﻿236 
  Scientific 
  Intelligence. 
  

  

  liquid 
  was 
  seen 
  on 
  the 
  surface 
  of 
  the 
  quicksilver, 
  in 
  quantity 
  

   about 
  2-xjVtt 
  P 
  art 
  °f 
  the 
  column 
  of 
  air. 
  The 
  gasometer 
  was 
  at 
  

   another 
  time 
  charged 
  with 
  carburetted 
  hydrogen, 
  and 
  placed 
  in 
  the 
  

   receiving 
  tube 
  with 
  its 
  mouth 
  immersed 
  in 
  the 
  quicksilver; 
  it 
  was 
  

   subjected 
  to 
  different 
  pressures, 
  and 
  it 
  began 
  to 
  liquefy 
  at 
  about 
  

   40 
  atmospheres, 
  and 
  at 
  1200 
  atmospheres 
  the 
  whole 
  was 
  liquefied. 
  

   " 
  These 
  instances 
  of 
  apparent 
  condensation 
  of 
  gaseous 
  fluids 
  were 
  

   first 
  observed 
  in 
  January, 
  1822 
  ; 
  but 
  for 
  want 
  of 
  chymical 
  knowl- 
  

   edge 
  requisite 
  to 
  ascertain 
  the 
  exact 
  nature 
  of 
  the 
  liquids 
  pro- 
  

   duced, 
  I 
  did 
  not 
  pursue 
  the 
  inquiry 
  further," 
  etc., 
  etc. 
  

  

  9. 
  On 
  the 
  Value 
  of 
  pi 
  for 
  rapid 
  Electrical 
  Oscillations; 
  by 
  

   Charles 
  E. 
  St. 
  John 
  (communicated). 
  — 
  In 
  my 
  paper 
  " 
  On 
  Wave- 
  

   Lengths 
  of 
  Electricity 
  on 
  Iron 
  Wires," 
  in 
  a 
  recent 
  number 
  of 
  this 
  

   Journal 
  (vol. 
  xlviii, 
  311). 
  I 
  gave 
  as 
  a 
  by 
  product 
  of 
  my 
  investiga- 
  

   tion 
  the 
  value 
  ja 
  = 
  385. 
  Various 
  estimates 
  have 
  been 
  made 
  for 
  

   this 
  quantity, 
  but 
  there 
  has 
  been 
  a 
  lack 
  of 
  experimental 
  data. 
  A 
  

   late 
  paper 
  by 
  Ignaz 
  Klemencic 
  in 
  Wiedemann's 
  Annalen, 
  No. 
  12, 
  

   1894, 
  contains 
  the 
  following 
  values 
  of 
  the 
  permeability 
  in 
  case 
  of 
  

   oscillations 
  of 
  100,000 
  per 
  second 
  : 
  

  

  Soft 
  iron 
  ju= 
  118 
  

  

  Steel 
  pi 
  = 
  106 
  to 
  115 
  

  

  This 
  value 
  of 
  jjl 
  led 
  me 
  to 
  reexamine 
  my 
  own 
  results, 
  and 
  recal- 
  

   culation 
  shows 
  an 
  arithmetical 
  error, 
  by 
  which 
  the 
  values 
  were 
  

   multiplied 
  by 
  4, 
  so 
  that 
  the 
  true 
  approximate 
  value 
  yield 
  by 
  the 
  

   data 
  is 
  96, 
  the 
  separate 
  values 
  being 
  pi 
  = 
  107, 
  pi 
  = 
  97*5, 
  pi 
  = 
  83*5 
  

   for 
  the 
  different 
  specimens 
  of 
  iron. 
  These 
  are 
  somewhat 
  lower 
  

   than 
  the 
  results 
  found 
  by 
  Klemencic, 
  but 
  in 
  my 
  experiments 
  the 
  

   rate 
  of 
  oscillation 
  was 
  much 
  higher. 
  

  

  In 
  this 
  connection 
  a 
  remark 
  made 
  by 
  Mr. 
  Oliver 
  Heavyside 
  in 
  

   his 
  Electrical 
  Papers, 
  vol. 
  i, 
  p. 
  361, 
  is 
  interesting. 
  He 
  says 
  that 
  

   pi 
  is 
  eminently 
  variable 
  but 
  that 
  pi 
  = 
  100 
  is 
  a 
  fair 
  average 
  value. 
  

   Both 
  Klemencic's 
  results 
  and 
  my 
  own 
  confirm 
  this 
  assumption. 
  

  

  Berlin, 
  Jan. 
  10, 
  1895. 
  

  

  10. 
  National 
  Academy 
  of 
  Sciences 
  on 
  Electrical 
  Measure- 
  

   ment. 
  — 
  In 
  July, 
  1894, 
  an 
  act 
  of 
  Congress 
  was 
  passed 
  to 
  define 
  

   and 
  establish 
  the 
  units 
  of 
  electrical 
  measure. 
  By 
  this 
  law, 
  

   Congress 
  made 
  it 
  the 
  duty 
  of 
  the 
  National 
  Academy 
  of 
  Sciences 
  

   to 
  prescribe 
  and 
  publish 
  specifications 
  necessary 
  for 
  the 
  practical 
  

   application 
  of 
  the 
  definitions 
  of 
  certain 
  units 
  of 
  electrical 
  measure 
  

   adopted 
  in 
  the 
  act. 
  This 
  law 
  (H. 
  R. 
  6500), 
  approved 
  July 
  12, 
  

   1894, 
  is 
  as 
  follows: 
  — 
  

  

  An 
  Act 
  to 
  Define 
  and 
  Establish 
  the 
  Units 
  of 
  Electrical 
  Measure. 
  

  

  Be 
  it 
  enacted 
  by 
  the 
  Senate 
  and 
  House 
  of 
  Representatives 
  of 
  the 
  United 
  States 
  of 
  

   America 
  in 
  Congress 
  assembled, 
  That 
  from 
  and 
  after 
  the 
  passage 
  of 
  this 
  Act 
  the 
  

   legal 
  units 
  of 
  electrical 
  measure 
  in 
  the 
  United 
  States 
  shall 
  be 
  as 
  follows 
  : 
  

  

  First. 
  The 
  unit 
  of 
  resistance 
  shall 
  be 
  what 
  is 
  known 
  as 
  the 
  international 
  ohm, 
  

   which 
  is 
  substantially 
  equal 
  to 
  one 
  thousand 
  million 
  units 
  of 
  resistance 
  of 
  the 
  

   centimeter-gram-second 
  system 
  of 
  electro-magnetic 
  units, 
  and 
  is 
  represented 
  by 
  

   the 
  resistance 
  offered 
  to 
  an 
  unvarying 
  electric 
  current 
  by 
  a 
  column 
  of 
  mercury 
  at 
  

  

  