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  Scientific 
  Intelligence. 
  

  

  8. 
  Phosphorescence 
  at 
  Low 
  Temperatures. 
  — 
  Raoul, 
  Pictet 
  

   and 
  Allschul 
  exposed 
  tubes 
  containing 
  sulphides 
  of 
  calcium, 
  

   strontium 
  and 
  barium 
  to 
  a 
  strong 
  sunlight 
  for 
  definite 
  periods 
  of 
  

   time 
  and 
  then 
  placed 
  them 
  in 
  liquid 
  nitrous 
  oxide, 
  the 
  tempera- 
  

   ture 
  of 
  which 
  was 
  estimated 
  at 
  —140°. 
  After 
  remaining 
  in 
  the 
  

   freezing 
  mixture 
  for 
  twelve 
  minutes 
  they 
  were 
  taken 
  out 
  and 
  the 
  

   renewal 
  of 
  the 
  phosphorescent 
  appearance 
  was 
  observed. 
  At 
  first 
  

   no 
  light 
  could 
  be 
  observed, 
  gradually, 
  however, 
  light 
  appeared 
  

   in 
  the 
  warmer 
  portions 
  of 
  the 
  tubes 
  and 
  extended 
  to 
  lower 
  portions. 
  

   After 
  five 
  minutes 
  the 
  tubes 
  became 
  as 
  bright 
  as 
  they 
  were 
  

   before 
  they 
  were 
  placed 
  in 
  the 
  freezing 
  mixture. 
  To 
  determine 
  

   the 
  limits 
  of 
  the 
  phenomena 
  the 
  tubes 
  were 
  placed 
  in 
  alcohol 
  

   cooled 
  to 
  —80°, 
  as 
  the 
  tubes 
  took 
  the 
  temperature 
  of 
  the 
  alcohol 
  

   the 
  phosphorescence 
  diminished 
  and 
  totally 
  disappeared 
  at 
  —65°. 
  

   The 
  portions 
  of 
  the 
  tube 
  above 
  the 
  alcohol 
  phosphoresced 
  strongly. 
  

   Before 
  the 
  colored 
  phosphorescence, 
  whether 
  blue, 
  green 
  or 
  orange, 
  

   entirely 
  disappeared, 
  the 
  tubes 
  assumed 
  a 
  yellow 
  color. 
  — 
  Zeit- 
  

   schrift 
  fur 
  physikalishe 
  Chemie, 
  vol. 
  xv, 
  part 
  3, 
  p. 
  386. 
  j. 
  t. 
  

  

  9. 
  Telegraphing 
  without 
  wires. 
  — 
  At 
  a 
  meeting 
  of 
  the 
  Physical 
  

   Society 
  held 
  in 
  Berlin, 
  Nov. 
  16, 
  Professor 
  Rubens 
  gave 
  an 
  

   account 
  of 
  experiments 
  on 
  this 
  subject. 
  On 
  the 
  banks 
  of 
  the 
  

   Wannsee 
  near 
  Potsdam 
  two 
  electrodes 
  were 
  sunk 
  in 
  the 
  water 
  at 
  

   a 
  distance 
  of 
  500 
  meters 
  from 
  each 
  other 
  and 
  a 
  current 
  of 
  fifty- 
  

   five 
  accumulators 
  was 
  sent 
  through 
  them. 
  From 
  each 
  of 
  the 
  

   boats 
  connected 
  by 
  a 
  cable 
  an 
  electrode 
  was 
  immersed 
  in 
  the 
  

   water 
  and 
  a 
  telephone 
  inserted 
  into 
  the 
  connection. 
  When 
  the 
  

   current 
  of 
  the 
  accumulators 
  was 
  broken 
  an 
  effect 
  was 
  perceived 
  

   in 
  the 
  telephone 
  at 
  a 
  distance 
  of 
  4-5 
  kilometres. 
  Small 
  islands 
  

   lying 
  between 
  the 
  boats 
  and 
  the 
  shore 
  had 
  no 
  influence 
  on 
  the 
  

   transmission 
  of 
  the 
  signals. 
  — 
  Nature, 
  Dec. 
  20, 
  1894. 
  j. 
  t. 
  

  

  10. 
  Calculation 
  and 
  measure 
  of 
  small 
  coefficients 
  of 
  Self 
  induc- 
  

   tion. 
  — 
  In 
  the 
  study 
  of 
  electric 
  waves, 
  the 
  oscillators 
  and 
  resona- 
  

   tors 
  have, 
  in 
  general, 
  small 
  coefficients 
  of 
  self-induction 
  and 
  it 
  

   becomes 
  important 
  to 
  obtain 
  an 
  accurate 
  value 
  of 
  these 
  coeffi- 
  

   cients. 
  Max 
  Wien 
  discusses 
  the 
  various 
  mathematical 
  formulae 
  

   for 
  parallel 
  wires, 
  circles, 
  rectangles, 
  etc., 
  and 
  gives 
  an 
  experi- 
  

   mental 
  method 
  also 
  of 
  determining 
  the 
  values 
  of 
  the 
  coefficients. 
  

   The 
  student 
  will 
  find 
  an 
  interesting 
  use 
  of 
  Maxwell's 
  geometri- 
  

   cal 
  mean 
  distance 
  in 
  the 
  paper. 
  — 
  Ann. 
  der 
  Physik 
  und 
  Chemie, 
  

   No. 
  13, 
  1894, 
  pp. 
  928-947. 
  J. 
  t. 
  

  

  11. 
  Self-induction 
  in 
  iron 
  loires. 
  — 
  Klemencic 
  shows 
  that 
  in 
  

   general 
  the 
  magnetic 
  permeability 
  is 
  different 
  in 
  the 
  circular 
  and 
  

   axial 
  directions. 
  Iron 
  wires 
  may 
  be 
  said 
  to 
  be 
  magnetically 
  double 
  

   refracting. 
  In 
  soft 
  iron 
  the 
  permeability 
  is 
  smaller 
  around 
  the 
  

   axis 
  than 
  in 
  the 
  direction 
  of 
  the 
  axis. 
  Hard 
  iron 
  in 
  the 
  process 
  

   of 
  drawing, 
  obtains 
  a 
  stronger 
  permeability 
  axially 
  than 
  in 
  the 
  

   circular 
  direction. 
  This 
  is 
  also 
  the 
  case 
  with 
  Bessemer 
  steel. 
  — 
  

   Ann. 
  der 
  Physik 
  und 
  Chemie, 
  No. 
  13, 
  1894, 
  pp. 
  1053-1061. 
  

  

  J. 
  T. 
  

  

  