﻿730 
  

  

  Mr. 
  H. 
  E. 
  Watson 
  on 
  some 
  

  

  Baryta 
  1505 
  

  

  Flake 
  White 
  

  

  .. 
  5-52 
  

  

  Zinc 
  White 
  

  

  . 
  . 
  582 
  

  

  Blue 
  Verditer 
  

  

  .. 
  232 
  

  

  

  . 
  . 
  3-44 
  

  

  Cobalt 
  Blue 
  

  

  .. 
  268 
  

  

  

  .. 
  2-42 
  

  

  Antwerp 
  Blue 
  

  

  Indigo 
  

  

  .. 
  1-32 
  

   .. 
  2-21) 
  

  

  

  .. 
  0-68 
  

  

  Emerald 
  Chromium 
  Oxide 
  . 
  

   Emerald 
  Green 
  

  

  .. 
  7-00 
  

   .. 
  417 
  

  

  Cobalt 
  Green 
  

  

  .. 
  4-14 
  

  

  Malachite 
  Green 
  

  

  Verditer 
  

  

  .. 
  2-88 
  

   .. 
  357 
  

  

  Sap 
  Green 
  

  

  .. 
  3-89 
  

   , 
  4-38 
  

  

  Terra 
  Yerte 
  

  

  Chromium 
  Green 
  Oxide 
  .... 
  

   Yellow 
  Lake 
  

  

  .. 
  214 
  

   .. 
  2-20 
  

   .. 
  5-36 
  

  

  Cadmium 
  Yellow 
  

  

  .. 
  2 
  82 
  

  

  Aureolin 
  

  

  .. 
  4-48 
  

  

  Chrome 
  Yellow 
  

  

  . 
  383 
  

  

  King's 
  Yellow 
  

  

  Zinc 
  Yellow 
  

  

  .. 
  635 
  

   .. 
  4-75 
  

  

  Strontium 
  Yellow 
  

  

  6 
  00 
  

  

  Lemon 
  Yellow 
  

  

  .. 
  530 
  

  

  Naples 
  Yellow 
  

  

  7-25 
  

  

  Pale 
  Naples 
  Yellow 
  

  

  .. 
  4-87 
  

  

  Bright 
  Naples 
  Yellow 
  

  

  .. 
  4-23 
  

  

  Indian 
  Yellow 
  207 
  

  

  Gamboge 
  — 
  

  

  Yellow 
  Ochre 
  362 
  

  

  Raw 
  Sienna 
  very 
  great 
  

  

  Madder 
  Orange 
  very 
  great 
  

  

  Red 
  Lead 
  641 
  

  

  Deep 
  Chrome 
  391 
  

  

  Vermillion 
  8'42 
  

  

  Scarlet 
  Lake 
  2"63 
  

  

  Carmine 
  L57 
  

  

  Rose 
  Madder 
  627 
  

  

  Crimson 
  Lake 
  3 
  - 
  12 
  

  

  Alizarin 
  Scarlet 
  2*49 
  

  

  Alizarin 
  Crimson 
  215 
  

  

  Madder 
  Carmine 
  56 
  at 
  least 
  

  

  Venetian 
  Red 
  4*42 
  

  

  Light 
  Red 
  2-29 
  

  

  Indian 
  Red 
  1*16 
  

  

  Purple 
  Lake 
  1-68 
  

  

  Madder 
  Red 
  P98 
  

  

  Purple 
  Madder 
  2-22 
  

  

  Burnt 
  Sienna 
  (V08 
  

  

  Brown 
  Madder 
  1 
  '49 
  

  

  Raw 
  Umber 
  164 
  

  

  Burnt 
  Umber 
  108 
  

  

  Vandyke 
  Brown 
  186 
  

  

  Bitumen 
  T76 
  

  

  Bistre 
  1*67 
  

  

  Sepia 
  — 
  

  

  Ivory 
  Black 
  P61 
  

  

  Part 
  III. 
  — 
  The 
  Absorption 
  Spectra 
  of 
  Paints. 
  

  

  The 
  absorption 
  spectra 
  of 
  about 
  fifty 
  of 
  the 
  most 
  important 
  

   paints 
  have 
  been 
  measured. 
  The 
  instrument 
  used 
  was 
  the 
  

   spectrophotometer 
  designed 
  by 
  Dr. 
  Mees, 
  and 
  kindly 
  lent 
  to 
  

   me 
  by 
  him. 
  It 
  is 
  fully 
  described 
  in 
  the 
  Revue 
  des 
  Sciences 
  

   Photographiques, 
  Feb. 
  1905, 
  but 
  the 
  principle 
  of 
  it 
  is 
  that 
  

   two 
  spectra 
  are 
  brought 
  into 
  juxtaposition 
  by 
  means 
  of 
  an 
  

   Albrecht's 
  prism. 
  The 
  light 
  forming 
  one 
  of 
  them 
  comes 
  

   from 
  a 
  standard 
  source, 
  and 
  can 
  be 
  cut 
  down 
  by 
  means 
  of 
  

   two 
  Nicol 
  prisms 
  until 
  the 
  intensity 
  of 
  the 
  light 
  in 
  any 
  given 
  

   portion 
  of 
  the 
  two 
  spectra 
  (cut 
  out 
  by 
  means 
  of 
  a 
  slit) 
  is 
  the 
  

   same. 
  When 
  this 
  is 
  so, 
  the 
  percentage 
  of 
  light 
  coming 
  from 
  

   the 
  unknown 
  source 
  is 
  proportional 
  to 
  the 
  square 
  of 
  the 
  

   cosine 
  of 
  the 
  angle 
  through 
  which 
  the 
  nicol 
  is 
  turned. 
  The 
  

   prism 
  was 
  of 
  the 
  constant 
  deviation 
  type, 
  and 
  the 
  wave- 
  

   length 
  of 
  the 
  light 
  seen 
  through 
  the 
  slit 
  could 
  be 
  read 
  off 
  on 
  

   a 
  scale. 
  

  

  For 
  purposes 
  of 
  observation 
  the 
  paints 
  were 
  painted 
  on 
  

   strips 
  of 
  dull 
  white 
  paper, 
  in 
  size 
  about 
  3x2 
  ins. 
  Half 
  the 
  

   paper 
  was 
  left 
  bare, 
  and 
  the 
  whole 
  illuminated 
  with 
  an 
  Auer 
  

  

  