﻿316 
  Massrs. 
  J. 
  N. 
  Lockyer 
  and 
  W. 
  C. 
  Roberts 
  [Mar. 
  18, 
  

  

  lime 
  block 
  was 
  raised 
  to 
  a 
  white 
  heat 
  by 
  the 
  action 
  of 
  the 
  blowpipe. 
  As 
  

   the 
  glass 
  plates 
  rapidly 
  became 
  clouded 
  by 
  the 
  condensation 
  of 
  the 
  me- 
  

   tallic 
  vapours, 
  it 
  was 
  necessary 
  to 
  adopt 
  an 
  arrangement 
  by 
  which 
  they 
  

   could 
  be 
  easily 
  replaced. 
  We 
  may 
  state 
  that, 
  among 
  the 
  precautions 
  

   which 
  we 
  adopted 
  in 
  order 
  to 
  assure 
  ourselves 
  that 
  oxides 
  were 
  not 
  pre- 
  

   sent 
  to 
  disturb 
  the 
  accuracy 
  of 
  the 
  results, 
  one 
  of 
  the 
  glass 
  plates 
  was 
  

   removed 
  at 
  the 
  conclusion 
  of 
  each 
  experiment, 
  and 
  the 
  presence 
  of 
  an 
  

   excess 
  of 
  hydrogen 
  conclusively 
  proved 
  by 
  igniting 
  it 
  at 
  the 
  open 
  

   end. 
  

  

  "We 
  were 
  enabled 
  at 
  any 
  time, 
  by 
  modifying 
  the 
  conditions 
  of 
  the 
  gas- 
  

   supply, 
  to 
  introduce 
  the 
  spectrum 
  of 
  the 
  oxyhydrogen 
  flame. 
  It 
  may 
  

   further 
  be 
  stated 
  that, 
  with 
  few 
  exceptions,, 
  the 
  metals 
  were 
  previously 
  

   melted 
  in 
  a 
  stream 
  of 
  hydrogen 
  and 
  enclosed, 
  until 
  experimented 
  on, 
  in 
  

   sealed 
  glass 
  tubes. 
  "We 
  ascertained 
  that 
  the 
  effect 
  of 
  oxides, 
  and 
  of 
  the 
  

   metallic 
  rain 
  due 
  to 
  condensation, 
  was 
  to 
  produce 
  a 
  general 
  absorption 
  

   obviously 
  different 
  from 
  the 
  special 
  effects 
  of 
  absorption 
  which 
  we 
  now 
  

   proceed 
  to 
  record. 
  

  

  Details 
  op 
  the 
  Experiments. 
  

   Silver. 
  

  

  Fifty 
  grammes 
  of 
  pure 
  metal 
  were 
  placed 
  in 
  the 
  cavity 
  (C), 
  and 
  this 
  

   amount 
  produced 
  a 
  continuous 
  supply 
  of 
  vapour 
  for 
  about 
  10 
  minutes. 
  

  

  "With 
  the 
  smaller 
  thickness 
  given 
  by 
  the 
  first 
  lime 
  block, 
  and 
  with 
  a 
  

   less 
  powerful 
  blast, 
  the 
  spectrum 
  of 
  silver 
  consisted 
  of 
  an 
  absorption 
  in 
  

   the 
  blue 
  which 
  at 
  times 
  extended 
  almost 
  to 
  the 
  green. 
  

  

  "With 
  the 
  elongated 
  tube 
  and 
  a 
  stronger 
  blast 
  an 
  exquisite 
  channelled- 
  

   space 
  absorption 
  was 
  observed, 
  the 
  channels 
  being 
  far 
  enough 
  apart 
  to 
  

   render 
  them 
  very 
  conspicuous 
  in 
  the 
  field 
  of 
  view 
  ; 
  at 
  the 
  same 
  time 
  

   there 
  was 
  continuous 
  absorption 
  in 
  the 
  blue. 
  It 
  was 
  specially 
  observed 
  

   that 
  there 
  was 
  no 
  absorption 
  in 
  the 
  red. 
  

  

  It 
  may 
  be 
  interesting 
  to 
  note 
  that 
  the 
  vapour 
  of 
  silver 
  when 
  condensed 
  

   into 
  fine 
  particles, 
  escaping 
  into 
  an 
  atmosphere 
  of 
  hydrogen, 
  is 
  blue 
  by 
  

   reflected 
  light. 
  

  

  Copper. 
  

  

  "With 
  the 
  greatest 
  thickness 
  only 
  a 
  continuous 
  absorption 
  in 
  the 
  blue 
  

   could 
  be 
  obtained. 
  

  

  Sodium. 
  

  

  Only 
  the 
  clarTc 
  D 
  line 
  was 
  observed, 
  no 
  traces 
  of 
  channelled-space 
  

   absorption 
  being 
  visible. 
  

  

  Calcium. 
  

  

  "We 
  operated 
  upon 
  a 
  small 
  piece 
  of 
  metal 
  prepared 
  by 
  the 
  late 
  Dr. 
  

   Matthiessen, 
  but 
  no 
  result 
  was 
  obtained. 
  

  

  