﻿Chemistry 
  and 
  Physics. 
  465 
  

  

  (complementary 
  to 
  the 
  violet) 
  and 
  the 
  pure 
  red 
  color 
  sensation. 
  

   From 
  this 
  equation 
  and 
  from 
  the 
  sensation 
  equation 
  of 
  the 
  

   bichromate 
  color 
  already 
  found, 
  the 
  composition 
  of 
  the 
  yellow 
  

   was 
  determined. 
  By 
  matching 
  white 
  with 
  a 
  mixture 
  of 
  the 
  

   yellow 
  and 
  the 
  violet, 
  the 
  sensation 
  equation 
  to 
  white 
  was 
  deter- 
  

   mined. 
  The 
  other 
  colors 
  of 
  the 
  spectrum 
  were 
  then 
  used 
  in 
  

   forming 
  white, 
  and 
  from 
  their 
  luminosity 
  equations 
  their 
  percent- 
  

   age 
  composition 
  in 
  sensations 
  were 
  calculated. 
  The 
  percentage 
  

   curves 
  are 
  shown. 
  The 
  results 
  so 
  obtained 
  were 
  applied 
  to 
  

   various 
  spectrum 
  luminosity 
  curves, 
  and 
  the 
  sensation 
  curves 
  

   obtained. 
  The 
  areas 
  of 
  these 
  curves 
  were 
  found, 
  and 
  the 
  ordi- 
  

   nates 
  of 
  the 
  green 
  and 
  violet 
  curves 
  increased, 
  so 
  that 
  both 
  their 
  

   areas 
  were 
  respectively 
  equal 
  to 
  that 
  of 
  the 
  red. 
  This 
  gave 
  three 
  

   new 
  curves 
  in 
  which 
  the 
  sensations 
  to 
  form 
  white 
  were 
  shown 
  by 
  

   equal 
  ordinates. 
  

  

  A 
  comparison 
  of 
  the 
  points 
  in 
  the 
  spectrum 
  where 
  the 
  curves 
  

   cut 
  one 
  another, 
  and 
  of 
  those 
  found 
  by 
  the 
  red 
  and 
  green 
  blind 
  

   as 
  matching 
  white, 
  show 
  that 
  the 
  two 
  sets 
  are 
  identical, 
  as 
  they 
  

   should 
  be. 
  The 
  curves 
  of 
  Koenig, 
  drawn 
  on 
  the 
  same 
  supposi- 
  

   tion, 
  are 
  called 
  attention 
  to, 
  and 
  the 
  difference 
  between 
  his 
  and 
  

   the 
  new 
  determination 
  pointed 
  out. 
  

  

  The 
  red 
  below 
  the 
  red 
  lithium 
  line, 
  as 
  already 
  pointed 
  out, 
  

   excites 
  but 
  one 
  (the 
  red) 
  sensation, 
  whilst 
  the 
  green 
  sensation 
  is 
  

   felt 
  in 
  greatest 
  purity 
  at 
  A. 
  5140, 
  and 
  the 
  blue 
  at 
  \ 
  4580, 
  as 
  at 
  

   these 
  points 
  they 
  are 
  mixed 
  only 
  with 
  the 
  sensation 
  of 
  white, 
  the 
  

   white 
  being 
  of 
  that 
  whiteness 
  which 
  is 
  seen 
  outside 
  the 
  color 
  

   fields.— 
  Proc. 
  Boy. 
  Soc, 
  No. 
  419. 
  

  

  II. 
  Geology 
  and 
  Mineralogy. 
  

  

  1. 
  Geology 
  of 
  the 
  Aspen 
  Mining 
  District^ 
  Colorado 
  ; 
  by 
  Josiah 
  

   Edward 
  Spurr 
  ; 
  pp. 
  250, 
  pi. 
  liii, 
  with 
  atlas 
  containing 
  sheets 
  

   XXX, 
  1898, 
  U. 
  S. 
  Geological 
  Survey, 
  C. 
  D. 
  Walcott, 
  Director. 
  

   Monograph 
  XXXI. 
  — 
  The 
  detailed 
  study 
  of 
  the 
  Aspen 
  District, 
  

   made 
  by 
  Mr. 
  Spurr, 
  has 
  resulted 
  in 
  an 
  admirable 
  solution 
  of 
  a 
  

   difficult 
  geological 
  problem. 
  The 
  monograph, 
  while 
  it 
  is 
  pri- 
  

   marily 
  intended 
  for 
  those 
  directly 
  interested 
  in 
  mining, 
  contains 
  

   much 
  that 
  is 
  of 
  interest 
  from 
  a 
  scientific 
  point 
  of 
  view, 
  and 
  is 
  a 
  

   valuable 
  addition 
  to 
  the 
  literature 
  of 
  Mining 
  Geology. 
  The 
  con- 
  

   tents 
  are 
  briefly 
  as 
  follows 
  : 
  

  

  Introduction, 
  by 
  Mr. 
  S. 
  F. 
  Emmons, 
  geologist 
  in 
  charge. 
  

   Chapter 
  I. 
  Description 
  of 
  rock 
  formation. 
  

   " 
  11. 
  General 
  descriptive 
  geology. 
  

  

  " 
  III. 
  Detailed 
  description 
  of 
  various 
  mines 
  and 
  pro- 
  

   ductive 
  localities. 
  

   " 
  IV. 
  Chemical 
  geology. 
  

  

  " 
  V. 
  Surface 
  changes 
  since 
  ore 
  deposition. 
  Appendix. 
  

  

  The 
  accompanying 
  atlas 
  with 
  its 
  carefully 
  prepared 
  sheets, 
  and 
  

  

  the 
  many 
  plates 
  in 
  the 
  book 
  itself 
  illustrate 
  clearly 
  the 
  structure 
  

  

  Am. 
  Jour. 
  Sci.— 
  Fourth 
  Ser.'es 
  \^ol. 
  YIII, 
  No. 
  48. 
  — 
  December, 
  1899. 
  

   32 
  

  

  