WORK    ON    COAL. 
209 
the  place  of  the  coal  in  the  above  scheme  of  classification  is  definitely  fixed,  and  in  a  general 
way,  impurities  being  excluded,  the  true  value  of  the  coal  is  also  fixed.  The  groups  pro- 
posed are  put  forward  tentatively.  From  the  analyses  at  hand  they  seem  to  represent  all 
the  grades  of  coal  with  which  we  are  acquainted,  but  it  is  possible  that  with  further  data  t  he 
limits  of  the  groups  may  be  changed  to  some  extent.  It  is  not  probable,  however,  that  this 
change  will  be  serious,  and  it  is  hoped  that  the  limiting  figures  as  given  will  stand. 
There  is  no  sharp  separation  between  the  lignites  and  the  lowest  grade  bituminous  coals, 
but  the  above  grouping  probably  represents  the  facts  in  the  case.  It  is  possible,  however, 
that  in  future  work  the  carbon-hydrogen  ratio  of  some  ligintes  may  be  slightly  higher  than 
that  of  some  bituminous  coals.  It  is  anticipated  that  there  will  always  be  a  certain  amount 
of  merging  along  this  line,  but  according  to  the  present  scheme  the  lignites  fall  within  one 
general  group,  and  hence  it  seems  to  apply  to  them  as  well  as  to  the  bituminous  coals. 
GEOGRAPHIC    DISTRIBUTION    OF    SAMPLES. 
The  geologist  is  more  or  less  interested  in  the  question  of  what  coals  were  tested  and  how 
well  the  samples  represent  the  entire  coal  fields  of  the  United  States.  It  is  difficult  to  show 
in  a  brief  way  these  facts.  The  following  table  gives  the  distribution  of  the  samples  which 
had  been  tested  up  to  January  1,  1906,  and  these  are  compared  with  the  production  of  the 
various  States  for  the  year  1904  and  also  with  the  estimated  area  of  the  coal  fields  within  the 
various  States: 
Comparative  table  showing  'production,  number  of  tests,  and  area  of  coal  fields  of  the  various 
States. 
State. 
Production 
in  1904. 
Number 
of  mines 
sampled. 
Estimated 
area  of 
coal  fields. 
Short  tons. 
11,262,046 
2,009,451 
78, 888 
6,658,355 
390, 191 
3,  480 
36,475,060 
10,934,379 
1,046.539 
6,  519.  933 
6, 333,  307 
7, 566; 482 
4,813,622 
1.342,840 
4, 108,  308 
1,358,919 
1,452,325 
200,  128 
24,  434, 812 
111,540 
97,952,267 
4,782.211 
1,195.944 
1,493.027 
3,583,914 
3,137,681 
32, 602, 819 
5, 178,  556 
4 
1 
1 
Sq.  milts. 
0.000 
2,500 
California 
200 
7,000 
Georgia 
f                107 
North  Carolina 
1 50 
Idaho 
12 
11 
0 
5 
5 
8 
42, '.)()() 
Indiana 
6,500 
Indian  Territory 
17,000 
10,000 
Kansas ...                                                                   
15.000 
Kentucky 
16,980 
4:30 
7,500 
4 
1 
2 
3 
8 
14.000 
32, 000 
New  Mexico 
2.700 
North  Dakota ■ 
28,620 
Ohio ! 
12.000 
Oregon                                                                                       
300 
8 
12,200 
4,400 
Texas 
o 
35.000 
Utah                                                                                          
2,500 
Virginia .                                                                      
4 
1,550 
100 
21 
2 
24, 780 
8,000 
