﻿Chemistry 
  and 
  Physics. 
  379 
  

  

  silica 
  walls 
  often 
  resulting 
  in 
  the 
  fracture 
  of 
  the 
  container, 
  

   the 
  automatic 
  increase 
  in 
  pressure 
  requiring 
  frequent 
  pumping, 
  

   the 
  relative 
  complexity 
  of 
  construction 
  making 
  repairs 
  trouble- 
  

   some, 
  etc. 
  Accordingly, 
  a 
  brief 
  account 
  of 
  a 
  new 
  cadmium 
  lamp 
  

   designed 
  and 
  tested 
  by 
  F. 
  Bx\tes, 
  which 
  seems 
  to 
  be 
  free 
  from 
  

   ;all 
  of 
  the 
  serious 
  inconveniences 
  pertaining 
  to 
  the 
  earlier 
  forms, 
  

   ma}^ 
  not 
  be 
  without 
  interest. 
  

  

  The 
  fundamental 
  idea 
  was 
  to 
  find 
  a 
  chemical 
  element 
  that 
  

   would 
  readily 
  alloy 
  with 
  cadmium 
  and 
  possess 
  a 
  relatively 
  low 
  

   vapor 
  pressure. 
  It 
  was 
  discovered 
  by 
  trial 
  that 
  the 
  rare 
  metal 
  

   .gallium 
  fulfilled 
  the 
  conditions 
  admirably. 
  The 
  author 
  says: 
  

   ' 
  ' 
  In 
  fact, 
  the 
  addition 
  of 
  a 
  few 
  drops 
  of 
  gallium 
  to 
  ten 
  or 
  fifteen 
  

   cubic 
  centimetres 
  of 
  cadmium 
  completely 
  changed 
  the 
  texture 
  

   of 
  the 
  latter, 
  rendering 
  it 
  relatively 
  soft 
  and 
  greatly 
  reducing 
  

   Its 
  tensile 
  strength. 
  Subsequently 
  it 
  was 
  discovered 
  that 
  upon 
  

   distilling 
  the 
  cadmium 
  from 
  the 
  alloy 
  at 
  a 
  pressure 
  of 
  0-001 
  mm. 
  

   of 
  mercury, 
  the 
  minute 
  quantity 
  of 
  gallium 
  carried 
  through 
  was 
  

   sufficient 
  to 
  completely 
  change 
  the 
  character 
  of 
  the 
  cadmium 
  and 
  

   to 
  prevent 
  adhesion 
  between 
  the 
  cadmium 
  and 
  the 
  walls 
  of 
  the 
  

   lamp." 
  

  

  When 
  finally 
  filled 
  and 
  sealed 
  off 
  from 
  the 
  pump, 
  the 
  shape 
  

   of 
  the 
  lamp 
  was 
  that 
  of 
  the 
  letter 
  U 
  inverted, 
  f! 
  , 
  the 
  lower 
  ends 
  

   consisting 
  of 
  vertical 
  capillary 
  tubes. 
  The 
  total 
  internal 
  vol- 
  

   ume 
  of 
  the 
  silica 
  envelope 
  was 
  about 
  ten 
  cm 
  3 
  . 
  The 
  electrodes 
  

   were 
  made 
  of 
  tungsten 
  wires 
  which 
  projected 
  above 
  the 
  upper 
  

   >ends 
  of 
  the 
  capillaries 
  into 
  the 
  gallium-softened 
  cadmium. 
  The 
  

   lower 
  ends 
  of 
  these 
  wires 
  and 
  of 
  the 
  capillary 
  tubes 
  were 
  closed 
  

   with 
  lead 
  seals 
  of 
  the 
  type 
  described 
  by 
  Sand. 
  The 
  precautions 
  

   taken 
  in 
  filling 
  a 
  lamp 
  of 
  this 
  kind 
  may 
  not 
  be 
  recounted 
  in 
  this 
  

   place. 
  

  

  The 
  lamp 
  may 
  be 
  started 
  by 
  heating 
  with 
  a 
  flame 
  to 
  vaporize 
  

   some 
  of 
  the 
  metal. 
  The 
  lead 
  seals 
  alone 
  must 
  be 
  kept 
  cool 
  by 
  

   directing 
  a 
  current 
  of 
  air 
  against 
  them. 
  The 
  energy 
  required 
  

   may 
  be 
  conveniently 
  obtained 
  from 
  the 
  ordinary 
  110 
  volt 
  light- 
  

   ing 
  mains. 
  The 
  lamp 
  will 
  operate 
  continuously 
  with 
  a 
  current 
  

   as 
  small 
  as 
  3 
  amperes 
  accompanied 
  by 
  a 
  drop 
  of 
  14 
  volts 
  across 
  

   the 
  terminals. 
  ''The 
  most 
  satisfactory 
  results, 
  however, 
  are 
  

   secured 
  with 
  a 
  current 
  of 
  about 
  7 
  amperes 
  and 
  a 
  drop 
  across 
  

   the. 
  terminals 
  of 
  about 
  25 
  volts. 
  Under 
  this 
  condition 
  a 
  prac- 
  

   tically 
  pure 
  cadmium 
  spectrum 
  of 
  great 
  brilliancy 
  is 
  obtained. 
  ' 
  ' 
  

   The 
  fact 
  that 
  the 
  author 
  found 
  it 
  difficult 
  to 
  bring 
  out 
  even 
  a 
  

   few 
  of 
  the 
  gallium 
  lines 
  is 
  just 
  what 
  might 
  have 
  been 
  predicted 
  

   from 
  the 
  spectroscopic 
  behavior 
  of 
  this 
  metal 
  and 
  the 
  conditions 
  

   of 
  excitation 
  prevailing 
  inside 
  the 
  lamp. 
  — 
  Phil. 
  Mag., 
  39, 
  353, 
  

   1920. 
  h. 
  s. 
  u. 
  

  

  6. 
  The 
  Inertia 
  of 
  a 
  Sphere 
  Moving 
  in 
  a 
  Liquid. 
  — 
  In 
  connec- 
  

   tion 
  with 
  certain 
  war-work 
  on 
  the 
  oscillating 
  mine 
  G. 
  Cook 
  had 
  

   occasion 
  to 
  make 
  some 
  observations 
  on 
  the 
  speed 
  and 
  linear 
  

   -acceleration 
  of 
  spherical 
  solids 
  falling 
  in 
  water. 
  It 
  has 
  been 
  

  

  