the  conductivity. 


VARIATIONS  OF '  CONDUCTIVITY. 


207 


Thus,  a  layer  of  copper  reduced  by  hydrogen,  which  does  not 
become  conducting  under  the  influence  of  the  electric  spark  or 
otherwise,  will  become  so  on  being  submitted  to  a  pressure  of 
500  grammes  to  the  square  centimetre  (7  Ib.  per  square  inch). 
Instead  of  using  pressure,  I  employed  as  a  conductor  in  some 
experiments  a  very  fine  coating  of  powdered  copper  spread  on 
a  sheet  of  unpolished  glass  or  ebonite  E  (fig.  3),  7  centimetres 
long  and  2  centimetres 
broad.  A  layer  of  this 
kind,  polished  with  a 
burnisher,  has  a  very 
variable  resistance. 
With  a  little  care  one 
can  prepare  sheets  which 
are  more  or  less  sensi- 
tive to  electrical  action. 
Metal  powders  or 
metal  filings  are  not 
the  only  sensitive  sub- 
stances, as  powdered 
galena,  which  is  slightly 
conducting  under  pres- 
sure, conducts  much 
better  after  having  been  submitted  to  electrical  influence. 
Powdered  binoxide  of  manganese  is  not  very  sensitive  unless 
mixed  with  powdered  antimony  and  compressed. 

Making  use  of  the  A  arrangement  with  very  short  sparks 
at  s  (tig.  1),  the  phenomenon  of  increased  conductivity  can  be 
observed  with  platinised  and  silvered  glass,  also  with  glass 
covered  with  gold,  silver,  and  aluminium  foil.  Some  of  the 
mixtures  employed  had  the  consistency  of  paste.  These  were 
mixtures  of  colza  oil  and  iron,  or  antimony  filings,  and  of  ether 
or  petroleum  and  aluminium,  and  plumbago,  &c.  Other  mix- 
tures were  solid.  If  we  make  a  mixture  of  iron  filings  and 
Canada  balsam,  melted  in  a  water  bath,  and  pour  the  paste 
into  a  little  ebonite  cup,  the  ends  of  which  are  closed  by 
metallic  rods,  a  substance  is  obtained  which  solidifies  on  cool- 
ing. The  resistance  of  such  a  mixture  is  lowered  from  several 
megohms  to  a  few  hundred  ohms  by  an  electric  spark.  Similar 
results  are  obtained  with  a  solid  rod  composed  of  fused  flowers 


Fig.  3. 


298  APPENDIX   C. 

of  sulphur  and  iron  or  aluminium  filings,  also  by  a  mixture 
of  melted  resin  and  aluminium  filings.  In  the  preparation 
of  these  solid  sensitive  mixtures,  care  must  be  taken  that  the 
insulating  substance  should  only  form  a  small  percentage  of 
the  whole. 

Some  interesting  results  are  also  obtained  with  mixtures  of 
sulphur  and  aluminium,  and  with  resin  and  aluminium,  when 
in  a  state  of  powder.  When  cold  these  mixtures,  as  a  rule,  do 
not  conduct  either  directly  or  after  they  have  been  exposed  to 
electrical  influences,  but  they  become  conducting  on  combining 
pressure  with  electrical  influences.  Thus,a  mixture  of  flowers-of- 
sulphur  and  aluminium  filings  in  equal  volumes  was  placed  in  a 
glass  tube  24  mm.  in  diameter.  The  weight  of  the  mixture  was 
20  grammes,  and  the  height  of  the  column  22  mm.,  with  a  pres- 
sure of  186  grammes  per  square  centimetre  (2£  Ib.  per  square 
inch).  The  mixture  is  not  conducting,  but  after  exposure  to 
electrical  influence,  obtained  by  the  A  arrangement,  the  resist- 
ance falls  to  90  ohms.  In  a  similar  manner  a  mixture  of 
selenium  and  aluminium,  placed  in  a  tube  99  mm.  long,  was 
not  conducting  until  after  it  was  exposed  to  the  combined  in- 
fluence of  pressure  and  electricity. 

The  following  is  one  of  the  group  of  numerous  experiments 
of  a  slightly  different  character.  A  mixture  of  flowers-of- 
sulphur  and  fine  aluminium  filings,  containing  two  of  sulphur 
to  one  of  aluminium,  is  placed  in  a  cylindrical  glass  tube  35 
mm.  long.  By  means  of  a  piston,  a  pressure  of  20  kilogrammes 
per  square  centimetre  (284  Ib.  per  square  inch)  was  applied. 
It  was  only  necessary  to  connect  the  column  for  10  seconds  to 
the  poles  of  a  25-cell  battery,  for  the  resistance  originally  in- 
finite to  be  reduced  to  4000  ohms. 

The  arrangement  shown  in  fig.  4  illustrates  another  order  of 
experiment.  Two  rods  of  copper  were  oxidised  in  the  flame  of 
a  Bunsen  burner,  and  were  then  arranged  to  lie  across  each 
other,  as  shown,  and  were  connected  to  the  terminals  of  the 
arm  of  a  Wheatstone  bridge,  the  high  resistance  of  the  circuit 
being  due  to  the  layers  of  oxide.  Amongst  the  many  measure- 
ments made,  I  found,  in  one  case,  a  resistance  of  80,000  ohms, 
which,  after  exposure  to  the  influence  of  the  electric  spark, 
was  reduced  to  7  ohms.  Analogous  effects  are  obtained  with 
oxidised  steel  rods.  Another  pretty  experiment  is  to  place  a 


VARIATIONS   OF  CONDUCTIVITY.  209 

cylinder  of  copper,  with  an  oxidised  hemispherical  head,  on  a 
sheet  of  oxidised  copper.  Before  exposure  to  the  influence  of 
the  electric  spark,  the  oxide  offers  considerable  resistance. 
The  experiment  can  be 
repeated  several  times  by 
merely  moving  the  cylin- 
der from  one  place  to 
another  on  the  oxidised 
sheet  of  copper,  thus 
showing  that  the  pheno- 
menon only  takes  place 
at  the  point  of  contact  of 
the  two  layers  of  oxide. 

It  may  be  worth  noting 
that,  for  most  of  the  sub- 
stances enumerated,  an 
elevation  of  temperature 

diminishes  the  resistance,  but  the  effect  of  a  rise  of  tempera- 
ture is  transient,  and  is  incomparably  less  than  the  effect  due 
to  currents  of  high  potential.  For  a  few  substances  the  two 
effects  are  opposed. 

Restoration  of  Original  Resistance. — The  conductivity  caused 
by  the  various  electrical  influences  lasts  sometimes  for  a  long 
period  (twenty-four  hours  or  more),  but  it  is  always  possible  to 
make  it  rapidly  disappear,  particularly  by  a  shqck. 

The  majority  of  substances  tested  showed  an  increase  of 
resistance  on  being  shaken  previous  to  being  submitted  to  any 
special  electrical  influence,  bat  after  having  been  influenced 
the  effect  of  shock  is  much  more  marked.  The  phenomenon  is 
best  seen  with  the  metallic  filings,  but  it  can  also  be  observed 
with  metallised  ebonite  sheets  with  mixtures  of  liquid  insulators 
and  metallic  powders,  mixtures  of  metallic  filings  and  insulating 
substances  (compressed  or  not  compressed),  and  finally  with 
solid  bodies. 

I  observed  the  return  to  original  resistance  in  the  following 
manner  : — 

The  sensitive  substance  was  placed  at  K  (fig.  1),  and  formed 
part  of  a  circuit  which  included  a  Daniell  cell  and  galvanometer. 
At  first  no  current  passes.  Sparks  are  then  caused  at  s,  and 
tl»«i  needle  of  the  galvanometer  is  permanently  deflected.  On 


300  APPENDIX  C.    . 

smartly  tapping  the  table  supporting  the  ebonite  cup  in  which 
the  sensitive  substance  is  contained,  the  original  condition  is 
completely  restored.  When  the  electric  action  has  been  of  u 
powerful  character,  violent  blows  are  necessary.  I  employed 
for  the  purpose  of  these  shocks  a  hammer  fixed  on  the  table, 
the  blows  of  which  could  be  regulated. 

With  some  substances,  when  feebly  electrified,  the  return 
seemed  to  be  spontaneous,  although  it  was  slower  than  the 
return  of  the  galvanometer  needle  to  equilibrium.  This  resto- 
ration of  the  original  resistance  is  attributable  to  surrounding 
trepidations,  as  it  was  only  necessary  to  walk  about  the  room 
at  a  distance  of  a  few  metres,  or  to  shake  a  distant  wall.  This 
spontaneous  return  to  original  resistance  after  w.eak  electrical 
action  was  visible  with  a  mixture  of  equal  parts  cf  fine  selenium 
and  tellurium  pow/lers.  The  restoration  of  resistance  by  shock 
was  not  observable  so  long  as  the  electrical  influence  was  at 
work. 

After  having  been  submitted  to  powerful  electric  action, 
shock  does  not  seem  to  entirely  restore  substances  to  their 
original  state  ;  in  fact,  the  substances  generally  show  greater 
sensitiveness  to  electric  action.  Thus,  a  mixture  of  colza  oil 
and  antimony  powder  being  exposed  to  the  influence  of  arrange- 
ment A,  a  spark  of  5  mm.  was  at  first  necessary  to  break  down 
the  resistance  ;  but  after  the  conductivity  had  been  made  to 
disappear  by  means  of  blows,  a  spark  of  only  1  mm.  was  suffi- 
cient to  again  render  the  substance  conducting.  Finely 
powdered  aluminium  has  an  extremely  high  resistance.  A 
vertical  column  of  powdered  aluminium  5  mm.  long  of  4  square 
cms.  cross-section,  submitted  to  considerable  pressure,  com- 
pletely stopped  the  current  from  a  Daniell  cell.  The  influence 
of  arrangement  A  produced  no  effect,  but,  by  direct  contact 
with  a  Leyden  jar,  the  resistance  was  reduced  to  50  ohms.  The 
effect  of  shock  was  then  tried,  and  after  this  the  sparks  pro- 
duced by  arrangement  A  were  able  to  reduce  the  resistance. 

The  following  experiment  is  also  of  the  same  kind  :  Alum- 
inium filings  placed  in  a  parallelipidic  trough  completely  stopped 
the  current  from  a  Daniell  cell,  and  the  resistance  offered  to  a 
single  cell  remained  infinite  after  the  trough  had  been  placed 
in  the  circuit  of  25  sulphate  of  mercury  cells  for  10  seconds. 
The  aluminium  was  next  placed  in  circuit  with  a  battery  of  75 


VARIATIONS   OF  CONDUCTIVITY.  SOI 

cells  ;  a  single  Daniell  cell  was  then  able  to  send  a  current 
through  the  substance.  The  original  resistance  was  restored 
by  shock,  but  not  the  original  condition  of  things,  since  a  single 
cell  was  able  to  send  a  current  after  the  aluminium  had  been 
circuited  for  10  seconds  with  a  battery  of  only  25  cells.  I  may 
add  that  if  the  restoration  of  resistance  was  brought  about  by 
a  violent  shock,  it  was  necessary  to  place  the  aluminium  in 
circuit  with  75  cells  for  one  minute  before  the  resistance  was 
again  broken  down. 

It  must  be  observed  that  electrical  influence  is  not  always 
necessary  to  restore  conductivity  after  an  apparent  return  to 
the  original  resistance,  repeated  feeble  blows  being  sometimes 
successful  in  bringing  this  about.  Both  in  the  case  of  slow 
return  by  time  and  sudden  return  by  shock,  the  original  value 
of  the  resistance  is  often  increased.  Eods  of  Carre  carbon,  1 
metre  long  and  1  mm.  in  diameter,  were  particularly  noticeable 
for  this  phenomenon. 

Return  to  Original  Resistance  by  Temperature  Elevation. — A 
plate  of  coppered  ebonite  rendered  conducting  by  electricity, 
and  placed  close  to  a  gas-jet,  quickly  regained  its  original 
resistance.  A  solid  rod  of  resin  and  aluminium,  or  of  sulphur 
and  aluminium,  rendered  conducting  by  connection  to  the  poles 
of  a  small  battery,  will  regain  its  original  resistance  by  shock  ; 
but  if  the  conducting  state  has  been  caused  by  powerful  means, 
such,  for  instance,  as  direct  contact  with  a  Leyden  jar,  shock 
no  longer  has  any  effect,  at  least  such  a  shock  as  the  fragile 
nature  of  the  material  can  stand.  A  slight  rise  of  temperature, 
however,  has  the  desired  result.  By  suitably  regulating  the 
electric  action  it  is  possible  to  get  a  substance  into  such  a 
condition  that  the  warmth  of  the  fingers  suffices  to  annul  con- 
ductivity. 

Influence  of  Surroundings. — Electric  action  gives  rise  to  no 
alteration  of  resistance  when  the  substance  is  entirely  within  a 
closed  metal  box.  The  sensitive  substance,  in  circuit  with  a 
Daniell  cell  and  a  galvanometer,  is  placed  inside  a  brass  box 
(fig.  5).  The  absence  of  current  is  ascertained,  the  circuit 
broken,  and  the  box  closed.  A  Wimshurst  machine  is  then 
worked  a  little  way  off,  and  will  be  found  to  have  had  no 
effect.  The  same  result  will  be  obtained  if  the  circuit  is  kept 
closed  during  the  time  the  Wimshurst  machine  is  in  operation. 


302 


APPENDIX  C. 


Fig.  6. 


If  a  wire  connected  at  some  point  to  the  circuit  is  passed  out 
tb rough  a  hole  in  the  box  to  a  distance  of  20  to  50  cms.,  the 
influence  of  the  Wimshurst  machine  makes  itself  felt.  On 

tapping  the  lid  to  re- 
store resistance,  the 
galvanometer  needle 
remains  deflected  so 
long  as  the  sparks 
continue  to  pass.  If, 
however,  the  wires 
are  pushed  in  so  that 
they  only  project  a 
few  millimetres,  the 
sparks  still  passing, 
a  few  taps  suffice  to 
bring  back  the  needle 
to  zero.  On  touch- 
ing the  end  of  the 
wire  with  the  fingers  or  a  piece  of  metal,  conductivity  is  imme- 
diately restored.  The  movements  of  the  galvanometer  needle 
xvere  rendered  visible  in  these  experiments  by  looking  through 
apiece  of  wide-mesh  wire-gauze  with  a  telescope.  The  re- 
spective position  of  the  things  was  reversed  ;  that  is  to  say, 
a  Ruhmkorff  coil  and  a  periodically  discharged  Leyden  jar 
were  placed  inside,  and  the  sensitive  substance  outside,  the 
box,  with  the  same  results. 

In  some  later  experiments  with  a  larger  metallic  case,  and 
with  the  Daniell  cell,  sensitive  substance,  delicate  galvan- 
ometer, and  Wheatstone  bridge  placed  inside,  I  found  that  a 
double  casing  was  necessary  in  order  to  absolutely  suppress  all 
effects.  A  glass  covering  afforded  no  protection. 

Considerations  on  tfte  Mechanism  of  the  Effects  produced. — 
What  conclusions  are  we  to  draw  from  the  experiments  de- 
scribed ?  The  substances  employed  in  these  investigations 
were  not  conductors,  since  the  metallic  particles  composing 
them  were  separated  from  each  other  in  the  midst  of  an  in- 
sulating medium.  It  was  not  surprising  that  currents  of  high 
potential,  and  especially  currents  induced  by  discharges,  should 
spark  across  the  insulating  intervals.  But  as  the  conductivity 
persisted  afterwards,  even  for  the  weakest  therrno  electric 


VARIATIONS   OF   CONDUCTIVITY.  303 

currents,  there  is  some  ground  for  supposing  that  the  insulating 
medium  is  transformed  by  the  passage  of  the  current,  and  that 
certain  actions,  such  as  shock  and  rise  of  temperature,  bring 
about  a  modification  of  this  new  state  of  the  insulating  body. 
Actual  movement  of  the  metallic  particles  cannot  be  imagined 
in  experiments  where  the  particles  in  a  layer  a  few  millimetres 
thick  were  fixed  in  an  invariable  relative  position  by  extreme 
pressures,  reaching  at  times  to  more  than  100  kilogrammes 
per  square  cm.  (1420  Ib.  to  the  square  inch).  Moreover,  in  the 
case  of  solid  mixtures,  in  which  the  same  variations  of  re- 
sistance were  produced,  displacement  seems  out  of  the  question. 
To  explain  the  persistence  of  the  conductivity  after  the  cessation 
of  the  electrical  influence,  are  we  to  suppose  in  the  case  of 
metallic  filings  a  partial  volatilisation  of  the  particles  creating 
a  conducting  medium  between  the  grains  of  metal  ?  In  the 
case  of  mixtures  of  metallic  powders  and  insulating  substances 
agglomerated  by  fusion,  are  we  to  suppose  that  the  thin  in- 
sulating layers  are  pierced  by  the  passage  of  very  small  sparks, 
and  that  the  holes  left  behind  are  coated  with  conducting 
material  ?  If  this  explication  is  admissible  for  induced  cur- 
rents, it  must  hold  good  for  continuous  currents.  If  so,  we 
must  conclude  that  these  mechanical  actions  may  be  produced 
by  batteries  of  only  10  to  20  volts  electromotive  force,  and 
which  only  cause  an  insignificant  current  to  pass.  The  following 
experiment  is  worth  quoting  in  this  connection  : — 

A  circuit  was  formed  by  a  Daniell  cell,  a  sensitive  galvan- 
ometer, and  some  aluminium  filings  in  an  ebonite  cup.  The 
galvanometer  needle  remained  at  zero.  The  filings  were  cut 
out  of  this  circuit,  and  switched  for  one  minute  into  circuit 
with  a  battery  of  43  sulphate  of  mercury  cells.  On  being  re- 
placed in  the  first  circuit,  the  filings  exhibited  high  conductivity. 
The  result  was  the  same  when  10  or  20  cells  were  employed,  or 
when  the  current  was  diminished  by  interposing  in  the  circuit 
a  column  of  distilled  water,  40  cm.  long  and  20  mm.  in  diameter. 
The  cells  used  (platinum,  sulphate  of  mercury,  sulphate  of  zinc, 
zinc)  had  a  high  internal  resistance.  Thus,  43  cells  (60  volts), 
when  short  circuited,  only  gave  a  current  of  5  nYHliamp&res. 
The  same  battery,  with  the  column  of  distilled  water  in  circuit 
only,  caused  a  deflection  of  100  mm.  on  a  scale  one  metre  off, 
with  an  astatic  galvanometer  wound  with  50,000  turns.  We 


304  APPENDIX  C. 

can,  therefore,  see  how  infinitesimally  small  the  initial  current 
must  have  been  when  the  filings  were  added  to  the  circuit.  The 
battery  acted,  therefore,  essentially  by  virtue  of  its  electro- 
motive force. 

If  mechanical  displacement  of  particles  or  transportation  of 
conducting  bodies  seem  inadmissible,  it  is  probable  that  there 
is  a  modification  of  the  insulator  itself,  the  modification  per- 
sisting for  some  time  by  virtue  of  a  sort  of  "  coercive  force." 
An  electric  current  of  high  potential,  which  would  be  com- 
pletely stopped  by  a  thick  insulating  sheet,  may  be  supposed  to 
gradually  traverse  the  very  thin  dielectric  layers  between  the 
conducting  particles,  the  passage  being  effected  very  rapidly  if 
the  electric  pressure  is  great,  and  more  slowly  if  the  pressure 
is  less. 

Increase  of  Resistance. — An  increase  of  resistance  was  observed 
in  these  investigations  less  often  than  a  diminution  ;  neverthe- 
less, a  number  of  frequently  repeated  experiments  enable  me  to 
say  that  increase  of  resistance  is  not  exceptional,  and  that  the 
conditions  under  which  it  takes  place  are  well  defined.  Short 
columns  of  antimony  or  aluminium  powder,  when  subjected  to 
a  pressure  of  about  1  kilogramme  per  square  cm.  (14'2  Ib.  per 
square  inch),  and  offering  but  a  low  resistance,  exhibited  an 
increase  of  resistance  under  the  influence  of  a  powerful  electri- 
fication. Peroxide  of  lead,  a  fairly  good  conductor,  always 
exhibited  an  increase,  so  also  did  some  kinds  of  platinised 
glass,  while  others  showed  alternate  effects.  For  instance,  a 
sheet  of  platinised  glass,  which  offered  a  resistance  of  700  ohms, 
became  highly  conducting  after  150  sulphate  of  mercury  cells 
had  been  applied  to  it  for  10  seconds.  This  condition  of  con- 
ductivity was  annulled  by  contact  with  a  charged  Leyden  jar, 
and  reappeared  after  again  applying  150  cells  for  10  seconds, 
and  so  on.  Similar  effects  were  obtained  with  a  thin  layer  of  a 
mixture  of  selenium  and  tellurium  poured,  when  fused,  into  a 
groove  in  a  sheet  of  mica  placed  between  two  copper  plates. 
These  alternations  were  always  observed  several  times  in  suc- 
cession, and  at  intervals  of  several  days. 

These  augmentations  and  alternations  are  in  no  way  incom- 
patible with  the  hypothesis  of  a  physical  modification  of  the 
insulator  by  electrical  influence. 


RESEARCHES   OF  mOF.   D.    E.   HUGHES.  305 


APPENDIX  D. 

RESEARCHES  OF  PROF.  D.  E.  HUGHES,  F.K.S.,  IN  ELECTRIC 

WAVES  AND  THEIR  APPLICATION  TO  WlRELESS  TELEGRAPHY, 

1879-1886. 

It  may  be  desirable  to  place  briefly  on  record  the  circum- 
stances under  which  the  following  remarkable  communication 
was  written. 

While  revising  the  last  sheets  of  this  work,  it  occurred  to  the 
author  to  ask  Sir  William  Crook  es  for  some  particulars  of  the 
experiments  to  which  he  alluded  in  his  'Fortnightly'  article, 
some  passages  from  which  are  quoted  on  pp.  201-203.  On  April 
22,  1899,  Sir  William  replied  as  follows  :— 

DEAR  MR  FAHIE, — The  experiments  referred  to  at  page 
176  of  my  'Fortnightly'  article  as  having  taken  place  "some 
years  ago"  were  tried  by  Prof.  Hughes  when  experimenting 
with  the  microphone. 

I  have  not  ceased  since  then  urging  on  him  to  publish  an 
account  of  his  experiments.  I  do  not  feel  justified  in  saying 
more  about  them,  but  if  you  were  to  write  to  him,  telling  him 
what  I  say,  it  might  induce  him  to  publish. 

It  is  a  pity  that  a  man  who  was  so  far  ahead  of  all  other 
workers  in  the  field  of  wireless  telegraphy  should  lose  all  the 
credit  due  to  his  great  ingenuity  and  prevision. — Believe  rue, 
very  truly  yours,  WILLIAM  CROOKES. 

On  receipt  of  this  letter  I  wrote  to  Prof.  Hughes.  In  reply 
he  said  : — 

"Your  letter  of  26th  instant  has  brought  upon  me  a  flood 
of  old  souvenirs  in  relation  to  my  past  experiments  on  aerial 
telegraphy.  They  were  completely  unknown  to  the  general 
public,  and  I  feared  that  the  few  distinguished  men  who  saw 
them  had  forgotten  them,  or  at  least  had  forgotten  how  the 
results  shown  them  were  produced.  .  .  . 

"  At  this  late  date  I  do  not  wish  to  set  up  any  claim  to 
U 


506  APPENDIX  D. 

priority,  as  I  have  never  published  a  word  on  the  subject;  and 
it  would  be  unfair  to  later  workers  in  the  same  field  to  spring 
an  unforeseen  claimant  to  the  experiments  which  they  have 
certainly  made  without  any  knowledge  of  my  work." 

On  second  (and  my  readers  will  say,  wiser)  thoughts,  Prof. 
Hughes  sent  me  the  following  letter,  in  the  eliciting  of  which 
I  consider  myself  especially  fortunate  and  privileged  : — 

40  LAXGHAM  STREET,  W.,  April  29,  1899. 

DEAR  SIR, — In  reply  to  yours  of  the  26th  inst.,  in  which 
you  say  that  Sir  "William  Crookes  has  told  you  that  he  saw 
some  experiments  of  mine  on  aerial  telegraphy  in  about  De- 
cember 1879,  of  which  he  thinks  I  ought  to  have  published  an 
account,  and  of  which  you  ask  for  some  information,  I  beg  to 
reply  with  a  few  leading  experiments  that  I  made  on  this 
subject  from  1879  up  to  188G  :— 

In  1879,  being  engaged  upon  experiments  with  my  micro- 
phone, together  with  my  induction  balance,  I  remarked  that  at 
some  times  I  could  not  get  a  perfect  balance  in  the  induction 
balance,  through  apparent  want  of  insulation  in  the  coils  ;  but 
investigation  showed  me  that  the  real  cause  was  some  loose 
contact  or  microphonic  joint  excited  in  some  portion  of  the 
circuit.  I  then  applied  the  microphone,  and  found  that  it  gave 
a  current  or  sound  in  the  telephone  receiver,  no  matter  if  the 
microphone  was  placed  direct  in  the  circuit  or  placed  inde- 
pendently at  several  feet  distance  from  the  coils,  through  which 
an  intermittent  current  was  passing.  After  numerous  experi- 
ments, I  found  that  the  effect  was  entirely  caused  by  the 
extra  current,  produced  in  the  primary  coil  of  the  induction 
balance. 

Further  researches  proved  that  an  interrupted  current  in 
any  coil  gave  out  at  each  interruption  such  intense  extra  cur- 
rents that  the  whole  atmosphere  in  the  room  (or  in  several 
rooms  distant)  would  have  a  momentary  invisible  charge, 
which  became  evident  if  a  microphonic  joint  was  used  as  a  re- 
ceiver with  a  telephone.  This  led  me  to  experiment  upon  the 
best  form  of  a  receiver  for  these  invisible  electric  waves,  which 
evidently  permeated  great  distances,  and  through  all  apparent 
obstacles,  such  as  walls,  &c.  I  found  that  all  microphonic  con- 
tacts or  joints  were  extremely  sensitive.  Those  formed  of  a 
hard  carbon  such  as  coke,  or  a  combination  of  a  piece  of  coke 


RESEARCHES   OF  PROF.   D.  E.   1IUGUES.  307 

resting  upon  a  bright  steel  contact,  were  very  sensitive  and 
self-restoring  ;  whilst  a  loose  contact  between  metals  was 
equally  sensitive,  but  would  cohere,  or  remain  in  full  contact, 
after  the  passage  of  an  electric  wave. 

The  sensitiveness  of  these  microphonic  contacts  in  metals 
has  since  been  rediscovered  by  Mons.  Ed.  Branly  of  Paris, 
and  by  Prof.  Oliver  Lodge,  in  England,  by  whom  the  name  of 
"  coherer  "  has  been  given  to  this  organ  of  reception  ;  but,  as 
we  wish  this  organ  to  make  a  momentary  contact  and  not 
cohere  permanently,  the  name  seems  to  me  ill-suited  for  the 
instrument.  The  most  sensitive  and  perfect  receiver  that  I 
have  yet  made  does  not  cohere  permanently,  but  recovers  its 
original  state  instantly,  and  therefore  requires  no  tapping  or 
mechanical  aid  to  the  separation  of  the  contacts  after  moment- 
arily being  brought  into  close  union. 

I  soon  found  that,  whilst  an  invisible  spark  would  pro- 
duce a  thermo-electric  current  in  the  microphonic  contacts 
(sufficient  to  be  heard  in  the  telephone  in  its  circuit),  it 
was  far  better  and  more  powerful  to  use  a  feeble  voltaic  cell 
in  the  receiving  circuit,  the  microphonic  joint  then  acting 
as  a  relay  by  diminishing  the  resistance  at  the  contact, 
under  the  influence  of  the  electric  wave  received  through 
the  atmosphere. 

I  will  not  describe  the  numerous  forms  of  the  transmitter 
and  receiver  that  I  made  in  1879,  all  of  which  I  wrote  down  in 
several  volumes  of  manuscripts  in  1879  (but  these  have  never 
been  published),  and  most  of  which  can  be  seen  here  at  my 
residence  at  any  time  ;  but  I  will  confine  myself  now  to  a  few 
salient  points.  I  found  that  very  sudden  electric  impulses, 
whether  given  out  to  the  atmosphere  through  the  extra  current 
from  a  coil  or  from  a  frictional  electric  machine,  equally  affected 
the  microphonic  joint,  the  effect  depending  more  on  the  sudden 
high  potential  effect  than  on  any  prolonged  action.  Thus,  a 
spark  obtained  by  rubbing  a  piece  of  sealing-wax  was  equally 
effective  as  a  discharge  from  a  Leyden  jar  of  the  same  poten- 
tial.1 The  rubbed  sealing-wax  and  charged  Leyden  jar  had  no 
effect  until  they  were  discharged  by  a  spark,  and  it  was  evi- 
dent that  this  spark,  however  feeble,  acted  upon  the  whole 
surrounding  atmosphere  in  the  form  of  waves  or  invisible  rays, 

1  Prof.  Lodge  subsequently  and  independently  observed  this  fact,  and 
illustrates  it  beautifully  iu  his  '  Work  of  Hertz,'  pp.  27,  28,— J,  J.  F. 


SOS  APPENDIX  D. 

the  laws  of  which  I  could  not  at  the  time  determine.  Hertz, 
however,  by  a  series  of  original  and  masterly  experiments, 
proved  in  1887-89  that  they  were  real  waves  similar  to  light, 
but  of  a  lower  frequency,  though  of  the  same  velocity.  In 
1879,  whilst  making  these  experiments  on  aerial  transmission, 
I  had  two  different  problems  to  solve  :  1st,  What  was  the  true 
nature  of  these  electrical  aerial  waves,  which  seemed,  whilst 
not  visible,  to  spurn  all  idea  of  insulation,  and  to  penetrate  all 
space  to  a  distance  undetermined.  2nd,  To  discover  the  best 
receiver  that  could  act  upon  a  telephone  or  telegraph  instru- 
ment, so  as  to  be  able  to  utilise  (when  required)  these  waves 
for  the  transmission  of  messages.  The  second  problem  came 
easy  to  me  when  I  found  that  the  microphone,  which  I  had 
previously  discovered  in  1877-78,  had  alone  the  power  of 
rendering  these  invisible  waves  evident,  either  in  a  telephone 
or  a  galvanometer,  and  up  to  the  present  time  I  do  not  know 
of  anything  approaching  the  sensitiveness  of  a  microphonic 
joint  as  a  receiver.  Branly's  tube,  now  used  by  Marconi,  was 
described  in  my  first  paper  to  the  Royal  Society  (May  8,  1878) 
as  the  microphone  tube,  filled  with  loose  filings  of  zinc  and 
silver ;  and  Prof.  Lodge's  coherer  is  an  ordinary  steel  micro- 
phone, used  for  a  different  purpose  from  that  in  which  I  first 
described  it.1 

During  the  long  -  continued  experiments  on  this  subject, 
between  1879  and  1880,  many  curious  phenomena  came  out 
which  would  be  too  long  to  describe.  I  found  that  the  effect 

1  Prof.  Hughes  is  rightly  regarded  as  the  real  discoverer  of  the  elec- 
trical behaviour  of  a  bad  joint  or  loose  contact,  the  study  of  which  in  his 
hands  has  given  us  the  microphone  ;  but  as  in  the  case  of  Hertzian-wave 
effects  before  Hertz,  so,  long  before  Hughes,  "  mere  phenomena  of  loose 
contact,"  as  Sir  George  Stokes  called  them,  must  have  often  manifested 
themselves  in  the  working  of  electrical  apparatus.  For  an  interesting 
example  see  Arthur  Schuster's  paper  read  before  the  British  Association 
in  1874  (or  abstract,  'Telegraphic  Journal,'  vol.  ii.  p.  .289),  where  the 
effects  are  described  as  a  new  discovery  in  electricity,  and  disguised 
under  the  title  of  the  paper,  "On  Unilateral  Conductivity."  Schuster 
suspected  the  cause — "Two  wires  screwed  together  may  not  touch  each 
other,  but  be  separated  by  a  thin  layer  of  air  " — but  he  missed  its  real 
significance.  The  phenomenon  was  a  kind  of  bye-product,  cropped  up 
while  he  was  engaged  on  other  work,  and  so  was  not  pursued  far  enough. 
— J.  J.  F. 


RESEARCHES   OF  TROF.   D.   E.   HUGHES.  309 

of  the  extra  current  in  a  coil  was  not  increased  by  having  an 
iron  core  as  an  electro-magnet  —  the  extra  current  was  less 
rapid,  and  therefore  less  effective.  A  similar  effect  of  a 
delay  was  produced  by  Leyden-jar  discharges.  The  material 
of  the  contact-breaker  of  the  primary  current  had  also  a  great 
effect.  Thus,  if  the  current  was  broken  between  two  or  one 
piece  of  carbon,  no  effect  could  be  perceived  of  aerial  waves, 
even  at  short  distances  of  a  few  feet.  The  extra  current  from 
a  small  coil  without  iron  was  as  powerful  as  an  intense  spark 
from  a  secondary  coil,  and  at  that  time  my  experiments 
seemed  to  be  confined  to  the  use  of  a  single  coil  of  my  in- 
duction balance,  charged  by  six  Daniell  cells.  With  higher 
battery  power  the  extra  current  invariably  destroyed  the  in- 
sulation of  the  coils. 

In  December  1879  I  invited  several  persons  to  see  the  re- 
sults then  obtained.  Amongst  others  who  called  on  me  and 
saw  my  results  were — 

Dec.  1879.— Mr  W.  H.  Preece,  F.RS. ;  Sir  William  Oookes, 
F.RS.  ;  Sir  W.  Koberts  -  Austen,  F.RS.;  Prof.  W.  Grylls 
Adams,  F.RS.  ;  Mr  W.  Grove. 

Feb.  20,  1880.— Mr  Spottiswoode,  Pres.  RS. ;  Prof.  Huxley, 
F.RS.  ;  Sir  George  Gabriel  Stokes,  F.RS. 

Nov.  7,  1888.— Prof.  Dewar,  F.RS. ;  Mr  Lennox,  Eoyal 
Institution. 

They  all  saw  experiments  upon  aerial  transmission,  as  al- 
ready described,  by  means  of  the  extra  current  produced  from 
a  small  coil  and  received  upon  a  semi-metallic  microphone, 
the  results  being  heard  upon  a  telephone  in  connection  with 
the  receiving  microphone.  The  transmitter  and  receiver  were 
in  different  rooms,  about  GO  feet  apart.  After  trying  success- 
fully all  distances  allowed  in  my  residence  in  Portland  Street, 
my  usual  method  was  to  put  the  transmitter  in  operation  and 
walk  up  and  down  Great  Portland  Street  with  the  receiver  in 
my  hand,  with  the  telephone  to  the  ear. 

The  sounds  seemed  to  slightly  increase  for  a  distance  of  60 
yards,  then  gradually  diminish,  until  at  500  yards  I  could 
no  longer  with  certainty  hear  the  transmitted  signals.  What 
struck  me  as  remarkable  was  that,  opposite  certain  houses,  I 
could  hear  better,  whilst  at  others  the  signals  could  hardly  be 
perceived.  Hertz's  discovery  of  nodal  points  in  reflected  waves 


310  AJTEXDIX  D. 

(in  1887-89)  has  explained  to  me  what  was  then  considered  a 
mystery. 

At  Mr  A.  Stroll's  telegraph  instrument  manufactory  Mr 
Stroll  and  myself  could  hear  perfectly  the  currents  trans- 
mitted from  the  third  storey  to  the  basement,  but  I  could  not 
detect  clear  signals  at  my  residence  about  a  mile  distant.  The 
innumerable  gas  and  water  pipes  intervening  seemed  to  absorb 
or  weaken  too  much  the  feeble  transmitted  extra  currents  from 
a  small  coil. 

The  President  of  the  Royal  Society,  Mr  Spottiswoode,  to- 
gether with  the  two  lion,  secretaries,  Prof.  Huxley  and  Prof. 
G.  Stokes,  called  upon  me  on  February  20,  1880,  to  see  my 
experiments  upon  aerial  transmission  of  signals.  The  experi- 
ments shown  were  most  successful,  and  at  first  they  seemed 
astonished  at  the  results  ;  but  towards  the  close  of  three  hours' 
experiments  Prof.  Stokes  said  that  all  the  results  could  be 
explained  by  known  electro  -  magnetic  induction  effects,  and 
therefore  he  could  not  accept  my  view  of  actual  aerial  electric 
waves  unknown  up  to  that  time,  but  thought  I  had  quite 
enough  original  matter  to  form  a  paper  on  the  subject  to  be 
read  at  the  Eoyal  Society. 

I  was  so  discouraged  at  being  unable  to  convince  them  of  the 
truth  of  these  aerial  electric  waves  that  I  actually  refused  to 
write  a  paper  on  the  subject  until  I  was  better  prepared  to 
demonstrate  the  existence  of  these  waves  ;  and  I  continued  my 
experiments  for  some  years,  in  hopes  of  arriving  at  a  perfect 
scientific  demonstration  of  the  existence  of  aerial  electric  waves 
produced  by  a  spark  from  the  extra  currents  in  coils,  or  from 
frictional  electricity,  or  from  secondary  coils.  The  triumphant 
demonstration  of  these  waves  was  reserved  to  Prof.  Hertz,  who 
by  his  masterly  researches  upon  the  subject  in  1887-89  com- 
pletely demonstrated  not  only  their  existence  but  their  identity 
with  ordinary  light,  in  having  the  power  of  being  reflected  and 
refracted,  &c.,  with  nodal  points,  by  means  of  which  the  length 
of  the  waves  could  be  measured.  Hertz's  experiments  were 
far  more  conclusive  than  mine,  although  he  used  a  much  less 
effective  receiver  than  the  microphone  or  coherer. 

I  then  felt  it  was  now  too  late  to  bring  forward  my  previous 
experiments  ;  and  through  not  publishing  my  results  and  means 
employed,  I  have  been  forced  to  see  others  remake  the  dis- 


HESEARCHES   OF   PHOF.   D.   E.   HUGHES.  311 

coveries  I  had  previously  made  as  to  the  sensitiveness  of  the 
niicrophonic  contact  and  its  useful  employment  as  a  receiver 
for  electric  aerial  waves. 

Amongst  the  earliest  workers  in  the  field  of  aerial  trans- 
mission I  would  draw  attention  to  the  experiments  of  Prof. 
Henry,  who  describes  in  his  work,  published  by  the  Smithsonian 
Institute,  Washington,  D.C.,  U.S.A.,  vol.  i.  p.  203  (date  un- 
known, probably  about  1850),  how  he  magnetised  a  needle  in 
a  coil  at  30  feet  distance,  and  magnetised  a  needle  by  a  dis« 
charge  of  lightning  at  eight  miles'  distance.1 

Marconi  has  lately  demonstrated  that  by  the  use  of  the 
Hertzian  waves  and  Branly's  coherer  he  has  been  enabled  to 
transmit  and  receive  aerial  electric  waves  to  a  greater  distance 
than  previously  ever  dreamed  of  by  the  numerous  discoverers 
and  inventors  who  have  worked  silently  in  this  field.  His  efforts 
at  demonstration  merit  the  success  he  has  received  ;  and  if  (as 
I  have  lately  read)  he  has  discovered  the  means  of  concentrating 
these  waves  on  a  single  desired  point  without  diminishing  their 
power,  then  the  world  will  be  right  in  placing  his  name  on  the 
highest  pinnacle  in  relation  to  aerial  electric  telegraphy. — 
Sincerely  yours,  D.  E.  HUGHES. 

J.  J.  FA  HIE,  Esq., 
Claremont  Hill,  St  Helier's,  Jersey. 

On  the  publication  of  this  letter  in  the  c  Electrician '  (May 
5,  1899),  Mr  John  Munro  called  on  Prof.  Hughes,  and  was 
accorded  the  privilege  of  inspecting  his  apparatus,  mostly  self- 
made  and  of  the  simplest  materials,  and  his  note-books,  filled 
with  experiments  in  ink  or  pencil,  dated  or  dateless,  and  some 
marked  "  extraordinary,"  "  important,"  and  so  on.  An  interest- 

1  The  'Polytechnic  Review,'  March  25,  1843,  says  :  "  Professor  Henry 
communicated  to  the  American  Society  that  he  had  succeeded  in  mag- 
netising needles  by  the  secondary  current  in  a  wire  more  than  220  feet 
distant  from  the  wire  through  which  the  primary  current,  excited  by  a 
single  spark  from  an  electrical  machine,  was  passing."  Indeed  Prof. 
Henry  noted  many  cases  of  what  we  now  call  Hertzian-wave  effects,  but 
what  he  and  every  one  else  in  those  days  thought  were  only  extraordinary 
cases  of  induction.  Many  experimenters  after  Henry  must  have  observed 
similar  effects.  See  for  example  'Telegraphic  Journal,'  February  15, 
1S76,  p.  61,  on  "The  '  Etheric'  Force"  ;  and  the  '  Electrician,'  vol.  xliii. 
p.  204.— J.  J.  F. 


312  APPENDIX   D. 

ing  account  of  this  interview  was  afterwards  published  by  Mr 
Munro,1  from  which  I  make  a  few  extracts,  as  they  help  to 
illustrate  and  supplement  the  Professor's  own  account. 

After  satisfying  himself  as  to  the  cause  of  the  trouble  in 
his  induction  -  balance  experiments  as  stated  above  (p.  296), 
Prof.  Hughes  joined  a  single  cell  B  (fig.  1)  in  circuit  with  a 
clockwork  interrupter  i,  and  the  primary  coil  c  of  the  induction 
balance.  This  "transmitter"  was  connected  by  a  wire  w, 
several  feet  in  length,  to  the  "receiver,"  which  consisted  of  a 
telephone  T  in  circuit  with  a  microphone  M.  With  such  an 
arrangement  the  "  extra  spark  "  of  the  transmitter  was  always 
heard  in  the  telephone.  These  sounds  were  found  to  vary  with 
the  conditions  of  the  experiment :  thus,  with  an  electromotive 
force  of  ^  volt  the  sound  was  stronger  than  with  several  cells  ; 
it  was  also  louder  and  clearer  when  the  contact  points  of  the 


Fig.  1, 

interrupter  were  of  metal — not  metal  to  carbon,  or  carbon  to 
carbon.  Again,  an  iron  core  in  the  coil  c,  though  productive 
of  a  stronger  spark,  rather  diminished  than  increased  the  cor- 
responding sound  in  the  telephone.  Indeed,  the  spark  from 
the  Faraday  electro-magnet  of  the  Eoyal  Institution,  excited 
by  a  large  Grove  battery,  had  little  effect,  and  even  a  dynamo 
at  work  beside  the  receiver  gave  a  very  poor  result. 

Prof.  Hughes  tried  many  experiments  to  satisfy  himself  that 
his  receiver  (his  microphone  and  telephone)  was  influenced  by 
the  extra  spark  solely,  and  not  by  the  ordinary  electro-magnetic 
induction.  He  inserted  coils  in  the  transmitting  and  receiving 
circuits,  placing  them  parallel,  and  at  right  angles  to  each  other 
— that  is,  in  positions  favourable  and  unfavourable  to  such 
induction — but  without  modifying  the  effect.  He  also  reduced 
the  number  of  turns  of  wire  on  the  coil  c,  and  even  removed 
1  'Electrical  Review,'  June  2,  1899. 


UESEAttCIIES  BY  PROF.   D.    E.    HUGHES. 


313 


it  altogether,  connecting  the  battery  and  interrupter  by  only 
three  inches  of  wire,  and  still  heard  the  sounds  as  distinctly  as 
before.  That  electro-static  induction  had  no  part  in  the  phe- 
nomenon was  shown  by  inserting  charged  conductors  of  large 
surface  (for  example  metal  discs)  in  the  two  circuits  and  shift- 
ing their  positions  with  respect  to  each  other  without  producing 
any  effect  on  the  receiver. 

Having  concluded  from  these  and  numerous  other  observa- 
tions that  the  results  were  conductive  in  principle  rather  than 
inductive,  and  were  due  to  electrical  impulses  or  waves  set  in 
motion  by  the  sparks  at  the  interrupter  and  filling  all  the  sur- 
rounding space,  Prof.  Hughes  set  himself  to  find  the  most  sen- 


sitive  form  of  microphone  to  receive  the  waves.  Contacts  of 
metal  were  found  to  be  apt  to  stick  together,  or  "cohere,"  as 
we  now  say.  A  microphone  which  is  both  sensitive  and  self- 
restoring  or  non-cohering  is  made  with  a  carbon  contact  resting 
lightly  on  bright  steel,  as  shown  in  fig.  2,  where  c  is  a  carbon 
pencil  touching  a  needle  N,  and  s  an  adjustable  spring  of  brass 
by  which  the  pressure  of  the  contact  can  be  regulated  by 
means  of  the  disc  D.  An  extremely  sensitive  but  easily  de- 
ranged form  of  microphone  is  shown  in  fig.  3,  where  s  is  a 
steel  hook,  and  c  a  fine  copper  wire  with  a  loop  on  the  end 
which  has  been  oxidised  and  smoked  in  the  flame  of  a  spirit- 
lamp.  The  carbonised  loop  and  steel  hook  are  placed  in  a  small 
bottle  B  for  safety. 


314 


APPENDIX  D. 


Another  form  of  microphone  which  the  Professor  tried  was 
a  tube  containing  metal  filings,  which  forestalls  the  Branly 
tube,  but  as  the  coherence  of  the  filings  was  a  disadvantage  he 
abandoned  it.  Contacts  of  iron  and  mercury  were  sensitive, 
but  very  troublesome  ;  while  contacts  of  iron  and  steel  cohered, 
but  were  sensitive,  and  kept  well  when  immersed  in  a  mixture 
of  petroleum  and  vaseline,  which,  though  an  insulator,  does  not 
bar  the  electric  waves. 

Some  of  these  microphone  arrangements  were  found  to  be 
very  sensitive  to  small  charges  of  electricity — far  more  so  than 
the  gold-leaf  electroscope  and  the  quadrant  electrometer.  Even 
a  metal  filing  on  a  stick  of  sealing-wax  carried  enough  elec- 
tricity from  a  Leyden  jar  to  affect  the  microphone  and  give  a 


GFEET  GAP 


Fig.  4. 


Second  room. 


sound  in  the  telephone,  while  it  had  no  effect  on  the  electro- 
scope or  the  electrometer. 

With  such  delicate  receivers  Prof.  Hughes  discarded  the 
connecting  wire  w  in  fig.  1,  thus  separating  the  receiver  from 
the  transmitter,  and  producing  the  germ  of  a  wireless  tele- 
graph. His  first  experiment  of  this  kind  was  made  between 
October  15  and  24,  1879,  the  transmitter  being  in  one  room 
and  the  receiver  in  an  adjoining  room,  but  a  wire  from  the 
receiver  limited  the  air  gap  to  about  6  feet.  Fig.  4,  which  is 
roughly  copied  from  the  Professor's  own  diagram,  shows  the 
arrangement,  where  w  is  the  wire,  B  the  battery,  I  the  inter- 
rupter, c  the  coil,  T  the  telephone,  M  the  microphone,  and  E,  E' 
the  earth  (gas-pipes).  In  another  experiment,  made  about  the 


RESEARCHES   BY'PEOF.    D.    E.   HUGHES. 


315 


M 


Fis 


middle  of  November  187.9,  he  connected  a  fender  to  the  inter- 
rupter "to  act  as  a  radiator,"  and  afterwards,  instead  of  the 
fender,  he  used  wires  (answering  to  the  "wings"  of  Hertz)  on 
both  transmitting  and  receiving  apparatus,  the  wires  being 
stiffened  with  laths  to  hold  them  in  place. 

The  use  of  an  "  earth  "  connection  led  him  to  try  the  effect 
of  joining  the  telephone  to  a  gas-pipe  of  lead,  and  the  micro- 
phone to  a  water-pipe  of  iron,  as  shown  in  fig.  5.  The  result 
was  an  improved  sound  in  the  telephone,  and  he  concluded 
that  the  different  metals  formed 
a  weak  "earth  battery,"  from 
•which  a  permanent  current  ran 
through  the  circuit.  On  this 
supposition  he  reasoned  that  the 
" electric  waves  influencing  the 
microphone,  and  perhaps  chang- 
ing its  resistance,  would  rapidly 
alter  the  strength  of  this  current, 
and  so  account  for  the  heightened 
effects  in  the  telephone.  Acting  on 
this  idea,  he  included  an  E.M.F. 

in  the  receiving  circuit.  A  single  cell  was  more  than  enough, 
and  had  to  be  reduced  to  as  little  as  r^th  of  a  volt  in  order 
not  to  permanently  break  down  the  contact  resistance  of  the 
microphone. 

"Thus,"  says  Mr  Munro,  "  Prof.  Hughes  had  step  by  step  put 
together  all  the  principal  elements  of  the  wireless  telegraph 
as  we  know  it  to-day,  and  although  he  was  groping  in  the 
dark  before  the  light  of  Hertz  arose,  it  is  little  short  of 
magical  that  in  a  few  months,  even  weeks,  and  by  using  the 
simplest  means,  he  thus  forestalled  the  great  Marconi  advance 
by  nearly  twenty  years  !  " 

In  the  fifty  years  (just  completed)  of  a  brilliant  professorial 
career  at  Cambridge,  Sir  George  Stokes  has  given,  times  out  of 
number,  sound  advice  and  helpful  suggestions  to  those  who 
have  sought  him  ;  but  in  this  case,  as  events  show,  the  great 
weight  of  his  opinion  has  kept  back  the  clock  for  many  years. 
With  proper  encouragement  in  1879-80  Prof.  Hughes  would 
have  followed  up  his  clues,  and,  with  his  extraordinary  keenness 
in  research,  there  can  be  no  doubt  that  he  would  have  antici- 


316  ArPENDIX  E. 

pated  Hertz  in  tlie  complete  discovery  of  electric  waves,  and 
Marconi  in  the  application  of  them  to  wireless  telegraphy,  and 
so  have  altered  considerably  the  course  of  scientific  history. 

As  a  recent  commentator  pithily  says  :  "  Hughes's  experi- 
ments of  1879  were  virtually  a  discovery  of  Hertzian  waves 
before  Hertz,  of  the  coherer  before  Branl}r;  and  of  wireless 
telegraphy  before  Marconi  and  others."  The  writer  goes  on  to 
say,  "  Prof.  Hughes  has  a  great  reputation  already,  but  these 
latter  experiments  will  add  enormously  to  it,  and  place  him 
among  the  foremost  electricians  of  all  time  "  1 — praise  which, 
knowing  the  learned  professor  as  I  do,  I  consider  none  too 
great. 


APPENDIX   E. 

REPRINT  OF  SIGNOR  G.  MARCONI'S  PATENT. 

No.  12,039,  A.D.  1590. 

Date  of  Application,  2nd  June  1806.     Complete  Specification 
'Left,  2nd  Mar.  1897;  Accepted,  2nd  July  1897. 

PROVISIONAL  SPECIFICATION. 

IMPROVEMENTS   IN   TRANSMITTING   ELECTRICAL   IMPULSES  AND 
SIGNALS,    AND    IN   APPARATUS   THEREFOR. 

I,  Guglielmo  Marconi,  of  71  Hereford  Eoad,  Bayswater,  in 
the  county  of  Middlesex,  do  hereby  declare  the  nature  of  this 
invention  to  be  as  follows  : — 

According  to  this  invention  electrical  actions  or  manifesta- 
tions are  transmitted  through  the  air,  earth,  or  water  by  means 
of  electric  oscillations  of  high  frequency. 

At  the  transmitting  station  I  employ  a  Ruhmkorff  coil 
having  in  its  primary  circuit  a  Morse  key,  or  other  appliance 

i  The  'Globe,'  May  12,  1899.  Prof.  Hughes  died,  full  of  honours,  on 
January  22,  1900,  aged  sixty-nine.  See,  amongst  other  obituary  notices, 
the  'Times/  January  21,  and  the  '  Electrician,'  January  26. 


REPRINT   OF  SIGNOR  G.    MARCONI'S  PATENT.       317 

for  starting  or  interrupting  the  current,  and  its  pole  appliances 
(such  as  insulated  balls  separated  by  small  air  spaces  or  high 
vacuum  spaces,  or  compressed  air  or  gas,  or  insulating  liquids 
kept  in  place  by  a  suitable  insulating  material,  or  tubes  separ- 
ated by  similar  spaces  and  carrying  sliding  discs)  for  producing 
the  desired  oscillations. 

I  find  that  a  lluhmkorff  coil,  or  other  similar  apparatus, 
works  much  better  if  one  of  its  vibrating  contacts  or  brakes  011 
its  primary  circuit  is  caused  to  revolve,  which  causes  the 
secondary  discharge  to  be  more  powerful  and  more  regular, 
and  keeps  the  platinum  contacts  of  the  vibrator  cleaner  and 
preserves  them  in  good  working  order  for  an  incomparably 
longer  time  than  if  they  were  not  revolved,  I  cause  them  to 
revolve  by  means  of  a  small  electric  motor  actuated  by  the 
current  which  works  the  coil,  or  by  another  current,  or  in  some 
cases  I  employ  a  mechanical  (non-electrical)  motor. 

The  coil  may,  however,  be  replaced  by  any  other  source  of 
high  tension  electricity. 

At  the  receiving  instrument  there  is  a  local  battery  circuit 
containing  an  ordinary  receiving  telegraphic  or  signalling  in- 
strument, or  other  apparatus  which  may  be  necessary  to  work 
from  a  distance,  and  an  appliance  for  closing  the  circuit,  the 
latter  being  actuated  by  the  oscillations  from  the  transmitting 
instrument. 

The  appliance  I  employ  consists  of  a  tube  containing  con- 
ductive powder,  or  grains,  or  conductors  in  imperfect  contact, 
each  end  of  the  column  of  powder  or  the  terminals  of  the 
imperfect  contact  or  conductor  being  connected  to  a  metallic 
plate,  preferably  of  suitable  length  so  as  to  cause  the  system 
to  resonate  electrically  in  unison  with  the  electrical  oscillations 
transmitted  to  it.  In  some  cases  I  give  these  plates  or  con- 
ductors the  shape  of  an  ordinary  Hertz  resonator  consisting  of 
two  semicircular  conductors,  but  with  the  difference  that  at 
the  spark-gap  I  place  one  of  my  sensitive  tubes,  whilst  the 
other  ends  of  the  conductors  are  connected  to  small  con- 
densers. 

I  have  found  that  the  best  rules  for  making  the  sensitive 
tubes  are  as  follows  : — 

1st.  The  column  of  powder  ought  not  to  be  long,  the  effects 
being  better  in  sensitiveness  and  regularity  with  tubes  contain- 


318  APPENDIX  E. 

ing  columns  of  powder  or  grains  not  exceeding  two-thirds  of 
an  inch  in  length. 

2nd.  The  tube  containing  the  powder  ought  to  be  sealed. 

3rd.  Each  wire  which  passes  through  the  tube,  in  order  to 
establish  electrical  communication,  ought  to  terminate  with 
pieces  of  metal  or  small  knobs  of  a  comparatively  large  surface, 
or  preferably  with  pieces  of  thicker  wire,  of  a  diameter  equal 
to  the  internal  diameter  of  the  tube,  so  as  to  oblige  the  powder 
or  grains  to  be  corked  in  between. 

4th.  If  it  is  necessary  to  employ  a  local  battery  of  higher 
E.M.F.  than  that  with  which  an  ordinarily  prepared  tube  will 
work,  the  column  of  powder  must  be  longer  and  divided  into 
several  sections  by  metallic  divisions,  the  amount  of  powder  or 
grains  in  each  section  being  practically  in  the  same  condition 
as  in  a  tube  containing  a  single  section.  When  no  oscillations 
are  sent  from  the  transmitting  instrument  the  powder  or  im- 
perfect contact  does  not  conduct  the  current,  and  the  local 
battery  circuit  is  broken  ;  but  when  the  powder  or  imperfect 
contact  is  influenced  by  the  electrical  oscillations,  it  conducts 
and  closes  the  circuit. 

I  find,  however,  that  once  started,  the  powder  or  contact 
continues  to  conduct  even  when  the  oscillations  at  the  trans- 
mitting station  have  ceased  ;  but  if  it  be  shaken  or  tapped, 
the  circuit  is  broken. 

I  do  this  tapping  automatically,  employing  the  current 
which  the  sensitive  tube  or  contact  had  allowed  to  begin  to 
flow  under  the  influence  of  the  electric  oscillations  from  the 
transmitting  instrument  to  work  a  trembler  (similar  to  that  of 
an  electric  bell),  which  hits  the  tube  or  imperfect  contact,  and 
so  stops  the  current  and,  consequently,  its  own  movement,  which 
had  been  generated  by  the  said  current,  which  by  this  means 
automatically  and  almost  instantaneously  interrupts  itself  until 
another  oscillation  from  the  transmitting  instrument  repeats 
the  process.  Whilst  for  certain  purposes  I  prefer  working  the 
trembler  and  the  instruments  on  the  same  circuit  which  con- 
tains the  sensitive  tube  or  contact,  for  other  purposes  I  prefer 
working  the  trembler  and  the  instruments  on  another  circuit, 
which  is  made  to  work  in  accordance  with  the  first  by  means 
of  a  relay.  It  is  by  means  of  actions  from  the  current,  which 
the  sensitive  tube  or  contact  allows  to  pass  when  the  oscilla- 


REPRINT   OF   SIGNOE  G.   MARCONI'S   PATENT.       319 

tions  influence  it,  that  I  prefer  starting  the  apparatus  that  has 
to  interrupt  automatically  the  same  current. 

In  order  to  prevent  the  action  of  the  self-induction  of  the 
local  circuits  on  the  sensitive  tube  or  contact,  and  also  to  de- 
stroy the  perturbating  effect  of  the  small  spark  which  occurs  at 
the  breaking  of  the  circuit  inside  the  tube  or  imperfect  contact, 
and  also  at  the  vibrating  contact  of  the  trembler  or  at  the 
movable  contact  of  the  relay,  I  put  in  derivation  across  thos*» 
parts  where  the  circuit  is  periodically  broken  a  condenser  of 
suitable  capacity,  or  a  coil  of  suitable  resistance  and  self-in- 
duction, so  that  its  self-induction  may  neutralise  the  self- 
induction  of  the  said  circuits  ;  or  preferably  I  employ  in 
derivation  on  different  parts  of  the  circuit  conductors  or 
so-called  semi-conductors  of  high  resistance  and  small  self- 
induction,  such  as  bars  of  charcoal  or  preferably  tubes  contain- 
ing water  or  other  suitable  liquid,  in  electrical  communication 
with  those  conductors  of  the  local  circuits  which  are  liable  in 
course  of  self-induction  to  assume  such  differences  of  potential 
as  to  transmit  jerky  currents  such  as  would  influence  the 
sensitive  tube  or  contact  so  as  to  prevent  its  working  with 
regularity. 

In  some  cases,  however,  I  find  it  suitable  to  employ  an  in- 
dependent trembler  moved  by  the  current  from  another 
battery.  This  trembler  is  prevented  from  generating  jerking 
or  vibrating  currents  by  means  of  the  appliances  which  I  have 
described.  This  trembler  is  kept  going  all  the  time  during 
which  one  expects  oscillations  to  be  transmitted,  and,  as 
already  described,  the  powder  or  imperfect  contact  closes  the 
circuit  of  a  local  battery,  in  which  are  included  the  instruments 
which  one  desires  to  work,  for  the  time  during  which  the  elec- 
trical oscillations  are  transmitted,  breaking  the  circuit  in  case 
of  the  mechanical  vibrations  as  soon  as  the  oscillations  from  the 
transmitting  machine  cease.  When  transmitting  through  the 
air,  and  it  is  desired  that  the  signal  or  electrical  action  should 
only  be  sent  in  one  direction,  or  when  it  is  necessary  to  trans- 
mit electrical  effects  to  the  greatest  possible  distance  without 
wires,  I  place  the  oscillation  producer  at  the  focus  or  focal  line 
of  a  reflector  directed  to  the  receiving  station,  and  I  place  the 
tube  or  imperfect  contact  at  the  receiving  instrument  in  a 
similar  reflector  directed  towards  the  transmitting  instrument. 


320  APPENDIX   E. 

When  transmitting  through  the  eartli  or  water  I  connect  one 
end  of  the  tube  or  contact  to  eartli  and  the  other  end  to  con- 
ductors or  plates,  preferably  similar  to  each  other,  in  the  air 
and  insulated  from  earth. 

I  find  it  also  better  to  connect  the  tube  or  imperfect  contact 
to  the  local  circuit  by  means  of  thin  wires  or  across  two  small 
coils  of  thin  and  insulated  wire  preferably  containing  an  iron 
nucleus. 

Dated  this  second  day  of  June  189G. 

GUGLIELMO  MARCONI. 


COMPLETE   SPECIFICATION. 

IMPROVEMENTS   IN   TRANSMITTING   ELECTRICAL   IMPULSES 
AND   SIGNALS,   AND    IN   APPARATUS   THEREFOR. 

I,  Guglielmo  Marconi,  of  67  Talbot  Road,  "VVestbourne 
Park,  formerly  residing  at  71  Hereford  Eoad,  Bays  water,  in 
the  county  of  Middlesex,  do  hereby  declare  the  nature  of  this 
invention  and  in  what  manner  the  same  is  to  be  performed  to 
be  particularly  described  and  ascertained  in  and  by  the  follow- 
ing statement : — 

My  invention  relates  to  the  transmission  of  signals  by  means 
of  electrical  oscillations  of  high  frequency,  which  are  set  up  in 
space  or  in  conductors. 

In  order  that  my  specification  may  be  understood,  and  be- 
fore going  into  details,  I  will  describe  the  simplest  form  of  my 
invention  by  reference  to  figure  1. 

In  this  diagram  A  is  the  transmitting  instrument  and  B  is 
the  receiving  instrument,  placed  at  say  £  mile  apart. 

In  the  transmitting  instrument  R  is  an  ordinary  induction 
coil  (a  Ruhmkorff  coil  or  transformer). 

Its  primary  circuit  c  is  connected  through  a  key  D  to  a  battery 
E,  and  the  extremities  of  its  secondary  circuit  F  are  connected 
to  two  insulated  spheres  or  conductors  G  H  fixed  at  a  small 
distance  apart. 

When  the  current  from  the  battery  E  is  allowed  to  pass 
through  the  primary  of  the  induction  coil,  sparks  will  take 
place  between  the  spheres  G  ri,  and  the  space  all  around  the 


REPRINT  OF  SIGNOR  G.   MARCONI'S  PATENT.        321 


spheres  suffers  a  perturbation  in  consequence  of  these  electrical 
rays  or  surgings. 

The  arrangement  A  is  commonly  called  a  Hertz  radiator,  and 
the  effects  which  propagate  through  space  Hertzian  rays. 

The  receiving  instrument  B  consists  of  a  battery  circuit  J, 
which  includes  a  battery  or  cell  K,  a  receiving  instrument  L, 
and  a  tube  T  containing  metallic  powder  or  filings,  each  end 


Fig.  1. 


of  the  column  of  filings  being  also  connected  to  plates  or  con- 
ductors M  N  of  suitable  size,  so  as  to  be  preferably  tuned  with 
the  length  of  wave  of  the  radiation  emitted  from  the  trans- 
mitting instruments. 

The  tube  containing  the  filings  may  be  replaced  by  an  imper- 
fect electrical  contact,  such  as  two  unpolished  pieces  of  metal 
in  light  contact,  or  coherer,  &c. 

The  powder  in  the  tube  T  is,  under  ordinary  conditions,  a 
non-conductor  of  electricity,  and  the  current  of  the  cell  K  can- 
not pass  through  the  instrument  ;  but  when  the  receiver  is 
influenced  by  suitable  electrical  waves  or  radiation  the  powder 
in  the  tube  T  becomes  a  conductor  (and  remains  so  until  the 
tube  is  shaken  or  tapped),  and  the  current  passes  through  the 
instrument. 

By  these  means  electrical  waves  which  are  set  up  in  the 
X 


322 


APPENDIX  E. 


transmitting  apparatus  affect  the  receiving  instrument  in  such 
a  manner  that  currents  are  caused  to  circulate  in  the  circuit  J, 
and  may  be  utilised  for  deflecting  a  needle,  which  thus  re- 
sponds to  the  impulse  coming  from  the  transmitter. 

Figures  -2,  3,  4,  &c.,  show  various  more  complete  arrange- 
ments of  the  simple  form  of  apparatus  illustrated  in  figure  1. 

I  will  describe  these  figures  generally  before  proceeding  to 
describe  the  improvements  in  detail. 

Figure  2  is  a  diagrammatic  front  elevation  of  the  instru- 
ments of  the  receiving  station,  in  which  k  k  are  the  plates 
corresponding  to  M  N  in  figure  1.  g  is  the  battery  correspond  - 


Fig.  2. 


ing  to  K,  h  is  the  reading  instrument  corresponding  to  L,  n  is  a 
relay  working  the  reading  instrument  h  in  the  ordinary 
manner,  p  is  a  trembler  or  tapper,  similar  to  that  of  an 
electric  bell,  which  is  moved  by  the  current  that  works  the 
instrument. 

Figure  3  is  a  diagrammatic  front  elevation  of  the  instru- 
ments at  the  transmitting  station,  in  which  e  e  are  two  metallic 
spheres  corresponding  to  G  n  in  figure  1. 

c  is  an  induction  coil  corresponding  to  R.  6  is  a  key  corres- 
ponding to  D,  and  a  is  a  battery  corresponding  to  E. 

Figure  4  is  a  vertical  section  of  the  radiator  or  oscillation 
producer  mounted  in  the  focal  line  of  a  cylindrical  parabolic 


REPRINT  OF   SIGNOR  G.   MARCONI'S  PATENT.       323 

reflector  f  in  wliicli  a  side  view  of  the  spheres  e  e  of  figure  3 
is  given. 

Figure  5  is  a  full-sized  view  of  the  receiving  plates  k  k  and 
sensitive  tube^'. 

Figure  5A  is  a  modified  form  of  sensitive  tube. 

Figure  6  is  a  modification  of  the  oscillation  producer  in  which 
the  spheres  e  e  and  d  d  are  mounted  in  an  ebonite  tube  d3. 

Figure  7  is  another  modification  of  the  oscillation  producer 
in  which  the  spheres  are  substituted  by  hemispheres. 

Figure  8  is  a  modified  form  of  receiver  in  which  the  plates 
k  Jc  are  curved  instead  of  being  straight. 

Figure  9  is  another  form  of  transmitter  in  which  two  large 
metallic  plates  t2  t2  are  employed. 

Figure  10  shows  a  modification  of  the  arrangements  at  the 
transmitting  station,  and  figure  11  a  modification  of  the  ar- 
rangements of  the  receiving  station,  which  enables  one  to  signal 
through  obstacles  such  as  hills  or  mountains. 

Figure  12  shows  a  detector  which  is  useful  for  determining 
the  proper  length  of  the  plates  kk  of  the  receivers. 

Figure  13  shows  an  improved  interrupter  (make-and-break) 
which  is  applicable  to  the  induction  coil  of  the  transmitter. 

Figure  14  shows  a  water  resistance,  the  use  of  which  shall  be 
explained. 

My  invention  relates  in  great  measure  to  the  manner  in 
which  the  above  apparatus  is  made  and  connected  together. 
With  some  of  these  forms  I  am  able  to  obtain  Morse  signals, 
and  to  work  ordinary  telegraphic  instruments  and  other  appar- 
atus ;  and  with  modifications  of  the  above  apparatus  it  is 
possible  to  transmit  signals  not  only  through  comparatively 
small  obstacles  such  as  brick  walls,  trees,  &c.,  but  also  through 
or  across  masses  of  metal,  or  hills,  or  mountains,  which  may 
intervene  between  the  transmitting  and  receiving  instruments. 

I  will  first  describe  my  improvements  which  are  applicable 
to  the  receiving  instruments. 

My  first  improvement  consists  in  automatically  tapping  or 
disturbing  the  powder  in  the  sensitive  tube,  or  in  shaking  the 
imperfect  contact,  so  that  immediately  the  electrical  stimulus 
from  the  transmitter  has  ceased,  the  tube  or  imperfect  contact 
regains  its  ordinary  non-conductive  state.  This  part  of  my 
invention  is  illustrated  in  figure  2,  in  which  j  represents  the 


324 


APPENDIX   E. 


^V^ctf 


!  LJ 


Fig.  3. 


J 


Fig.  4. 


Fig.  5. 


d4 


Fig.  6. 


REPRINT   OF   SIGNOR   G.   MARCONI'S   PATENT.       325 


Fig.  8. 


Fig.  9. 


Fig.  10. 


nJ 
' 


Fig.  11. 


*{'     ""    J      - 
Fig.  12. 


Fig.  13. 


n 


A 

Fig.  14. 


326  APPENDIX   E. 

sensitive  tube  and  p  the  trembler  or  tapper.  The  current 
which  flows  through  the  sensitive  tube  or  contact,  and  which 
is  commenced  under  the  influence  of  the  electrical  oscillations 
from  the  transmitting  instrument,  is  allowed  to  actuate 
(directly,  or  indirectly  by  means  of  a  relay)  the  trembler, 
which  is  similar  to  an  electric  bell.  This  trembler  must  be  so 
arranged,  as  hereinafter  explained,  that  the  effect  of  the  spark- 
ing at  its  vibrating  contacts,  and  the  jerky  currents  caused  by 
self-induction,  &c.,  are  neutralised  or  removed. 

The  small  hammer  of  the  trembler  hits  the  tube  or  imperfect 
contact  and  so  stops  the  current,  and  consequently  its  own 
movement,  which  had  been  generated  by  the  said  current ;  and 
by  this  means  the  current  automatically  and  almost  instantan- 
eously interrupts  itself  until  another  oscillation  from  the 
transmitting  instrument  again  makes  the  sensitive  tube  or 
imperfect  contact  a  conductor. 

I  find,  however,  that  the  current  which  can  be  started  by 
the  sensitive  tube  or  contact  is  not  sufficiently  strong  to  work 
an  ordinary  trembler  and  receiving  instrument. 

To  overcome  this  difficulty,  instead  of  obliging  the  current  of 
the  circuit  which  contains  the  sensitive  tube  or  contact  to  work 
the  trembler  and  instrument,  I  use  the  said  current  for  working 
a  sensitive  relay  n  (figure  2),  which  closes  and  opens  the  circuit  of 
a  stronger  battery  r,  preferably  of  the  Leclanche  type.  This 
current,  which  is  much  stronger  than  the  current  which  runs 
through  the  sensitive  tube  or  contact,  works  the  trembler  and 
other  instruments.  To  prevent  the  sparks  and  jerks  of  current 
which  would  be  caused  by  the  self-induction  of  the  relay  from 
interfering  with  the  action  of  the  receiver,  certain  means  must 
be  taken  similar  to  those  referred  to  above  in  reference  to  the 
trembler  or  tapper,  which  will  be  explained  hereafter.  In  the 
apparatus  I  have  made  I  have  found  that  the  relay  n  should  be 
one  possessing  small  self-induction,  and  wound  to  a  resistance 
of  about  1000  ohms.  It  should  preferably  be  able  to  work 
regularly  with  a  current  of  a  milliampere  or  less.  The  trembler 
or  tapper  p  on  the  circuit  of  the  relay  n  is  similar  in  construc- 
tion to  that  of  a  small  electric  bell,  but  having  a  shorter  arm. 
I  have  used  a  trembler  wound  to  1000  ohms  resistance,  having 
a  core  of  good  soft  iron  hollow  and  split  lengthways  like  most 
electro-magnets  used  in  telegraph  instruments. 


IIEP1UNT   OF   SIGNOIl   G.   MARCONI'S   PATENT.       327 

The  trembler  must  be  carefully  adjusted.  Preferably  the 
blows  should  be  directed  slightly  upwards,  so  as  to  prevent  the 
filings  from  getting  caked.  In  place  of  tapping  the  tube  the 
powder  can  be  disturbed  by  slightly  moving  outwards  and 
inwards  one  or  both  of  the  stops  of  the  sensitive  tube  (see 
figure  5,  j1  j2),  the  trembler  p  (figure  2)  being  replaced  by  a 
small  electro-magnet  or  magnets  or  vibrator  whose  armature 
is  connected  to  the  stop. 

I  ordinarily  work  the  receiving  instrument  k,  which  may  be 
of  any  description,  by  a  derivation  as  shown  from  the  circuit, 
which  works  the  trembler  p.  It  can  also,  however,  be  worked 
in  series  with  the  trembler. 

It  is  desirable  that  the  receiving  instrument,  if  on  a  deriva- 
tion of  the  circuit  which  includes  the  trembler  or  tapper,  should 
preferably  have  a  resistance  equal  to  the  resistance  of  the 
trembler  p. 

A  further  improvement  consists  in  the  mode  of  construction 
of  the  sensitive  tube. 

I  have  noticed  that  a  sensitive  tube  or  imperfect  contact, 
such  as  is  shown  in  figure  1  T,  is  not  perfectly  reliable. 

My  tube  as  shown  in  figure  5  is,  if  carefully  constructed, 
absolutely  reliable,  and  by  means  of  it  the  relay  and  trembler 
£c.,  can  be  worked  with  regularity  like  any  other  ordinary 
telegraphic  instrument. 

In  figure  5,j  is  the  sensitive  tube  containing  two  metallic 
plugs  j'2  connected  to  the  battery  circuit,  between  which  is 
placed  powder  of  a  conductive  material  jl.  The  two  plugs 
should  preferably  be  made  of  silver,  or  may  be  two  short  pieces 
of  thick  silver  wire  of  the  same  diameter  as  the  internal 
diameter  of  the  tube^',  so  as  to  fit  tightly  in  it.  The  plugs^'2^'2 
are  joined  to  two  pieces  of  platinum  wire  j3.  The  tube  is 
closed  and  sealed  on  to  the  platinum  wires  j 3  at  both  ends. 
Many  metals  can  be  employed  for  producing  the  powder  or 
filings  j\  but  I  prefer  to  use  a  mixture  of  two  or  more  different 
metals.  I  find  hard  nickel  to  be  the  best  metal,  and  I  prefer 
to  add  to  the  nickel  filings  about  four  per  cent  of  hard  silver 
filings,  which  increase  greatly  the  sensitiveness  of  the  tube  to 
electric  oscillations.  By  increasing  the  proportion  of  silver 
powder  or  grains  the  sensitiveness  of  the  tube  also  increases  ; 
but  it  is  better  for  ordinary  work  not  to  use  a  tube  of  too  great 


328  APPENDIX  E. 

sensitiveness,  as  it  might  be  influenced  by  atmospheric  or  other 
electricity. 

The  sensitiveness  can  also  be  increased  by  adding  a  very 
small  amount  of  mercury  to  the  filings  and  mixing  up  until 
the  mercury  is  absorbed.  The  mercury  must  not  be  in  such  a 
quantity  as  to  clot  or  cake  the  filings  :  an  almost  imperceptible 
globule  is  sufficient  for  a  tube.  Instead  of  mixing  the  mercury 
with  the  powder,  one  can  obtain  the  same  effects  by  slightly 
amalgamating  the  inner  surfaces  of  the  plugs  which  are  to  be 
in  contact  with  the  filings.  Very  little  mercury  must  be  used, 
just  sufficient  to  brighten  the  surface  of  the  metallic  plugs 
without  showing  any  free  mercury  or  globules. 

The  size  of  the  tube  and  the  distance  between  the  two 
metallic  stops  or  plugs  may  vary  under  certain  limits  :  the 
greater  the  space  allowed  for  the  powder,  the  larger  or  coarser 
ought  to  be  the  filings  or  grains. 

I  prefer  to  make  my  sensitive  tubes  of  the  following  size — 
the  tube  j  is  1^  inch  long  and  y1^  or  ^  of  an  inch  internal 
diameter.  .The  length  of  the  stops  j2  is  about  £  of  an  inch, 
and  the  distance  between  the  stops  or  plugs  j2j2  is  about  3^ 
of  an  inch. 

I  find  that  the  smaller  or  narrower  the  space  is  between  the 
plugs  in  the  tube,  the  more  sensitive  it  proves ;  but  the  space 
cannot  under  ordinary  circumstances  be  excessively  shortened 
without  injuring  the  fidelity  of  the  transmission. 

Care  must  be  taken  that  the  plugs  j2j.2  fit  the  tube  exactly, 
as  otherwise  the  filings  might  escape  from  the  space  between 
the  stops,  which  would  soon  destroy  the  action  of  the  sensitive 
tube. 

The  metallic  powders  ought  not  to  be  fine,  but  rather  coarse, 
as  can  be  produced  by  a  large  and  rough  file. 

The  powder  should  preferably  be  of  uniform  grain  or  thick- 
ness. 

All  the  very  fine  powder  or  the  excessively  coarse  powder 
ought  to  be  removed  from  it  by  blowing  or  sifting. 

It  is  also  desirable  that  the  powder  or  grains  should  be  dry 
and  free  from  grease  or  dirt,  and  the  files  used  in  producing  the 
same  ought  to  be  frequently  washed  and  dried,  and  used  when 
warm. 

The  powder  ought  not  to  be  compressed  between  the  plugs, 


REPRINT   OF   SIGNOR   G.   MARCONI'S  PATENT.       329 

but  rathor  loose,  and  in  such  a  condition  that  when  the  tube 
is  tapped  the  powder  may  be  seen  to  move  freely. 

The  tubej  may  be  sealed,  but  a  vacuum  inside  it  is  not 
essential,  except  the  slight  vacuum  which  results  from  having 
heated  it  while  sealing  it.  Care  should  also  be  taken  not  to 
heat  the  tube  too  much  in  the  centre  when  sealing  it,  as  it 
would  oxidise  the  surfaces  of  the  silver  stops,  and  also  the 
powder,  which  would  diminish  its  sensitiveness.  I  have  used, 
in  sealing  the  tubes,  a  hydrogen  and  air  flame. 

A  vacuum  is,  however,  desirable,  and  I  have  used  one  of 
about  yoVu  °f  an  atmosphere  obtained  by  a  mercury  pump. 

In  this  case  a  small  glass  tube  must  be  joined  to  a  side  of  the 
tubey  (figure  5),  which  is  put  in  communication  with  the  pump 
and  afterwards  sealed  in  the  ordinary  manner. 

If  the  sensitive  tube  has  been  well  made,  it  should  be 
sensitive  to  the  inductive  effect  of  an  ordinary  electric  bell 
when  the  same  is  working  from  one  to  two  yards  from 
the  tube. 

A  sensitive  tube  well  prepared  should  also  instantly  in- 
terrupt the  current  passing  through  it  at  the  slightest  tap  or 
shake,  provided  it  is  inserted  in  a  circuit  in  which  there  is  little 
self-induction  and  small  electro-motive  force,  such  as  a  single 
cell. 

In  order  to  keep  the  sensitive  tube  j  in  good  working  order 
it  is  desirable,  but  not  absolutely  necessary,  not  to  allow  more 
than  one  milliampere  to  flow  through  it  when  active. 

If  a  stronger  current  is  necessary  3  several  tubes  may  be  put 
in  parallel,  provided  they  all  get  shaken  by  the  tapper  or 
trembler ;  but  this  arrangement  is  not  always  quite  as  satis- 
factory as  the  single  tube. 

It  is  preferable,  when  using  sensitive  tubes  of  the  type  I 
have  described,  not  to  insert  in  the  circuit  with  it  more  than 
one  cell  of  the  Leclanche'  type,  as  a  higher  electro- motive  force 
than  1'5  volts  is  apt  to  pass  a  current  through  the  tube,  even 
when  no  oscillations  are  transmitted. 

I  can,  however,  construct  sensitive  tubes  capable  of  working 
with  a  higher  electro-motive  force. 

Fig.  5A  shows  one  of  these  tubes.  In  this  tube,  instead  of 
one  space  or  gap  filled  with  filings,  there  are  several  spaces  jljlt 
separated  by  plugs  of  tight-fitting  silver  wire.  A  tube  thus 


330  APPENDIX   E. 

constructed — observing  also  the  rules  of  construction  of  my 
tubes  in  general — will  work  satisfactorily  if  the  electro-motive 
force  of  the  battery  in  circuit  with  the  tube  is  equal  to  about 
1*2  volts  multiplied  by  the  number  of  gaps. 

With  this  tube  also  it  is  well  not  to  allow  a  current  of  more 
than  one  milliampere  to  pass  through  it. 

Figure  5  also  shows  the  plates  k  k,  which  are  joined  to  each 
end  of  the  sensitive  tube,  and  which  correspond  to  the  plates 
M  N  in  figure  1. 

The  plates  k  (figure  5)  are  of  copper  or  other  metal,  about 
half  an  inch  or  more  broad,  and  may  be  about  ^  of  an  incli 
thick,  and  preferably  of  such  a  length  as  to  be  electrically  tuned 
with  the  length  of  the  wave  of  the  electrical  oscillations 
transmitted. 

The  means  I  adopt  for  fixing  the  proper  length  of  the  plates 
k  k  is  as  follows  :  I  stick  a  rectangular  strip  of  tinfoil  (see 
figure  12)  m  about  20  inches  long  (the  length  depends  on  the 
supposed  length  of  the  wave  that  one  is  measuring),  by  means 
of  a  weak  solution  of  gum,  on  to  a  glass  plate  m1  (figure  12) ; 
then  by  means  of  a  very  sharp  penknife  or  point  and  ruler  I  cut 
across  the  middle  of  the  tinfoil,  leaving  a  mark  of  division  m2. 
If  this  glass  plate  is  held  a  few  feet  away  from  the  origin  of  the 
electrical  disturbances,  and  in  such  a  position  that  the  strips  of 
tinfoil  are  about  parallel  to  the  line  joining  the  centres  of  the  two 
spheres  in  the  transmitting  apparatus,  sparks  will  jump  from 
one  strip  to  the  other  at  m2.  When  the  length  of  the  strips  of 
tinfoil  m  has  been  so  adjusted  as  to  approximate  to  the  length 
of  wave  emitted  from  the  oscillator,  the  sparking  will  occur  at 
a  greater  distance  from  the  oscillation  producer  when  the  strips 
are  of  suitable  length.  By  shortening  or  lengthening  the 
strips,  therefore,  it  is  easy  to  find  the  length  most  appropriate 
to  the  length  of  wave  emitted  by  the  oscillation  producer. 
The  length  so  found  is  the  proper  length  for  the  plates  k,  or 
rather  these  should  be  about  half  an  inch  shorter  on  account 
of  the  length  of  the  sensitive  tube  j  (figure  5)  connected 
between  them. 

The  plates  k,  tube./,  &c.,  are  fastened  to  a  thin  glass  tube  o, 
preferably  not  longer  than  12  inches,  firmly  fixed  at  one  end  to 
a  firm  piece  of  wood  o2,  or  the  sensitive  tube^'  may  be  fixed 
firmly  at  both  ends — i.e.,  preferably  grasped  near  the  ends  of 


11EPRINT   OF   SIGNOR   0.   MAKCONl'S   PATENT.        331 

the  tube  containing  the  powder,  and  not  at  the  ends  of  the 
tube  o  o,  which  serves  as  support. 

By  means  of  a  tube  with  multiple  gaps,  as  shown  in  figure 
5A,  it  is  also  possible  to  work  the  trembler  and  also  the  signal- 
ling or  other  apparatus  direct  on  the  circuit  which  contains  the 
sensitive  tube,  but  I  prefer  when  possible  to  work  with  the 
single-gap  tube  and  the  relay  as  shown.  With  a  sensitive  and 
specially  constructed  trembler  it  is  also  possible  to  work  the 
trembler  with  the  single-gap  tube  in  series  with  it  without  a 
relay. 

In  order  to  increase  the  distance  at  which  the  receiver  can 
be  actuated  by  the  radiation  from  the  transmitter,  I  place  the 
receiver  (i.e.,  the  sensitive  tube  and  plates)  in  the  focal  line  of 
a  cylindrical  parabolic  reflector  I  (figure  2),  preferably  of  copper, 
and  directed  towards  the  transmitting  station. 

In  determining  the  proper  length  of  the  plates  of  the  re- 
ceiver by  means  of  the  detector  shown  in  figure  12,  it  is 
desirable  to  try  the  detector  in  the  focus  or  focal  line  of  the 
reflector,  because  the  length  of  the  strips  or  plates  which  gives 
the  best  result  in  a  reflector  differs  slightly  from  the  length 
which  gives  the  best  results  without  reflectors. 

The  reflector  I  (figure  2)  should  be  preferably  in  length  and 
opening  not  less  than  double  the  length  of  wave  emitted  from 
the  transmitting  instrument. 

It  is  slightly  advantageous  for  the  focal  distance  of  the  re- 
flector to  be  equal  to  one-fourth  or  three-fourths  of  the  wave- 
length of  the  oscillation  transmitted. 

The  plates  k  (figure  2)  may  be  replaced  by  tubes  or  other 
forms  of  conductors. 

A  further  improvement  has  for  its  object  to  prevent  the 
electrical  disturbances  which  are  set  up  by  the  trembler  and 
other  apparatus  in  proximity  or  in  circuit  with  the  tube  from 
themselves  restoring  the  conductivity  of  the  sensitive  tube 
immediately  after  the  trembler  has  destroyed  it,  as  has  been 
described. 

This  I  effect  by  introducing  into  the  circuits  at  the  places 
marked  p1,  jt?2,  q,  /i1,  in  figure  2  high  resistances  having  as  little 
self-induction  as  possible.  The  action  of  the  high  resistances  is 
that,  while  preventing  any  appreciable  quantity  of  the  current 
from  passing  through  them  when  the  apparatus  is  working, 


332  APPENDIX  E. 

they  nevertheless  afford  an  easy  path  for  the  currents  of  high 
tension  which  would  be  formed  at  the  moment  when  the 
circuit  is  broken,  and  thus  prevent  sparking  at  contacts  or 
sudden  jerks  of  currents,  which  would  restore  or  maintain  the 
conductivity  of  the  sensitive  tube. 

These  coils  may  con veniently  be  made  by  winding  the  wire 
(preferably  of  platinoid)  on  the  bight,  as  it  is  sometimes 
termed,  or  double  wound,  to  prevent  them  producing  self- 
induction. 

In  figure  2,  p2  is  one  of  these  resistance  coils  which  is  inserted 
in  a  circuit  connecting  the  vibrating  contacts  of  the  trembler 
p.  I  have  used  in  the  apparatus  a  coil  which  had  a  resistance 
about  four  times  the  resistance  of  the  trembler  p. 

pl  represents  a  similar  resistance  (also  of  about  four  times 
the  resistance  of  the  trembler)  inserted  in  parallel  across 
the  terminals  of  the  trembler. 

A  similar  resistance  g,  figure  2,  is  placed  in  parallel  on  the 
terminals  of  the  relay  n  (i.e.,  the  terminals  which  are  connected 
to  the  circuit  containing  the  sensitive  tube). 

The  coil  q  should  preferably  have  a  resistance  of  about  three 
or  four  times  the  resistance  of  the  relay. 

A  similar  resistance  hl  of  about  four  times  the  resistance  of 
the  instrument  is  inserted  in  parallel  across  the  terminals  of 
the  instrument. 

In  parallel  across  the  terminals  of  the  relay  (i.e.,  correspond- 
ing to  the  circuit  worked  by  the  relay)  it  is  well  to  have  a 
liquid  resistance  s  constituted  of  a  series  of  tubes,  one  of  which 
is  shown  full  size  in.  figure  14  partially  filled  with  water  acidu- 
lated with  sulphuric  acid.  The  number  of  these  tubes  in 
series  across  the  said  terminals  ought  to  be  about  ten  for  a 
circuit  of  15  volts,  so  as  to  prevent,  in  consequence  of  their 
counter  electro -motive  force,  the  current  of  the  local  battery 
from  passing  through  them,  but  allowing  the  high  tension  jerk 
of  current  generated  at  the  opening  of  the  circuit  in  the  relay 
to  pass  smoothly  across  them  without  producing  perturbating 
sparks  at  the  movable  contact  of  the  relay. 

A  double-wound  platinoid  resistance  may  be  used  instead  of 
the  water  resistance,  provided  its  resistance  be  about  20,000 
ohms. 

A  resistance  similar  to  h  should  be  inserted  in  parallel  on 


REPRINT  OF  SIGNOR   G.   MARCONI'S  PATENT.       333 

the  terminals  of  any  apparatus  or  resistance  which  may  be 
apt  to  give  self-induction  and  which  is  near  or  connected  to 
the  receiver. 

Condensers  of  suitable  capacity  may  be  substituted  for  the 
above-mentioned  coils,  but  I  prefer  using  coils  or  water  re- 
sistances. 

Another  improvement  has  for  its  object  to  prevent  the  high 
frequency  oscillations  set  up  across  the  plates  of  the  receiver 
by  the  transmitting  instrument,  which  should  pass  through  the 
sensitive  tube,  from  running  round  the  local  battery  wires 
and  thereby  weakening  their  effect  on  the  sensitive  tube  or 
contact. 

This  I  effect  by  connecting  the  battery  wires  to  the  sensitive 
tube  or  contact,  or  to  the  plates  attached  to  the  tube  through 
small  coils  (see  &  in  the  figures)  possessing  self-induction, 
which  may  be  called  choking  coils,  formed  by  winding  in  the 
ordinary  manner  a  short  length  (about  a  yard)  of  thin  and 
well-insulated  wire  round  a  core  (preferably  containing  iron) 
two  or  three  inches  long. 

Another  improvement  consists  in  a  modified  form  of  the 
plates  connected  to  the  sensitive  tube,  in  order  to  make  it 
possible  to  mount  the  receiver  in  an  ordinary  circular  parabolic 
reflector.  This  part  of  my  invention  is  illustrated  in  figure  8,  in 
which  I  is  an  ordinary  concave  reflector.  In  this  case  the  plates 
k  k  are  curved  and  connected  at  one  end  to  the  sensitive  tube.;', 
and  at  the  other  to  a  small  condenser  formed  by  two  metallic 
plates  k*  of  about  one  inch  square  or  more,  facing  each  other 
with  a  very  thin  piece  of  insulating  material  k*  between  them. 
p  is  the  trembler.  The  condenser  may  be  omitted  without 
much  altering  the  effects  obtainable. 

The  connection  to  the  local  circuit  is  made  through  two 
small  choking  coils  k1  k1  as  already  described. 

The  adjustment  of  the  whole  is  similar  to  that  already  de- 
scribed for  the  other  receivers. 

The  receiver  should  be  put  in  such  a  position  as  to  intercept 
the  reflected  ring  of  radiations  which  exists  behind  or  before 
the  focus  of  the  reflector,  and  ought  to  be  preferably  tuned 
with  the  length  of  wave  of  the  oscillation  transmitted,  in  similar 
manner  to  that  before  described,  except  that  a  ring  of  tinfoil 
with  a  single  cut  through  it  is  employed. 


334  APPENDIX  E. 

I  will  now  describe  my  improvements  which  are  applicable 
to  the  transmitting  instruments. 

My  first  improvement  consists  in  employing  four  spheres  for 
producing  the  electrical  oscillations. 

This  part  of  my  invention  is  illustrated  in  figure  3,  d  d,  e  s, 
and  in  figure  6,  d  d,  e  e.  The  spheres  d  d,  figure  3,  are  con- 
nected to  the  terminals  c1  of  the  secondary  circuit  of  the  induc- 
tion coil  c.  The  spheres  d  d  are  carried  by  insulating  supports 
dldl. 

Preferably  the  supports  d1  consist  of  plates  of  ebonite  having 
holes  to  receive  the  balls,  which  are  fixed  by  heating  them 
sufficiently  to  fuse  the  ebonite  and  then  holding  them  in  place 
until  they  cool.  e  e  are  two  similar  balls  on  supports  e1  e1, 
whose  distance  apart  can  be  adjusted  by  ebonite  bolts  and  nuts 
e*  e2  acting  against  other  nuts  e3.  e4  is  a  flexible  membrane, 
preferably  of  parchment  paper,  glued  to  the  supports  e1  and 
forming  a  vessel  which  is  filled  with  dielectric  liquid,  prefer- 
ably vaseline-oil  slightly  thickened  with  vaseline. 

The  oil  or  insulating  liquid  between  the  spheres  e  e  increases 
the  power  of  the  radiation,  and  also  enables  one  to  obtain  con- 
stant effects,  which  are  not  easily  obtained  if  the  oil  is 
omitted. 

The  balls  d  and  e  are  preferably  of  solid  brass  or  copper,  and 
the  distance  they  should  be  apart  depends  on  the  quantity  and 
electro-motive  force  of  the  electricity  employed,  the  effect  in- 
creasing with  the  distance  (especially  by  increasing  the  dis- 
tance between  the  spheres  d  and  the  spheres  e)  so  long  as  the 
discharge  passes  freely.  With  an  induction  coil  giving  an 
ordinary  8-inch  spark  the  distance  between  e  and  e  should  be 
from  oV  *°  3*0  °f  an  incn>  and  the  distance  between  d  and  e 
about  one  inch. 

When  it  is  desired  that  the  signal  should  only  be  sent  in  one 
direction,  I  place  the  oscillation  producer  in  the  focus  or  focal 
line  of  a  reflector  directed  to  the  receiving  station. 

/  (figure  3)  and  /  (figure  4)  show  the  cylindrical  parabolic 
reflector  made  by  bending  a  metallic  sheet,  preferably  of  brass 
or  copper  to  form,  and  fixing  it  to  metallic  or  wooden  ribs  fL 
(figure  3). 

Other  conditions  being  equal,  the  larger  the  balls  the  greater 
is  the  distance  at  which  it  is  possible  to  communicate.  I  have 


KEPKINT   OF   S1GNOR   G.   MARCONI'S  PATENT.       335 

generally  used  balls  of  solid  brass  of  4  inches  diameter,  giving 
oscillations  of  10  inches  length  of  wave. 

Instead  of  spheres,  cylinders  or  ellipsoids,  &c.,  may  be  em- 
ployed. 

Preferably  the  reflector  applied  to  the  transmitter  ought  to 
be  in  length  and  opening  the  double  at  least  of  the  length  of 
wave  emitted  from  the  oscillator. 

If  these  conditions  are  satisfied,  and  with  a  suitable  receiver, 
a  transmitter  furnished  with  spheres  of  4  inches  diameter  con- 
nected to  an  induction  coil  giving  a  10-inch  spark  will  transmit 
signals  to  two  miles  or  more. 

If  a  very  powerful  source  of  electricity  giving  a  very  long 
spark  be  employed,  it  is  preferable  to  divide  the  spark-gap 
between  the  central  balls  of  the  oscillator  into  several  smaller 
gaps  in  series.  This  may  be  done  by  introducing  between  the 
big  balls  smaller  ones  (of  about  half  an  inch  diameter)  held  in 
position  by  ebonite  frames. 

Figure  6  shows  a  more  compact  form  of  oscillation  producer. 
In  this  each  pair  of  balls  d  and  e  is  fixed  by  heat  or  otherwise 
in  the  end  of  tubes  d2  of  insulating  material,  such  as  ebonite  or 
vulcanite.  The  tubes  d"  fit  tightly  in  another  similar  tube  d3 
having  covers  d*,  through  which  pass  the  rods  d*  connecting 
the  balls  d  to  the  conductors.  One  (or  both)  of  the  rods  d*  is 
connected  to  the  ball  d  by  a  ball-and-socket  joint,  and  has  a 
screw  thread  upon  it  working  in  a  nut  in  the  cover  d4.  By 
turning  the  rod,  therefore,  the  distance  of  the  balls  e  apart  can 
be  adjusted,  d6  are  holes  in  the  tube  ds,  through  which  the 
vaseline-oil  can  be  introduced  into  the  space  between  the 
balls  e. 

A  further  improvement  consists  in  causing  one  of  the  con- 
tacts of  the  vibrating  brake  applied  to  the  induction  coil  to 
revolve  rapidly. 

This  improvement  has  for  its  object  to  maintain  the  plat- 
inum contacts  of  the  interrupter  in  good  working  order,  and  to 
prevent  them  sticking,  &c. 

This  part  of  my  invention  is  illustrated  in  figure  3  (c2, 
c3,  c4). 

I  obtain  this  result  by  having  a  revolvable  central  core  c* 
(figure  3  and  figure  13)  in  the  ordinary  screw  c3,  which  is  in 
communication  with  the  platinum  contacts.  I  cause  the  said 


336  APPENDIX   E. 

central  core  with  one  of  the  platinum  contacts  attached  to  it 
to  revolve  by  coupling  it  to  a  small  electric  motor  c4. 

This  motor  can  be  worked  by  the  same  circuit  that  works 
the  coil,  or  if  necessary  by  a  separate  circuit — the  connections 
are  not  shown  in  the  drawing. 

By  this  means  the  regularity  and  power  of  the  discharge  of 
an  ordinary  induction  coil  with  a  trembler  brake  are  greatly 
improved. 

The  induction  coil  c  (figure  3)  may,  however,  be  replaced  by 
any  other  source  of  high-tension  electricity. 

When  working  with  large  amounts  of  energy  it  is,  however, 
better  to  keep  the  coil  of  the  transformer  constantly  working 
for  the  time  during  which  one  is  transmitting,  and,  instead  of 
interrupting  the  current  of  the  primary,  interrupting  the  dis- 
charge of  the  secondary. 

In  this  case  the  contacts  of  the  key  should  be  immersed 
in  oil,  as  otherwise,  owing  to  the  length  of  the  spark,  the 
current  will  continue  to  pass  after  the  contacts  have  been 
separated. 

A  further  improvement  has  for  its  object  to  facilitate  the 
focussing  of  the  electric  rays. 

This  part  of  my  invention  is  illustrated  in  figure  7,  in  which 
a  view  is  given  of  the  modified  oscillation  producer  mounted  in 
the  focus  of  an  ordinary  parabolic  reflector/. 

The  oscillator  in  this  case  is  different  from  the  one  I  have 
previously  described,  because  instead  of  being  constituted  of 
two  spheres  it  is  made  of  two  hemispheres  e  e  separated  by  a 
small  space  filled  with  oil  or  other  dielectric.  The  spark  be- 
tween the  hemispheres  takes  place  in  the  dielectric  from  small 
projections  at  the  centres  of  the  hemispheres.  The  working 
and  adjusting  of  this  oscillator  are  similar  to  that  of  the  one 
previously  described. 

This  arrangement  may  be  also  solidly  mounted  in  an  ebonite 
tube,  as  shown  in  figure  6. 

A  receiver  which  may  be  used  with  this  transmitter  is 
shown  in  figure  8,  and  has  already  been  described. 

It  is  not  essential  to  have  a  reflector  at  the  transmitters  and 
receivers,  but  in  their  absence  the  distance  at  which  one  can 
communicate  is  much  smaller. 

Figure  9  shows  another  modified  form  of  transmitter  with 


REPRINT   OF   SIGNOR  G.   MARCONI'S   PATENT.       337 

which  one  can  transmit  signals  to  considerable  distances  with- 
out using  reflectors. 

In  figure  9,  tt  are  two  poles  connected  by  a  rope  tlt  to  which 
are  suspended  by  means  of  insulating  suspenders  two  metallic 
plates  t2  fi  connected  to  the  spheres  e  (in  oil,  or  other  dielectric, 
as  before)  and  to  the  other  balls  t3  in  proximity  to  the  spheres  c1, 
which  are  in  communication  with  the  coil  or  transformer  c. 
The  balls  i3  are  not  absolutely  necessary,  as  the  plates  t2  may 
be  made  to  communicate  with  the  coil  or  transformer  by  means 
of  thin  insulated  wires.  The  receiver  I  adopt  with  this  trans- 
mitter is  similar  to  it,  except  that  the  spheres  e  are  replaced 
by  the  sensitive  tube  or  imperfect  contact  j  (figure  5),  whilst 
the  spheres  £3  may  be  replaced  by  the  choking  coils  &l  in  com- 
munication with  the  local  circuit.  If  a  circular-tuned  receiver 
of  large  size  be  employed,  the  plates  fi  may  be  omitted  from  the 
receiver.  I  have  observed  that,  other  conditions  being  equal, 
the  larger  the  plates  at  the  transmitter  and  receiver,  and  the 
higher  they  are  from  earth,  and  to  a  certain  extent  the  farther 
apart  they  are,  the  greater  is  the  distance  at  which  correspond- 
ence is  possible. 

For  permanent  installations  it  is  convenient  to  replace  the 
plates  by  metallic  cylinders  closed  at  one  end,  and  put  over  the 
pole  like  a  hat,  and  resting  on  insulators.  By  this  arrange- 
ment no  wet  can  come  to  the  insulators,  and  the  effects  obtain- 
able are  better  in  wet  weather. 

A  cone  or  hemisphere  may  be  used  in  place  of  a  cylinder.  The 
pole  employed  ought  preferably  to  be  dry  and  tarred. 

Where  obstacles,  such  as  many  houses  or  a  hill  or  moun- 
tains, intervene  between  the  transmitter  and  the  receiver,  I 
have  devised  and  adopt  the  arrangement  shown  in  figures 
10  and  11. 

In  the  transmitting  instrument,  figure  10,  I  connect  one  of 
the  spheres  d  to  earth  E  preferably  by  a  thick  wire,  and  the 
other  to  a  plate  or  conductor  #,  which  may  be  suspended  on  a 
pole  v  and  insulated  from  earth.  Or  the  spheres  d  may  be 
omitted  and  one  of  the  spheres  e  be  connected  to  earth  and 
the  other  to  the  plate  or  conductor  u. 

At  the  receiving  station,  figure  11,  I  connect  one  terminal  of 
the  sensitive  tube  or  imperfect  contact.;'  to  earth  E,  preferably 
also  by  a  thick  wire,  and  the  other  to  a  plate  or  conductor  wt 

Y 


338  APPENDIX    E. 

preferably  similar  to  u.  The  plate  w  may  be  suspended  on  a 
pole  x,  and  should  be  insulated  from  earth.  The  larger  the 
plates  of  the  receiver  and  transmitter,  and  the  higher  from 
the  earth  the  plates  are  suspended,  the  greater  is  the  distance 
at  which  it  is  possible  to  communicate  at  parity  of  other 
conditions. 

The  figure  does  not  show  the  trembler  or  tapping  arrange- 
ment. kl  kl  are  the  choking  coils,  which  are  connected  to  the 
battery  circuit,  as  has  been  explained  with  reference  to  the 
previous  figures. 

At  the  receiver  it  is  possible  to  pick  up  the  oscillations  from 
the  earth  or  water  without  having  the  plate  w.  This  may  be 
done  by  connecting  the  terminals  of  the  sensitive  tube  j  to 
two  earths,  preferably  at  a  certain  distance  from  each  other  and 
in  a  line  with  the  direction  from  which  the  oscillations  are 
coming.  These  connections  must  not  be  entirely  conductive, 
but  must  contain  a  condenser  of  suitable  capacity,  say  of  one 
square  yard  surface  (parafined  paper  as  dielectric). 

Balloons  can  also  be  used  instead  of  plates  on  poles,  provided 
they  carry  up  a  plate  or  are  themselves  made  conductive  by 
being  covered  with  tinfoil.  As  the  height  to  which  they  may 
be  sent  is  great,  the  distance  at  which  communication  is 
possible  becomes  greatly  multiplied.  Kites  may  also  be  suc- 
cessfully employed  if  made  conductive  by  means  of  tinfoil. 

When  working  the  described  apparatus,  it  is  necessary  either 
that  the  local  transmitter  and  receiver  at  each  station  should 
be  at  a  considerable  distance  from  each  other,  or  that  they 
should  be  screened  from  each  other  by  metal  plates.  It  is 
sufficient  to  have  all  the  telegraphic  apparatus  in  a  metal  box 
(except  the  reading  instrument),  and  any  exposed  part  of  the 
circuit  of  the  receiver  enclosed  in  metallic  tubes  which  are  in 
electrical  communication  with  the  box  (of  course  the  part  of 
the  apparatus  which  has  to  receive  the  radiation  from  the  dis- 
tant station  must  not  be  enclosed,  but  possibly  screened 
from  the  local  transmitting  instrument  by  means  of  metallic 
sheets). 

When  the  apparatus  is  connected  to  the  earth  or  water  the 
receiver  must  be  switched  out  of  circuit  when  the  local  trans- 
mitter  is  at  work,  and  this  may  also  be  done  when  the  apparatus 
is  not  earthed. 


T1EPRINT   OF   SIGNOR   G.   MARCONI'S   PATENT.        339 

Having  now  particularly  described  and  ascertained  the 
nature  of  my  said  invention,  and  in  what  manner  the  same  is 
to  be  performed,  I  declare  that  what  I  claim  is — 

1.  The  method  of  transmitting  signals  by  means  of  electrical 
impulses  to  a  receiver  having  a  sensitive  tube  or  other  sensitive 
form  of  imperfect  contact  capable  of    being  restored   with 
certainty  and  regularity  to  its  normal  condition  substantially 
as  described. 

2.  A  receiving  instrument  consisting  of  a  sensitive  imperfect 
contact  or  contacts,  a  circuit  through  the  contact  or  contacts, 
and  means  for  restoring  the  contact  or  contacts,  with  certainty 
and  regularity,  to  its  or  their  normal  condition  after  the  receipt 
of  an  impulse  substantially  as  described. 

3.  A  receiving  instrument  consisting  of  a  sensitive  imperfect 
contact  or  contacts,  a  circuit  through  the  contact  or  contacts, 
and  means  actuated  by  the  circuit  for  restoring  with  certainty 
and  regularity  the  contact  or  contacts  to  its  or  their  normal 
condition  after  the  receipt  of  an  impulse. 

4.  In  a  receiving  instrument  such  as  is  mentioned  in  claims 
2  and  3,  the  use  of  resistances  possessing  low  self-induction, 
or  other  appliances  for  preventing  the  formation  of  sparks  at 
contacts  or  other  perturbating  effects. 

5.  The  combination  with  the  receivers  such  as  are  mentioned 
in  claims  2  and  3  of  resistances  or  other  appliances  for  pre- 
venting the  self-induction  of  the  receiver  from  affecting  the 
sensitive  contact  or  contacts  substantially  as  described. 

6.  The  combination  with  receivers  such  as  herein  above  re- 
ferred to  of  choking  coils  substantially  as  described. 

7.  In  receiving  instruments  consisting  of  an  imperfect  con- 
tact or  contacts  sensitive  to  electrical  impulses,  the   use  of 
automatically  working  devices  for  the  purpose  of  restoring  the 
contact   or   contacts  with   certainty   and   regularity   to   their 
normal  condition  after  the  receipt  of  an  impulse  substantially 
as  herein  described. 

8.  Constructing  a  sensitive  non-conductor  capable  of  being 
made  a  conductor  by  electrical  impulses  of  two  metal  plugs  or 
their  equivalents,  and  confining  between  them  some  substance 
such  as  described. 

9.  A  sensitive  tube  containing  a  mixture  of  two  or  more 
powders,  grains,  or  filings,  substantially  as  described. 


3-10  APPENDIX   E. 

10.  The  use  of  mercury  in  sensitive  imperfect  electrical  con- 
tacts substantially  as  described. 

11.  A  receiving  instrument  having  a  local  circuit,  including 
a  sensitive  imperfect  electrical  contact  or  contacts,  and  a  relay 
operating   an   instrument   for   producing   signals,    actions,   or 
manifestations  substantially  as  described. 

12.  Sensitive  contacts  in  which  a  column  of  powder  or  filings 
(or   their   equivalent)   is  divided   into   sections  by  means   of 
metallic  stops  or  plugs  substantially  as  described. 

13.  Keceivers  substantially  as  described  and  shown  in  figures 
5  and  8. 

14.  Transmitters  substantially  as  described  and  shown  at 
figures  6  and  7. 

15.  A  receiver  consisting  of  a  sensitive  tube  or  other  imper- 
fect contact  inserted  in  a  circuit,  one  end  of  the  sensitive  tube 
or  other  imperfect  contact  being  put  to  earth  whilst  the  other 
end  is  connected  to  an  insulated  conductor. 

16.  The  combination  of  a  transmitter  having  one  end  ot  its 
sparking  appliance  or  poles  connected  to  earth,  and  the  other 
to  an  insulated  conductor,  with  a  receiver  as  is  mentioned  in 
claim  15. 

17.  A  receiver  consisting  of  a  sensitive  tube  or  other  imper- 
fect contact  inserted  in  a  circuit,  and  earth  connections  to  each 
end  of  the  sensitive  contact  or  tube  through  condensers  or  their 
equivalent. 

18.  The  modifications  in  the  transmitters  and  receivers,  in 
which  the  suspended  plates  are  replaced  by  cylinders  or  the 
like  placed  hat- wise  on  poles,  or  by  balloons  or  kites  substan- 
tially as  described. 

19.  An  induction  coil  having  a  revolving  make  and  break 
substantially  as  and  for  the  purposes  described. 

Dated  this  2nd  day  of  March  1807. 

GUGLIELMO  MAKCONL 


...         Of  THE 

UNIVERSITY 

O'r         ,,Tx 

£ALIF 


INDEX. 


Action-at-a-distance  v.  action- 
by-contact  referred  to,  177, 
191. 

Air  vibrations,  table  of,  192. 

Armstrong,  Lord,  on  skin-deep 
penetration  of  high  -  tension 
electricity,  286. 

Ascoli,  Prof.,  on  Marconi's  law 
of  distance,  215. 

Auticatelephor  of  Edwards,  10. 

Balloons,  to  support  telegraph 
wires,  67. 

Bell,  Prof.  Graham,  his  photo- 
phone  referred  to,  6 — experi- 
ments in  signalling  through 
water,  91  —  applicable  to 
ships  at  sea,  93. 

Beron,  plan  for  wireless  tele- 
graph referred  to,  65. 

Blake,  Prof.  Lucien,  induction 
between  neigbouring  circuits, 
80  —  experiments  on  com- 
munication with  lightships, 
121 — and  with  moving  vessel, 
122. 

Blissett,  signalling  across  water 
referred  to,  111. 

Blondell,  Prof.,  his  detector, 
250. 

Bonelli,  experiments  in  wireless 
telegraphy  referred  to,  29 — 


system  of  train  signals  re- 
ferred to,  101. 

Bose,  Prof.  Chunder,  his  ex- 
citer, 192 — his  detector,  206. 

Bouchotte,  experiments  in  wire- 
less telegraphy  referred  to, 
29. 

Bourbouze,  signalling  through 
water  of  the  Seine,  66. 

Branly,  Prof.  E.,  his  detector 
or  "  radio  -  conductor,"  194, 
199 — on  obstacles  to  Hertzian 
waves,  222  —  researches  on 
conductivity  under  electrical 
influence,  292  et  seq. 

Brooke,  Sir  W.  O'S.,  experi- 
ments in  signalling  through 
water,  39. 

Brown,  A.  C.,  his  invention  of 
the  photophone  referred  to, 
6  —  on  train  telegraphy  by 
induction,  101 — on  signalling 
across  breaks  in  cables,  175. 

Call  -  bell  arrangements,  160, 
172. 

Calzecchi-Onesti,  early  observa- 
tions on  the  coherer  prin- 
ciple, 198 — his  detector,  199 
— as  a  seismological  recorder, 
ib. 

Carty,    on    the    electro  -  static 


342 


INDEX. 


effects  in  telephone  circuits, 
referred  to,  143. 

Channing,  I)r,  on  distant  cur- 
rents picked  up  in  telephone 
circuits,  76  —  on  induction 
between  two  telephone  cir- 
cuits, 80. 

Clerk-Maxwell,  Prof.,  his  elec- 
tro-magnetic theory  of  light, 
177,  265  et  seq.,  280  et  seq. 

Coherer.     See  Detector. 

Condenser,  use  of,  in  wireless 
telegraphy,  85,  95. 

Crookes,  Sir  W.,  forecast  of  the 
Marconi  system,  201  —  his 
letter  to  the  author  re  Prof. 
Hughes's  early  experiments, 
305. 

Currents,  electric,  Poynting's 
theory  of,  184 — modern  views 
of,  280  et  seq. 

D'Asar,  Russo,  experiments  in 
Hertz  -  wave  telegraphy  re- 
ferred to,  233. 

Davy,  Edward,  method  of  sig- 
nalling based  on  electricity 
and  sound,  6 — first  inventor 
of  the  relay  principle,  7,  38— 
proposals  for  train  signalling, 
100. 

De  la  Rive,  Prof.  A.,  explana- 
tion of  "Galvanic  Music " re- 
ferred to,  90. 

De  la  Rive,  L.     See  Sarasin. 

Dering,  G,  E.,  early  telegraphic 
apparatus,  48 — his  lightning- 
guards  anticipate  those  of 
Siemens  and  others,  ib.  — 
proposals  for  bare-wire  sub- 
aqueous telegraph,  49 — act- 
ually attempted,  53. 

Detector,  Highton's  gold-leaf, 
42 -Prof.  Hertz's,  181,  194 
— for  Hertzian  waves,  vari- 
ous, 194  et  seq.,  249,  306  ft. 
'  seq. — action  of  detector,  210. 


Dolbcar,  Prof.,  electro  -  static 
method  of  telegraphy,  94 — 
compared  with  Marconi's,  97 
— successful  up  to  13  miles, 
99. 

Douat,  experiments  in  wireless 
telegraphy  referred  to,  29. 

Dufour,  H. ,  inductive  effect  of 
one  circuit  on  a  distant  one, 
79. 

Earth,   conductivity  of  the,  3, 

83,  136. 
ti        electrification  of  the,  2, 

81. 
ii        part  of  the,  in  Preece's 

system,  152. 
i»        part  of  the,  in  Marconi's 

system,  214. 
Earth-battery,  first  proposal  of 

the,  20. 

ti  applications     of 

the,  20, 2 1,72. 

Earth  circuit,  discovery  of  the, 

3. 
Earth  -  currents     or     leakages, 

140. 
Earthquakes,  suggested  electric 

origin  of,  2. 

Edison,  T.  A.,  "  Etheric  Force  " 
of,   referred    to,    98,    309  — 
electro  -  static     train     teleg- 
raphy,  103  —  potentiality  of 
the  system,   108 — its  use  on 
railways,  1 09 — application  to 
long-distances,  110. 
Edwards,     his    auticatelephor 
(?  a  pneumatic  telegraph),  9. 
Electric  eye,  the,  5,  180,  270. 
Electricity,   definitions    of,    by 

Faraday  and  others,  139. 
Electricity,     atmospheric,     for 

signalling,  68. 
ii  atmospheric,    ap- 

paratus for  ob- 
serving, 204, 
206. 


INDEX. 


343 


Electricity  and  light,  relation 
between,  262  et  seq. 

Electro-magnets,  Morse's,  31 — 
Edward  Davy's,  Page's,  and 
Royal  House's  referred  to,  38. 

Ether  vibrations,  table  of,  11)2. 
ti  theory  of  the,  262  et  wq. 

Etheric  Force,  the,  referred  to, 
OS,  311. 

Evershed,  Sydney,  attempt  to 
communicate  with  lightships 
by  induction  through  coils, 
127— his  delicate  relay,  100. 

Exciters,  Hertzian-wave,  vari- 
ous, 181,  192,  193,  207,  247. 

Exploding  by  Hertz- waves  re- 
ferred to,  72,  212,  223. 

Fahie,  J.  J.,  suggestions  for  a 
photophone  referred  to,  6 — 
on  signalling  across  breaks  in 
telegraph  wires,  175 — letters 
to,  from  Profs.  Crook es  and 
Hughes,  305. 

Faraday,  Prof.,  definition  of 
electricity,  139 — greatness  of 
his  work  referred  to,  2G5. 

Fessenden,  Prof.,  transformer 
for  Hertz -wave  telegraphy, 
239. 

Fleming,  Prof.,  on  Marconi's 
cross  -  Channel  experiments, 
236. 

Gauss,  Prof.,  suggests  use  of 
railway  rails  in  place  of  wires, 
3 — suggests  use  of  earth-bat- 
tery in  telegraphy,  20. 

Gintl,  experiments  in  wireless 
telegraphy  referred  to,  29. 

Gott,  J.,  on  earth  electrification 
and  "leakages,"  80  —  their 
applicability  to  telegraphy 
without  wires,  82. 

Granier,  his  balloon- supported 
telegraph  line  referred  to, 
67. 


Granville,  W.  P.  See  Smith 
and  Granville. 

Guarini-Foresio,  automatic  re- 
peater for  Marconi  signals 
referred  to,  224. 

Haworth,  John,  unintelligible 
proposals  for  a  wireless  tele- 
graph, 56 — extracts  from  his 
patent  specification,  58  — 
Cromwell  Varley's  comments 
upon,  61. 

Heaviside,  A.  W.,  signalling  to 
bottom  of  coal-pit  by  electro- 
magnetic induction,  146. 

Henry,  Prof.  Joseph,  observa- 
tions of  (probably)  electric- 
wave  effects,  90,  311— his 
life  and  work  referred  to, 
90  —  on  high  tension  and 
lightning  discharges  along 
conductors,  184,  277  —  on 
proper  construction  of  light- 
ning-conductors, 279. 

Hertz,  Prof.,  researches  on  elec- 
tric oscillations,  how  started, 
179  — his  exciter,  180  — his 
detector,  181 — effect  of  re- 
sonance, ib. — effect  of  ultra- 
violet light,  182  — electric 
waves  in  space,  ib. — velocity 
of,  183— reflection  of,  184— 
propagation  along  wires,  ib. 
— screening  eifect  of  metals, 
185  —  electric  radiation  190 
—  electric  refraction,  191  — 
value  of  his  work,  ib.,  272, 
283. 

Highton,  Henry,  proposals  for 
(1)  wireless,  (2)  bare  wire, 
and  (3)  badly  insulated  wire 
telegraphs,  40,  45 — his  gold- 
leaf  detector,  42  —  his  new 
insulating  material,  47 — and 
other  inventions,  48. 

Hughes,  Prof.,  remedy  for  in- 
duction between'  telegraph 


344 


INDEX. 


wires  referred  to,  75  —  ex- 
periments in  wireless  teleg- 
graphy,  203,  305  et  seq.— 
discovers  electric  waves,  306 
— his  detectors,  ib.  et  seq. 

Impedance  (choking)  coils,  good 
effect  of,  211. 

Impulsion-cell  as  a  detector  re- 
ferred to,  194. 

Induction,  between  wires  on 
same  poles,  early  notice  of, 
75 — Prof.  Hughes's  remedy 
for,  ib. — effect  of  one  tele- 
phone circuit  on  another,  80 
— electro-magnetic,  early  ob- 
servations on,  89 — Preece  on, 
143  —  electro -static,  141  — 
Carty  on,  143. 

Insulation,  telephony  without, 
80. 

Interference  in  Hertz-wave  sig- 
nalling, 241,  243,  245,  259. 

Jackson,  Capt.,  R.N.,  experi- 
ments in  Hertz-wave  signal- 
ling, 206. 

Jervis-Smith,  Rev.  F.,  experi- 
ments on  Hertz-wave  signal- 
ling, 206. 

Johnston,  W.  P., experiments  on 
signalling  across  rivers,  111. 

Joule,  welding  by  electricity 
referred  to,  23  —  elongation 
of  iron  under  magnetic  strain 
referred  to,  90. 

Kelvin,  Lord,  referred  to,  29, 
38,  178,  229,  266,  272,  286 
— his  law  of  electric  oscilla- 
tions, 179. 

Kerr,  Dr,  researches  on  light, 
267. 

Langdon  -  Davies,  his  phono- 
phore,  wide-spreading  effects 
of,  124,  260. 


Laws  of  distance,  Stevenson's, 
1 26  —  Preece's,  1 47  —  Mar- 
coni's, 214 — Ascoli's,  215. 

Le  Bon,  on  obstacles  to  Mar- 
coni waves,  221. 

Light  and  electricity,  relation 
between,  262  et  seq. — electric 
light,  Lindsay's,  18 — ultra- 
violet, effect  of,  on  sparks, 
182 — signalling  by  means  of, 
ib. 

Light  of  the  future,  274. 

ti      electro  -  magnetic   theory 
of,  177,  265. 

Lightning  and  the  telephone, 
75 — and  Marconi  apparatus, 
214,  227 — oscillatory  nature 
of,  287 — magnetises  a  needle, 
311. 

Lightning-conductors,  construc- 
tion of,  214,  277, 
287. 
ii         guards,  48,  194,  196. 

Lindsay,  J.  B.,  his  life  and 
work,  13 — on  future  uses  of 
electricity,  16,  20 — experi- 
ments in  electric  lighting,  18 
— proposals  for  a  telegraph 
to  America  by  means  of 
bare  wire  and  earth-batteries, 
20 — welding  by  electricity, 
23  —  telegraphy  without 
wires,  ib.  —  Preece's  recol- 
lection of,  28 — paper  read 
before  British  Association, 
29  —  death  and  memorial, 
32. 

Lodge,  Prof.,  law  of  distance 
in  coil  method,  126  —  con- 
ception of  electricity,  139 — 
his  detectors,  193,  250 — his 
lightning  -  guard,  194  —  his 
syntonised- wave  method,  246 
et  seq. — his  newest  proposals, 
254  —  on  relation  between 
light  and  electricity,  262  et 
seq. 


INDEX. 


345 


Loom  is,  Mahlon,  use  of  atmos- 
pheric electricity  fur  signal- 
ling, 68. 

Marconi,  G.,  merit  of  his  work, 
200, 22,5 — apparatus  tor  short 
distances,  206 — for  long  dis- 
tances, 212 — law  of  distance, 
214  — exciters,  207,  232  — 
detectors,  208  —  speed  of 
working,  212 — theory  of  his 
method,  215 — first  trials,  217 
- — Italian  experiments,  219 — 
obstacles  to  signalling,  220 — 
effect  of  lightning,  227 — public 
trials  and  installations,  228 
et  seq.  —  for  ships  in  a  fog, 
232  —  new  transformer,  237 
—  American  Navy  Board 
report,  242  —  interference 
effects,  2.45 — field  of  utility, 
254  et  seq. — future  of,  259 — 
first  patent  specification,  re- 
print of,  316  at  stq. 

Mdhuish,  \V.  F. ,  bare  wire 
system  for  river  crossings, 
114. 

Metals,  screening  effect  of,  185 
et  seq. 

Microphone,  discovery  of  the, 
308. 

Minchin,  Prof.,  impulsion-cell 
as  a  detector,  194 — his  ex- 
periments referred  to,  204. 

Morse,  Prof.,  experiments  in 
signalling  across  water,  10 — 
his  first  electro-magnets,  31. 

Mower,  J.  H.,  signalling  across 
Atlantic  without  wires,  65. 

Munro,  John,  on  Prof.  Hughes's 
researches  quoted,  311  et  seq. 

Music,  galvanic,  referred  to, 
89. 

Nelson,  Henry,  communication 
between  ships  at  sea  referred 

to,  82. 


Obstacles,  effect  of,  in  Marconi 

system,  220.     See  also  Metals 

and  Water. 
Oscillations,    electric,    law    of, 

178 — Hertz's   researches    on, 

179  et  seq. 
Oscillator.     See  Exciter. 

Page,  Prof.,  his  electro-magnets 
referred  to,  38 — discovery  of 
galvanic  music  referred  to, 
89. 

Phonophore,  wide  -  spreading 
effects  of,  124,  260. 

Photophone,  suggestions  for,  by 
Fahie  and  Brown,  6 — Graham 
Bell's,  ib. 

Pierce,  Prof.,  on  sensitiveness 
of  the  telephone,  74. 

Popoff,  Prof.,  experiments  in 
Hertz-wave  telegraphy,  204. 

Poynting,  Prof.,  theory  of  elec- 
tric currents,  184. 

Preece,  Sir  W.,  connection  with 
Lindsay's  early  experiments, 
28 — on  currents  through  the 
earth,  136,  140,  143— signal- 
ling across  the  Solent,  137 — 
nature  of  electricity,  139 — 
electro-static  induction,  141 
— electro-magnetic  induction, 
143  —  signalling  by  electro- 
magnetic induction,  144 — 
laws  of  current  and  signal- 
ling distance,  146 — practical 
trials  of  system,  147  —  on 
screening  effect  of  water,  146, 
150  —  theoretical  considera- 
tions, 153  — utility  of  system, 
157  —  inter  -  planetary  com- 
munication, 158  —  practical 
installations,  ib.  —  new  ex- 
periments referred  to,  160 — 
on  obstacles  to  Hertz-waves, 
222. 

Radiation,  electric.    See  Waves. 


346 


INDEX. 


Railways,  use  of  rails  for  signal- 
ling, 3  —  telegraph  systems 
for,  referred  to,  100. 

Rathbone,  Charles,  on  distant 
currents  picked  up  by  tele- 
phone, 75. 

Rathenau,  Prof.  E.,  experi- 
ments in  signalling  across 
water,  130. 

Rayleigh,  Lord,  sensitiveness  of 
telephone  to  high  frequency 
currents,  132. 

Reflection,  electric.    See  Waves. 

Reflectors  for  Hertz-wave  tele- 
graphs, 212,  217,  232, 
255. 

Refraction,  electric.    See  Waves. 

Relays,  first  proposed  by  Ed- 
ward Davy,  7,  38 — Wilkins' 
and  others,  38 — Evershed's, 
160— Smith  and  Granville's, 
172  —  Stevenson's,  206  —  for 
Hertz-wave  telegraphs,  224. 

Resonance,  electric,  90,  151, 
153,  181,  211,  246,  254, 
315. 

Resonator,  electric.  See  De- 
tector. 

Righi,  Prof.,  his  exciter,  192, 
193,  207— his  detector,  194. 

Rovelli,  his  detector  referred 
to,  206. 

Rowland,  Prof.,  on  the  nature 
of  electric  currents,  280 — on 
lightning  and  lightning-con- 
ductors, 287. 

Rutherford,  Prof.,  experiments 
in  Hertz  -  wave  telegraphy, 
204. 

Sacher,  Prof.,  inductive  effect 
of  one  circuit  on  a  distant 
one,  79. 

Salvd,  glimmering  of  electrifi- 
cation of  the  earth  and  its 
applicability  to  signalling 
across  the  seas,  1. 


Sarasin  and  De  la  Rive,  on 
velocity  of  electric  waves, 
183  — their  exciter,  193. 

Schiifer,  Bela,  experiments  on 
Hertz-wave  telegraphy,  233. 

Schilling,  Baron,  referred  to,  2 
— his  needle  telegraph,  20. 

Schuster,  Prof.,  glimmering  of 
the  microphonic  principle, 
308. 

Schwendler,  experiments  on 
signalling  across  water  re- 
ferred to,  111. 

Selenium  effect,  194 — discovery 
of,  26S. 

Senlicq  d'Andres,  signalling 
proposal  based  on  electricity 
and  sound,  8. 

Sennett,  A.  R. ,  signalling  pro- 
posal based  on  electricity  and 
sound,  8. 

Shadows,  electric,  190. 

Siemens'  Serrated- Plate  Light- 
ning-Guard anticipated,  48. 

Slaby,  Prof.,  experiments  in 
Hertz-wave  telegraphy,  218, 
224 — tribute  to  Marconi,  225 
—detector,  228. 

Smith,  Willoughby,  on  electro- 
magnetic induction,  89 — sug- 
gests train  telegraphy  by 
induction,  102 — on  communi- 
cation with  lighthouses  and 
lightships,  161. 

Smith,  Willoughby  S.,  and 
Granville,  W.  P.,  modifica- 
tion of  Willoughby  Smith's 
plan,  165  —  practically  in- 
stalled, 169  — novel  "call" 
apparatus,  172  —  difficulties 
of  the  installation,  173 — an 
old  friend  in  a  new  guise, 
174. 

Sommerring,  experiment  in  sig- 
nalling through  water,  2. 

Steinheil,  Prof.,  discovery  of 
the  earth-circuit,  3 — experi- 


INDEX. 


347 


ments  in  signalling  through 
the  earth,  4  —  suggests  a 
thermophone,  5 — experiments 
with  earth-batteries  referred 
to,  20. 

Stevenson,  C.  A.,  plans  for 
communicating  with  ships, 
119 — tried  in  America,  121 
—  plan  based  on  induction 
between  coils,  122 — law  of 
distance,  126 — attempted  ap- 
plication by  Evershed,  127 — 
metallic-powder  relay,  206. 

Stokes,  Prof. ,  influence  on  Prof. 
Hughes 's  researches,  310, 
315. 

Syntony.     See  Resonance. 

Telegraphy,  sympathetic,  re- 
ferred to,  1 — by  electricity 
and  heat,  5 — by  electricity 
and  sound,  6,  8— pneumatic 
and  hydraulic,  10 — by  bare 
wires,  21,  41,46,  50,  72,113— 
conductive  methods,  2,  4,  10, 
2.'},  33,  39,  45,  56,  65,  66,  85, 
91,  111,  120,  130,  137,  161 
— by  atmospheric  electricity, 
08 — by  electro- magnetic  in- 
duction, 88,  101,  102,  122, 
144 — by  electro-static  induc- 
tion, 90,  94,  101,  103— by 
Hertz- waves  (?  Dolbear),  97  — 
Zickler,  182  —  Popoff  and 
others,  204 — Lodge,  »&.,  246 
—  Marconi,  206,  313  - 
Hughes,  305. 

Telegraphy,     train,    early    sys- 
tems, 100. 

ii  wireless,       future 

of,  259  et  >teq. 

Telephone,  compressed-air,  re- 
ferred to,  8 — sensitiveness  to 
stray  currents,  74-80,  136, 
143 — effect  of  lightning  on, 
75 — and  badly  insulated  line, 
80  — sensitiveness  varies  with 


frequency  of  currents,  132 — • 
optical,  referred  to,  134  — 
as  detector  of  Hertz -waves, 
194. 

Telephone  circuits,  electro  - 
static  effects  in,  143. 

Tesla,  Nikola,  his  conception 
of  electricity,  140 — proposals 
for  Hertz  -  wave  telegraphs, 
203,  261— his  oscillators  re- 
ferred to,  208,  228. 

Thermophone,  suggested  by 
Steinheil,  5. 

Thompson,  Prof.  Silvanus,  on 
the  future  of  wireless  teleg- 
raphy, 259. 

Threlfall,  Prof.,  suggestion  of 
a  Hertz-wave  telegraph,  201. 

Train  telegraphy,  early  systems 
of,  100. 

Trowbridge,  Prof.  John,  on  the 
earth  as  a  conductor,  82 — 
signalling  by  conduction 
method,  85  —  by  electro- 
magnetic induction,  87 — by 
electro-static  induction,  90. 

Tuma,  Dr,  experiments  in  Hertx- 
wave  telegraphy  referred  to, 
228. 

Tuning,    electric.      See    Reson- 


Van  Reese,  experiments  in 
wireless  signalling  referred 
to,  29. 

Varley,  Cromwell,  comments  on 
Haworth's  plan,  61 — his  own 
experiments  in  wireless  sig- 
nalling, 63. 

Varley,  S.  A.,  observations  of 
coherer  principle,  1 94  —  his 
lightning-bridge,  196. 

Vibrations,  ether  and  air,  table 
of,  192. 

Water,  screening  effect  of,  128, 
146,  150,  223. 


348 


INDEX. 


Waves,  electric,  formation  of, 
178,  180  — velocity  of,  183 
— reflection  of,  184  —  along 
wires,  ib.  —  radiation  and 
refraction  of,  190  —  various 
lengths  of,  192,  208,  213. 

Wehnelt,  his  electrolytic  con- 
tact -  breaker  referred  to, 
208. 

Welding,  electric,  23. 

Weston,    his    relay   and    volt- 


meter, 38,  39  — his  galvan- 
ometer referred  to,  227. 
Wilkins,  J.  W. ,  experiments  in 
wireless  telegraphy,  33 — his 
detector,  36  —  its  use  in 
America,  38 — anticipates  the 
Weston  relay,  39. 

Zickler,  Prof.  K.,  use  of  ultra- 
violet light  for  signalling  by 
Hertz- waves,  182. 


THE    END. 


BV   WILLIAM    BI.Af'KWOOD   AND   SON'S. 


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BRADDON.    Thirty  Years  of  Shikar.    By  Sir  EDWARD  BRADDON, 

K.C.M.G.  With  Illustrations  by  G.  D.  Giles,  and  Map  of  Oudh  Forest  Tracts 
and  Nepal  Terai.  Demy  8vo,  18s. 

BROWN,     The  Forester  :  A  Practical  Treatise  on  the  Planting 

and  Tending  of  Forest-trees  and  the  General  Management  of  Woodlands.  By 
JAMES  BROWN,  LL.D.  Sixth  Edition,  Enlarged.  Edited  by  JOHN  NISBET,  D.CBc., 
Author  of  '  British  Forest  Trees, '  &c.  In  2  vols.  royal  8vo,  with  350  Illustra- 
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BRUCE. 

In  Clover  and  Heather.    Poems  by  WALLACE  BRUCE.     New 

and  Enlarged  Edition.    Crown  8vo,  3s.  6d. 

A  limited  number  of  Copies  of  the  First  Edition,  on  large  hand-made  paper,  12s.  fid. 

Here's   a    Hand.      Addresses    and    Poems.      Crown   8vo,   5s. 

Large  Paper  Edition,  limited  to  100  copies,  price  21s. 

BURBIDGE. 

Domestic  Floriculture,  Window  Gardening,  and  Floral  Decora- 
tions. Being  Practical  Directions  for  the  Propagation,  Culture,  and  Arrangement 
of  Plants  and  Flowers  as  Domestic  Ornaments.  By  P.  W.  BURBIDGE.  Second 
Edition.  Crown  8vo  with  numerous  Illustrations,  7s.  6d. 

Cultivated   Plants :    Their   Propagation    and    Improvement. 

Including  Natural  and  Artificial  Hybridisation,  Raising  from  Seed  Cuttings, 
and  Layers,  Grafting  and  Budding,  as  applied  to  the  Families  and  Genera  ID 
Cultivation.  Crown  8vo,  with  numerous  Illustrations,  IPs.  Cd 

BURKE.     The  Flowering  of  the  Almond  Tree,  and  other  Poems. 

By  CHRISTIAN  BURKE.    Pott  4to,  5s. 

BURROWS. 

The  History  of  the  Foreign  Policy  of   Great   Britain.     By 

MONTAGU  BURROWS,  Chichele  Professor  of  Modern  History  in  the  University  of 
Oxford;  Captain  R.N. ;  F.S.A.,  Ac.;  "Officier  de  1'Instruction  Publique," 
France.  New  Edition,  revised.  Crown  8vo,  6s. 

BURTON. 

The  History  of  Scotland :    From  Agricola's  Invasion  to  the 

Extinction  of  the  last  Jacobite  Insurrection.  By  JOHN  HILL  BURTON,  D.C.L., 
Historiographer- Royal  for  Scotland.  Cheaper  Edition.  In  8  vols.  Crown  8vo, 
3s.  6d.  each. 

The  Book-Hunter.     A  New  Edition,  with  specially  designed 

Title-page  and  Cover  by  JOSEPH  BROWN.  Printed  on  antique  laid  paper  Post 
8vo,  3s.  tid. 

The  Scot  Abroad.     Uniform  with  '  The  Book  -  Hunter.'    Post 

8vo,  3s.  6d. 

BUTE. 

The    Roman    Breviary :    Reformed   by   Order  of    the  Holy 

(Ecumenical  Council  of  Trent ;  Published  by  Order  of  Pope  St  Pius  V.  ;  and 
Revised  by  Clement  VIII.  and  Urban  VIII.  ;  together  with  the  Offices  since 
granted.  Translated  out  of  Latin  into  English  by  JOHN,  MARQUESS  OF  BUTE, 
K.T.  New  Edition,  Revised  and  Enlarged.  In  4  vols.  crown  Svo,  and  in  1  vol. 
crown  4to.  [In  the  press. 

The  Alt  us  of  St  Columba.     With  a   Prose   Paraphrase   and 

Notes.     By  JOHN,  MARQUESS  OF  BUTE,  K.T.     In  paper  cover,  2s.  6d. 

Sermones,     Fratris     Adse,     Ordinh     Prsemonstratensis,     &c. 

Twenty-eight  Discourses  of  Adam  Scotus  of  Whithorn,  hitherto  unpublished ; 
to  which  is  added  a  Collection  of  Notes  by  the  same,  illustrative  of  the  rule  of 
St  Augustine.  Edited,  at  the  desire  of  the  late  MARQUESS  OF  BUTE,  K.T.,  LL.D., 
&c.,  by  AVALTER  DE  GRAY  BIRCH,  LL.D.,  F.S.A.,  of  the  British  Museum,  &c. 
Royal  Svo,  25s.  net. 

BUTE,    MACPHAIL,    AND    LONSDALE.     The  Arms  of  the 

Royal  and  Parliamentary  Burghs  of  Scotland.  By  JOHN,  MARQUESS  OF  BUTE, 
K.T.,  J.  R.  N.  MACPHAIL,  and  H.  W.  LONSDALE.  With  131  Engravings  on 
wood,  and  11  other  Illustrations.  Crown  4to.  £2,  2s.  net. 

BUTE,  STEVENSON,  AND  LONSDALE.     The  Arms  of  the 

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J.  H.  STEVENSON,  and  H.  W.  LONSDALE.  With  numerous  Illustrations.  In  1 
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BUTLER. 

The  Ancient  Church  and  Parish  of  Abernethy,  Perthshire. 

An  Historical  Study.  By  Rev.  D.  BUTLER,  M.A.,  Minister  of  the  Parish.  With 
13  Collotype  Plates  and  a  Map.  Crown  4to,  25s.  net. 

John  Wesley  and  George  Whitefield  in  Scotland;   or,  The 

Influence  of  the  Oxford  Methodists  on  Scottish  Religion.    Crown  8vo,  5s. 

Henry  Scougal  and  the  Oxford  Methodists ;  or,  The  Influence 

of  a  Religious  Teacher  of  the  Scottish  Church.    Fcap.  8vo,  2s.  6d. 

BUTT. 

Theatricals  :  An  Interlude.    By  BEATRICE  MAY  BTTTT.    Crown 

8vo,  6s. 

Miss  Molly.    Cheap  Edition,  2s. 

Eugenie.     Crown  8vo,  6s.  6d. 

Elizabeth,  and  other  Sketches.    Crown  8vo,  6s. 

Delicia.     New  Edition.     Crown  8vo,  2s.  6d. 

CADELL.     Sir  John  Cope  and  the  Rebellion  of  1745.     By  the 

late  General  Sir  ROBERT  CADELL,  K.C.B.,  Royal  (Madras)  Artillery.  With  2 
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CAFFYN.    Seventy-One  not  Out,  the  Reminiscences  of  William 

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Eleven,  of  the  Anglo-American  Team  of  1859,  and  of  the  Anglo-Australian  Teams 
of  1861  and  1863.  Edited  by  "Mid-On."  With  numerous  Illustrations. 
Second  Edition.  Crown  8vo,  6s. 

CAIRD.     Sermons.     By  JOHN    CAIRD,  D.D.,  Principal  of  the 

University  of  Glasgow.    Seventeenth  Thousand.    Fcap.  8vo,  5s. 

CALDWELL.  Schopenhauer's  System  in  its  Philosophical  Sig- 
nificance (the  Shaw  Fellowship  Lectures,  1893).  By  WILLIAM  CALDWELL,  M.A., 
D.Sc.,  Professor  of  Moral  and  Social  Philosophy,  Northwestern  University, 
U.S.A. ;  formerly  Assistant  to  the  Professor  of  Logic  and  Metaphysics,  Edin., 
and  Examiner  in  Philosophy  in  the  University  of  St  Andrews.  Demy  8vo, 
10s.  6d.  net. 

CALL  WELL. 

The  Effect  of  Maritime  Command  on  Land  Campaigns  since 

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Tactics  of  To-day.  Second  Impression.   Crown  8vo,  2s.  6d.  net. 
CAMPBELL.     Balmerino  and  its  Abbey.     A  Parish   History, 

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Minister  of  Balmerino ;  Author  of  '  A  History  of  the  Celtic  Church  in  Scotland.' 
A  New  Edition.  With  an  Appendix  of  Illustrative  Documents,  a  Map  of  the 
Parish,  and  upwards  of  40  Illustrations.  Demy  8vo,  30s.  net. 

CAPES. 

From  Door  to  Door.    By  BERNARD  CAPES.    Crown  8vo,  6s. 

Our  Lady  of  Darkness.     Crown  8vo,  6s. 

The  Adventures  of  the  Comte  de  la  Muette  during  the  Reign 

of  Terror.    Crown  8vo,  6s. 

CAREY.     Monsieur  Martin  :  A  Romance  of  the  Great  Northern 

War.    By  WYMOND  CAREY.    In  1  vol.  crown  8vo.  [In  the  press. 

CHARTERIS.  Canonicity ;  or,  Early  Testimonies  to  the  Exist- 
ence and  Use  of  the  Books  of  the  New  Testament.  Based  on  Kirchhpffer's 
'Quellensammlung.'  Edited  by  A.  H.  CHARTERIS,  D.D.,  Professor  of  Biblical 
Criticism  in  the  University  of  Edinburgh.  8vo,  18s. 

CHESNEY.    The  Dilemma.    By  General  Sir  GEORGE  CHESNEY, 

K.C.B.    A  New  Edition.    Crown  8vo,  2s. 


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CHRISTISON.    Early  Fortifications  in  Scotland :  Motes,  Camps, 

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CHRISTISON,  M.D.,  P.R.C.P.E.,  Secretary  of  the  Society  of  Antiquaries  of  Scot- 
land. With  379  Plans  and  Illustrations  and  3  Maps.  Pcap.  4to,  21s.  net. 

CHURCH  AND  FAITH.    Being  Essays  on  the  Teaching  of  the 

Church  of  England.  By  Dr  WACE,  Dean  FARRAR,  Dr  WRIGHT,  Rev.  R.  E. 
BARTLETT,  Principal  DRURY,  Canon  MEYRICK,  Professor  MOULE,  Chancellor 
SMITH,  MONTAGUE  BARLOW,  Sir  RICHARD  TEMPLE,  Bart.,  E.  H.  BLAKENEY,  and 
J.  T.  TOMLINSON.  With  Introduction  by  the  LORD  BISHOP  OF  HEREFORD.  Second 
Edition.  Post  8vo,  7s.  6d.  net. 

CHURCH  SERVICE  SOCIETY. 

A  Book  of  Common  Order :  being  Forms  of  Worship  issued 

by  the  Church  Service  Society.  Seventh  Edition,  carefully  revised.  In  1  vol. 
crown  8vo,  cloth,  3s.  6d. ;  French  morocco,  5s.  Also  in  2  vols.  crown  8vo, 
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Order  of  Divine  Service  for  Children.    Issued  by  the  Church 

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CLIFFORD.     Bush-Whacking,  and  other  Sketches.     By  HUGH 

CLIFFORD,  C.M.G.,  Author  of  'In  Court  and  Kampong,'  'Studies  in  Brown 
Humanity,'  &c.  Second  Impression.  Crown  8 vo,  6s. 

CLOUSTON.    The  Lunatic  at  Large.     By  J.  STOKER  CLOUSTON. 

Fourth  Impression.     Crown  8vo,  6s.     CHEAP  EDITION,  6d. 

COLLINS. 

A  Scholar  of  his  College.    By  W.   E.  W.   COLLINS.    Crown 

8vo,  6s. 

The  Don  and  the  Undergraduate.     A  Tale  of  St  Hilary's 

College,  Oxford.    Second  Impression.    Crown  8vo,  6s. 

COLQUHOUN.    The  Moor  and  the  Loch.    Containing  Minute 

Instructions  in  all  Highland  Sports,  with  Wanderings  over  Crag  and  Corrie, 
Flood  and  Fell.  By  JOHN  COLQUHOUN.  Cheap  Edition.  With  Illustrations. 
Demy  8vo,  10s.  6d. 

CONDER. 

The  Bible  and  the   East.     By  Lieut. -Col.  C.   R.   CONDER, 

R.E.,  LL.D.,  D.C.L.,  M.R.A.S.,  Author  of  'Tent  Work  in  Palestine,1  &c.  With 
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The  Hittites  and  their  Language.    With  Illustrations  and 

Map.    Post  8vo,  7s.  fid. 

The  Hebrew  Tragedy.    Crown  8vo,  3s. 
CONRAD.    Lord  Jim.    A  Tale.    By  JOSEPH  CONRAD,  Author  of 

'  The  Nigger  of  the  Narcissus,'  '  An  Outcast  of  the  Islands,'  '  Tales  of  Unrest,'  &c. 
Second  Impression.  Crown  8vo,  6s. 

CONSTABLE.    Marrables'   Magnificent  Idea.     By  F.   C.   CON- 
STABLE, Author  of  '  The  Curse  of  Intellect,'  &c.    Crown  8vo,  6s. 

CORNFORD.     R.  L.  Stevenson.      "Modern  English  Writers." 

By  L.  COPE  CORNFORD.    Second  Edition.    Crown  8vo,  2s.  6d. 

COUNTY  HISTORIES  OF   SCOTLAND.     In  demy  8vo  vol- 
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Prehistoric  Scotland  and  its  Place  in  European  Civilisation. 

Being  a  General  Introduction  to  the  "County  Histories  of  Scotland."  By 
ROBERT  MUNRO,  M.A.,  M.D.,  Author  of  'Prehistoric  Problems,1  'The  Lake- 
Dwellings  of  Europe,'  &c.  With  numerous  Illustrations. 

Fife  and  Kinross.     By  ^NEAS  J.  G.  MACKAY,  LL.D.,  Sheriff 

of  these  Counties. 

Dumfries  and  Galloway.    By  Sir  HERBERT  MAXWELL,  Bart., 

M.P.    Second  Edition. 


William  Blackwood  &  Sons.  9 

COUNTY  HISTORIES  OF  SCOTLAND. 

Moray   and    Nairn.      By  CHARLES  RAMPINI;  LL.D.,  Sheriff 

of  Dumfries  and  Galloway. 

Inverness.     By  J.  CAMERON  LEES,  D.D. 

Roxburgh,  Selkirk,  and  Peebles.     By  Sir  GEORGE  DOUGLAS, 

Bart. 

Aberdeen  and  Banff.    By  WILLIAM  WATT,  Editor  of  Aberdeen 

'  Daily  Free  Press.' 

Edinburgh  and  Linlithgow.      By  WILLIAM  KIRK  DICKSON, 

Advocate.  [In  the  press. 

CRAIK.     A  Century  of  Scottish  History.     From  the  Days  before 

the  '45  to  those  within  living  Memory.    By  Sir  HENRY  CRAIK,  K.C.B.,  M.A. 
(Oxon.),  Hon.  LL.D.  (Glasgow).     2  vols.  demy  8vo,  30s.  net. 

CRAWFORD.    Saracinesca.    By  F.  MARION  CRAWFORD,  Author 

of  'Mr  Isaacs,1  &c.,  &c.     Crown  8vo,  3s.  6d.     People's  Edition,  6d. 

CRAWFORD. 

The  Doctrine  of  Holy  Scripture  respecting  the  Atonement. 

By  the  late  THOMAS  J.  CRAWFORD,  D.D.,  Professor  of  Divinity  in  the  University 
of  Edinburgh.     Fifth  Edition.    8vo,  12s. 

The  Fatherhood  of  God,  Considered  in  its  General  and  Special 

Aspects.    Third  Edition,  Revised  and  Enlarged.    8vo,  9s. 

The  Preaching  of  the  Cross,  and  other  Sermons.     8vo,  7s.  6d. 
The  Mysteries  of  Christianity.     Crown  8vo,  7s.  6d. 
CROSS.     Impressions  of  Dante,  and  of  the  New  World  ;  with  a 

Few  Words  on  Bimetallism.     By  J.  W.  CROSS,  Editor  of  '  George  Eliot's  Life,  as 
relsted  in  her  Letters  and  Journals.'    Post  8vo,  6s. 

CURSE  OF  INTELLECT.   Third  Edition.  Fcap.  8vo,  2s.  6d.  net. 
CUSHING.    The  Blacksmith  of  Voe.    By  PAUL  GUSHING,  Author 

of  '  The  Bull  i1  th'  Thorn,'  '  Cut  with  his  own  Diamond.'    Cheap  Edition.    Crown 
8vo,  3s.  6d. 

DA  VIES.      Norfolk    Broads   and   Rivers;   or,  The  Waterways, 

Lagoons,  and  Decoys  of  East  Anglia.     By  G.  CHRISTOPHER  DAVIES.     Illustrated 
with  Seven  full-page  Plates      New  and  Cheaper  Edition.     Crown  8vo,  6s. 

DESCARTES.  The  Method,  Meditations,  and  Principles  of  Philo- 
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New  Introductory  Essay,  Historical  and  Critical,  on  the  Cartesian  Philosophy. 
By  Professor  VJEITCH,  LL.D.,  Glasgow  University.  Eleventh  Edition.  6s.  6d. 

DICKSON.     Life  of  Major-General  Sir  Robert  Murdoch  Smith, 

K.C.M.G.,  Royal  Engineers.    By  his  Son-in-law,  WILLIAM  KIRK  DICKSON.    With 
Portraits  and  other  Illustrations.     Demy  Svo,  15s.  net. 

DOUGLAS. 

The  Ethics  of  John  Stuart  Mill.      By  CHARLES    DOUGLAS, 

M.A.,  D.Sc.,  M.P.,  late  Lecturer  in  Moral  Philosophy,  and  Assistant  to  the  Pro- 
fessor of  Moral  Philosophy  in  the  University  of  Edinburgh.     Post  Svo,  6s.  net. 

John  Stuart  Mill :  A  Study  of  his  Philosophy.     Crown  Svo, 

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DRUMMOND.     A  King's  Pawn.    A  Romance.     By  HAMILTON 

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IO 


List  of  Books  Published  by 


ELIOT. 

George  Eliot's  Life,  Related  in  Her  Letters  and  Journals. 

Arranged  and  Edited  by  her  husband,  J.  W.  CROSS.  With  Portrait  and  other 
Illustrations.  Third  Edition.  3  vols.  post  8vo,  42s. 

George  Eliot's  Life.     With  Portrait  and  other  Illustrations. 

New  Edition,  in  one  volume.    Crown  8vo,  7s.  6d. 

Works  of  George  Eliot  (Library  Edition).     10  volumes,  small 

demy  8vo.  With  Photogravure  Frontispieces,  from  Drawings  by  William 
Hatherell,  R.I.,  Edgar  Bundy,  R.I.,  Byam  Shaw,  R.I.,  A.  A.  Van  Anrooy,  Maurice 
Greiffenhagen,  Claude  A.  Shepperson,  R.I.,  E.  J.  Sullivan,  and  Max  Cowper. 
Gilt  top,  10s.  6d.  net  each  volume. 


ADAM  BEDE. 

THE  MILL  ON  THE  FLOSS. 
ROMOLA. 

SCENES  OF  CLERICAL  LIFE. 
SILAS  MARNER  ;  BROTHER  JACOB  ; 
THE  LIFTED  VEIL. 


FELIX  HOLT,  THE  RADICAL. 

MlDDLEMARCH. 

DANIEL  DERONDA. 

THE  SPANISH  GYPSY  ;  JUBAL. 

ESSAYS;  THEOPHRASTUS  SUCH. 


Works  of  George  Eliot  (Warwick  Edition).    12  volumes,  cloth, 

limp,  gilt  top,  2s.  net  per  volume  ;  leather,  limp,  gilt  top,  2s.  6d.  net  per  volume ; 
leather,  gilt  top,  with  book-marker,  3s.  net  per  volume. 


ADAM  BEDE.     826  pp. 
THE  MILL  ON  THE  FLOSS.     828  pp. 
FELIX  HOLT,  THE  RADICAL.     718  pp. 
ROMOLA.     900  pp. 

SCENES  OF  CLERICAL  LIFE.     624  pp. 
SILAS    MARNER;    BROTHER    JACOB;    THE 
LIFTED  VEIL.     560  pp. 


MIDDLEMARCH.      2  vols.     664  and  630  pp. 
DANIEL    DERONDA.      2    vols.      616    and 

636  pp. 

THE  SPANISH  GYPSY  ;  JUBAL. 
ESSAYS;   THEOPHRASTUS  SUCH. 


Works  of   George   Eliot  (Standard   Edition).      21    volumes, 

crown  8vo.  In  buckram  cloth,  gilt  top,  2s.  6d.  per  vol. ;  or  in  roiburghe 
binding,  3s.  6d.  per  vol. 

ADAM  BEDE.  2  vols.— THB  MILL  ON  THE  FLOSS.  2  vols.— FELIX  HOLT,  THK 
RADICAL.  2  vols.— ROMOLA.  2  vols.— SCENES  OF  CLERICAL  LIFE.  2  vols.— 

MlDDLEMARCH.      3  VOls. — DANIEL   DERONDA.      3  VOlS. — SlLAS  MARNER.      1  VOl. 

— JUBAL.    1  vol.— THK  SPANISH  GYPSY.    1  vol.— ESSAYS.    1  vol.— THEOPHRAS- 
TUS SUCH.    1  vol. 

Life  and   Works    of   George    Eliot    (Cabinet    Edition).      24 

volumes,  crown  8vo,  price  £6.  Also  to  be  had  handsomely  bound  in  half  and  full 
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Novels  by  George  Eliot.    New  Cheap  Edition.    Printed  on 

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Adam  Bede.  3s.  6d.— The  Mill  on  the  Floss.  3s.  6d.— Scenes  of  Clerical  Life. 
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8s.  6d.—  Romols.  3s.  6d.— Middlemarch.  7s.  6d.— Daniel  Deronda.  7s.  6d. 

Essays.    New  Edition.     Crown  8vo,  5s. 

Impressions  of  Theophrastus  Such.     New  Edition.     Crown 

8vo,  5s. 

The  Spanish  Gypsy.    New  Edition.    Crown  8vo,  5s. 

The    Legend    of    Jubal,   and    other    Poems,   Old    and    New. 

New  Edition.    Crown  8vo,  5s. 

Silas  Marner.    New  Edition,  with  Illustrations  by  Keginald 

Birch.     Crown  8vo,  6s. 

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William  Blackwood  &  Sons.  n 


ELIOT. 

Adam  Bede.    Pocket  Edition.     In  3  vols.  pott  8vo,  3s.  net; 

bound  in  leather,  4s.  6d.  net.  Popular  Edition,  royal  8vo,  in  paper  cover, 
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late  ALEXANDER  F.  MITCHELL,  D.D.,  LL.D.,  Emeritus  Professor  of  Church 
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In  Preparation. 


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