﻿432 
  E. 
  A. 
  Daly 
  — 
  Geology 
  of 
  Pigeon 
  Point, 
  Minnesota. 
  

  

  one 
  to 
  two 
  centimeters 
  in 
  thickness, 
  4 
  to 
  8 
  centimeters 
  wide, 
  

   and 
  2*5 
  meters 
  in 
  ascertained, 
  minimum 
  length. 
  These 
  lath- 
  

   like 
  bodies 
  all 
  lie 
  in 
  the 
  bedding 
  planes 
  of 
  the 
  argillite. 
  The 
  

   low 
  side 
  walls 
  of 
  each 
  ribbon 
  are 
  usually 
  sharp 
  and 
  are 
  per- 
  

   pendicular 
  to 
  the 
  bedding. 
  None 
  of 
  the 
  smaller 
  ribbons 
  ap- 
  

   pears 
  to 
  have 
  uparched 
  the 
  overlying 
  sedimentary 
  rock, 
  or 
  to 
  

  

  Fig. 
  5. 
  

  

  a 
  

  

  1 
  _-_-_- 
  

  

  2 
  

   1 
  

  

  cm. 
  om/ttecL 
  

  

  Fig. 
  5. 
  Cross-sections 
  (a, 
  b, 
  c) 
  and 
  partial 
  ground-plan 
  (d, 
  e) 
  of 
  ribbon 
  

   injections 
  of 
  red 
  rock 
  (dotted), 
  cutting 
  thin 
  metargillit-ic 
  layers 
  {2), 
  between 
  

   beds 
  of 
  micaceous 
  quartzite 
  (Z). 
  Figs, 
  d 
  and 
  e 
  represent 
  the 
  two 
  extremities 
  

   of 
  an 
  observed 
  ribbon 
  seen 
  in 
  plan. 
  With 
  other 
  ribbons 
  the 
  kind 
  of 
  termi- 
  

   nation 
  shown 
  in 
  d 
  is 
  the 
  more 
  common. 
  All 
  drawings 
  are 
  to 
  natural 
  scale. 
  

   Diagram 
  c 
  refers 
  to 
  the 
  largest 
  observed 
  ribbon. 
  

  

  have 
  caused 
  the 
  slightest 
  depression 
  in 
  the 
  rock 
  underlying 
  the 
  

   ribbon. 
  The 
  cross-section 
  is 
  here 
  conspicuously 
  rectangular 
  

   (fig. 
  5, 
  a 
  and 
  5). 
  On 
  the 
  other 
  hand 
  the 
  largest 
  ribbon 
  has 
  

   decidedly 
  arched 
  its 
  roof 
  (H^. 
  5, 
  c). 
  At 
  their 
  extremities 
  the 
  

   ribbons 
  either 
  thin 
  out 
  to 
  sharp 
  points 
  (fig. 
  5, 
  d) 
  or 
  end 
  abruptly 
  

  

  