﻿134 
  Winchell 
  and 
  Miller 
  — 
  Dust 
  fall 
  of 
  March, 
  1918. 
  

  

  GL 
  F. 
  Wright 
  of 
  Oberlin, 
  Ohio. 
  He 
  writes 
  that 
  it 
  was 
  

   collected 
  from 
  a 
  protected 
  roof 
  in 
  Oberlin, 
  where 
  it 
  fell 
  

   on 
  March 
  12, 
  1918. 
  This 
  dustfall 
  was 
  preceded 
  by 
  a 
  

   darkened 
  sky, 
  and 
  produced 
  a 
  visible 
  discoloration 
  on 
  

   the 
  roofs. 
  A 
  microscopic 
  examination 
  of 
  it 
  shows 
  that 
  

   it 
  is 
  strikingly 
  similar 
  in 
  composition 
  and 
  size 
  to 
  the 
  dust 
  

   which 
  fell 
  in 
  Madison; 
  it 
  consists 
  of 
  the 
  same 
  minerals, 
  

   the 
  same 
  spores 
  and 
  other 
  organic 
  fragments, 
  and 
  also 
  

   the 
  same 
  diatoms, 
  although 
  the 
  last 
  named 
  seem 
  to 
  be 
  

   decidedly 
  rarer 
  than 
  in 
  the 
  dust 
  which 
  fell 
  in 
  Wisconsin. 
  

  

  University 
  of 
  Wisconsin, 
  Madison. 
  

  

  SCIENTIFIC 
  INTELLIGENCE. 
  

  

  I. 
  Chemistry 
  and 
  Physics. 
  

  

  1. 
  The 
  Atomic 
  Weight 
  of 
  Argon. 
  — 
  A. 
  Leduc 
  has 
  determined 
  

   the 
  density 
  and 
  compressibility 
  of 
  argon, 
  using 
  a 
  sample 
  of 
  the 
  

   gas 
  which 
  had 
  been 
  almost 
  completely 
  freed 
  from 
  helium 
  and 
  

   neon 
  by 
  fractional 
  distillation 
  at 
  low 
  temperatures 
  after 
  absorp- 
  

   tion 
  by 
  charcoal, 
  and 
  which 
  was 
  further 
  purified 
  by 
  appropriate 
  

   processes 
  for 
  removing 
  small 
  amounts 
  of 
  nitrogen 
  oxygen, 
  mois- 
  

   ture, 
  etc., 
  until 
  its 
  specific 
  gravity 
  became 
  constant. 
  The 
  density 
  

   1-3787, 
  compared 
  with 
  air, 
  was 
  found, 
  while 
  Ramsay 
  and 
  Travers 
  

   had 
  found 
  1-379. 
  The 
  author 
  could 
  not 
  claim 
  from 
  the 
  accuracy 
  

   of 
  his 
  results 
  that 
  his 
  density 
  was 
  different 
  from 
  the 
  other. 
  

  

  The 
  compressibility 
  of 
  the 
  argon 
  was 
  found 
  to 
  be 
  0-9990 
  as 
  

   compared 
  with 
  an 
  ideal 
  gas, 
  while 
  that 
  of 
  oxygen 
  is 
  0-9992. 
  

   From 
  these 
  data, 
  the 
  molecular 
  weight 
  of 
  oxygen, 
  32, 
  and 
  the 
  

   specific 
  gravity 
  of 
  the 
  latter, 
  the 
  molecular 
  weight 
  of 
  argon, 
  which 
  

   is 
  the 
  same 
  as 
  its 
  atomic 
  weight, 
  was 
  calculated 
  as 
  follows 
  : 
  

   9990 
  1-3787 
  _ 
  

   61 
  X 
  9992 
  X 
  1-1053 
  ~ 
  d991 
  

  

  The 
  last 
  figure 
  is 
  uncertain, 
  so 
  that 
  the 
  accepted 
  atomic 
  weight 
  

   39-9 
  is 
  confirmed. 
  This 
  confirmation 
  is 
  important 
  because 
  the 
  

   atomic 
  weight 
  is 
  exceptional 
  in 
  being 
  larger 
  than 
  that 
  of 
  potas- 
  

   sium 
  (39T0), 
  the 
  element 
  which 
  follows 
  it 
  in 
  the 
  Periodic 
  

   Table. 
  Comptes 
  Rendus, 
  167, 
  70. 
  h. 
  l. 
  w. 
  

  

  2. 
  The 
  Emanation 
  Method 
  for 
  the 
  Determination 
  of 
  Thor- 
  

   ium. 
  — 
  G. 
  H. 
  Cartledge 
  has 
  applied 
  this 
  method 
  to 
  the 
  analysis 
  

   of 
  monazite 
  sands, 
  the 
  source 
  of 
  commercial 
  thorium 
  compounds. 
  

   The 
  emanation 
  method 
  is 
  well 
  known 
  in 
  its 
  application 
  to 
  the 
  

   determination 
  of 
  small 
  amounts 
  of 
  radium, 
  but 
  thorium 
  cannot 
  

   be 
  dealt 
  with 
  in 
  just 
  the 
  same 
  way 
  as 
  radium 
  on 
  account 
  of 
  the 
  

   very 
  short 
  period, 
  54 
  seconds, 
  of 
  the 
  thorium 
  emanation. 
  How- 
  

   ever, 
  the 
  author 
  has 
  been 
  able 
  to 
  apply 
  the 
  method 
  by 
  passing 
  

  

  