bmmons.]         COPPER    IN    RED    BEDS    OF    COLORADO    PLATEAU.  223 
Colorado  Plateau  region.  Before  proceeding,  however,  lo  a  detailed 
consideration  of  these  western  deposits,  I  will  briefly  consider  the 
various  genetic  theories  that  have  been  held  in  Europe  to  account  for 
the  Mansfeld  and  allied  deposits. 
The  Mansfeld  deposits  were  long  held  to  be  typical  examples  of  the 
chemical  precipitation  of  metallic  salts  contemporaneously  with  me- 
chanical deposition  of  the  sediments  in  inclosed  lakes  or  oceans  under 
the  reducing  influence  of  organic  remains.  The  metals  were  assumed 
to  be  held  in  solution  as  sulphates,  associated  with  the  usual  alkaline 
sulphates  of  sea  water.  The  latter  would  be  decomposed  by  the  action 
3f  organic  remains  with  an  evolution  of  sulphureted  hydrogen,  which 
in  its  turn  would  precipitate  the  metals  from  their  sulphate  solutions 
is  sulphides.  The  bent-up  position  of  the  fish  skeletons  found  in 
these  beds  was  held  by  Freiesleben  and  others  to  be  an  indication  that 
the  fish  inhabiting  these  waters  had  been  poisoned  by  the  sulphates 
3f  the  metals  held  in  solution.  It  was  assumed  that  sea  water  very 
generally  contains  small  amounts  of  copper  salts,  and  Dieulafait,  in 
1880,  had  shown  that  the  evaporated  salts  of  the  Mediterranean 
waters  contained  appreciable  amounts  of  copper,  and  estimated  that 
i  cubic  meter  of  sea  water  would  contain  one  one-hundredth  of  a 
strain  of  copper. 
As  studies  of  ore  deposits  assumed  a  more  objective  phase  there 
same  to  be  doubters  as  to  the  efficiency  of  this  theory.  It  was  observed 
hat  the  various  European  deposits  were  not  confined  to  a  single  defi- 
lite  horizon,  as  at  Mansfeld,  and  that  the  ores  occurred  in  connection 
with  fractures  and  other  disturbances. 
As  Posepny's  views  became  more  prevalent,  it  came  to  be  very  gen- 
rally  believed  that  even  the  Mansfeld  deposits  had  been  introduced 
ince  the  deposition  of  the  strata,  though  Von  Groddeck,  one  of  the 
nost  enlightened  of  the  German  writers  on  ore  deposits,  whose  near- 
less  to  that  region  should  have  given  special  opportunities  for  their 
study,  stoutly  maintained  their  sedimentary  origin  up  to  the  time  of 
lis  death.  Beck,  however,  in  his  text-book  on  ore  deposits,  classifies 
[ill  these  Triassic  or  Permian  deposits  among  his  epigenetic  or  later- 
formed  class. 
Of  late  years  there  has  been  a  recrudescence  of  the  theory  of  sedi- 
nentary  ore  deposition,  as  a  reaction  against  the  extreme  views  held 
jy  Posepny,  that  all  ore  deposits  are  of  later  origin  than  inclosing 
^ocks,  and  those  of  Vogt,  who  Avishes  to  refer  most  of  them  to  an  igne- 
ous source. 
Professor  Bergeat,  who  now  occupies  the  chair  of  Von  Groddeck  at 
he  mining  school  of  Clausthal,  is  a  leading  exponent  of  these  later 
news,  and  has  explained  to  me  personally  that  he  lavs  great  stress 
Upon  the  discovery  by  the  Russian  oceanographers  that  at  the  pics- 
