jINDGREN   and 
RAN  SO  ME. 
CRIPPLE    CREEK    DISTRICT,    COLORADO.  97 
ji  drainage  had  unusual  length — that  is,  that  one  mine  would  drain 
others  situated  at  a  distance.  Drainage  tunnels  were  then  under- 
taken, and  the  Chicago  and  Cripple  Creek,  the  Ophelia,  the  Standard, 
and  lately  the  El  Paso  tunnels  were  driven,  each  of  which  practically 
accomplished  the  drainage  of  a  large  part  of  the  district  almost  down 
to  its  own  level,  thus  showing  that  the  ground  water  is  limited  in 
quantity  and  is  more  of  the  nature  of  a  local  reservoir  than  a  "  sub- 
terranean sea." 
The  El  Paso  tunnel,' completed  in  the  winter  of  1903-4,  has  an  ele- 
vation of  8,7S3  feet  at  the  portal.  Within  a  short  time  it  effectually 
drained  not  only  the  Beacon  Hill  mines  but  also  the  Gold  Hill  mines, 
and  its  influence  extended  even  to  the  Last  Dollar  and  the  Elkton 
mines.  But  the  foregoing  statement  in  relation  to  draining  the  dis- 
trict must  be  so  modified  as  to  exclude  a  certain  part  on  the  eastern 
side,  comprising  the  mines  about  Independence  on  the  east  side  of 
Bull  Hill  and  those  on  Battle  Mountain  and  in  the  town  of  Victor,  in 
which  the  effect  of  the  El  Paso  tunnel  is  slight.  The  Findley,  Hull 
pity,  Vindicator,  and  Golden  Cycle  mines  about  the  town  of  Inde- 
jpendence  seem  to  occupy  a  separate  drainage  basin,  probably  divided 
Prom  the  main  area  by  masses  of  relatively  impermeable  rock. 
The  Portland,  Stratton's  Independence,  and  the  other  mines  near 
Victor  occupy  another  drainage  basin.  Of  these  the  Gold  Coin  and 
he  Stratton's  Independence  have  shafts  below  the  level  of  the  El  Paso 
unnel,  and  their  pumps  have  probably  drained  the  surrounding  terri- 
jjory  to  a  considerable  extent.  The  influence  of  the  drainage  tunnel 
n  the  Portland  mine  is  a  question  upon  which  opinions  differ. 
SUBTERRANEAN   GASES. 
During  the  earlier  years  of  Cripple  Creek  no  unusual  amount  of 
line  gases  was  observed,  but,  as  the  shafts  and  workings  deepened, 
veral  properties  began  to  experience  much  annoyance  and  even 
rious  interference  with  work,  often  in  spite  of  vigorous  measures 
r  ventilation.  These  gases  appear  to  issue  chiefly  from  the  breccia, 
pecially  where  it  is  of  porous  and  loose  texture;  but  they  sometimes 
dw  from  partly  open  vein  fissures  in  such  quantity  that  a  light  held 
p  to  the  fissures  is  immediately  extinguished. 
The  characteristics  of  the  gas  seemed  to  point  to  carbon  dioxide, 
d  it  is  generally  so  termed.  Preliminary  determinations  of  carbon 
oxide  by  a  portable  apparatus  yielded  percentages  which  seemed 
r  too  small  in  comparison  with  the  effects  of  the  gas  examined,  and 
to  the  belief  that  some  other  substance  was  present.     Samples 
re  then  collected  and  analyzed.     The  analysis  slunved  the  gas  to  be 
ixture  of  nitrogen  with  about  20  per  cent  carbon  dioxide  and  a 
iall  amount  of  oxygen. 
Bull.  260—05  m 7 
