CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull.  225. 
northern  slopes  fall  off  steeply  to  a  great,  undulating-  basin,  while  the 
southern  slopes  descend  very  gently  to  an  extensive  plateau  region. 
The  elevation  of  the  range  varies  from  6,500  feet  in  its  western  foot- 
hills, where  it  dips  under  Kamas  Prairie,  to  12,400  on  Mount  Agassiz, 
L2,500  on  Hayden  Peak,  13,200  on  Mount  Tokewana,  13,250  on  Mount 
Lovenia,  and  13,486  (corrected)  on  Emmons  Peak. 
An  oval  central  area  is  encircled  by  a  series  of  generally  continuous, 
nonsymmetrical  ridges,  with  steep  inward-facing  scarps  and  more 
gentle  outfacing  slopes.  Dissection  has  reduced  the  inclosed  interior 
plateau  to  a  region  of  strong  relief  characterized  by  an  exceedingly  nar- 
row, steep-sided  main  east- west  divide,  which  rises  into  isolated  peaks 
and  falls  off  steeply  to  the  north  and  south  to  heads  of  great  canyons. 
These  canyons,  especially  those  draining  to  the  south,  are  character- 
ized by  broad,  flaring,  high-lying,  upper  levels,  deeply  trenched  by 
very  narrow,  steep-sided  gorges.  In  the  western  part  of  the  range 
some  of  these  headward  portions,  on  emerging  from  the  interior  area, 
continue  north  or  south  along  radial  courses  through  the  encircling 
ridges  and  down  their  gentle  outfacing  slopes.  Others  on  reaching 
these  ridges  turn  abruptly  and  escape  by  longitudinal  valleys,  whose 
alluvial  bottoms  are  terraced  and  trenched.  A  third  class  of  streams, 
which  are  characteristically  short  and  not  graded,  head  near  the  crests 
of  these  encircling  ridges  and  flow  down  inf acing  scarps  toward  the 
interior  of  the  area  (opposite  to  the  direction  of  prevailing  dip),  thence 
out  by  the  longitudinal  valleys.  In  the  eastern  part  of  the  range  the 
drainage  departs  from  these  simple  types.  Thus,  in  different  parts  of 
its  course,  Green  River  exhibits  characteristics  of  several  different 
types  of  drainage.  In  the  extreme  western  portion  of  the  range  Provo 
and  Weber  rivers,  the  master  streams  of  the  region,  pursue  longitudi- 
nal courses  for  a  large  portion  of  their  extent.  They  are  fed  not  only 
b}^  headwaters  of  transverse  radial  streams,  but  also  by  streams  flow- 
ing toward  the  interior  against  the  dip. 
In  brief,  the  range  is  an  elongated  dome  composed  of  a  deeply  dis- 
sected, central  plateau  and  encircling  cuestas.  The  dissection  of  the 
central  area  is  characterized  by  a  postmature  master  divide,  surmount- 
ing broad  glacial  amphitheaters,  which,  in  turn,  are  incised  by  deep, 
narrow  canyons.  Intermediate  between  the  eastern  and  western  por- 
tions of  the  range  the  drainage  is  largely  consequent;  at  the  eastern 
end  it  is  complex,  Green  River  probably  being  superimposed,  locally 
at  least;  and  in  the  western  portion  the  master  streams  follow  partially 
graded,  subsequent  courses,  and  obsequent  drainage  is  well  developed. 
Local  physiography. — The  iron  deposits  which  are  the  subject  of 
this  paper  lie  near  the  inner  margin  of  the  belt  of  encircling  cuestas, 
and  thus  immediately  outside  of  the  interior  plateau  region.  The  nar- 
row divide  in  which  they  occur  overlooks  eastward  the  broad  glacial 
amphitheater  of  the  upper  Duchesne  and  its  canyon,  and  westward  the 
