Am.  Jour.  Pharm.  1 
April,  1888.  / 
The  Origin  of  Petroleum, 
195 
nesinm,  aluminium,  silicium,  phosphorus,  sulphur,  chlorine,  potas- 
sium, calcium,  and  also  the  greater  part  of  their  combinations  have 
not  a  higher  gravity  than  2J  times  that  of  water.  Now,  states  Men- 
delejeff,  the  density  of  the  globe  is  found  to  be  live  times  that  of  water, 
consequently  in  the  centre  must  predominate  forms  of  matter  heavier 
than  those  composing  the  crust. 
Now  what  are  the  elements  of  a  heavy  atomic  weight  which  we 
ought  to  expect  to  meet  with  in  the  interior  of  the  earth  ?  Such  ele- 
ments ought  also  to  some  extent  be  found  in  the  crust,  as  when  the 
whole  earth  was  in  a  state  of  vapor,  the  heaviest  vapors  would  mix 
with  the  lightest,  in  accordance  with  the  law  of  Marriotte.  Further, 
the  elements  such  as  ought  to  be  found  in  the  earth's  interior,  ought 
also  to  be  in  large  quantity  in  the  solar  atmosphere,  if  the  earth  was 
originally  part  of  that  atmosphere. 
In  reviewing  the  different  elements  MendelejefP  finds  that  iron  only, 
satisfies  all  these  conditions.  Now  if  in  the  earth's  interior  iron  pre- 
dominates, whose  density  is  seven,  and  if  the  earth's  crust  is  composed 
of  substances  having  an  average  specific  gravity  of  about  three,  as  is 
found  to  be  the  fact,  the  specific  gravity  of  the  whole  earth  will  be 
equal  to  the  mean  of  these  two  densities  three  and  seven,  that  is,  it 
will  be  about  five.  Now  five  is  precisely  the  mean  density  of  the 
terrestrial  globe. 
Now,  says  Professor  MendelejefP,  in  what  state  ought  we  to  suppose 
the  iron  to  be  in  the  earth's  interior  in  order  to  solve  the  question 
under  consideration  ?  In  the  earth's  interior  there  has  never  existed 
but  a  very  small  quantity  of  oxygen,  for  the  reason  that  the  atomic 
weight  and  the  molecular  weight  of  this  gas  are  low,  and  further,  that 
oxygen,  as  w^  know,  cannot  be  liquefied  either  by  pressure  or  any 
other  force.  If  we  have  iron,  carbon  and  oxygen  at  a  high  tempera- 
ture, it  will  happen  that  the  combination  of  the  oxygen  will  take 
place  according  to  the  proportion  in  which  it  is  present.  If  there  be 
little  oxygen  and  much  iron  and  carbon,  it  is  with  the  carbon  that  all 
the  oxygen  will  combine,  and  the  iron  will  remain  free  or  will  be  car- 
buretted,  in  which  state  Professor  Mendelejeff  believes  it  no  doubt  is 
in  the  earth's  interior  in  conjunction  with  other  metallic  carbides. 
Now,  the  fissures  already  explained,  produced  by  the  elevation  of 
mountain  chains,  have  permitted  water  to  penetrate  to  the  depths  of 
the  earth  and  to  reach  these  metallic  carbides.  The  iron  and  other 
metals  combine  with  the  oxygen  of  the  water ;  hydrogen  is  in  part  set 
