﻿1875.] 
  Stratification 
  in 
  Electrical 
  Discharges 
  in 
  vacuo. 
  357 
  

  

  over 
  the 
  zinc 
  rod 
  of 
  one 
  cell, 
  and 
  drawing 
  the 
  silver 
  wire 
  of 
  the 
  next 
  

   cell 
  through 
  it 
  so 
  as 
  to 
  press 
  against 
  the. 
  zinc. 
  The 
  closing 
  of 
  the 
  

   cells 
  by 
  means 
  of 
  a 
  cork 
  prevents 
  the 
  evaporation 
  of 
  water, 
  and 
  not 
  only 
  

   avoids 
  this 
  serious 
  inconvenience, 
  but 
  also 
  contributes 
  to 
  the 
  effectiveness 
  

   of 
  the 
  insulation. 
  The 
  tubes 
  are 
  grouped 
  in 
  twenties 
  in 
  a 
  sort 
  of 
  test- 
  

   tube 
  rack, 
  having 
  four 
  short 
  ebonite 
  feet, 
  and 
  the 
  whole 
  placed 
  in 
  a 
  

   cabinet 
  2 
  ft. 
  7 
  in. 
  (78*74 
  centhns.) 
  high, 
  2 
  ft. 
  7 
  in. 
  wide, 
  and 
  2 
  ft. 
  7 
  in. 
  deep, 
  

   the 
  top 
  being 
  covered 
  with 
  ebonite 
  to 
  facilitate 
  working 
  with 
  the 
  appa- 
  

   ratus, 
  which 
  is 
  thus 
  placed 
  on 
  it 
  as 
  an 
  insulated 
  table. 
  

  

  The 
  electromotive 
  force 
  of 
  the 
  battery, 
  as 
  compared 
  wdth 
  a 
  Daniell's 
  

   (gravity) 
  battery, 
  was 
  found 
  to 
  be 
  as 
  1*03 
  to 
  1*, 
  its 
  internal 
  resistance 
  

   70 
  ohms 
  per 
  cell, 
  and 
  it 
  evolved 
  0*214 
  cub. 
  centim. 
  (0*0131 
  cub. 
  inches) 
  

   mixed 
  gas 
  per 
  minute 
  when 
  passed 
  through 
  a 
  mixture 
  of 
  1 
  volume 
  of 
  sul- 
  

   phuric 
  acid 
  and 
  8 
  volumes 
  of 
  water 
  in 
  a 
  voltameter 
  having 
  a 
  resistance 
  of 
  

   11 
  ohms. 
  The 
  striking-distance 
  of 
  1080 
  elements 
  between 
  copper 
  wire 
  ter- 
  

   minals, 
  one 
  turned 
  to 
  a 
  point, 
  the 
  other 
  to 
  a 
  flat 
  surface, 
  in 
  air 
  is 
  ^-g- 
  inch 
  

   (0*096 
  millim.) 
  to 
  inch 
  (0*1 
  millim.). 
  The 
  greatest 
  distance 
  through 
  

   which 
  the 
  battery-current 
  would 
  pass 
  continuously 
  in 
  vacuo 
  was 
  12 
  inches 
  

   (30*48 
  centims.) 
  between 
  the 
  terminals 
  in 
  a 
  carbonic 
  acid 
  residual 
  vacuum. 
  

   This 
  battery 
  has 
  been 
  working 
  since 
  the 
  early 
  part 
  of 
  November 
  1874, 
  

   with, 
  practically, 
  a 
  constant 
  electromotive 
  force. 
  

  

  Besides 
  2000 
  more 
  cells 
  like 
  those 
  just 
  described, 
  we 
  are 
  putting 
  

   together 
  2000 
  cells, 
  with 
  the 
  chloride 
  of 
  silver 
  in 
  the 
  form 
  of 
  rodr, 
  

   which 
  are 
  cast 
  on 
  the 
  flattened 
  silver 
  wires, 
  as 
  in 
  a 
  battery 
  described 
  

   by 
  De 
  La 
  E-ue 
  and 
  Miillerf, 
  but 
  in 
  other 
  respects 
  similar 
  to 
  the 
  

   battery 
  above 
  described, 
  the 
  glass 
  tubes 
  being, 
  however, 
  somewhat 
  larger 
  

   in 
  diameter 
  ; 
  the 
  rods 
  of 
  chloride 
  of 
  silver 
  are 
  enclosed 
  in 
  tubes 
  open 
  

   at 
  the 
  top 
  and 
  bottom, 
  and 
  formed 
  of 
  vegetable 
  parchment, 
  the 
  object 
  of 
  

   these 
  vegetable 
  -parchment 
  cases 
  being 
  to 
  prevent 
  contact 
  between 
  the 
  zinc 
  

   and 
  chloride-of-silver 
  rods. 
  The 
  internal 
  resistance 
  of 
  batteries 
  so 
  con- 
  

   structed 
  is 
  only 
  from 
  2 
  to 
  3 
  ohms 
  per 
  cell, 
  according 
  to 
  the 
  distance 
  of 
  the 
  

   zinc 
  and 
  chloride-of-silver 
  rods, 
  and 
  they 
  evolve 
  from 
  3 
  to 
  4*5 
  cub. 
  centims. 
  

   (0*18 
  to 
  0*27 
  cub. 
  inch) 
  per 
  minute, 
  in 
  a 
  voltameter 
  having 
  a 
  resistance 
  

   of 
  11 
  ohms. 
  Their 
  action 
  is 
  remarkably 
  constant. 
  

  

  For 
  the 
  experiments 
  detailed 
  below, 
  vacuum-tubes 
  were 
  generally 
  used 
  

   of 
  about 
  1| 
  to 
  2 
  inches 
  (3*8 
  to 
  5 
  centims.) 
  in 
  diameter, 
  and 
  from 
  6 
  to 
  8 
  inches 
  

   (15*24 
  to 
  20*32 
  centims.) 
  long 
  ; 
  also 
  prolate 
  spheroidal 
  vessels 
  6 
  inches 
  

   by 
  3 
  inches 
  (15*24 
  by 
  7*62 
  centims.). 
  The 
  terminals 
  are 
  of 
  various 
  

   forms, 
  and 
  from 
  4 
  inches 
  to 
  6 
  inches 
  (10*16 
  to 
  15*24 
  centims.) 
  apart, 
  and 
  

   made 
  of 
  aluminium 
  and 
  occasionally 
  of 
  magnesium 
  and 
  of 
  palladium, 
  

  

  * 
  Compared 
  with 
  a 
  Daniell's 
  battery, 
  in 
  which 
  the 
  zinc 
  is 
  immersed 
  in 
  dilute 
  sul- 
  

   phuric 
  acid 
  in 
  a 
  porous 
  cell, 
  its 
  electromotive 
  force 
  is 
  about 
  3 
  per 
  cent, 
  less 
  than 
  the 
  

   Daniell. 
  

  

  t 
  Journal 
  of 
  the 
  Chem. 
  Soc, 
  2nd 
  series, 
  vol. 
  vi. 
  p. 
  488; 
  Comptes 
  Eendus, 
  1868, 
  

   p. 
  794. 
  

  

  