﻿390 
  W. 
  F. 
  Hillebrand 
  — 
  Analyses 
  of 
  Uraninite. 
  

  

  oper 
  as 
  when 
  development 
  is 
  resorted 
  to. 
  Suitable 
  developers 
  

   will 
  doubtless 
  reduce 
  the 
  time 
  of 
  exposure. 
  

  

  The 
  plates 
  were 
  exposed 
  against 
  mercury, 
  not, 
  however, 
  to 
  

   the 
  spectrum, 
  as 
  with 
  Lippmann, 
  but 
  to 
  light 
  transmitted 
  by 
  

   strips 
  of 
  variously 
  colored 
  glass, 
  one 
  object 
  being 
  to 
  determine 
  

   whether 
  the 
  ordinary 
  colors 
  of 
  objects, 
  consisting, 
  as 
  they 
  do, 
  

   of 
  a 
  mixture 
  of 
  rays 
  of 
  several 
  different 
  wave 
  lengths, 
  would 
  

   be 
  reproduced 
  with 
  the 
  same 
  fidelity 
  as 
  were 
  the 
  pure 
  rays 
  of 
  

   the 
  spectrum. 
  The 
  composition 
  of 
  the 
  light 
  transmitted 
  by 
  

   the 
  strips 
  of 
  colored 
  glass 
  employed 
  as 
  determined 
  by 
  the 
  spec- 
  

   troscope 
  is 
  shown 
  in 
  the 
  following 
  table 
  : 
  

  

  Red 
  : 
  All 
  the 
  red 
  with 
  distinct 
  traces 
  of 
  orange 
  and 
  green. 
  

   Orange: 
  The 
  entire 
  spectrum 
  reduced 
  in 
  intensity. 
  

   Green 
  : 
  A 
  band 
  extending 
  from 
  the 
  middle 
  of 
  the 
  blue 
  to 
  the 
  

   middle 
  of 
  the 
  red. 
  

  

  Blue 
  : 
  Blue, 
  with 
  bands 
  throughout 
  the 
  green 
  and 
  red. 
  

   Purple 
  : 
  Green 
  and 
  red. 
  

  

  The 
  results 
  obtained, 
  though 
  by 
  no 
  means 
  conclusive 
  at 
  all 
  

   points, 
  seem 
  to 
  indicate 
  : 
  First, 
  that 
  mixed 
  colors 
  may 
  be 
  

   reproduced 
  with 
  some 
  fair 
  degree 
  of 
  accuracy, 
  though 
  some 
  

   curious 
  modifications 
  sometimes 
  occur. 
  Thus, 
  a 
  thickening 
  of 
  

   the 
  film 
  between 
  exposure 
  and 
  final 
  drying, 
  will 
  occasionally 
  

   change 
  all 
  the 
  colors 
  in 
  the 
  direction 
  of 
  the 
  red 
  end 
  of 
  the 
  

   spectrum. 
  A 
  shortening 
  of 
  the 
  distance 
  between 
  the 
  thin 
  

   plates, 
  and 
  a 
  consequent 
  displacement 
  toward 
  the 
  violet, 
  on 
  the 
  

   other 
  hand, 
  may 
  be 
  produced 
  by 
  allowing 
  the 
  incident 
  light 
  to 
  

   strike 
  the 
  reflecting 
  surface 
  of 
  mercury, 
  at 
  an 
  angle 
  other 
  than 
  

   the 
  normal, 
  thus 
  shortening 
  the 
  distance 
  between 
  the 
  maxima 
  

   which 
  mark 
  the 
  layers 
  of 
  reflecting 
  deposit 
  in 
  the 
  sensitive 
  

   film. 
  Second, 
  that 
  an 
  exposure 
  sufficiently 
  long 
  to 
  give 
  a 
  clear 
  

   image 
  of 
  the 
  red 
  is 
  quite 
  certain 
  to 
  obliterate 
  the 
  blue 
  by 
  over- 
  

   exposure. 
  Third, 
  that 
  an 
  over-exposure 
  may 
  completely 
  reverse 
  

   the 
  colors, 
  causing 
  the 
  original 
  colors 
  to 
  appear 
  on 
  the 
  reverse, 
  

   and 
  the 
  complementary 
  on 
  the 
  film 
  side 
  of 
  the 
  plate. 
  

  

  Art. 
  XXXIX. 
  — 
  New 
  Analyses 
  of 
  Uraninite; 
  by 
  TV. 
  F. 
  

   Hillebrand. 
  

  

  Since 
  the 
  publication 
  of 
  a 
  former 
  paper 
  on 
  the 
  occurrence 
  

   of 
  nitrogen 
  in 
  uraninite 
  and 
  on 
  the 
  composition 
  of 
  uraninite 
  

   in 
  general* 
  no 
  advance 
  has 
  been 
  made 
  toward 
  clearing 
  up 
  the 
  

   mystery 
  surrounding 
  the 
  composition 
  of 
  that 
  mineral, 
  although 
  

  

  *This 
  Journal, 
  III, 
  xl, 
  p. 
  384; 
  Bull. 
  U. 
  S. 
  Geol. 
  Survey, 
  No. 
  78, 
  1889-1890, 
  

   p. 
  43. 
  

  

  