﻿Wadsworth 
  — 
  Trap 
  Range 
  of 
  Keweenawan 
  Series. 
  417 
  

  

  The 
  most 
  interesting 
  feature 
  is 
  the 
  discovery 
  for 
  the 
  first 
  

   time 
  of 
  diamonds 
  in 
  meteoric 
  iron.* 
  This 
  might 
  have 
  been 
  

   predicted 
  from 
  the 
  fact 
  that 
  all 
  the 
  constituents 
  of 
  meteoric 
  

   iron 
  have 
  been 
  found 
  in 
  meteoric 
  stones, 
  and 
  vice 
  ve?*sa, 
  

   although 
  in 
  different 
  proportions. 
  

  

  The 
  incrustation 
  of 
  what 
  is 
  probably 
  aragonite 
  shown 
  by 
  

   some 
  of 
  the 
  masses 
  has 
  rarely 
  been 
  noticed 
  (I 
  find 
  two 
  records 
  

   by 
  J. 
  Lawrence 
  Smith 
  which 
  he 
  states 
  to 
  be 
  unique, 
  and 
  both 
  

   of 
  these 
  were 
  from 
  regions 
  south 
  of 
  this 
  one). 
  The 
  incrusta- 
  

   tion 
  is 
  especially 
  interesting 
  as 
  showing 
  that 
  the 
  meteoric 
  irons 
  

   must 
  have 
  been 
  imbedded 
  a 
  long 
  time, 
  as 
  the 
  formation 
  of 
  

   aragonite 
  would 
  be 
  exceedingly 
  slow 
  in 
  this 
  dry 
  climate. 
  

  

  The 
  remarkable 
  quantity 
  of 
  oxidized 
  black 
  fragmental 
  

   material 
  that 
  was 
  found 
  at 
  those 
  points, 
  where 
  the 
  greatest 
  

   number 
  of 
  small 
  fragments 
  of 
  meteoric 
  iron 
  were 
  found, 
  would 
  

   seem 
  to 
  indicate 
  that 
  an 
  extraordinarily 
  large 
  mass 
  of 
  probably 
  

   500 
  or 
  600 
  pounds 
  (226'796. 
  or 
  272156 
  kilos) 
  had 
  become 
  

   oxidized 
  while 
  passing 
  through 
  the 
  air 
  and 
  was 
  so 
  weakened 
  

   in 
  its 
  internal 
  structure 
  that 
  it 
  had 
  burst 
  into 
  pieces 
  not 
  long 
  

   before 
  reaching 
  the 
  earth, 
  

  

  Art. 
  XLV. 
  — 
  The 
  South 
  Trap 
  Mange 
  of 
  the 
  Keweenawan 
  

   Series; 
  by 
  M. 
  E. 
  Wadsworth, 
  State 
  Geologist 
  of 
  

   Michigan. 
  

  

  Iisr 
  a 
  former 
  communication 
  published 
  in 
  the 
  August 
  num- 
  

   ber 
  of 
  this 
  Journal, 
  it 
  was 
  shown 
  that 
  the 
  eastern 
  or 
  supposed 
  

   Potsdam 
  sandstone, 
  east 
  of 
  the 
  copper-bearing 
  rocks, 
  underlies, 
  

   in 
  an 
  apparently 
  conformable 
  synclinal 
  fold, 
  a 
  limestone 
  of 
  

   Trenton 
  or 
  of 
  some 
  adjacent 
  Lower 
  Silurian 
  formation. 
  It 
  

   was 
  then 
  suggested 
  that 
  the 
  contorted 
  state 
  of 
  the 
  -sandstone 
  

   might 
  have 
  some 
  weight 
  in 
  deciding 
  the 
  relative 
  age 
  of 
  the 
  

   eastern 
  sandstone 
  and 
  the 
  adjacent 
  copper-bearing 
  rocks. 
  

  

  In 
  endeavoring 
  to 
  contribute 
  something 
  to 
  the 
  solution 
  of 
  

   the 
  relation 
  of 
  these 
  two 
  series 
  of 
  rocks, 
  a 
  party 
  under 
  the 
  

   charge 
  of 
  Mr. 
  A. 
  E. 
  Seaman 
  of 
  the 
  Michigan 
  Geological 
  Sur- 
  

   vey 
  was 
  directed 
  to 
  go 
  to 
  " 
  Silver 
  Mountain," 
  and 
  thence 
  to 
  

   study 
  the 
  " 
  South 
  Trap 
  Range," 
  in 
  order 
  to 
  ascertain, 
  if 
  pos- 
  

   sible, 
  the 
  exact 
  relations 
  of 
  the 
  lava 
  flows 
  of 
  that 
  range 
  and 
  

   the 
  eastern 
  sandstone. 
  Part 
  of 
  this 
  work 
  has 
  been 
  done, 
  and, 
  

  

  * 
  Attention 
  may 
  be 
  called 
  to 
  the 
  discovery 
  by 
  Haidinger 
  (1846) 
  of 
  cubic 
  crystals 
  

   of 
  a 
  graphitic 
  carbon 
  in 
  the 
  Arva 
  meteoric 
  iron, 
  and 
  also 
  of 
  somewhat 
  similar 
  

   crystals 
  from 
  the 
  Youngdegin, 
  W. 
  Australia 
  iron, 
  described 
  by 
  Fletcher 
  (1887) 
  

   under 
  the 
  name 
  of 
  cliftonite. 
  Both 
  have 
  been 
  regarded 
  as 
  pseudomorphs 
  after 
  

   diamond. 
  

  

  