﻿G. 
  H. 
  Stone 
  — 
  Asphaltum 
  of 
  Utah 
  and 
  Colorado. 
  149 
  

  

  yield 
  no 
  paraffin, 
  or 
  at 
  most 
  a 
  mere 
  trace 
  to 
  solvents 
  and 
  boil- 
  

   ing 
  water, 
  and 
  a 
  considerably 
  larger 
  proportion 
  after 
  destruc- 
  

   tive 
  distillation. 
  They 
  approach 
  cannel 
  coal 
  in 
  composition, 
  

   but 
  contain 
  a 
  very 
  large 
  proportion 
  of 
  ash, 
  so 
  that 
  none 
  of 
  

   them 
  contain 
  more 
  than 
  10, 
  or 
  perhaps 
  20 
  per 
  cent 
  of 
  carbon- 
  

   aceous 
  matter. 
  The 
  richer 
  layers 
  are 
  commonly 
  known 
  in 
  

   western 
  Colorado 
  as 
  " 
  oil 
  rock," 
  and 
  burn 
  readily 
  with 
  a 
  bright, 
  

   furious 
  flame, 
  leaving 
  pieces 
  of 
  shale 
  having 
  the 
  same 
  size 
  and 
  

   shape 
  as 
  they 
  had 
  before 
  being 
  burned. 
  These 
  facts 
  indicate 
  

   that 
  in 
  their 
  natural 
  state 
  these 
  bituminous 
  shales 
  (they 
  all 
  

   contain 
  so 
  much 
  lime 
  as 
  to 
  be 
  more 
  nearly 
  marls 
  than 
  shales) 
  

   are 
  asphaltic 
  rather 
  than 
  paraffinic 
  rocks. 
  The 
  richer 
  layers 
  

   are 
  seldom 
  more 
  than 
  4 
  feet 
  thick 
  and 
  are 
  found 
  in 
  the 
  midst 
  

   of 
  low 
  grade 
  rocks 
  (shales, 
  marls, 
  and 
  limestones). 
  At 
  one 
  

   place 
  I 
  noted 
  ten 
  of 
  the 
  rich 
  layers 
  each 
  two 
  to 
  four 
  feet 
  

   thick, 
  distributed 
  at 
  intervals 
  through 
  about 
  400 
  feet 
  of 
  rock. 
  

  

  3. 
  Bituminous 
  Limestones. 
  — 
  Limestones 
  and 
  marls 
  consti- 
  

   tute 
  a 
  large 
  part 
  of 
  the 
  Tertiary 
  rocks 
  of 
  the 
  region 
  under* 
  

   discussion, 
  i. 
  e. 
  of 
  the 
  asphalt-bearing 
  formations. 
  Almost 
  all 
  

   the 
  limestones 
  are 
  somewhat 
  bituminous, 
  and 
  some 
  strata 
  will 
  

   burn 
  like 
  the 
  shales.. 
  They 
  are 
  colored 
  from 
  gray 
  to 
  yellowish- 
  

   brown, 
  light 
  color, 
  rather 
  than 
  blackish 
  like 
  the 
  bituminous 
  

   shales. 
  ITsually 
  they 
  do 
  not 
  contain 
  distinct 
  fossils, 
  but 
  are 
  

   often 
  oolitic, 
  pisolitic 
  or. 
  coarser 
  concretionary, 
  i. 
  e. 
  they 
  are 
  

   semi-crystalline. 
  Fetid 
  layers 
  are 
  not 
  rare, 
  and 
  some 
  of 
  them 
  

   are 
  particularly 
  offensive. 
  Cavities 
  in 
  the 
  bituminous 
  lime- 
  

   stones 
  are 
  often 
  filled 
  with 
  hard 
  asphalt, 
  in 
  some 
  places 
  taking 
  

   the 
  form 
  of 
  Wurtzilite, 
  in 
  other 
  places 
  Uintaite. 
  The 
  color 
  of 
  

   the 
  Uintaite 
  varies 
  from 
  the 
  deepest 
  black 
  to 
  brown 
  and 
  even 
  

   gray-brown. 
  The 
  lighter 
  colors 
  are 
  found 
  in 
  the 
  centers 
  of 
  

   the 
  lumps 
  or 
  in 
  the 
  cavities 
  less 
  open 
  to 
  the 
  air. 
  I 
  have 
  found 
  

   asphalt 
  in 
  five 
  classes 
  of 
  cavities 
  in 
  these 
  limestones. 
  

  

  1. 
  In 
  small 
  irregular 
  or 
  somewhat 
  amygclaloidal 
  cavities 
  in 
  

   fine 
  granular 
  limestone 
  and 
  having 
  no 
  visible 
  outlets. 
  

  

  2. 
  In 
  fractures 
  that 
  cross 
  the 
  strata 
  for 
  only 
  a 
  short 
  distance 
  

   (gash 
  veins 
  of 
  the 
  miners). 
  

  

  3. 
  In 
  deep 
  fissures 
  (true 
  fissure 
  veins). 
  

  

  4. 
  In 
  caves 
  or 
  channels 
  of 
  subterranean 
  streams, 
  in 
  which 
  

   the 
  asphalt 
  was 
  brought 
  in 
  after 
  the 
  stalagmitic 
  growths 
  were 
  

   completed 
  or 
  nearly 
  so. 
  

  

  5. 
  In 
  the 
  interior 
  of 
  shells, 
  or 
  in 
  the 
  cavities 
  found 
  in 
  the 
  

   centers 
  of 
  concretions 
  and 
  nodules 
  contained 
  in 
  the 
  limestone. 
  

  

  The 
  limestone 
  yields 
  on 
  destructive 
  distillation 
  several 
  per 
  cent 
  

   of 
  volatile 
  and 
  combustible 
  carbonaceous 
  matter. 
  In 
  all 
  cases 
  un- 
  

   less 
  in 
  the 
  fissure 
  veins 
  and 
  stream 
  caves 
  it 
  is 
  evident 
  that 
  the 
  as- 
  

   phalt 
  must 
  have 
  been 
  derived 
  from 
  the 
  country 
  rock, 
  i. 
  e. 
  a 
  bitu- 
  

   minous 
  liquid 
  oozed 
  out 
  of 
  the 
  limestone 
  into 
  the 
  cavities. 
  Since 
  

  

  