378  CONTRIBUTIONS   TO   ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
CHARACTER  OF  THE  COAL. 
The  coal  from  practically  every  seam  mined  in  the  quadrangle 
makes  excellent  coke,  and  it  is  equally  good  for  steaming  and  domestic 
purposes.  About  one-third  of  the  entire  output  of  coal  in  the  State 
is  made  into  coke.  To  the  proximity  of  such  great  deposits  of  coking- 
coal  and  iron  ore  that  exists  in  the  Birmingham  district,  Alabama 
owes  its  prominence  as  an  iron-producing  State. 
While  the  coal  is  of  excellent  coking  quality,  much  of  it  is  too 
dirty  as  it  comes  from  the  mines  to  be  made  at  once  into  coke.  It 
is  necessary  to  wash  it  first.  By  "  dirty  "  is  meant  that  the  coal 
is  mixed  with  a  large  proportion  of  clay,  shale,  bone,  etc.,  that  would 
impair  the  quality  of  the  coke.  The  presence  of  such  material  is 
due  to  the  many  partings,  by  which  the  coals  of  this  region  are 
broken  into  thin  benches,  and  in  many  cases  this  mixture  is  so  inti- 
mate that  in  mining  it  is  impracticable  or  impossible  to  separate 
the  foreign  matter  from  the  coal. 
This  separation  is  effected  by  washing,  Avhich  consists  in  bringing 
the  slack  or  crushed  coal  into  water  in  such  a  way  that  the  impurities, 
being  heavier  than  the  coal,  settle  to  the  bottom,  leaving  the  coal 
above.  The  process  is  continuous,  the  particles  of  clay,  shale,  etc., 
being  drawn  off  from  the  bottom  and  the  coal  spilling  over  above. 
The  washing  is  done  by  rather  elaborate  mechanical  contrivances, 
of  which  no  description  will  be  attempted  here.  By  washing  much 
coal  is  made  suitable  for  coking  that  apparently  could  not  other- 
wise be  used  or  could  only  be  made  into  an  inferior  grade  of  coke. 
A  washer  is  therefore  an  important  part  of  the  equipment  of  several 
large  mines  operating  in  the  quadrangle,  of  which  the  coal  is  largely 
coked.  There  is  one  each  at  Central,  Searles,  Brookwood,  Johns,  and 
Adger.  Experiments  recently  made  at  the  coal-testing  plant  at  the 
Louisiana  Purchase  Exposition  and  reported  in  United  States  Geo- 
logical Survey  Bulletin  No.  2G1  showed  that  dirty  slack,  otherwise  of 
little  value,  could  be  so  improved  by  washing  as  to  folly  equal  lump 
coal  in  steam-producing  power.  This  suggests  that  dirty  slack  to  be 
used  for  steaming  purposes  could  be  profitably  washed,  as,  in  fact, 
has  been  the  experience  at  certain  western  mines,  and  that  washing 
might  be  extended  with  profit  to  other  mines  in  the  quadrangle  and 
the  slack  utilized  for  other  than  coking  purposes. 
The  chemical  composition  of  the  various  seams  that  are  now  mined 
is  exhibited  by  the  analyses  in  the  subjoined  tables.  Eleven  of  these 
analyses  were  made  by  E.  E.  Somermeier,  under  the  direction  of 
N.  W.  Lord,  at  the  coal  testing  plant  at  the  Louisiana  Purchase  Exposi- 
tion. The  samples  were  taken  in  the  following  manner :  A  section  of 
uniform  width  and  depth  was  cut  from  a  working  face  of  the  coal 
seam  from  top  to  bottom,  such  portions  being  rejected  as  are  rejected  in 
