498  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
retort  it  is  drawn  off  into  a  settling  pan,  in  which  it  is  kept  at  a  tem- 
perature sufficiently  high  to  maintain  it  in  a  liquid  condition.  From 
the  settling  pan  the  sulphur  is  run  into  cast-iron  molds,  which  have  a 
capacity  of  about  250  pounds  each,  and  are  in  the  form  of  a  frustum 
of  a  cone.  In  these  molds  the  sulphur  is  allowed  to  stand  from  thirty- 
six  to  forty-eight  hours.  When  it  is  cooled  the  sulphur  is  dumped  out 
and  broken  up  into  small  pieces.  It  is  then  put  through  a  crusher, 
which  reduces  it  to  what  is  called  pea  size.  The  sulphur  is  placed  on 
the  market  in  this  form  in  sacks  containing  100  pounds,  or  it  is  ground 
by  buhrstones  to  flour  sulphur  and  put  up  into  sacks  containing  110 
pounds. 
In  this  region  the  question  of  fuel  is  important.  The  use  of  coal 
would  necessitate  its  transportation  from  a  long  distance.  Fortunately, 
however,  on  some  of  the  mountains  in  the  neighborhood  of  the  mines 
there  is  a  sufficient  growth  of  wood  to  supply  fuel  as  well  as  timbers 
for  the  mines. 
Geology  of  the  region. — The  writer  attempted  an  examination  of 
only  the  region  immediately  near  the  sulphur  mines.  His  route  of 
travel  to  them  was  from  Mill  City,  the  first  station  northeast  of  Hum- 
boldt House,  along  the  wagon  road  from  this  place  which  joins  the 
one  from  Humboldt  House  in  the  valle}^  of  Humboldt  River.  As  is' 
commonly  the  case'in  this  portion  of  Nevada,  the  country  presents  two 
types  of  topography — desert  valleys  and  barren  mountain  ranges. 
Humboldt  River  usually  has  but  small  volume  where  it  is  crossed.  It 
is  bordered  by  a  sagebrush  desert  about  10  miles  wide.  The  moun- 
tains west  of  the  river  in  the  vicinity  of  Humboldt  House  are  known 
as  the  Montezuma  Range.  The  wagon  road  crosses  a  low  divide  in 
them  and  descends  into  a  narrow  valley,  to  the  west  of  which  are  the 
Kamma  Mountains,  in  which  are  the  sulphur  mines.  The  Kamma 
Mountains  form  a  crescentic  mass,  the  curve  opening  to  the  west. 
They  are  divided  into  three  groups,  which  may  be  denominated  the 
southwestern,  middle,  and  northern  groups.  The  wagon  road  over 
which  the  sulphur  is  hauled  from  the  mines  passes  between  the  central 
and  northern  groups. 
The  rocks  which  constitute  the  northern  group,  as  shown  on  the 
maps  of  the  fortieth  parallel,  consist  of  a  mass  of  rhyolite,  forming 
the  main  mountains..  Along  their  western  border,  on  the  lower  slopes, 
there  is  an  irregular  area  of  water-laid  deposits  of  Tertiaiy  age.  These 
Tertiary  rocks,  in  which  the  sulphur  deposits  occur,  consist  of  frag- 
ments of  volcanics  and  beds  of  tuffs  which  in  places  have  been  largely 
altered  since  their  deposition.  These  are  regarded  as  part  of  the 
Truckee  Miocene,  which  is  found  at  numerous  localities  in  that  portion 
of  Nevada.  At  the  sulphur  mines  the  rocks  are  very  siliceous  and  are 
cemented  by  quartz  and  chalcedony,  and  in  some  instances  carry 
globular  masses  of  hyalite  or  are  coated  with  a  layer  of  that  mineral, 
a  transparent,  glassy  variety  of  opal  or  amorphous  silica.     There  is 
