﻿378 
  Scientific 
  Intelligence. 
  

  

  — 
  0-720 
  X 
  10 
  6 
  being 
  assumed 
  for 
  the 
  liquid. 
  All 
  the 
  other 
  gases 
  

   studied 
  were 
  referred, 
  in 
  turn, 
  to 
  air 
  as 
  fundamental 
  substance. 
  

   The 
  magnetic 
  field 
  was 
  produced 
  by 
  a 
  Weiss 
  electromagnet, 
  the 
  

   pole 
  pieces 
  of 
  which 
  were 
  adjusted 
  at 
  1 
  cm. 
  apart. 
  For 
  an 
  

   exciting 
  current 
  of 
  10 
  amperes 
  the 
  region 
  of 
  the 
  field 
  involved 
  

   had 
  an 
  intensity 
  of 
  20,000 
  gauss. 
  

  

  The 
  numerical 
  data 
  obtained 
  are 
  of 
  sufficient 
  general 
  scientific 
  

   value 
  to 
  merit 
  quotation. 
  The 
  specific 
  susceptibilities 
  (x) 
  when 
  

   multiplied 
  by 
  10 
  6 
  are 
  given 
  as 
  +23-85, 
  +104-1, 
  0-423, 
  —0-265, 
  

   — 
  0-360, 
  — 
  5-86 
  and 
  — 
  1-982, 
  and 
  the 
  magnetic 
  susceptibilities 
  (#r 
  

   •10 
  6 
  ) 
  as 
  +0-03084. 
  +0-1488, 
  —0-000836, 
  —0-000331, 
  —0-000452, 
  

   — 
  00104, 
  and 
  — 
  00001781 
  for 
  air, 
  oxygen, 
  carbon 
  dioxide, 
  chem- 
  

   ically 
  pure 
  nitrogen, 
  atmospheric 
  nitrogen, 
  argon, 
  and 
  hydrogen, 
  

   respectively. 
  The 
  specific 
  susceptibilities 
  are 
  referred 
  to 
  the 
  

   state 
  at 
  20° 
  C, 
  and 
  the 
  volume 
  susceptibilities 
  to 
  that 
  at 
  0° 
  C. 
  

   and 
  76 
  cm. 
  pressure. 
  

  

  The 
  usual 
  assumption 
  that 
  the 
  specific 
  susceptibility 
  of 
  a 
  gas 
  

   is 
  independent 
  of 
  the 
  pressure 
  was 
  found 
  to 
  be 
  valid, 
  within 
  

   the 
  limits 
  of 
  experimental 
  error, 
  throughout 
  the 
  entire 
  range 
  of 
  

   pressures 
  employed, 
  that 
  is, 
  from 
  1 
  to 
  68 
  atmospheres. 
  The 
  

   excellent 
  agreement 
  between 
  the 
  values 
  obtained 
  for 
  air 
  by 
  

   direct 
  experimentation 
  and 
  by 
  calculation 
  from 
  the 
  like 
  data 
  for 
  

   the 
  separate 
  constituents 
  of 
  air 
  showed 
  not 
  only 
  that 
  the 
  num- 
  

   bers 
  are 
  dependable 
  but 
  also 
  that 
  the 
  additive 
  law 
  underlying 
  

   the 
  computation 
  holds. 
  Incidentally, 
  it 
  was 
  found 
  that 
  the 
  sus- 
  

   ceptibility 
  of 
  air 
  may 
  not 
  be 
  calculated 
  from 
  that 
  of 
  oxygen 
  

   alone 
  but 
  that 
  the 
  susceptibilities 
  of 
  argon 
  and 
  nitrogen 
  have 
  to 
  

   be 
  taken 
  into 
  account 
  too, 
  as 
  the 
  last 
  named 
  gases 
  contribute 
  

   about 
  one 
  per 
  cent, 
  to 
  the 
  total 
  magnetism 
  of 
  air. 
  Another 
  

   important 
  fact 
  brought 
  out 
  by 
  the 
  investigation 
  under 
  review 
  

   is 
  that 
  gaseous 
  carbon 
  dioxide 
  is 
  diamagnetic, 
  whereas 
  hereto- 
  

   fore 
  it 
  had 
  been 
  supposed 
  to 
  be 
  paramagnetic. 
  The 
  last 
  part 
  

   of 
  the 
  paper 
  deals 
  with 
  the 
  bearing 
  of 
  the 
  experimental 
  data 
  

   on 
  the 
  various 
  theories 
  of 
  magnetism. 
  The 
  conclusion 
  finally 
  

   reached 
  is 
  that, 
  with 
  the 
  addition 
  of 
  a 
  few 
  reasonable 
  auxiliary 
  

   assumptions, 
  the 
  theory 
  of 
  K. 
  Honda 
  and 
  J. 
  Okubo 
  accounts 
  for 
  

   the 
  observed 
  facts, 
  — 
  quantitatively 
  as 
  well 
  as 
  qualitatively, 
  — 
  

   better 
  than 
  anv 
  of 
  the 
  other 
  theories 
  proposed 
  up 
  to 
  the 
  present 
  

   time.— 
  Phil. 
  Mag., 
  39, 
  305, 
  1920. 
  h. 
  s. 
  u. 
  

  

  5. 
  A 
  New 
  Cadmium 
  Vapor 
  Arc 
  Lamp. 
  — 
  Intense 
  sources 
  of 
  

   practically 
  monochromatic 
  radiations 
  are 
  important 
  for 
  many 
  

   investigations 
  in 
  physical 
  optics 
  and 
  spectroscopy 
  but, 
  unfortu- 
  

   nately, 
  the 
  number 
  of 
  such 
  sources 
  at 
  present 
  available 
  is 
  very 
  

   small. 
  Lamps 
  containing 
  pure 
  cadmium 
  in 
  transparent 
  silica 
  

   envelopes 
  have 
  indeed 
  been 
  designed 
  and 
  successfully 
  used 
  

   (Michelson, 
  Fabry 
  and 
  Buisson, 
  et 
  al.) 
  . 
  The 
  employment 
  of 
  

   these 
  lamps, 
  however, 
  is 
  usually 
  attended 
  by 
  serious 
  difficulties, 
  

   such 
  as: 
  the 
  necessity 
  for 
  keeping 
  the 
  lower 
  portions 
  of 
  the 
  

   lamp 
  cooled 
  by 
  running 
  water, 
  the 
  adhesion 
  of 
  the 
  metal 
  to 
  the 
  

  

  