474  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
sive  flow  was  effective  in  metamorphosing  the  nearby  limestones,  and 
its  ejection  may  be  causatively  related  to  the  folding  and  brecciation 
of  these  beds.  Whatever  the  cause,  the  significant  fact  remains  that 
at  the  south  end  of  the  Hozel  Range,  in  the  immediate  vicinity  of 
occurrences  of  asphaltic  matter,  the  limestone  country  rock  is  folded 
and  brecciated  and  cut  and  capped  by  a  basic  extrusive. 
The  occurrence  of  this  asphaltic  substance  appears,  so  far  as  now 
knoAvn,  to  be  restricted  to  the  shallow  littoral  portion  of  Great  Sail 
Lake,  one- fourth  to  1  mile  out  from  the  present  shore  line,  immedi- 
ately southeast  of  the  Rozel  Hills,    It  there  exudes  through  the  uncon 
soli  da  ted  material  on  the  bottom  of  the  lake  and  bubbles  up  into  th( 
water  in  the  form  of  hollow  spherical  or  tubular  masses  1  to  2  inches 
in  length,  and  of  threads  and  hairs  G  to  18  inches  in  length.     These 
small  masses  spot  the  bottom  in  great  numbers  throughout  this  area 
At-  certain  points  the  emissions  are  concentrated  into  consider  abl< 
seepages  or  "pitch  springs,"  1  to  2  feet  in  diameter.     The  source  ol 
these  seepages  appears  to.  those  who  have  prospected  this  ground  m 
be  a  bed  of  ashpalt  2  or  3  feet  thick,  which  was  encountered  80  fee 
below  the  present  lake  bed,  and  an  underlying  series  of  asphalt! 
beds  3  to  5  feet  thick,  which  alternate  with  beds  of  clay  to  a  deptl 
of  140  feet,  at  least.     In  the  vicinity  of  these  seepages  the  asphalt! 
matter  cements  the  calcareous  oolitic  deposits  of  the  lake  bottom  ini 
a  bituminous  limestone.     This  forms  numerous  low  islets,  1  to  50  fee 
in  diameter,  which  are  distributed  in  rough  alignment.     This  align 
ment  and  the  presence  of  intensely  brecciated  zones  in  the  limeston 
on  the  mainland  suggest  the  possibility  that  the  seepages  may  b 
along  zones  of  fracture.     These  may  have  served  merely  to  ope 
exits  for  the  iluid  asphalt  in  unconsolidated  lake  beds,  or  may  haj 
also  delivered  it  from  deeper  reservoirs  in  underlying  bed  rock  int 
its  present  position.     In  brief,  the  asphalt  occurs  either  in  bituminou 
oolitic  limestone,  as  the  cement,  or  in  springs,  as  liquid  asphalt  froi 
beds  3  to  5  feet  thick,  intercalated  with  clay  beds  at  a  depth  of  80  t\ 
140  feet. 
In  character  this  substance  is  opaque,  brownish-black,  oily,  vij 
cous.  and  strongly  asphaltic  in  odor.     Its  consistency  varies 
with  the  temperature,  from  a  thin,  semiliquid  state  at  body 
peratures  to  a  rigid,  brittle  state  in  outdoor  winter  temper 
which  permits  it  to  be  chipped  with  a  pick.     The  composition  hi 
been  studied  and  numerous  analyses  have  been  published  in  curre|4|ir 
mining  magazines,  which  show  high  percentages  of  asphalt  and  oil.! 
The  results  of  two  chemical  examinations  of  the  asphaltic  prodrj 
have  been  placed  at  the  disposal  of  the  writer,  one  by  Mr.  A.  M 
Dow,  inspector  of  asphalts  for  the  District  of  Columbia,  Avh 
analyzed    a    sample    collected    in    1903    by    Hon.    Thomas    Kearro] 
n,    vm 
readibij 
ly  ten? 
rat  ure:  •, 
Jl, 
