﻿Notes 
  upon 
  the 
  Lithology 
  of 
  the 
  Adirondacks. 
  103 
  

   I. 
  Hypersthene. 
  

  

  O 
  Ratio. 
  Radicals. 
  At. 
  Ratio. 
  Quant. 
  Ratio. 
  

  

  Silica 
  50.33 
  26,842 
  23.488 
  0.8389 
  3.3554 
  

  

  Titanic 
  Acid 
  . 
  07 
  . 
  028 
  . 
  042 
  . 
  0009 
  . 
  0035 
  

  

  Alumina 
  3.36 
  1.566 
  1.794 
  0.0229 
  0.1973 
  

  

  Ferric 
  Oxide 
  1.03 
  0.309 
  0.721 
  0.0064 
  0.0386"^ 
  

  

  Ferrous 
  Oxide 
  .... 
  19.40 
  4.31115.089 
  0.2716 
  0.5432 
  

  

  Manganous 
  Oxide. 
  0.71 
  0.160 
  0.550 
  0.0029 
  0.0058 
  > 
  

  

  Lime 
  2.77 
  0.791 
  1.979 
  0.0495 
  0.0989 
  

  

  Magnesia 
  21.40 
  8.553 
  12.847 
  0.5353 
  1.0706 
  

  

  Water 
  1.14 
  

  

  100.21 
  

  

  The 
  other 
  variety, 
  II, 
  occurs 
  in 
  broadly-foliated, 
  dark-green 
  

   masses, 
  with 
  a 
  metallic 
  lustre, 
  and 
  specific 
  gravity 
  3. 
  386. 
  

  

  II. 
  DlALLAGE. 
  

  

  Radicals. 
  Eq. 
  Ratio. 
  

  

  Silica 
  46.28 
  21.600 
  3.086 
  j 
  

  

  TitanicAcid 
  0.59 
  0.354 
  0.028 
  V 
  2.1 
  

  

  Alumina 
  7.38 
  3.927 
  0.432 
  ) 
  

  

  Ferric 
  Oxide 
  2.21 
  1.547 
  0.084^ 
  

  

  Ferrous 
  Oxide 
  14.80 
  11.510 
  0.411 
  

  

  Lime 
  18.78 
  13.410 
  0.670^ 
  

  

  Magnesia 
  8.91 
  5.346 
  0.445 
  

  

  Water 
  1.115 
  

  

  100.065 
  

  

  These 
  two 
  minerals 
  represent 
  the 
  most 
  important 
  varieties 
  

   of 
  the 
  pyroxenic 
  constituent 
  in 
  these 
  Adirondacks, 
  although 
  

   others 
  occur 
  as 
  well, 
  together 
  with 
  hornblende, 
  the 
  latter 
  as 
  is 
  

   shown 
  by 
  the 
  microscopic 
  examination 
  of 
  the 
  sections, 
  being 
  

   frequently 
  derived 
  from 
  alteration 
  of 
  the 
  foregoing. 
  

  

  I 
  have 
  the 
  pleasure 
  to 
  acknowledge 
  the 
  co-operation 
  of 
  my 
  

   assistants. 
  Dr. 
  G-. 
  A. 
  Prochazka 
  and 
  Mr. 
  W. 
  E. 
  Hoyt, 
  in 
  the 
  

   performance 
  of 
  the 
  foregoing 
  analyses. 
  

  

  IY. 
  Microscopic 
  Examination 
  of 
  Rock 
  Sections. 
  

   The 
  rock-sections, 
  9 
  in 
  number, 
  were 
  ground 
  by 
  Mr. 
  A. 
  A. 
  

   Julien, 
  of 
  the 
  School 
  of 
  Mines, 
  New 
  York. 
  The 
  numbers 
  cor- 
  

   respond 
  to 
  those 
  employed 
  in 
  Part 
  II 
  of 
  this 
  article. 
  

  

  