PENNSYLVANIA.  321 
The  main  bench,  which  is  over  1  feet  thick,  contains  a  very  thin 
streak  of  shale,  but  its  exact  position  was  not  noted. 
Two  other  mines,  also  on  the  southern  lobe  of  this  block,  are  the  new 
one  owned  by  the  Conemaugh  Coal  Company  (No.  15)  and  the  mine  on 
the  Arnold  farm  (No.  16),  which  used  to  supply  the  American  Sheet 
Steel  Compaivy  mill  at  the  mouth  of  Blacklegs  Creek,  but  is  now  oper- 
ated only  for  country  trade.  At  the  Conemaugh  mine  the  parting  or 
"band  slate"  is  usually  from  1  to  2  inches  thick,  but  it  thickens  in 
places  to  1  foot.  The  "draw  slate,"  from  6  inches  to  1  foot  thick,  is 
taken  down  in  entry,  but  can  be  held  in  rooms.  The  total  thickness 
of  coal  is  practically  the  same  as  in  other  mines  at  this  end  of  the  field. 
TONNAGE. 
Allowing  1,560  tons  to  the  acre  for  each  foot,  the  Pittsburg  seam, 
which  averages  7  feet  of  workable  coal  in  this  field,  contains  10,920 
tons  to  the  acre.  There  are  probably  8,000  acres  of  merchantable  coal 
remaining  in  the  field,  or  87,360,000  tons.  If  by  most  advantageous 
methods  of  working  70  per  cent  of  this  coal  can  be  mined,  the  total 
product  of  the  field  as  it  now  stands  would  be  61,152,000  tons. 
QUALITY  OF  THE  COAL. 
In  the  following  table  nine  anatyses  of  the  Pittsburg  coal  in  the 
Elders  Ridge  field  are  given.  Four  of  these,  made  by  Mr.  A.  S. 
McCreath,  were  published  by  the  second  geological  surve}7  of  Penn- 
sylvania, in  the  reports  of  Armstrong  and  Indiana  counties,  in  1878. 
The  other  five  are  new,  and,  so  far  as  is  known,  are  published  here 
for  the  first  time. 
The  Avonmore  analysis  was  furnished  b}7  the  superintendent  of  the 
mine,  and  the  method  of  sampling  the  coal  was  not  stated. 
The  Arnold  analyses  were  furnished  by  the  Conemaugh  Coal  Com- 
pany, with  the  statement  that  the  samples  "were  taken  in  the  usual 
way  in  which  this  work  is  done,  viz,  a  narrow  slip  from  top  to  bottom, 
getting  in  an  equal  amount  of  both  bench  and  breast  coal." 
The  samples  for  the  Iselin  and  Holsten  analyses  were  collected  by  the 
writer.  In  taking  the  samples  a  cut  was  made  at  a  working  face  from 
top  to  bottom  of  that  portion  of  the  seam  which  is  marketed.  The 
samples  were  mixed  and  quartered  and  sealed  in  glass  fruit  jars.  The 
analyses  of  the  Iselin  and  Holsten  coal  samples  were  made  in  the 
chemical  laboratory  of  the  United  States  Geological  Survey  by  Mr. 
George  Steiger  and  Mr.  Eugene  C.  Sullivan,  respectively. 
Bull.  225—04 21 
