COAL   OF   BRIDGER   FIELD,    MONTANA.  187 
The  quality  of  the  coal  has  not  been  determined  chemically,  but 
probably  it  is  similar  to  that  of  the  same  coal  bed  where  it  outcrops 
at  Bridger,  Mont.  The  coal  bed  is  thicker  and  cleaner  at  Silvertip 
than  it  is  at  Bridger,  and  for  this  reason  it  would  seem  probable  that 
extensive  developments  will  follow. 
BRIDGER   COAL  FIELD// 
The  most  productive  of  the  fields  described  in  this  paper  is  that 
lying  along  the  west  side  of  Clark  Fork,  in  southern  Montana.  This 
field  may  be  known  as  the  Bridger  coal  field,  from  the  name  of  the 
principal  town  and  of  one  of  the  largest  mines.  The  field  extends 
from  the  south  side  of  T.  7  S.,  R.  23  E.  of  the  Montana  meridian, 
northward  for  25  miles.  The  part  of  the  field  treated  in  this 
report  is  bounded  on  the  north  by  the  north  side  of  T.  4  S.,  R.  22  E., 
about  4  miles  north  of  Joliet,  Mont. 
The  coal  beds  are  the  same  as  those  in  the  Silvertip  coal  field, 
belonging  to  the  Eagle  sandstone.  They  cross  the  State  line  from 
Wyoming  in  T.  9  S.,  R.  25  E.  On  the  Wyoming  side  of  the  line  these 
beds  are  not  workable.  West  of  Frannie,  Wyo.,  they  have  prac- 
tically disappeared,  being  represented  only  by  a  few  thin  layers  of 
coal  in  a  mass  of  black  carbonaceous  shale. 
The  southernmost  point  of  workable  coal  is  in  the  NW.  }  NW.  \ 
sec.  2,  T.  9  S.,  R.  24  E.,  where  the  bed  is  exposed  on  both  sides  of  a 
gulch  that  cuts  deeply  into  the  Eagle  sandstone.  On  the  north  side 
of  this  gulch  the  following  section  was  obtained : 
Section  of  Eagle  coal  4\  miles  west  of  Scribner,  Mont.,  in  sec.  2,  T.  9  S.,  R.  24  E. 
Ft.    in. 
Sandstone,  massive,  gray 27 
Shale,  coaly 2 
Coal 6 
Bone 6 
Coal 2 
Shale,  dark,  coaly 2 
Alternating  layers  of  sandstone  and  pale  bluish-gray  shale 15 
Total  coal 2     6 
The  coal  is  exposed  in  two  prospect  drifts  which  have  not  been 
worked  for  many  years.  On  the  south  side  of  the  gulch  the  coal 
is  not  workable,  being  only  14  inches  thick.  Northward  through 
T.  8  S.,  Rs.  23  and  24  E.,  the  coals  of  the  Eagle  sandstone  arc  too 
thin  to  work;  but  in  T.  7  S.,  K.  23  E.,  they  Rre  of  workable 
thickness. 
a  The  writer  is  indebted  to  N.  TI.  Darton's  paper  on  the  Coals  of  Cnti.oii  Comity.  Mont.  (Bull.  1'.  S. 
Geoi.  Survey  No.  310,  1907,  pp.  I 7  I  193),  (or  supplementary  data  on  this  coal  field 
