﻿H. 
  E. 
  Gregory 
  — 
  Andesites 
  from 
  Maine, 
  369 
  

  

  black 
  iron 
  ore 
  in 
  long 
  threads 
  or 
  lines 
  of 
  partly 
  connected 
  dots 
  

   ■which 
  are 
  arranged 
  to 
  form 
  barbed 
  arrows 
  or 
  network, 
  of 
  fibers 
  

   which 
  cross 
  at 
  angles 
  of 
  60° 
  and 
  90°, 
  thus 
  imitating 
  the 
  sagenite 
  

   structure 
  of 
  rutile. 
  

  

  The 
  groundmass 
  is 
  of 
  long, 
  stringy, 
  narrow, 
  frayed 
  out 
  

   microlites 
  of 
  feldspar 
  with 
  trachytic 
  structure. 
  Measurements 
  

   of 
  many 
  laths 
  gave 
  practically 
  a 
  parallel 
  extinction, 
  thus 
  indi- 
  

   cating 
  oligoclase. 
  Expansion 
  structure 
  is 
  developed 
  where 
  the 
  

   vesicular 
  areas 
  are 
  large 
  enough 
  to 
  affect 
  the 
  orientation 
  of 
  the 
  

   minute 
  laths 
  constituting 
  the 
  main 
  body 
  of 
  the 
  rock. 
  

  

  Andesite 
  Ash 
  Beds. 
  — 
  Beds 
  of 
  vojcanic 
  ash 
  of 
  an 
  andesite 
  

   character 
  are 
  represented 
  in 
  the 
  region 
  covered 
  by 
  this 
  report. 
  

   They 
  are 
  particularly 
  abundant 
  about 
  Castle 
  Hill 
  and 
  will 
  be 
  

   discussed 
  in 
  another 
  place. 
  

  

  