﻿190 
  Mr. 
  A. 
  Norman 
  Shaw 
  on 
  Interference 
  

  

  values 
  of 
  a 
  less 
  than 
  60° 
  the 
  series 
  was 
  used, 
  and 
  for 
  the 
  

   .remainder 
  the 
  tables 
  of 
  elliptic 
  integrals 
  : 
  — 
  

  

  a. 
  

  

  cr. 
  

  

  a. 
  

  

  ff. 
  

  

  10°... 
  

  

  1001 
  

   1-004 
  

   1009 
  

   1-015 
  

   1024 
  

   1-035 
  

   1-047 
  

   1-062 
  

   1079 
  

  

  100° 
  

  

  1098 
  

  

  1-118 
  

  

  1-141 
  

  

  1-165' 
  

  

  1190 
  

  

  1-216 
  

  

  1-241 
  

  

  1-261 
  

  

  1-273 
  

  

  20 
  ... 
  

  

  110 
  

  

  30 
  .. 
  

  

  120 
  

  

  40 
  

  

  130 
  

  

  50 
  

  

  140 
  

  

  60 
  .... 
  

  

  150 
  

  

  70 
  

  

  160 
  

  

  80 
  

  

  90 
  .. 
  

  

  170 
  

  

  180 
  

  

  

  

  

  Corresponding 
  to 
  a 
  = 
  7r, 
  it 
  is 
  easy 
  to 
  see 
  directly 
  from 
  the 
  

   integral 
  (7) 
  that 
  (putting 
  k=l) 
  

  

  <r 
  = 
  i 
  f 
  l 
  ' 
  

  

  cos 
  6dd> 
  = 
  -=1-2732. 
  

  

  7T 
  

  

  XI. 
  Interference 
  Phenomena 
  with 
  Gamma 
  Rays. 
  By 
  A. 
  

   Norman 
  Shaw, 
  M.Sc, 
  1851 
  Exhibition 
  Scholar 
  of 
  Ale 
  Gill 
  

   University, 
  Montreal; 
  Research 
  Student 
  of 
  Gonville 
  and 
  

   Caius 
  College, 
  Cambridge 
  *. 
  

  

  dye 
  

   [Plate 
  V.] 
  

  

  TJ 
  ECENT 
  experiments 
  by 
  Friedrich, 
  Knipping, 
  and 
  Laue 
  f 
  

   _t\» 
  and 
  many 
  other 
  investigators, 
  have 
  shown 
  that 
  Hont- 
  

   gen 
  rays 
  can 
  exhibit 
  phenomena 
  analogous 
  to 
  the 
  interference 
  

   of 
  light. 
  As 
  the 
  intervals 
  of 
  a 
  diffraction 
  grating 
  must 
  be 
  

   approximately 
  of 
  the 
  same 
  order 
  of 
  magnitude 
  as 
  the 
  wave- 
  

   lengths 
  to 
  be 
  examined, 
  it 
  had 
  hitherto 
  been 
  impossible 
  to 
  

   obtain 
  a 
  grating 
  fine 
  enough 
  to 
  affect 
  a 
  beam 
  of 
  Rontgen 
  

   rays. 
  Laue, 
  however, 
  found 
  that 
  the 
  regular 
  arrangement 
  

   of 
  the 
  atoms 
  or 
  molecules 
  in 
  crystals 
  provided 
  a 
  grating 
  in 
  

   three 
  dimensions 
  which 
  was 
  suitable 
  for 
  affecting 
  waves 
  of 
  

   the 
  order 
  10" 
  8 
  to 
  10" 
  9 
  cm. 
  in 
  length. 
  It 
  was 
  thought 
  

   desirable 
  to 
  test 
  the 
  effect 
  of 
  such 
  a 
  grating 
  or 
  space-lattice 
  

   on 
  a 
  beam 
  of 
  7 
  rays. 
  

  

  In 
  attempting 
  to 
  apply 
  Laue's 
  methods 
  to 
  the 
  case 
  of 
  

   7 
  rays, 
  two 
  difficulties 
  appeared. 
  (1) 
  The 
  ordinary 
  second- 
  

   ary 
  effects 
  were 
  much 
  more 
  intense 
  than 
  for 
  X-rays, 
  with 
  

   the 
  result 
  that 
  the 
  consequent 
  fogging 
  of 
  the 
  photographic 
  

  

  * 
  Communicated 
  by 
  Professor 
  Sir 
  J. 
  J. 
  Thomson, 
  O.M., 
  F.R.S. 
  

   t 
  Laue, 
  Sitzungsber. 
  der 
  Kon. 
  Bayerischen 
  Akad. 
  der 
  Wiss. 
  p. 
  303 
  ; 
  

   June, 
  and 
  p. 
  363, 
  July 
  1912. 
  

  

  