370  Physiological  Characteristics  of  Acetylene.  {AuiUgu"t' 
Pharm. 
1914. 
mines,  mine  air  may  present  a  considerable  departure  from  the 
composition  of  outside  air. 
All  ordinary  foreign  gases  were  known  to  the  early  miners  as 
"  damps/'  from  the  German  damf,  meaning  vapor,  the  specific  desig- 
nation being  indicated  by  an  individual  prefix.  Thus,  the  gas  charac- 
terized by  its  tendency  to  extinguish  the  flame  was  called  black- 
damp,  or,  since  it  tends  to  produce  suffocation,  choke-damp;  the 
damp  producing  increased  brilliancy  of  light,  white-damp ;  that  with 
a  marked  stink,  stink-damp ;  that  which  readily  took  fire,  fire-damp ; 
the  gas  resulting  from  burning  or  explosion,  after-damp,  etc.  These 
names  were  applied  long  before  the  composition  of  the  respective 
gases  was  known.  In  consequence  of  the  indefinite  basis  of  the 
classification,  an  individual  name  was  in  many  instances  applied  to 
mixtures  that  presented  wide  variation  in  composition. 
Black-damp,  on  chemical  analysis,  has  ordinarily  proved  to  be 
a  mixture  of  carbon  dioxide  and  nitrogen,  the  proportion  of  carbon 
dioxide  varying  from  very  little  up  to  15  per  cent,  or  perhaps  excep- 
tionally 20  per  cent.  As  it  is  always  mixed  with  more  or  less  air, 
a  corresponding  amount  of  oxygen  is  present.  Other  gases,  such  as 
methane  (fire-damp),  carbon  monoxide  (white-damp),  hydrogen- 
sulphide  (stink-damp),  also  water  vapor,  may  be  present  in  greater 
or  less  amount. 
We  may  well  ask,  then,  what  the  name  black-damp  indicates. 
Does  it  mean  carbon  dioxide,  which  is  the  characteristic  constituent ; 
does  it  mean  the  carbon  dioxide-nitrogen  mixture;  is  it  the  carbon 
dioxide-nitrogen-air  mixture;  or  is  it  the  combination  of  any  of  these 
with  other  gases  that  are  present  in  the  mine  air?  Unfortunately, 
there  has  been  no  unanimity  of  usage  in  regard  to  this  term,  it  having 
been  used  by  different  writers  in  almost  every  one  of  the  above  pos- 
sible meanings. 
If  we  were  to  establish  anew  the  definition  of  the  term,  it  would 
be  doubtless  wise  to  adopt  a  scientific  meaning.  As  the  matter  stands, 
our  meaning  should  be  decided  by  priority,  which  is  that  black-damp 
is  not  simply  carbon  dioxide  but  rather  a  mixture  of  that  with  nitro- 
gen in  varying  proportions,  but  we  must  not  forget  the  different 
usages  of  individual  authors. 
Our  problem  is :  How  does  the  admixture  of  black-damp  modify 
the  respirability  of  mine  air  and  how  is  this  indicated  by  the  oil  and 
acetylene  flames?  It  requires  no  facts  other  than  those  now  before 
us  id  appreciate  that  it  affects  respirability  in  two  ways.    It  dimin- 
