260 
ON  DYNAMIC  OR  VOLTAIC  ELECTRICITY. 
that  the  wire  retains  a  charge  for  more  than  half  an  hour  after 
connexion  with  the  voltaic  battery  has  been  broken.  Professor 
Faraday  stated  that  he  had  witnessed  this  effect  at  the  Gutta 
Percha  Works,  where  one  hundred  miles  of  wire  were  immersed 
in  the  canal.  After  communication  with  a  volatic  battery  of 
great  intensity,  the  wire  became  charged  with  electricity,  in  the 
same  manner  as  a  Leyden  jar,  and  he  received  a  succession  of 
forty  small  shocks  from  the  wire,  after  it  had  been  charged  and 
the  connexion  with  the  battery  broken.  No  such  effect  takes 
place  when  the  coils  of  wire  are  suspended  in  the  air,  because  in 
the  latter  case  there  is  no  external  conducting  substance.  The 
storing-up  of  the  electricity  in  the  wire  when  immersed  in  water 
is  exactly  similar'  to  the  retention  of  electricity  in  a  Leyden  jar, 
and  the  phenomena  exhibited  correspond  exactly  with  those  of 
static  electricity,  proved  in  this  manner,  as  had  previously  been 
proved  by  charging  a  Leyden  jar  with  a  voltaic  battery,  that 
dynamic  and  static  electricity  are  only  different  conditions  of  the 
same  force  ;  one  being  great  in  quantity,  but  of  low  intensity, 
whilst  the  latter  is  small  in  quantity,  but  of  great  intensity.  Some 
interesting  facts  connected  with  the  conduction  of  electricity  have 
also  been  disclosed  by  the  working  of  the  submarine  telegraph, 
which  Professor  Faraday  said  confirmed  the  opinion  he  had  ex~ 
pressed  twenty  years  ago,  that  the  conducting  power  of  bodies 
varies  under  different  circumstances.  In  the  original  experiments 
by  Professor  Wheatstone,  to  ascertain  the  rapidity  with  which 
electricity  is  transmitted  along  copper  wire,  it  was  found  that  an 
electric  spark  passed  through  a  space  of  280,000  miles  in  a 
second.  Subsequent  experiments  with  telegraph  wires  have  given 
different  results,  not  arising  from  inaccuracy  in  the  experiments, 
but  from  conditions  of  the  conducting  wires.  It  has  been  deter- 
mined that  the  velocity  of  transmission  through  iron  wire  is 
16,000  miles  in  a  second,  whilst  it  does  not  exceed  2700  miles  in 
the  same  space  of  time  in  the  telegraph  wire  between  London  and 
Brussels,  a  great  portion  of  which  is  submerged  in  the  German 
Ocean.  The  retardation  of  the  force  in  its  passage  through 
insulated  wire  immersed  in  water  is  calculated  to  have  an  import- 
ant practical  bearing  in  effecting  a  telegraphic  communication 
with  America;  for  it  was  stated  that,  in  a  length  of  2000  miles, 
three  or  more  waves  of  electric  force  might  be  transmitting  at 
the  same  time,  and  that  if  the  current  be  reversed,  a  signal  sent 
