and  the  Magnetic  Relations  of  the  Heavenly  Bodies.       351 
If  by  the  above  researches  of  Quincke  the  production  of  an 
electric  current  by  the  mechanical  displacement  of  liquid  par- 
ticles has  been  proved,  the  reverse  experiments,  showing  the 
generation  of  a  streaming  movement  of  a  liquid  by  making 
an  electrical  current  to  pass  through  it,  have  long  been  known 
under  the  name  of  u  electrical  endosmose." 
The  experiments  made  for  this  purpose,  however,  only  showed 
positive  results  if  a  porous  wall  retarded  the  movements  of  the 
liquids.  Using  tubes  filled  with  liquid  and  passing  an  electrical 
current  through  them,  no  movement  of  the  liquid  could  be  shown, 
although  Wiedemann  in  his  researches  on  this  subject  only  con- 
sidered the  porous  wall  to  be  a  system  of  narrow  tubes,  and  as- 
cribed the  negative  results  to  the  small  quantity  of  electricity 
passing  through  the  liquid. 
Armstrong*,  the  inventor  of  the  steam  electrical  machine,  was 
the  first  to  observe  the  formation  of  a  continuous  current  of  water 
produced  by  an  electrical  current  without  a  porous  diaphragm. 
He  joined  two  well-pointed  glasses  filled  with  water,  and 
standing  at  a  distance  of  0*4  inch  from  each  other,  by  a  damp 
thread  of  silk :  connecting  one  of  the  glasses  with  the  boiler, 
which  was  negatively  electrified,  and  the  other  with  the  earth, 
the  water  flowed  in  the  form  of  a  column  in  the  direction  of  the 
positive  current.  Soon  the  silk  thread  was  pulled  into  the  glass 
which  was  joined  to  the  earth,  and  hence  moved  in  the  opposite 
direction  to  the  column  of  water.  Then  the  water  remained  a  few 
seconds,  sometimes  even  a  few  minutes,  in  the  form  of  an  arc 
between  the  two  glasses.  During  this  time  no  change  of  volume 
of  the  liquids  in  either  of  the  two  glasses  could  be  observed. 
When  particles  of  dust  were  thrown  over  the  surface  of  the 
water,  they  indicated  a  double  current — an  exterior  current  di- 
rected from  the  positive  to  the  negative  glass,  and  an  interior 
current  in  the  opposite  direction. 
A  short  time  ago  Quincke  f  not  only  confirmed  this  fact 
by  careful  experiments  modified  in  many  ways,  but  he  also 
reproduced  it  by  leading  a  strong  current  of  voltaic  electricity 
through  capillary  tubes.  Quincke  proved,  by  finely  divided  sub- 
stances suspended  in  the  moving  liquids,  quite  generally  the 
existence  of  a  double  current. 
He  introduced  grains  of  starch  into  the  liquid  of  a  capillary 
tube  of  about  0*4  millim.  diameter.  When  the  liquid  had 
entirely  filled  the  tube,  an  electrical  current  was  led  through 
*  Phil.  Mag.  vol.  xxiii.  p.  199  (1843).     Pogg.  Ann.  vol  lx.  p.  355. 
t  Pogg.  Ann.  vol.  cxiii.  p.  513  (1861). 
