530  HISTORY  OF  PETROLEUM  OR  ROCK  OIL. 
portion  is  equal  to  from  19-5  to  21«0  per  cent.  The  mineral 
from  the  Acton  copper  mine  is  much  harder  and  less  friable, 
and  approaches  to  anthracite  in  its  characters.  When  heated 
it  gives  off  watery  vapor  without  any  bituminous  odor.  Its  loss 
by  heat  was  6-0  per  cent.,  and  the  residue  of  ash  was  equal  to 
2-2  per  cent. 
An  evidence  of  the  presence  of  the  unaltered  petroleum  in 
almost  all  the  Lower  Silurian  limestones  is  furnished  by  the 
bituminous  odor  which  they  generally  exhibit  when  heated, 
struck,  or  dissolved  in  acids.  In  some  cases  petroleum  is  found 
filling  cavities  in  these  limestones,  as  at  Riviere  a  la  Rose 
(Montmorenci,)  where  it  flows  in  drops  from  a  fossil  coral  of 
the  birdseye  limestone;  and  at  Pakenham,  where  it  fills  the 
cavities  of  large  ortKoceratites  in  the  Trenton.  From  some 
specimens  nearly  a  pint  of  petroleum  has  been  obtained.  It  is 
also  said  to  occur  in  the  township  of  Lancaster  in  the  same  for- 
mation. The  presence  of  petroleum  in  the  Lower  Silurian 
rocks  of  New  York  is  shown  in  the  township  of  Guilderland, 
near  Albany,  where,  according  to  Beck,  considerable  quantities 
of  petroleum  are  collected  upon  the  surface  of  a  spring  which 
rises  through  the  Hudson  River  or  Loraine  shales.  On  the 
great  Manitoulin  Island,  also,  according  to  Mr.  Murray,  a  pe- 
troleum spring  issues  from  the  Utica  State,  and  he  has  de- 
scribed another  at  Albion  Mills,  near  Hamilton,  rising  through 
the  red  shales  of  the  Medina  group;  these  have  probably  their 
origin  in  the  Lower  Silurian  limestones,  which  may  in  some  lo- 
calities prove  to  be  valuable  sources  of  petroleum. 
In  the  Upper  Silurian  and  Devonian  rocks  bitumen  is  much 
more  abundant.  Eaton  long  since  described  petroleum  as  exud- 
ing from  the  Niagara  limestone,  and  this  formation  throughout 
Monroe  County,  in  western  New  York,  is  described  by  Mr.  Hall 
as  a  granular  crystalline  dolomite,  including  small  laminse  of 
bitumen,  which  gives  it  a  resinous  lustre.  When  the  stone  is 
burned  for  lime  the  bitumen  is  sometimes  so  abundant  as  to  flow 
like  tar  from  the  kiln.  In  the  Corniferous  limestone,  at  Black 
Rock,  on  the  Niagara  River,  petroleum  is  described  as  occurring 
in  cavities,  generally  in  the  cells  of  fossil  corals,  from  which, 
when  broken,  it  flows  in  considerable  quantities.  It  also  occurs 
in  similar  conditions  in  the  Cliff  limestone  (Devonian)  of 
Ohio. 
