118  On  the  Influence  of  Pipes  on  Lightning. 
from  a  lightning-conductor  through  a  few  feet  of  air  or  stone  to 
a  great  system  of  gas-  and  water-mains,  extending  in  large  towns 
for  miles,  than  by  the  short  line  of  metal  extended  in  the  ground 
which  forms  the  usual  termination  of  a  lightning-conductor. 
It  deserves  to  be  noticed  that  in  the  cases  of  lightning  dis- 
charge which  I  have  cited,  the  lightning-conductors  acted  effi- 
ciently in  protecting  the  buildings  from  damage  of  a  mechanical 
nature,  the  trifling  injury  to  the  church  tower  at  Kersal  Moor 
being  directly  attributable  to  the  presence  of  the  gas-pipe  in 
proximity  to  the  conductor.  Nor  would  there  have  been  any 
danger  from  fire  by  the  ignition  of  the  gas  if  all  the  pipes  used 
in  the  interior  of  the  buildings  had  been  made  of  iron  or  brass 
instead  of  lead;  for  all  the  cases  of  the  ignition  of  gas  by  light- 
ning which  have  come  under  my  observation  have  been  brought 
about  by  the  fusion  of  lead  pipes  in  the  line  of  discharge.  The 
substitution  of  brass  and  iron,  wherever  lead  is  used  in  the  con- 
struction of  gas- apparatus,  would,  however,  be  attended  with 
great  inconvenience  and  expense,  and  moreover  would  not  avert 
other  dangers  incident  to  the  disruptive  discharge  from  the  con- 
ductor to  the  gas-  and  water-pipes  within  a  building.  I  have 
therefore  recommended  that  in  all  cases  where  lightning-conduc- 
tors are  attached  to  buildings  fitted  up  with  gas-  and  water-pipes, 
the  lower  extremity  of  the  lightning-conductor  should  be  bound 
in  good  metallic  contact  with  one  or  other  of  such  pipes  outside 
the  building.  By  attending  to  this  precaution  the  disruptive 
discharge  between  the  lightning-conductor  and  the  gas-  and 
water-pipes  is  prevented,  and  the  fusible  metal  pipes  in  the  in- 
terior of  the  building  are  placed  out  of  the  influence  of  the  light- 
ning discharge. 
Objections  have  been  raised  by  some  corporations  to  the  esta- 
blishment of  metallic  connexion  between  lightning-conductors  and 
gas-mains,  on  the  ground  that  damage  might  arise  from  ignition 
and  explosion.  These  objections  are  most  irrational,  as  gas 
will  not  ignite  and  explode  unless  mixed  with  atmospheric  air, 
and  the  passage  of  lightning  along  continuous  metallic  conduc- 
tors will  not  ignite  gas  even  when  mixed  with  air.  Moreover,  in 
every  case  of  the  ignition  of  gas  by  lightning,  the  discharge  is 
actually  transmitted  along  the  mains,  such  objections  notwith- 
standing. A  grave  responsibility  therefore  rests  upon  those 
who,  after  introducing  a  source  of  danger  into  a  building,  raise 
obstacles  to  the  adoption  of  measures  for  averting  this  danger. 
