﻿"226 
  REPORT 
  UNITED 
  STATES 
  GEOLOGICAL 
  SURVEY. 
  

  

  across 
  the 
  Lake 
  of 
  Geneva, 
  many 
  miles 
  beyond 
  its 
  present 
  limits. 
  

   Dependent 
  upon 
  the 
  moisture 
  derived 
  from 
  the 
  large 
  expanse 
  of 
  water 
  

   farther 
  south 
  was 
  the 
  existence 
  of 
  these 
  enormous 
  moving 
  ice-fields. 
  

   With 
  other 
  words, 
  though 
  indirectly 
  in 
  connection, 
  perhaps, 
  with 
  the 
  

   general 
  glacial 
  epoch, 
  their 
  perpetuation 
  was 
  directly 
  dependent 
  upon 
  

   local 
  causes. 
  As 
  the 
  sea 
  of 
  the 
  Sahara 
  receded, 
  the 
  prevailing 
  south- 
  

   westerly 
  wind 
  (fcBhn 
  of 
  Switzerland) 
  became 
  warmer, 
  the 
  mean 
  annual 
  

   temperature 
  rose, 
  and 
  the 
  size 
  of 
  the 
  glaciers 
  diminished 
  in 
  proportion. 
  

   According 
  to 
  Oh. 
  Martens,* 
  the 
  mean 
  temperature 
  of 
  Switzerland 
  would 
  

   to-day 
  require 
  a 
  fall 
  of 
  but 
  4° 
  0. 
  to 
  permit 
  glaciers 
  to 
  extend 
  once 
  more 
  

   as 
  far 
  as 
  the 
  city 
  of 
  Geneva. 
  

  

  B. 
  V. 
  Ootta 
  t 
  states, 
  in 
  his 
  clear 
  language, 
  that 
  in 
  the 
  course 
  of 
  time, 
  

   may 
  it 
  even 
  require 
  millions 
  of 
  years, 
  every 
  lake 
  destroys 
  itself. 
  The 
  

   water 
  contained 
  in 
  a 
  basin 
  will 
  never 
  rest 
  until 
  it 
  has 
  destroyed 
  such 
  

   portions, 
  the 
  destruction 
  of 
  which 
  will 
  result 
  in 
  the 
  disappearance 
  of 
  

   the 
  lake 
  itself. 
  Where 
  changes 
  of 
  niveau 
  do 
  not 
  take 
  place, 
  counter- 
  

   balancing 
  the 
  transporting 
  power 
  of 
  flowing 
  water, 
  the 
  tendency 
  of 
  all 
  

   streams 
  emptying 
  into 
  lakes 
  will 
  be 
  to 
  raise 
  the 
  level 
  of 
  its 
  bottom. 
  

   Thus 
  both 
  erosion 
  at 
  the 
  edges 
  of 
  a 
  lake 
  and 
  a 
  rising 
  of 
  its 
  bed 
  will 
  

   combine 
  to 
  produce 
  a 
  dry 
  valley 
  where 
  formerly 
  water 
  occupied 
  the 
  

   region. 
  To 
  these 
  is 
  added 
  the 
  destruction 
  by 
  evaporation, 
  and 
  we 
  have 
  

   three 
  mighty 
  factors 
  to 
  account 
  for 
  the 
  absence 
  of 
  bodies 
  of 
  water 
  

   in 
  the 
  numerous 
  valleys 
  of 
  our 
  western 
  country 
  that 
  bear 
  evidence 
  of 
  

   having 
  at 
  one 
  time 
  contained 
  them. 
  

  

  With 
  the 
  disappearance 
  of 
  these 
  lakes, 
  the 
  recession 
  and 
  eventual 
  

   destruction 
  of 
  the 
  ancient 
  glaciers 
  was 
  in 
  the 
  most 
  intimate 
  connection. 
  

   The 
  latter 
  were 
  totally 
  dependent 
  upon 
  the 
  former 
  for 
  their 
  existence, 
  

   and 
  both 
  came 
  to 
  a 
  termination 
  within 
  a 
  short 
  time 
  of 
  each 
  other. 
  

  

  Though 
  no 
  doubt 
  numerous 
  localities 
  may 
  be 
  found 
  in 
  Southern 
  

   Colorado, 
  where 
  small 
  glaciers 
  existed, 
  it 
  was 
  impossible, 
  during 
  the 
  

   time 
  we 
  spent 
  there 
  to 
  study 
  more 
  of 
  them 
  than 
  the 
  ones 
  especially 
  

   mentioned 
  above. 
  They 
  represent, 
  I 
  think, 
  the 
  most 
  typical 
  occurrences 
  

   of 
  that 
  section 
  of 
  the 
  country, 
  and 
  present 
  varied 
  features 
  of 
  great 
  

   interest. 
  

  

  B. 
  

  

  CATALOGUE 
  OF 
  THE 
  MINERALS 
  OF 
  COLORADO. 
  

  

  The 
  subjoined 
  list 
  of 
  minerals 
  was 
  prepared 
  as 
  nearly 
  complete 
  

   up 
  to 
  date 
  as 
  possible. 
  As 
  a 
  foundation 
  for 
  it, 
  the 
  list 
  published 
  in 
  the 
  

   Report 
  of 
  1873 
  (p. 
  355) 
  was 
  taken. 
  All 
  available 
  material 
  has 
  been 
  

   utilized 
  in 
  its 
  preparation. 
  I 
  am 
  indebted 
  for 
  information 
  both 
  through 
  

   the 
  medium 
  of 
  publications 
  and 
  personal 
  communications 
  to 
  the 
  follow- 
  

   ing 
  gentlemen 
  : 
  Oapt. 
  E. 
  L. 
  Berthoud, 
  of 
  Golden, 
  Col.; 
  Prof. 
  P. 
  Frazer, 
  

   E. 
  M., 
  Philadelphia; 
  Prof. 
  F. 
  A. 
  Genth, 
  of 
  the 
  University 
  of 
  Pennsyl- 
  

   vania 
  ; 
  Dr. 
  F. 
  V. 
  Hayden 
  ; 
  W. 
  H. 
  Holmes 
  ; 
  Dr. 
  O. 
  Loew 
  ; 
  Prof. 
  E. 
  J. 
  

   Mallet, 
  jr., 
  of 
  Rosita, 
  Col.; 
  A. 
  R. 
  Marvine; 
  Dr. 
  A. 
  C. 
  Peale; 
  Mr. 
  

   Peters, 
  E. 
  M., 
  Fairplay, 
  Col.; 
  Prof. 
  J. 
  F. 
  L. 
  Schirmer, 
  United 
  States 
  

   Mint, 
  Denver, 
  Col.; 
  A'. 
  Von 
  Schulz, 
  E. 
  M., 
  Black 
  Hawk, 
  Col., 
  and 
  J. 
  

   Alden 
  Smith, 
  Territorial 
  Geologist 
  of 
  Colorado. 
  

  

  Among 
  the 
  most 
  interesting 
  minerals 
  of 
  the 
  State 
  the 
  tellurium-com- 
  

  

  * 
  Vezian, 
  Prodrome 
  de 
  g^ologie, 
  torn, 
  i, 
  p. 
  421. 
  

   tGeologie 
  der 
  Gegeuwart, 
  1372, 
  }}. 
  357. 
  

  

  