AnAimiUst'  i9i4im']  Physiological  Characteristics  of  Acetylene.  373 
either  lamp  the  extinction  point  is  too  high  above  the  physiological 
warning  point  to  make  it  of  value  to  the  miner.  The  conditions  will 
have  been  recognized  before  the  extinction  point  is  reached.  Should, 
however,  the  physiological  warning  be  unheeded,  flame  extinction 
will  occur,  first  with  the  oil  and  then  with  the  acetylene  flame,  with 
either  in  ample  time  to  prevent  loss  of  life.  The  margin  of  safety, 
though  greater  with  the  oil  lamp,  is  adequate  with  the  acetylene. 
In  considering  the  influence  of  oxygen  decrease  on  flame  extinc- 
tion, I  shall  make  use  of  observations  made  by  Chester  S.  Heath, 
under  experimental  conditions  different  from  those  I  have  described. 
He  finds  that  with  moderate  motion  an  oil  flame  is  extinguished 
when  the  oxygen  is  reduced  to  16.5  per  cent. ;  in  still  air  to  16.2  per 
cent.  With  acetylene,  at  moderate  motion,  extinction  occurred  at 
12.6  per  cent,  and  was  dimmed  in  still  air  of  the  same  composition, 
being  extinguished  in  still  air  at  1 1.5  per  cent.  It  thus  appears  that 
the  oil  flame  is  extinguished  with  considerably  less  reduction  of 
oxygen  than  the  acetylene,  but  that  the  latter  is  extinguished  before 
the  reduction  is  fatal  to  man,  which  is  at  7  per  cent.  Moreover, 
in  actual  mining  conditions,  where  the  lamp  is  worn  on  the  head,  there 
will  be  sufficient  motion;  hence  extinction  will  occur  at  a  point 
somewhere  above  that  observed  with  the  experimental  conditions. 
Finally,  it  is  not  to  be  forgotten  that  the  condition  of  extreme 
oxygen  reduction  without  carbon  dioxide  increase,  which  was  present 
in  the  experimental  observations,  is  not  encountered  in  actual  mine 
air.  The  specific  action  of  carbon  dioxide  admixture,  that  will  be 
found  in  such  conditions,  will  add  its  effect  to  the  oxygen  decrease 
and  bring  about  the  extinction  of  an  acetylene  flame  at  a  point  which 
is  still  further  removed  from  unphysiological  atmospheric  conditions, 
and  hence  afford  an  increased  margin  of  safety. 
The  miner,  then,  may  conclude  that  a  given  admixture  of  black- 
damp  and  air  in  the  absence  of  other  foreign  gases  will  support 
life:  (1)  if  it  does  not  extinguish  flame;  (2)  if  it  does  not  produce 
markedly  increased  respiration.  Any  atmosphere  which  does  not 
give  these  warnings  is  respirable,  though  not  necessarily  desirable 
for  continuous  respiration.  It  does,  however,  give  warning  either 
physiological,  or  by  the  flame  of  acetylene  as  well  as  oil,  that  is 
adequate  to  prevent  loss  of  life. 
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