Am.  Jour.  Pharm.  ) 
December,  1920.  I 
Air  Pollution  by  Smoke. 
929 
which  invariably  follows  in  the  wake  of  a  thick  fog,  must  operate, 
though  to  a  lesser  degree,  on  the  general  health  of  the  community 
in  an  industrial  center  under  normal  conditions.  More  definite 
evidence  was  forthcoming  of  the  effects  of  smoke  on  vegetation. 
By  shutting  out  sunlight,  by  covering  the  leaf  and  blocking  the 
stomata  with  tar,  life  especially  that  of  evergreen  plants  and  trees 
is  seriously  affected.  Moreover,  the  sulphuric  acid  which  is  invar- 
iably associated  with  soot,  destroys  the  nitrifying  organisms  and 
removes  lime  from  the  soil  as  sulphate.  This  result  has  been  ob- 
served at  the  experimental  farm  at  Garforth  attached  to  the  Uni- 
versity of  Leeds,  where  the  difference  between  limed  and  unlimed 
soils  has  exhibited  in  a  remarkable  way  the  action  of  acid  soot. 
Another  indirect  result  has  been  the  diminished  value  of  grazing 
land  in  smoke-infected  areas,  in  consequence  of  which  the  rental 
of  these  pastures  has  steadily  decreased  from  year  to  year. 
Equally  striking  evidence  was  submitted  to  the  Committee  by 
Sir  Frank  Baines,  Director  of  H.  M.  Office  of  Works,  as  to  the 
serious  damage  occasioned  to  public  and  other  buildings  by  smoke 
and  other  impurities  in  the  atmosphere  and  especially  by  the  deposit 
of  acid  soot.  The  effect  in  most  cases  was  due  to  the  removal  of  the 
calcium  carbonate  (which  acts  as  a  cement  for  grains  of  siliceous 
material)  in  the  stone  becoming  dissolved  as  calcium  sulphate  and 
thus  causing  the  siliceous  particles  to  crumble  away.  In  the  opinion 
of  Sir  F.  Baines,  the  cost  of  repairs  and  upkeep  of  public  buildings 
and  monuments  (a  very  heavy  expense)  would  be  diminished  by 
one-half  if  the  smoke  and  the  accompanying  acid  could  be  eliminated. 
This  acid  soot  not  only  clings  to  vegetation  and  to  stone,  but 
corrodes  brick  and  metal  work,  attacks  fabrics,  leather  binding  of 
books,  and  discolors  paint.  The  Manchester  Air  Pollution  Advis- 
ory Board  find,  in  Manchester,  in  the  cost  of  washing  materials  alone 
apart  from  the  labor  involved,  that  more  than  £250,000  would  be 
saved  annually  by  the  absence  of  smoke.  A  very  careful  and 
exhaustive  inquiry  by  an  expert  committee  of  engineers,  architects, 
and  sciences  estimated  that  in  191 2,  in  Pittsburgh,  U.  S.  A.,  the 
cost  due  to  smoke  was  £4  per  head  of  the  population.  If  we  take 
as  a  rough  estimate  the  20  towns  of  the  United  Kingdom  of  over 
200,000  inhabitants  having  a  total  population  of  over  12  millions 
at  I  OS.  a  head,  we  get  a  sum  of  six  millions,  while  the  waste  occurring 
accruing  from  the  non-utilization  of  the  by-products  from  raw  coal, 
such  as  tar  oils,  sulphur,  ammonia,  and  cyanogen  compounds,  so 
