﻿Phosphorescence 
  produced 
  by 
  Electrification. 
  101 
  

  

  to 
  note 
  a 
  statement 
  of 
  E. 
  Becquerel 
  upon 
  the 
  effect 
  of 
  

   electric 
  sparks 
  on 
  phosphorescent 
  bodies. 
  In 
  his 
  work 
  en- 
  

   titled 
  La 
  Lumiere, 
  ses 
  Causes 
  et 
  ses 
  Ejfets*, 
  he 
  says: 
  — 
  " 
  In 
  

   order 
  to 
  submit 
  the 
  substances 
  to 
  the 
  action 
  of 
  electric 
  

   discharges 
  they 
  were 
  placed 
  directly 
  upon 
  an 
  insulated 
  stand 
  

   if 
  they 
  were 
  in 
  fragments, 
  or 
  in 
  tubes 
  if 
  they 
  were 
  in 
  the 
  

   state 
  of 
  powder, 
  in 
  such 
  a 
  manner 
  that 
  the 
  discharge-terminals 
  

   were 
  two 
  or 
  three 
  centimetres 
  apart. 
  One 
  or 
  many 
  electrical 
  

   discharges 
  were 
  then 
  passed 
  from 
  leyden-jars 
  between 
  the 
  

   terminals. 
  One 
  then 
  finds 
  that 
  not 
  only 
  the 
  bodies 
  in 
  question 
  

   become 
  phosphorescent 
  after 
  the 
  passage 
  of 
  the 
  discharge, 
  but 
  

   also, 
  as 
  one 
  sees 
  later, 
  they 
  are 
  made 
  phosphorescent 
  by 
  these 
  

   electrical 
  discharges 
  when 
  subjected 
  to 
  heat, 
  even 
  if 
  before 
  

   having 
  been 
  submitted 
  to 
  the 
  action 
  of 
  the 
  discharges, 
  they 
  

   had 
  been 
  calcined 
  so 
  long 
  as 
  to 
  be 
  entirely 
  deprived 
  of 
  the 
  

   power 
  of 
  phosphorescence 
  by 
  elevation 
  of 
  temperature. 
  The 
  

   electric 
  light 
  acts, 
  therefore, 
  like 
  sunlight, 
  but 
  with 
  greater 
  

   energy 
  by 
  reason 
  of 
  its 
  greater 
  intensity 
  on 
  account 
  of 
  the 
  

   position 
  of 
  the 
  bodies 
  ; 
  and 
  it 
  is 
  capable 
  of 
  making 
  bodies 
  

   acquire 
  phosphorescence 
  which 
  did 
  not 
  previously 
  possess 
  it. 
  

   There 
  is 
  no 
  necessity 
  for 
  submitting 
  fluorspar 
  or 
  the 
  diamond 
  

   to 
  heat 
  immediately 
  after 
  having 
  been 
  exposed 
  to 
  the 
  dis- 
  

   charges. 
  The 
  elevation 
  of 
  temperature 
  can 
  take 
  place 
  even 
  

   after 
  the 
  lapse 
  of 
  some 
  months/' 
  

  

  Becquerel 
  evidently 
  attributed 
  the 
  effects 
  observed 
  to 
  the 
  

   light 
  of 
  the 
  discharge; 
  for 
  he 
  says, 
  further 
  (p. 
  55, 
  ibid.), 
  

   " 
  The 
  electric 
  spark 
  acts 
  only 
  by 
  its 
  light, 
  but 
  its 
  action 
  is 
  

   more 
  energetic 
  than 
  that 
  of 
  sunlight 
  by 
  reason 
  of 
  its 
  great 
  

   intensity 
  and 
  the 
  proximity 
  of 
  the 
  source." 
  

  

  In 
  an 
  article 
  on 
  luminescence 
  by 
  E. 
  Wiedemann 
  and 
  

   G. 
  C. 
  Schmidt 
  t 
  the 
  conclusion 
  is 
  reached 
  that 
  the 
  violet 
  light 
  

   alone 
  of 
  electrical 
  discharges 
  does 
  not 
  cause 
  phosphorescence; 
  

   but 
  the 
  phosphorescence 
  is 
  due 
  to 
  peculiar 
  discharge-rays 
  

   analogous 
  to 
  cathode 
  rays. 
  M. 
  W. 
  Hoffman 
  J 
  has 
  confirmed 
  

   Wiedemann's 
  work. 
  The 
  latter 
  states, 
  " 
  no 
  entladungsstrahlen 
  

   could 
  be 
  detected 
  in 
  the 
  brush-discharge." 
  

  

  With 
  the 
  preparation 
  of 
  fluorite 
  we 
  have 
  mentioned 
  above 
  

   no 
  effect 
  was 
  produced 
  by 
  the 
  light 
  of 
  the 
  electrical 
  discharge. 
  

   It 
  was 
  submitted 
  according 
  to 
  the 
  method 
  of 
  Becquerel 
  to 
  

   the 
  light 
  of 
  the 
  spark 
  ; 
  and 
  it 
  was 
  also 
  exposed 
  to 
  the 
  light 
  

   of 
  burning 
  magnesium 
  and 
  to 
  that 
  of 
  the 
  voltaic 
  arc, 
  and 
  no 
  

   phosphorescent 
  effects 
  could 
  be 
  produced, 
  nor 
  by 
  subsequent 
  

  

  * 
  Paris, 
  1867, 
  vol. 
  i., 
  p. 
  55. 
  

  

  t 
  Wied. 
  Ann. 
  lvi. 
  1895, 
  p. 
  237. 
  

  

  | 
  Wied. 
  Ann. 
  No. 
  2, 
  1897, 
  p. 
  273. 
  

  

  