194 
The  Origin  of  Petroleum. 
Am,  Jour.  PhArm. 
AprU,  1888. 
to  Karne's  city,  one  can  trace  an  almost  straight  line  of  petroleum- 
bearing  wells,  parallel  to  the  Alleghany  chain  of  mountains. 
Xow,  he  states,  these  mountain  chains  have  been  formed  by  eleva- 
tion caused  by  the  slow  but  continuous  action  of  the  internal  forces  of 
the  earth.  This  elevation  has  produced  a  cleavage  at  the  summits  of 
the  mountains,  and  consequent  exposure  of  the  various  strata  which, 
prior  to  the  cleavage,  lay  one  above  the  other  in  a  horizontal  position. 
At  the  base,  a  similar  and  parallel  cleavage  would  be  formed.  This 
opening  would  be  filled  up  by  time,  but  after  going  a  certain  depth 
it  should  still  exist,  if  the  strata  which  are  raised  on  the  sides  of  the 
mountains  were  before  their  upheaval  almost  horizontal,  as  geology 
proves  them  to  have  been.  This  great  fissure  at  the  foot  of  the 
mountains  has  freed  a  passage  for  the  petroleum,  and  has  formed  at 
the  same  time  galleries  in  which  the  oil  has  entered  and  has  risen  from 
within  the  depths  of  the  earth,  where  in  ancient  times  its  formation 
had  taken  place. 
How  the  oil  is  produced  in  these  remote  depths  in  the  earth's  in- 
terior. Professor  Mendelejeff  now  proceeds  to  explain  by  an  elaborate 
but  highly  interesting  process,  of  which  I  must  limit  myself  to  giving 
you  but  a  very  abbreviated  outline.  He  humorously  remarks  that 
when  one  engages  in  a  study  connected  with  the  depths  of  the  earth, 
one  is  perforce  obliged  to  engage  in  the  depths  of  science  also.  Taking 
as  his  basis  the  well-known  theory  of  Laplace  of  the  earth's  creation, 
he  says  the  mass  of  vaporous  matter  (ultimately  to  form  our  planet) 
thrown  off  into  space  from  the  solar  atmosphere,  would  at  first  have 
the  form  of  a  ring,  analogous  to  that  of  Saturn.  In  this  ring,  in 
which  the  temperature  would  be  very  high,  all  the  elements  are  in  a 
state  of  vapor.  On  the  gradual  cooling  first  of  the  circumference, 
these  elements  would  condense  by  degrees,  and  chemical  combinations 
commence.  The  metals  uniting  with  oxygen  would  produce  oxides, 
which  would  fall  towards  the  centre  in  the  form  of  rain  or  snow,  de- 
composing again,  on  arriving  at  a  certain  depth.  This  is  the  reason, 
he  says,  why  in  the  crust  we  have  chiefly  elements  and  matter  whose 
vapors  have  a  low  density.  In  the  interior,  on  the  contrary,  would 
be  found  elements  Avhose  vapors  have  a  high  density. 
This  leads  us  to  the  conclusion  that  at  the  centre  of  the  earth  ought 
to  be  accumulated  elements  having  high  atomic  weights  ;  and  we 
know  that  the  lighter  elements  do  predominate  in  the  composition  of 
the  earth's  crust,  such  as  hydrogen,  carbon,  nitrogen,  oxygen,  ^mag- 
