ADAugust  im.m' }  Physiological  Characteristics  of  Acetylene.  369 
headache.  Analysis  of  the  sample  showed  7  per  cent,  of  carbon 
dioxide.  The  experiment  indicated  that  with  man  the  warning  point 
is  reached  below  7  per  cent,  of  carbon  dioxide. 
Such  experiments  lead  to  the  following  general  conclusions  re- 
garding the  physiological  effects  of  increasing  proportions  of  carbon 
dioxide.  There  is  increase  in  the  rate  of  breathing  which,  with 
3  per  cent,  dioxide,  has  become  so  marked  that  it  gives  unquestioned 
warning  to  the  subject  that  some  unusual  condition  of  the  air  is 
rendering  it  unsuited  for  breathing.  We  may  call  this  the  physio- 
logical warning  point  for  carbon  dioxide.  When  the  concentration 
reaches  8  to  10  per  cent.,  the  breathing  is  not  only  rapid  but  has 
become  very  labored,  a  condition  termed  dyspnea.  Beyond  15  per 
cent.,  further  concentration,  instead  of  increasing  respirations,  de- 
creases them  and  the  animal  becomes  narcotized,  quite  as  though 
a  substance  like  chloroform  had  been  administered.  At  a  concen- 
tration beyond  35  per  cent,  the  narcosis  becomes  fatal. 
I  have  gone  into  the  influence  of  oxygen  decrease  and  of  carbon 
dioxide  increase  on  breathing  and  on  life  because  these  are  condi- 
tions that  may  be  presented  by  the  air  in  mines.  Moreover,  the  oil 
lamp  has  been  relied  upon  to  indicate  to  the  miner  whether  or  not 
the  mine  air  is  fit  to  breathe,  air  that  sustains  the  flame  being  regarded 
as  safe  and  air  that  extinguishes  the  flame  as  unsafe  to  breathe. 
The  disadvantages  of  the  oil  lamp  are  all  too  apparent.  Its  dingy 
light  limits  the  working  capacity  of  the  miner,  due  to  poor  illumina- 
tion. Aside  from  working  capacity,  the  miner  is  not  so  well  able 
to  see  the  elements  of  danger  presented  by  weakness  in  overhanging 
strata  or  structures.  An  even  greater  disadvantage  is  the  production 
of  soot  by  the  flame.  This  both  adds  to  the  personal  discomfort, 
already  great,  and  also  to  the  danger  of  dust  explosions  by  addition 
of  the  soot  to  the  dust-laden  atmosphere.  These  conditions  render 
an  illuminant  that  is  brilliant  and  soot-free  a  very  great  advantage. 
The  acetylene  lamp  supplies  such  an  illuminant  in  an  admirable 
manner.  In  connection  with  its  use  it  is  desirable  to  determine  its 
relation  to  composition  of  mine  air,  so  that  the  miner  may  know  in 
what  way  and  to  what  extent  it  replaces  the  oil  lamp  as  an  index 
of  safety.  That  is  to  say,  we  have  here  a  problem  of  adjust- 
ment to  which  it  is  important  to  give  a  correct  and  definite  answer. 
First,  then,  let  us  consider  the  variations  in  composition  that 
may  be  presented  by  mine  air.  Because  of  the  limitations  of  access 
of  outside  air  and  especially  because  of  the  formation  of  gases  in 
