﻿676 
  Heavier 
  Gases 
  of 
  the 
  Helium 
  Group 
  in 
  Minerals. 
  

  

  Fig. 
  3. 
  

  

  ^ 
  /pump 
  

  

  Spectroscope 
  

  

  a. 
  Tute 
  for 
  introducing 
  gas 
  into 
  apparatus. 
  

   5. 
  Mercury 
  trough. 
  

   c. 
  Charcoal 
  bulb. 
  

   cl-d. 
  Sodium 
  potassium 
  electrodes. 
  

  

  e. 
  Vacuum-tubes. 
  

  

  f. 
  Graduated 
  capillary 
  for 
  measuring 
  gas, 
  

  

  (J. 
  Large 
  bulb 
  into 
  which 
  gas 
  is 
  allowed 
  to^^expand. 
  The 
  gas 
  is 
  

  

  compressed 
  into 
  "/" 
  and 
  measured. 
  

   h. 
  Air 
  trap. 
  

  

  