﻿470 
  

  

  Mr. 
  J. 
  Perry 
  on 
  the 
  

  

  [June 
  10, 
  

  

  Twenty 
  flint-glass 
  jars, 
  of 
  the 
  shape 
  shown 
  in 
  fig. 
  1, 
  are 
  now 
  being 
  

   examined. 
  The 
  composition 
  of 
  the 
  glass 
  of 
  each 
  jar 
  is 
  known 
  to 
  

   the 
  manufacturer, 
  and 
  glass 
  of 
  the 
  same 
  composition 
  as 
  that 
  of 
  any 
  

   particular 
  jar 
  is 
  readily 
  to 
  be 
  obtained. 
  The 
  diameter 
  of 
  the 
  bulbs 
  is 
  

   about 
  9-5 
  centims. 
  and 
  their 
  thickness 
  about 
  0*25 
  centim. 
  A 
  jar 
  is 
  filled 
  

   with 
  water 
  nearly 
  to 
  the 
  top 
  of 
  the 
  stem. 
  A 
  wet 
  cloth 
  covering 
  all 
  parts 
  

   of 
  the 
  bulb 
  and 
  stem 
  below 
  the 
  level 
  of 
  the 
  insulator 
  forms 
  an 
  outside 
  

   coating. 
  After 
  being 
  sealed, 
  the 
  jars 
  are 
  placed 
  in 
  running 
  water, 
  the 
  

   temperature 
  of 
  which 
  is 
  never 
  greater 
  than 
  50° 
  F., 
  nor 
  less 
  than 
  46° 
  F. 
  

   The 
  following 
  observations 
  have 
  been 
  made 
  : 
  — 
  

  

  Jar 
  No. 
  4. 
  Charged 
  994. 
  Opened 
  after 
  10 
  days. 
  No 
  charge 
  

   remaining. 
  

  

  „ 
  No. 
  9. 
  Charged 
  2085. 
  Opened 
  after 
  7 
  days 
  6 
  hours. 
  The 
  

  

  charge 
  remaining 
  was 
  276. 
  

   „ 
  No. 
  19. 
  Charged 
  1933. 
  Opened 
  after 
  10 
  days. 
  The 
  charge 
  

   remaining 
  was 
  868. 
  

  

  The 
  arrangement 
  shown 
  in 
  fig. 
  2 
  was 
  employed 
  to 
  determine 
  the 
  

   relation 
  between 
  temperature 
  and 
  electric 
  conductivity 
  in 
  a 
  flint-glass 
  

   jar. 
  The 
  jar 
  was 
  filled 
  to 
  the 
  height 
  A, 
  at 
  ordinary 
  temperature, 
  

   with 
  sulphuric 
  acid. 
  A 
  is 
  a 
  cork 
  supporting 
  the 
  glass 
  insulator 
  C, 
  with 
  

   the 
  lead 
  trough 
  D 
  containing 
  pumice 
  moistened 
  with 
  sulphuric 
  acid. 
  A 
  

   piece 
  of 
  platinum 
  wire 
  hangs 
  into 
  the 
  sulphuric 
  acid 
  and 
  terminates 
  in 
  a 
  

   loop 
  at 
  B, 
  so 
  that 
  the 
  inside 
  coating 
  of 
  the 
  jar 
  is 
  insulated. 
  A 
  stiff 
  wire, 
  

   MK, 
  soldered 
  to 
  the 
  electrode 
  of 
  the 
  guard-ring 
  electrometer, 
  passes 
  

   through 
  a 
  small 
  hole 
  at 
  K 
  without 
  touching 
  the 
  glass 
  insulator. 
  Con- 
  

   tact 
  between 
  B 
  and 
  this 
  wire 
  may 
  be 
  made 
  or 
  unmade 
  by 
  a 
  small 
  motion 
  

   of 
  the 
  apparatus. 
  E 
  is 
  surrounded 
  by 
  water. 
  L 
  is 
  a 
  thermometer, 
  J 
  

   a 
  stirrer. 
  I 
  supplies 
  water 
  when 
  necessary. 
  Gr 
  is 
  connected 
  with 
  the 
  

   outside 
  of 
  the 
  electrometer. 
  

  

  To 
  test 
  the 
  cleanness 
  of 
  the 
  glass 
  stem 
  from 
  A 
  to 
  B, 
  a 
  charge 
  was 
  

   given 
  to 
  the 
  jar 
  by 
  the 
  wire 
  KM. 
  After 
  a 
  certain 
  time 
  no 
  further 
  

   diminution 
  of 
  charge 
  was 
  observable 
  during 
  ten 
  minutes, 
  and 
  the 
  electro- 
  

   meter-wire 
  was 
  removed, 
  the 
  hole 
  K 
  being 
  closed. 
  The 
  charge 
  was 
  

   given 
  on 
  Friday. 
  On 
  Monday 
  it 
  was 
  found 
  that 
  less 
  than 
  20 
  per 
  cent, 
  

   had 
  been 
  lost, 
  a 
  proof 
  that 
  the 
  stem 
  was 
  clean, 
  and 
  that 
  the 
  insulation- 
  

   resistance 
  of 
  the 
  sides 
  of 
  the 
  bulb 
  was 
  very 
  considerable. 
  

  

  The 
  first 
  results 
  obtained 
  by 
  the 
  author 
  are 
  given 
  here 
  in 
  preference 
  

   to 
  those 
  which 
  have 
  since 
  been 
  obtained. 
  They 
  exhibit 
  the 
  joint 
  effects 
  

   of 
  polarization 
  and 
  true 
  conductivity, 
  and 
  are 
  instructive 
  when 
  examined 
  

   along 
  with 
  the 
  table 
  of 
  approximately 
  true 
  conductivity 
  given 
  below. 
  

   The 
  jar 
  was 
  charged 
  by 
  an 
  electrophorus 
  ; 
  when 
  polarization 
  had 
  sen- 
  

   sibly 
  ceased, 
  a 
  lamp 
  was 
  placed 
  under 
  the 
  vessel. 
  

  

  The 
  change 
  of 
  temperature 
  between 
  successive 
  readings 
  was 
  pretty 
  

   regular, 
  except 
  when 
  water 
  was 
  poured 
  in. 
  When 
  hot 
  water 
  was 
  poured 
  

   in 
  the 
  stirrer 
  was 
  kept 
  in 
  rapid 
  motion. 
  

  

  