﻿

  396 
  Mr. 
  L. 
  Vegard 
  : 
  Researches 
  upon 
  

  

  if 
  some 
  standard 
  could 
  be 
  used 
  giving 
  fringes 
  of 
  a 
  known 
  

   visibility 
  and 
  in 
  the 
  same 
  position 
  as 
  those 
  due 
  to 
  the 
  inter- 
  

   ferometer, 
  the 
  method 
  of 
  determining 
  the 
  half 
  -width 
  would 
  

   reduce 
  to 
  a 
  very 
  simple 
  photometric 
  determination. 
  

  

  As 
  the 
  standard 
  a 
  mica 
  plate 
  was 
  found 
  very 
  convenient, 
  

   which 
  was 
  placed 
  in 
  the 
  path 
  of 
  the 
  light 
  entering 
  the 
  inter- 
  

   ferometer, 
  and 
  inclined 
  at 
  such 
  an 
  angle 
  as 
  to 
  give 
  straight- 
  

   line 
  fringes 
  perpendicular 
  to 
  those 
  given 
  by 
  the 
  interfero- 
  

   meter 
  and 
  in 
  approximately 
  the 
  same 
  focal 
  plane. 
  A 
  simple 
  

   adjustment 
  of 
  the 
  angle 
  of 
  the 
  mica 
  plate 
  was 
  all 
  that 
  was 
  

   necessary 
  to 
  alter 
  the 
  width 
  of 
  the 
  mica 
  fringes 
  or 
  the 
  angle 
  

   of 
  intersection 
  of 
  the 
  two 
  sets, 
  so 
  as 
  to 
  make 
  them 
  similar 
  in 
  

   every 
  respect. 
  

  

  It 
  was 
  found 
  in 
  practice 
  that 
  when 
  the 
  fringes 
  formed 
  a 
  

   system 
  of 
  squares 
  the 
  points 
  of 
  equal 
  intensity 
  could 
  be 
  

   determined 
  with 
  considerable 
  exactitude. 
  

  

  For 
  absolute 
  measurements 
  of 
  the 
  half-width 
  of 
  the 
  spectral 
  

   line 
  this 
  standard 
  would 
  require 
  to 
  give 
  fringes 
  of 
  a 
  visibility 
  

   one 
  half 
  the 
  maximum. 
  But 
  if 
  comparative 
  measurements 
  

   only 
  were 
  required, 
  such 
  as 
  the 
  change 
  in 
  width 
  of 
  the 
  

   spectral 
  line 
  brought 
  about 
  by 
  different 
  conditions 
  of 
  tempe- 
  

   rature, 
  pressure, 
  &c, 
  operating 
  on 
  the 
  same, 
  this 
  method 
  

   would 
  find 
  a 
  very 
  practical 
  application. 
  It 
  should 
  therefore 
  

   be 
  of 
  special 
  service 
  in 
  following 
  such 
  modifications 
  in 
  the 
  

   constitution 
  of 
  radiating 
  atoms 
  as 
  are 
  brought 
  into 
  evidence 
  

   by 
  changes 
  in 
  their 
  spectral 
  lines. 
  

  

  Physical 
  Laboratory, 
  University 
  of 
  Toronto, 
  

   May 
  1, 
  1908. 
  

  

  XXXIII. 
  Researches 
  upon 
  Osmosis 
  and 
  Osmotic 
  Pressure. 
  By 
  

   L. 
  Vegakd, 
  Cand. 
  real. 
  (Research 
  Student 
  at 
  the 
  Cavendish 
  

   Laboratory, 
  Cambridge). 
  

  

  [Plate 
  IX.] 
  \J 
  

  

  «J 
  [Continued 
  from 
  p. 
  271.] 
  

  

  Measurements 
  of 
  Osmotic 
  Properties 
  of 
  Cane-Sugar 
  Solutions. 
  

  

  11. 
  rpHE 
  mode 
  of 
  operation 
  in 
  the 
  experiments 
  was 
  as 
  

  

  JL 
  follows 
  : 
  — 
  

  

  Before 
  each 
  trial 
  the 
  osmometer 
  was 
  cleaned 
  with 
  distilled 
  

  

  water 
  and 
  dried 
  by 
  filter-paper. 
  The 
  cell 
  was 
  filled 
  with 
  

  

  distilled 
  water 
  and 
  put 
  on 
  the 
  tap 
  by 
  the 
  rubber 
  tubing, 
  and 
  

  

  