﻿170 
  Prof. 
  A. 
  Battelli 
  on 
  the 
  Analogy 
  between 
  

  

  In 
  this 
  manner 
  I 
  only 
  obtained 
  a 
  very 
  slight 
  variation 
  in 
  

   the 
  photographic 
  impression. 
  

  

  This 
  experiment 
  goes 
  to 
  prove 
  that 
  the 
  radiation 
  emanating 
  

   from 
  the 
  posterior 
  surface 
  of 
  a 
  sheet 
  struck 
  by 
  the 
  cathodic 
  

   rays, 
  acts 
  in 
  the 
  same 
  manner 
  as 
  the 
  radiation 
  emitted 
  by 
  the 
  

   front 
  surface 
  of 
  the 
  sheet. 
  This 
  shows 
  that 
  the 
  power, 
  ob- 
  

   served 
  by 
  Thompson 
  as 
  possessed 
  by 
  the 
  rays 
  emanating 
  from 
  

   the 
  reflector 
  of 
  a 
  focus-tube, 
  could 
  also 
  be 
  noted 
  in 
  the 
  rays 
  

   emanating 
  from 
  the 
  anticathodic 
  surface 
  of 
  an 
  ordinary 
  

   Crookes's 
  tube, 
  if 
  this 
  surface 
  be 
  sufficientlv 
  thin. 
  

  

  12th 
  Experiment. 
  — 
  In 
  a 
  bulb 
  similar 
  to 
  that 
  of 
  fig. 
  1 
  the 
  

   two 
  photographic 
  cylinders 
  were 
  composed, 
  each 
  of 
  them, 
  of 
  

   three 
  small 
  cylinders 
  placed 
  in 
  a 
  line 
  and 
  respectively 
  covered 
  

   with 
  black 
  paper, 
  with 
  a 
  sheet 
  of 
  aluminium 
  and 
  one 
  of 
  pla- 
  

   tinum, 
  all 
  of 
  the 
  thickness 
  of 
  j§-q- 
  of 
  a 
  millimetre. 
  

  

  In 
  the 
  small 
  cylinder 
  covered 
  with 
  aluminium 
  an 
  impression 
  

   was 
  obtained 
  weaker 
  than 
  the 
  one 
  noted 
  in 
  the 
  small 
  cylinder 
  

   covered 
  with 
  paper 
  ; 
  and 
  on 
  the 
  small 
  cylinder 
  covered 
  with 
  

   platinum, 
  a 
  still 
  weaker 
  one 
  than 
  on 
  the 
  one 
  covered 
  with 
  

   aluminium, 
  both 
  in 
  front 
  and 
  at 
  the 
  back 
  of 
  the 
  reflector. 
  

  

  13th 
  Experiment. 
  — 
  Three 
  small 
  cylinders 
  prepared 
  respec- 
  

   tively 
  in 
  the 
  same 
  manner 
  as 
  in 
  the 
  12th 
  experiment 
  were 
  placed 
  

   at 
  the 
  same 
  moment 
  on 
  the 
  direct 
  line 
  followed 
  by 
  the 
  cathodic 
  

   rays 
  in 
  an 
  ordinary 
  Crookes's 
  tube. 
  

  

  The 
  same 
  results 
  were 
  obtained 
  as 
  in 
  the 
  preceding 
  experi- 
  

   ment 
  with 
  the 
  same 
  relations 
  between 
  the 
  respective 
  photo- 
  

   graphic 
  impressions. 
  -p. 
  , 
  „ 
  

  

  lUh 
  Experiment. 
  — 
  For 
  this 
  experiment 
  a 
  bulb 
  was 
  con- 
  

   structed 
  slightly 
  differing 
  from 
  the 
  preceding 
  ones. 
  This 
  

   also 
  was 
  spherical, 
  and 
  the 
  two 
  electrodes 
  entered 
  it 
  through 
  

   the 
  two 
  horizontal 
  tubes 
  A 
  and 
  B 
  (fig. 
  2), 
  and 
  the 
  reflector 
  

  

  