274  Methods  of  Studying  Coal        {  Aju J°uVj7harm" 
This  constituent,  which  is  the  record  of  ancient  forest  fires,  fre- 
quently retains  its  organization  so  perfectly  that  it  is  possible  to 
diagnose  the  type  of  tree  from  which  it  was  derived.  If  the  wood 
was  only  partially  charred  by  the  action  of  heat,  its  persistence  as 
such  in  coal  is  correspondingly  incomplete.  Sections  of  coal  ordi- 
narily reveal  two  sorts  of  material  showing  recognizable  structure: 
namely,  "Mother  of  Coal"  (relatively  rare)  and  spores  or  pollen 
of  the  higher  or  vascular  plants  (more  or  less  abundant).  In  addi- 
tion to  these  structurally  preserved  constituents,  combustible  min- 
erals are  largely  formed  of  a  brown  matrix  resulting  from  the  modi- 
fication in  the  course  of  ages  of  the  uncharred  woody  and  other 
gross  vegetable  remains.  With  the  fundamental  brown  of  highly 
modified  wood,  the  spores  contrast  by  their  golden  yellow  hue  and 
"  Mother  of  Coal "  by  its  intense  black  ( shading  into  brown  in  those 
portions  incompletely  charred).  The  mass  of  the  coal  has  been  sub- 
jected to  enormous  compression  during  the  ages  elapsed  since  its 
deposition  in  the  bottom  of  the  waters.  As  a  consequence  even  its 
structural  constituents  are  greatly  flattened  in  the  plane  of  the  hori- 
zontal bedding  or  laminaion. 
The  study  of  ultimate  organization  now  rendered  possible  by  im- 
proved technique  appears  to  finally  set  at  rest  the  controversy  which 
has  lasted  for  nearly  a  century  and  a  half,  in  regard  to  the  origin  of 
combustible  minerals.  The  generally  accepted  view  of  the  way  in 
which  coal  has  been  formed  is  that  it  is  essentially,  dynamically  and 
chemically  transformed  peat.  This  conception  which  took  its  origin 
with  von  Beroldingen  in  the  eighteenth  century,  has  had  its  main 
defenders  in  Germany  and  as  a  result  of  the  Teutonic  scientific 
hegemony  in  modern  times  has  been  widely  adopted  in  all  parts  of 
the  world.  In  contrast  to  this  hypothesis  is  the  more  logical  view, 
cherished  mainly  in  France,  that  coal  is  the  consequence  of  organic 
sedimentation  in  open  water.  •  This  opinion  has  been  ably  defended 
by  Renault,  Grand'Eury  and  many  others,  and  there  appears  now 
no  doubt  that  it  is  the  correct  one,  since  all  the  data  derived  from  the 
microscopic  study  of  coal,  which  must  apparently  ever  be  most 
cogent,  are  entirely  in  its  favor.  We  must  accordingly  regard  the 
hoardings  of  past  plant  life,  preserved  for  us  in  the  form  of  the 
various  coals  and  their  products,  petroleum  and  natural  gas,  as  hav- 
ing accumulated  not  in  peat  bogs  but  at  the  bottom  of  tranquil  lakes, 
not  in  situ,  but  as  the  result  of  water  transports. 
Botanical  Department,  Harvard  University, 
February,  1916. 
