﻿878 
  Prof. 
  McLennan 
  and 
  Mr. 
  Keys 
  on 
  the 
  Electrical 
  

   II. 
  Preliminary 
  Experiments. 
  

  

  In 
  order 
  to 
  obtain 
  an 
  estimate 
  o£ 
  the 
  insulating 
  power 
  of 
  

   liquid 
  air, 
  a 
  clean 
  copper 
  wire 
  A 
  was 
  connected 
  to 
  earth 
  and 
  

   suspended 
  in 
  a 
  Dewar 
  flask 
  0. 
  A 
  second 
  copper 
  wire 
  B 
  was 
  

   also 
  suspended 
  in 
  the 
  flask 
  in 
  such 
  a 
  way 
  as 
  to 
  touch 
  neither 
  

   the 
  wire 
  A, 
  nor 
  the 
  sides 
  or 
  the 
  base 
  of 
  the 
  flask 
  C. 
  The 
  

   wire 
  B 
  was 
  held 
  in 
  position 
  by 
  carefully 
  cleaned 
  ebonite 
  

   supports. 
  It 
  was 
  also 
  connected 
  to 
  the 
  free 
  quadrants 
  of 
  a 
  

   Dolazalek 
  electrometer 
  and 
  to 
  one 
  of 
  the 
  armatures 
  of 
  a 
  

   sulphur 
  condenser 
  of 
  about 
  2300 
  e.s.u. 
  capacity. 
  

  

  In 
  one 
  experiment 
  with 
  this 
  arrangement 
  the 
  electrode 
  B 
  

   and 
  its 
  connected 
  system 
  was 
  charged 
  when 
  the 
  flask 
  was 
  

   empty 
  to 
  one 
  quarter 
  of 
  a 
  volt 
  by 
  means 
  of 
  an 
  auxiliary 
  

   battery. 
  The 
  steady 
  deflexion 
  on 
  the 
  scale 
  corresponding 
  to 
  

   this 
  potential 
  was 
  99*5 
  mm. 
  In 
  order 
  to 
  test 
  the 
  insulating 
  

   power 
  of 
  the 
  system 
  the 
  connexion 
  of 
  the 
  auxiliary 
  battery 
  

   was 
  broken 
  and 
  the 
  leak 
  from 
  the 
  system 
  observed 
  for 
  an 
  

   hour. 
  The 
  rate 
  was 
  found 
  to 
  be 
  '48 
  mm. 
  per 
  minute, 
  which 
  

   was 
  not 
  very 
  high 
  considering 
  that 
  the 
  insulated 
  system 
  was 
  

   supported 
  by 
  a 
  number 
  of 
  pieces 
  of 
  ebonite 
  and 
  that 
  the 
  air 
  

   in 
  the 
  room 
  possessed 
  a 
  very 
  considerable 
  humidity, 
  since 
  the 
  

   experiments 
  were 
  conducted 
  in 
  the 
  summer 
  time. 
  The 
  Dewar 
  

   flask 
  was 
  then 
  filled 
  with 
  carefully 
  filtered 
  liquid 
  air 
  and 
  the 
  

   electrode 
  B 
  and 
  the 
  connected 
  system 
  again 
  charged 
  to 
  £ 
  

   of 
  a 
  volt. 
  The 
  deflexion 
  again 
  was 
  found 
  to 
  be 
  99*5 
  divisions, 
  

   and 
  when 
  the 
  auxiliary 
  battery 
  was 
  disconnected 
  the 
  second 
  

   time 
  the 
  leak 
  from 
  the 
  system 
  for 
  an 
  hour 
  was 
  found 
  to 
  

   be 
  only 
  at 
  the 
  rate 
  of 
  *56 
  mm. 
  p°r 
  minute. 
  This 
  showed 
  

   that 
  the 
  leak 
  from 
  the 
  whole 
  system 
  was 
  practically 
  the 
  

   same 
  when 
  the 
  Dewar 
  flask 
  contained 
  liquid 
  air 
  as 
  when 
  

   it 
  contained 
  only 
  ordinary 
  gaseous 
  air 
  at 
  atmospheric 
  

   pressure. 
  

  

  In 
  a 
  second 
  set 
  of 
  experiments, 
  the 
  Dewar 
  flask 
  was 
  in 
  

   turn 
  filled 
  with 
  amyl, 
  ethyl, 
  and 
  methyl 
  alcohol, 
  and 
  the 
  

   electrode 
  B 
  and 
  attached 
  system 
  was 
  joined, 
  with 
  each 
  liquid 
  

   in 
  the 
  flask 
  in 
  turn, 
  to 
  the 
  ^-volt 
  auxiliary 
  circuit. 
  With 
  the 
  

   amyl 
  alcohol 
  the 
  steady 
  deflexion 
  obtained 
  under 
  these 
  

   circumstances 
  was 
  only 
  97*5 
  mm., 
  with 
  ethyl 
  alcohol 
  76 
  mm., 
  

   and 
  with 
  methyl 
  63 
  mm. 
  With 
  these 
  deflexions 
  the 
  current 
  

   from 
  the 
  battery 
  to 
  the 
  electrode 
  was 
  equal 
  to 
  the 
  current 
  

   from 
  the 
  electrode 
  through 
  the 
  liquid 
  to 
  earth. 
  In 
  all 
  three 
  

   cases 
  when 
  the 
  auxiliary 
  charging 
  current 
  was 
  disconnected, 
  

   the 
  electrode 
  system 
  at 
  once 
  lost 
  its 
  charge 
  and 
  the 
  electro- 
  

   meter 
  needle 
  immediately 
  returned 
  to 
  the 
  zero 
  position. 
  These 
  

  

  