208  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1.905. 
exceed  the  amount  obtained  from  the  sample,  but  this  can  be  approximated  by  multiplying  by  certaS 
coefficients.  The  coefficients  determined  in  the  work  of  the  Geological  Survey  coal-testing  plant  las' 
year  will  not  be  strictly  applicable,  since  the  sampling  was  nol  done  under  this  system,  hut  they  an 
approximately  the  same  ami  can  he  used  until  more  accurate  coefficients  are  determined.  When  suffi- 
cient data  are  at  hand,  it  seems  possible  that  specific  coefficients  may  he  determined  for  certain  fields 
that  is,  a  coefficient  for  the  Appalachian  held,  another  coefficienl  for  the  Eastern  Interior  held,  etc.,  and 
finally,  coefficients  may  be  determined  for  local  subdivisions  of  the  larger  fields  or  Eor  certain  beds  of  cm 
within  those  fields. 
i;  All  descriptions  of  samples  should  state  definitely  how  the  samples  were  obtained,  so  that  the  readS 
may  judge  for  himself  the  value  of  the  results  obtained;  and  when  analyses  are  recalcula  led  the  coell'r 
cients  of  increase  or  decrease  should  he  given,  together  with  the  authority  for  using  this  coefficient  o) 
tl  e  data  on  which  it  was  determined. 
CLASSIFICATION    of    COALS. 
The  material  made  available  by  the  work  of  the  chemical  laboratory  led  to  another  line 
•  •f  investigation  that  is,  tlu-  classification  of  coals,  ll  has  been  generally  agreed  thai 
proximate  analyses  afford  no  adequate  basis  for  classification,  though  such  a  basis  was  pro- 
posed for  the  Pennsylvania  coals  many  years  ago.  This,  however,  failed  when  it  was 
applied  to  the  lignites  and  low-grade  bituminous  coals. 
As  a  result  of  tlu1  work  of  the  coal-testing  plant  there  became  a\  ailable  fifty-six  u It  iman 
analyses  of  coals  of  all  class* ss  from  brow  ti  lignite  to  anthracite,  and  this  seemed  to  afford  l 
favorable  opportunity  for  an  attempt  at  classification.  After  various  t  rials  I  he  ratio  of  th< 
carbon  to  the  hydrogen  seemed  to  present  the  best  basis  for  a  classification.  This  ratio  run 
from 26.7:  1  in  Pennsylvania  anthracite  to 9.4:1  in  Texas  brow  n  lignite.  'With  the  data  avail 
able  it  seems  as  if  eleven  groups  may  be  recognized  and  separated  by  such  a  scheme  o 
classification,  as  follows: 
Groups  .1 .  B,  'i nil  <  . 
Carbon-hydroga 
ratio. 
Graphite  and  anthracites  (only  one  representative     Pennsylvania  anthracite) 26.! 
Group  I>. 
Semianthracite  (nol  represented). 
Group  /•'. 
Semibituminous  (only  one  representative    highest  class  Arkansas  coal) 20.! 
Group  F. 
Highest  grade  bituminous  (besl  West  Virginia  and  western  A  rkansas  coals) 20      17 
Group  a. 
Second-grade  bituminous  (second-class  West   Virginia,  first  Chi:---  Kentucky  and   Alabama 
coals) 17       II.- 
Croup  II. 
Third-grade  bituminous  (first-class  Indian  Territory,  Kansas,  Missouri,  Iowa,  and  Illinois 
coals,  and  see. md -class  Kentucky  coals) 1 1.  I  n.'. .' 
Group  I. 
Lowest  grade  bituminous  (includes  majority  of  Iowa,  Missouri,  Illinois,  and  Indiana  coals 
and  some  of  the  Wyoming  and  Mont  a  mi  coals) 12.5   11.1 
Croup  J. 
Lignite  (includes  all  lignites,  both  }>rown  and  black,  that  were  tested) 11.2    '.>.: 
Group  K. 
Tat <i.  I 
It  is  not  expected  by  the  writer  thai  such  a  classification  will  ever  be  used  in  a  eoimnereia 
way.  The  trade  names  are  now  well  established,  and  it  is  not  feasible  to  attempt  to  replace 
them  by  such  a  scientific  classification  as  the  above.  There  is,  however,  demand  for  just 
such  a  classification  to  definitely  fix  the  position  and  the  relative  value  of  a  coal.  Fcl 
instance,  if  the  ultimate  analysis  of  a  sample  of  coal  shows  a  carbon-hydrogen  ratio  of  11: 13 
