ADAuiuU8t'  i9hi4rm'}  Physiological  Characteristics  of  Acetylene.  371 
ishes  the  proportion  of  oxygen  which,  if  reduced  to  10  per  cent., 
would  be  unphysiological  and  to  7  per  cent.,  fatal ;  and  it  increases 
carbon  dioxide  which,  when  present  to  the  amount  of  3  to  4  per  cent., 
would  produce  marked  increase  in  the  rate  of  breathing. 
As  to  when  the  change  in  composition,  especially  the  carbon 
dioxide  increase,  is  indicated  by  the  particular  flames,  has  been  the 
subject  of  personal  experimental  observations.  The  cabinet  employed 
in  the  experiment  previously  described  was  used.  In  the  earlier 
experiments  with  carbon  dioxide,  this  gas  was  fed  into  the  cabinet 
without  previous  admixture  with  air ;  in  the  later  ones  both  air  and 
carbon  dioxide  were  fed  into  the  cabinet  through  meters,  entering 
the  cabinet  through  a  common  tube.  Thus  they  were  well  mixed 
and  the  rate  of  flow  of  each  was  regulated.  Early  experiments  indi- 
cated that  various  factors  influenced  the  extinction  point,  both  for 
the  oil  and  acetylene  lamp.  Let  me  relate  what  these  factors  were 
and  how  they  exercised  their  influence. 
A.  Actylene  Gas  Pressure. — From  the  outset  it  was  observed 
that  the  pressure  under  which  the  acetylene  gas  was  fed  through 
the  burner  exercised  a  marked  influence  upon  the  extinction  point. 
That  is  to  say,  with  a  series  of  lamps  in  which  the  acetylene  gas 
pressure  varied,  as  indicated  by  the  character  of  the  flame,  it  was 
not  difficult,  in  a  mixture  of  increasing  proportion  of  carbon  dioxide, 
to  foretell  the  order  in  which  the  lamps  would  be  extinguished,  the 
lamps  with  higher  acetylene  pressure  going  out  first.  Indeed,  it 
was  frequently  observed,  where  the  escape  of  gas  from  the  burner 
was  under  such  slight  pressure  as  not  to  give  direction  to  the  flame, 
that  the  extinction  point  would  be  very  much  higher  than  was 
observed  with  the  ordinary  burning  flame.  Care  was  therefore 
exercised  to  make  our  observations  on  lamps  in  which  the  gas 
production  showed  a  normal  amount  of  pressure. 
B.  Air  Movement. — When  there  was  no  movement  of  air,  except- 
ing such  as  resulted  from  the  convection  currents  produced  by  the 
lamps  and  by  the  introduction  of  the  gas  mixture,  the  extinction 
points  were:  for  the  acetylene  lamps,  23  to  25  per  cent,  carbon 
dioxide;  for  the  oil  lamps,  12  to  14  per  cent,  carbon  dioxide.  With 
the  production  of  a  gentle  movement  of  the  air  by  fanning  against 
the  side  of  the  cabinet,  the  extinction  points  were  appreciably 
affected,  being  lowered  in  the  case  of  the  acetylene  lamps  to  22  to  17 
per  cent,  carbon  dioxide ;  in  the  case  of  oil  lamps  to  12  to  10  per  cent, 
carbon  dioxide. 
