on　many　particular　questions　of　dynamics　and　physics。　　When　he
  returned　from　Glasgow　to　Birkenhead　a　correspondence　commenced
  between　us；　which　was　continued　without　intermission　up　to　the　last
  days　of　his　life。　　It　commenced　with　a　well…sustained　fire　of
  letters　on　each　side　about　the　physical　qualities　of　submarine
  cables；　and　the　practical　results　attainable　in　the　way　of　rapid
  signalling　through　them。　　Jenkin　used　excellently　the　valuable
  opportunities　for　experiment　allowed　him　by　Newall；　and　his　partner
  Lewis　Gordon；　at　their　Birkenhead　factory。　　Thus　he　began　definite
  scientific　investigation　of　the　copper　resistance　of　the　conductor；
  and　the　insulating　resistance　and　specific　inductive　capacity　of
  its　gutta…percha　coating；　in　the　factory；　in　various　stages　of
  manufacture；　and　he　was　the　very　first　to　introduce　systematically
  into　practice　the　grand　system　of　absolute　measurement　founded　in
  Germany　by　Gauss　and　Weber。　　The　immense　value　of　this　step；　if
  only　in　respect　to　the　electric　telegraph；　is　amply　appreciated　by
  all　who　remember　or　who　have　read　something　of　the　history　of
  submarine　telegraphy；　but　it　can　scarcely　be　known　generally　how
  much　it　is　due　to　Jenkin。
  Looking　to　the　article　'Telegraph　（Electric）'　in　the　last　volume　of
  the　old　edition　of　the　'Encyclopaedia　Britannica；'　which　was
  published　about　the　year　1861；　we　find　on　record　that　Jenkin's
  measurements　in　absolute　units　of　the　specific　resistance　of　pure
  gutta…percha；　and　of　the　gutta…percha　with　Chatterton's　compound
  constituting　the　insulation　of　the　Red　Sea　cable　of　1859；　are　given
  as　the　only　results　in　the　way　of　absolute　measurements　of　the
  electric　resistance　of　an　insulating　material　which　had　then　been
  made。　　These　remarks　are　prefaced　in　the　'Encyclopaedia'　article　by
  the　following　statement：　　'No　telegraphic　testing　ought　in　future
  to　be　accepted　in　any　department　of　telegraphic　business　which　has
  not　this　definite　character；　although　it　is　only　within　the　last
  year　that　convenient　instruments　for　working；　in　absolute　measure；
  have　been　introduced　at　all；　and　the　whole　system　of　absolute
  measure　is　still　almost　unknown　to　practical　electricians。'
  A　particular　result　of　great　importance　in　respect　to　testing　is
  referred　to　as　follows　in　the　'Encyclopaedia'　article：　　'The
  importance　of　having　results　thus　stated　in　absolute　measure　is
  illustrated　by　the　circumstance；　that　the　writer　has　been　able　at
  once　to　compare　them；　in　the　manner　stated　in　a　preceding
  paragraph；　with　his　own　previous　deductions　from　the　testings　of
  the　Atlantic　cable　during　its　manufacture　in　1857；　and　with　Weber's
  measurements　of　the　specific　resistance　of　copper。'　　It　has　now
  become　universally　adapted　…　first　of　all　in　England；　twenty…two
  years　later　by　Germany；　the　country　of　its　birth；　and　by　France　and
  Italy；　and　all　the　other　countries　of　Europe　and　America　…
  practically　the　whole　scientific　world　…　at　the　Electrical　Congress
  in　Paris　in　the　years　1882　and　1884。
  An　important　paper　of　thirty　quarto　pages　published　in　the
  'Transactions　of　the　Royal　Society'　for　June　19；　1862；　under　the
  title　'Experimental　Researches　on　the　Transmission　of　Electric
  Signals　through　submarine　cables；　Part　I。　　Laws　of　Transmission
  through　various　lengths　of　one　cable；　by　Fleeming　Jenkin；　Esq。；
  communicated　by　C。　Wheatstone；　Esq。；　F。R。S。；'　contains　an　account
  of　a　large　part　of　Jenkin's　experimental　work　in　the　Birkenhead
  factory　during　the　years　1859　and　1860。　　This　paper　is　called　Part
  I。　　Part　II。　alas　never　appeared；　but　something　that　it　would　have
  included　we　can　see　from　the　following　ominous　statement　which　I
  find　near　the　end　of　Part　I。：　　'From　this　value；　the
  electrostatical　capacity　per　unit　of　length　and　the　specific
  inductive　capacity　of　the　dielectric；　could　be　determined。　　These
  points　will；　however；　be　more　fully　treated　of　in　the　second　part
  of　this　paper。'　　Jenkin　had　in　fact　made　a　determination　at
  Birkenhead　of　the　specific　inductive　capacity　of　gutta…percha；　or
  of　the　gutta…percha　and　Chatterton's　compound　constituting　the
  insulation　of　the　cable；　on　which　he　experimented。　　This　was　the
  very　first　true　measurement　of　the　specific　inductive　capacity　of　a
  dielectric　which　had　been　made　after　the　discovery　by　Faraday　of
  the　existence　of　the　property；　and　his　primitive　measurement　of　it
  for　the　three　substances；　glass；　shellac；　and　sulphur；　and　at　the
  time　when　Jenkin　made　his　measurements　the　existence　of　specific
  inductive　capacity　was　either　unknown；　or　ignored；　or　denied；　by
  almost　all　the　scientific　authorities　of　the　day。
  The　original　determination　of　the　microfarad；　brought　out　under　the
  auspices　of　the　British　Association　Committee　on　Electrical
  Standards；　is　due　to　experimental　work　by　Jenkin；　described　in　a
  paper；　'Experiments　on　Capacity；'　constituting　No。　IV。　of　the
  appendix　to　the　Report　presented　by　the　Committee　to　the　Dundee
  Meeting　of　1867。　　No　other　determination；　so　far　as　I　know；　of　this
  important　element　of　electric　measurement　has　hitherto　been　made；
  and　it　is　no　small　thing　to　be　proud　of　in　respect　to　Jenkin's　fame
  as　a　scientific　and　practical　electrician　that　the　microfarad　which
  we　now　all　use　is　his。
  The　British　Association　unit　of　electrical　resistance；　on　which　was
  founded　the　first　practical　approximation　to　absolute　measurement
  on　the　system　of　Gauss　and　Weber；　was　largely　due　to　Jenkin's　zeal
  as　one　of　the　originators；　and　persevering　energy　as　a　working
  member；　of　the　first　Electrical　Standards　Committee。　　The
  experimental　work　of　first　making　practical　standards；　founded　on
  the　absolute　system；　which　led　to　the　unit　now　known　as　the　British
  Association　ohm；　was　chiefly　performed　by　Clerk　Maxwell　and　Jenkin。
  The　realisation　of　the　great　practical　benefit　which　has　resulted
  from　the　experimental　and　scientific　work　of　the　Committee　is
  certainly　in　a　large　measure　due　to　Jenkin's　zeal　and　perseverance
  as　secretary；　and　as　editor　of　the　volume　of　Collected　Reports　of
  the　work　of　the　Committee；　which　extended　over　eight　years；　from
  1861　till　1869。　　The　volume　of　Reports　included　Jenkin's　Cantor
  Lectures　of　January；　1866；　'On　Submarine　Telegraphy；'　through　which
  the　practical　applications　of　the　scientific　principles　for　which
  he　had　worked　so　devotedly　for　eight　years　became　part　of　general
  knowledge　in　the　engineering　profession。
  Jenkin's　scientific　activity　continued　without　abatement　to　the
  end。　　For　the　last　two　years　of　his　life　he　was　much　occupied　with
  a　new　mode　of　electric　locomotion；　a　very　remarkable　invention　of
  his　own；　to　which　he　gave　the　name　of　'Telpherage。'　　He　persevered
  with　endless　ingenuity　in　carrying　out　the　numerous　and　difficult
  mechanical　arrangements　essential　to　the　project；　up　to　the　very
  last　days　of　his　work　in　life。　　He　had　completed　almost　every
  detail　of　the　realisation　of　the　system　which　was　recently　opened
  for　practical　working　at　Glynde；　in　Sussex；　four　months　after　his
  death。
  His　book　on　'Magnetism　and　Electricity；'　published　as　one　of
  Longman's　elementary　series　in　1873；　marked　a　new　departure　in　the
  exposition　of　electricity；　as　the　first　text…book　containing　a
  systematic　application　of　the　quantitative　methods　inaugurated　by
  the　British　Association　Committee　on　Electrical　Standards。　　In　1883
  the　seventh　edition　was　published；　after　there　had　already　appeared
  two　foreign　editions；　one　in　Italian　and　the　other　in　German。
  His　papers　on　purely　engineering　subjects；　though　not　numerous；　are
  interesting　and　valuable。　　Amongst　these　may　be　mentioned　the
  article　'Bridges；'　written　by　him　for　the　ninth　edition　of　the
  'Encyclopaedia　Britannica；'　and　afterwards　republished　as　a
  separate　treatise　in　1876；　and　a　paper　'On　the　Practical
  Application　of　Reciprocal　Figures　to　the　Calculation　of　Strains　in
  Framework；'　read　before　the　Royal　Society　of　Edinburgh；　and
  published　in　the　'Transactions'　of　that　Society　in　1869。　　But
  perhaps　the　most　important　of　all　is　his　paper　'On　the　Application
  of　Graphic　Methods　to　the　Determination　of　the　Efficiency　of
  Machinery；'　read　before　the　Royal　Society　of　Edinburgh；　and
  published　in　the　'Transactions；'　vol。　xxviii。　（1876…78）；　for　which
  he　was　awarded　the　Keith　Gold　Medal。　　This　paper　was　a　continuation
  of　the　subject　treated　in　'Reulaux's　Mechanism；'　and；　recognising
  the　value　of　that　work；　supplied　the　elements　required　to
  constitute　from　Reulaux's　kinematic　system　a　full　machine　receiving
  energy　and　doing　work。
  End