﻿4:4:4: 
  Scientific 
  Intelligence. 
  

  

  5. 
  The 
  new 
  Radio-active 
  /Substance, 
  Actinium. 
  — 
  A. 
  Debierne 
  

   gives 
  a 
  detailed 
  account 
  of 
  his 
  method 
  of 
  extracting 
  this 
  sub- 
  

   stance 
  from 
  pitchblende. 
  The 
  new 
  substance 
  produces 
  fluores- 
  

   cence, 
  photographic 
  impressions, 
  ionization 
  of 
  gases. 
  — 
  Gomptes 
  

   Rendus, 
  April 
  2, 
  1900, 
  pp. 
  906-908. 
  j. 
  t. 
  

  

  6. 
  Influence 
  of 
  temperature 
  on 
  the 
  potential-fall 
  in 
  rarefied 
  

   gases. 
  — 
  An 
  important 
  paper 
  on 
  this 
  subject 
  by 
  G. 
  C. 
  Schmidt 
  

   gives 
  a 
  detailed 
  account 
  of 
  the 
  methods 
  of 
  work 
  and 
  the 
  appa- 
  

   ratus. 
  The 
  Geissler 
  tubes 
  were 
  excited 
  by 
  a 
  storage 
  battery 
  of 
  

   1000 
  cells, 
  the 
  current 
  of 
  which 
  was 
  regulated 
  by 
  a 
  liquid 
  resist- 
  

   ance. 
  The 
  following 
  results 
  were 
  obtained 
  : 
  

  

  (1.) 
  Both 
  at 
  constant 
  pressure 
  and 
  with 
  constant 
  gas 
  density, 
  

   the 
  unstratitled 
  light 
  breaks 
  up 
  into 
  stratifications 
  with 
  increas- 
  

   ing 
  strength 
  of 
  current, 
  and 
  with 
  higher 
  temperature 
  and 
  strong 
  

   current 
  the 
  positive 
  light 
  retreats 
  to 
  the 
  anode 
  and 
  finally 
  the 
  

   discharge 
  becomes 
  dark. 
  

  

  (2.) 
  With 
  increase 
  of 
  temperature 
  of 
  the 
  anode 
  the 
  Glimm- 
  

   licht 
  extends 
  farther 
  and 
  farther 
  with 
  small 
  pressures. 
  The 
  

   increase 
  of 
  temperature 
  has 
  the 
  same 
  effect 
  as 
  increase 
  of 
  current 
  

   strength. 
  

  

  (3.) 
  The 
  gradient 
  in 
  the 
  positive 
  light 
  portion 
  of 
  the 
  tube 
  is 
  

   independent 
  of 
  the 
  cathode 
  fall. 
  

  

  (4.) 
  The 
  gradient 
  in 
  the 
  positive 
  unstratitled 
  light 
  with 
  con- 
  

   stant 
  gas 
  density, 
  independent 
  of 
  the 
  temperature. 
  

  

  (5.) 
  With 
  heating 
  under 
  constant 
  pressure 
  the 
  gradient 
  dimin- 
  

   ishes 
  in 
  the 
  positive 
  unstratified 
  light 
  and 
  more 
  slowly 
  than 
  the 
  

   gas 
  density. 
  

  

  (6.) 
  The 
  cathode 
  fall 
  is, 
  so 
  long 
  as 
  the 
  cathode 
  is 
  still 
  not 
  

   wholly 
  covered, 
  and 
  is 
  not 
  heated 
  to 
  a 
  white 
  heat, 
  independent 
  of 
  

   the 
  temperature. 
  

  

  (7.) 
  If 
  the 
  current 
  is 
  increased, 
  after 
  the 
  cathode 
  is 
  already 
  

   wholly 
  covered, 
  the 
  cathode 
  potential 
  increases, 
  and 
  in 
  proportion 
  

   with 
  the 
  current 
  strength. 
  

  

  (8.) 
  With 
  increasing 
  current 
  strength 
  the 
  gradient 
  increases 
  

   with 
  the 
  dark 
  discharge. 
  

  

  (9.) 
  With 
  constant 
  gas 
  density 
  the 
  gradient 
  increases 
  with 
  the 
  

   temperature 
  at 
  the 
  state 
  of 
  dark 
  discharge. 
  

  

  (10.) 
  With 
  constant 
  pressure 
  the 
  gradient 
  diminishes 
  with 
  the 
  

   temperature 
  during 
  the 
  dark 
  discharge. 
  

  

  (11.) 
  The 
  gradient 
  diminishes 
  from 
  the 
  anode 
  to 
  the 
  cathode 
  

   during 
  the 
  dark 
  discharge 
  ; 
  and 
  it 
  is 
  nearly 
  proportional 
  to 
  the 
  

   distance 
  from 
  the 
  cathode. 
  

  

  (12.) 
  With 
  increasing 
  temperature 
  the 
  whole 
  potential 
  dif- 
  

   ference 
  between 
  the 
  electrodes 
  diminishes 
  at 
  first 
  slowly 
  and 
  then 
  

   quickly. 
  It 
  reaches 
  a 
  minimum 
  and 
  then 
  begins 
  to 
  rise. 
  

  

  (13.) 
  The 
  minimum 
  of 
  the 
  potential 
  lies 
  with 
  one 
  and 
  the 
  same 
  

   tube 
  at 
  so 
  much 
  the 
  lower 
  temperature 
  as 
  the 
  initial 
  difference 
  of 
  

   potential 
  is 
  lower. 
  

  

  These 
  results 
  have 
  an 
  important 
  bearing 
  on 
  the 
  conditions 
  of 
  

   excitation 
  of 
  X-ray 
  tubes. 
  — 
  Ann. 
  der 
  Physik., 
  No. 
  4, 
  1900, 
  625- 
  

   647. 
  J. 
  t. 
  

  

  