﻿E. 
  0. 
  Eovey 
  — 
  Acid 
  Dike 
  in 
  the 
  Triassic 
  area. 
  291 
  

  

  the 
  results 
  given 
  in 
  column 
  A. 
  Column 
  B 
  gives 
  an 
  analysis 
  of 
  

   ]\ 
  T 
  ew 
  Haven 
  (West 
  Hock) 
  diabase 
  by 
  G-. 
  W. 
  Hawes,** 
  intro- 
  

   duced 
  for 
  the 
  sake 
  of 
  comparison 
  as 
  illustrating 
  the 
  normal 
  

   diabase. 
  The 
  analysis 
  given 
  in 
  column 
  A 
  was 
  made 
  on 
  mate- 
  

  

  A 
  ' 
  B 
  

  

  SiO 
  a 
  6013 
  51-78 
  

  

  Ti0 
  tr. 
  1-41 
  

  

  Al 
  2 
  6 
  3 
  ...- 
  20-47 
  12-79 
  

  

  Fe 
  2 
  3 
  1-04 
  3-59 
  

  

  FeO 
  0-72 
  8-25 
  

  

  MnO 
  tr. 
  0-44 
  

  

  MgO_. 
  1-15 
  7-63 
  

  

  CaO 
  2-59 
  10-70 
  

  

  Na,,0 
  __ 
  960 
  2-14 
  

  

  K,6 
  106 
  0-39 
  

  

  Ign. 
  (CO„and 
  H„0). 
  3-44 
  H,0 
  0'63 
  

  

  P 
  2 
  5 
  0-14 
  

  

  100-20 
  

  

  99-89 
  

  

  rial 
  dried 
  at 
  110° 
  C. 
  The 
  specific 
  gravity 
  of 
  the 
  rock 
  at 
  11° 
  C. 
  

   was 
  2-63 
  (Washington). 
  Since 
  the 
  powdered 
  rock 
  effervesces 
  

   rather 
  strongly 
  on 
  the 
  addition 
  of 
  cold 
  HC1 
  and 
  considerable 
  

   calcite 
  is 
  seen 
  under 
  the 
  microscope, 
  the 
  loss 
  on 
  ignition 
  must 
  

   be 
  largely 
  C0. 
  2 
  . 
  

  

  This 
  composition 
  indicates 
  that 
  the 
  rock 
  belongs 
  to 
  the 
  group 
  

   of 
  keratophyres 
  (or 
  possibly 
  the 
  bostonites 
  of 
  Rosenbusch), 
  

   though 
  the 
  percentage 
  of 
  A1 
  2 
  3 
  is 
  rather 
  high 
  and 
  the 
  soda 
  

   predominates 
  over 
  the 
  potash 
  to 
  a 
  greater 
  degree 
  than 
  usual. 
  

   About 
  ST 
  per 
  cent^ 
  of 
  the 
  rock 
  is 
  feldspar 
  and 
  it 
  would 
  all 
  

   seem 
  to 
  be 
  anorthoclase, 
  with 
  the 
  exception 
  of 
  the 
  albite 
  pheno- 
  

   crysts. 
  The 
  rock 
  shows 
  more 
  CaO 
  and 
  MgO 
  than 
  the 
  kerato- 
  

   phyres 
  quoted 
  by 
  Zirkel 
  in 
  his 
  ' 
  ; 
  Lehrbuch 
  der 
  Petrographie," 
  

   but 
  the 
  excess 
  of 
  the 
  former 
  may 
  be 
  accounted 
  for 
  by 
  the 
  

   amount 
  of 
  secondary 
  calcite 
  present 
  in 
  it. 
  

  

  One 
  of 
  the 
  striking 
  features 
  of 
  the 
  Triassic 
  igneous 
  rocks 
  

   of 
  the 
  Atlantic 
  border 
  from 
  Nova 
  Scotia 
  to 
  North 
  Carolina 
  is 
  

   their 
  uniformity 
  in 
  appearance 
  and 
  in 
  mineralogical 
  and 
  chem- 
  

   ical 
  composition. 
  Particular 
  emphasis 
  has 
  been 
  put 
  upon 
  this 
  

   feature 
  by 
  J. 
  D. 
  Danaf 
  and 
  it 
  has 
  been 
  referred 
  to 
  by 
  many 
  of 
  

   the 
  writers 
  on 
  these 
  Triassic 
  areas. 
  In 
  his 
  treatise 
  on 
  " 
  The 
  

   Newark 
  System," 
  I. 
  C. 
  Russell^ 
  has 
  noted 
  this 
  uniformity 
  in 
  

  

  *This 
  Journal, 
  III, 
  ix, 
  186, 
  1875, 
  and 
  U. 
  S. 
  Nat. 
  Mus. 
  Pre 
  a, 
  vol. 
  iv, 
  p. 
  132, 
  

   [1881] 
  1882. 
  

  

  | 
  This 
  Journal, 
  III, 
  vi, 
  104-115. 
  Also 
  in 
  his 
  Manual 
  of 
  Geology 
  and 
  else- 
  

   where. 
  

  

  X 
  Bull. 
  U. 
  S. 
  Geol. 
  Survey, 
  Xo. 
  85, 
  pp. 
  67, 
  68, 
  1892. 
  

  

  