﻿502 
  

  

  L. 
  Page 
  — 
  The 
  Photoelectric 
  Effect. 
  

  

  used 
  by 
  Herrmann,* 
  and 
  consisted 
  of 
  a 
  flexible 
  lead 
  tube, 
  J, 
  

   one 
  end 
  of 
  which 
  was 
  soldered 
  to 
  the 
  brass 
  rod, 
  K, 
  bearing 
  the 
  

   tool, 
  I, 
  while 
  the 
  other 
  end 
  was 
  fastened 
  to 
  the 
  glass 
  jar, 
  A. 
  

   In 
  operating 
  the 
  scraper, 
  the 
  metal 
  to 
  be 
  scraped 
  was 
  brought 
  

   under 
  the 
  scraper 
  by 
  rotating 
  the 
  plate, 
  Gr, 
  and 
  then 
  the 
  

   scraper 
  was 
  pressed 
  down 
  on 
  the 
  metal 
  while 
  the 
  plate, 
  G, 
  was 
  

  

  Fig. 
  1. 
  

  

  To 
  Electrometer 
  

  

  rotated 
  back 
  and 
  forth 
  through 
  a 
  small 
  angle. 
  In 
  all 
  cases 
  the 
  

   area 
  scraped 
  was 
  considerably 
  larger 
  than 
  that 
  exposed 
  by 
  the 
  

   aperture, 
  F. 
  In 
  this 
  way 
  the 
  field 
  near 
  to 
  the 
  region 
  exposed 
  

   to 
  the 
  light 
  was 
  not 
  complicated 
  by 
  the 
  presence 
  of 
  unscraped 
  

   surfaces. 
  It 
  was 
  found 
  to 
  be 
  not 
  at 
  all 
  difficult 
  to 
  scrape 
  

   appreciable 
  shavings 
  from 
  the 
  metallic 
  surfaces, 
  thus 
  securing 
  

   surfaces 
  that 
  were 
  fresh 
  and 
  uncontaminated. 
  Even 
  after 
  a 
  

   few 
  hours' 
  fatigue 
  in 
  low 
  vacuum 
  the 
  appearance 
  of 
  the 
  sur- 
  

   face 
  would 
  change 
  quite 
  noticeably 
  from 
  that 
  of 
  the 
  freshly 
  

   scraped 
  metal. 
  

  

  The 
  distance 
  of 
  the 
  surfaces 
  of 
  the 
  metal 
  disks 
  on 
  Gr 
  from 
  

   the 
  nearer 
  surface 
  of 
  E 
  was 
  2 
  mm 
  . 
  The 
  interior 
  of 
  the 
  glass 
  

   vessel 
  was 
  lined 
  with 
  brass 
  gauze 
  (not 
  shown 
  in 
  the 
  figure) 
  and 
  

   this 
  lining, 
  together 
  with 
  the 
  plate 
  B, 
  the 
  tube 
  D, 
  and 
  the 
  

   scraper 
  I 
  (which, 
  when 
  not 
  in 
  use, 
  was 
  fastened 
  at 
  a 
  distance 
  

   of 
  about 
  4 
  mm 
  from 
  the 
  nearest 
  point 
  of 
  G) 
  could 
  be 
  raised 
  to 
  

   any 
  desired 
  potential. 
  The 
  tube 
  H 
  was 
  kept 
  earthed 
  through- 
  

   out 
  the 
  experiment. 
  The 
  wire 
  M, 
  insulated 
  from 
  H 
  by 
  an 
  

   ebonite 
  and 
  an 
  amber 
  bushing, 
  connected 
  Gr 
  with 
  one 
  pair 
  of 
  

   quadrants 
  of 
  a 
  Dolezalek 
  electrometer. 
  The 
  other 
  pair 
  of 
  

   quadrants 
  was 
  earthed, 
  and 
  the 
  needle 
  charged 
  to 
  a 
  potential 
  

  

  *Karl 
  Herrmann, 
  Verh. 
  d. 
  Dentsch. 
  Phys. 
  Gesellsch., 
  xiv, 
  p. 
  557, 
  1912. 
  

  

  