in  determining  the  Direction  of  a  Discharge  of  Lightning.     117 
That  the  direction  of  the  electric  discharge  had  in  this  case 
been  determined  by  the  gas-pipes  which  passed  under  the  floor 
of  the  church,  was  evident  from  the  fact  that  the  watches  of 
several  members  of  the  congregation  who  were  seated  in  the  vi- 
cinity of  the  gas-mains  were  so  strongly  magnetized  as  to  be 
rendered  unserviceable. 
The  church  at  Crumpsall  is  about  a  mile  distant  from  that  at 
Kersal  Moor  j  and  the  ignition  of  the  gas  by  lightning,  which 
undoubtedly  caused  its  destruction,  is  not  so  distinctly  traceable 
as  it  is  in  other  cases  which  have  come  under  my  observation, 
because  the  evidences  of  the  passage  of  the  electric  discharge 
have  been  obliterated  by  the  fire.  From  information,  however, 
communicated  to  me  by  the  clerk  in  charge  of  the  building  as 
to  the  arrangement  of  the  gas-pipes,  the  most  probable  course 
of  the  electric  discharge  was  ultimately  found. 
The  church  is  provided  with  a  copper  lightning-conductor, 
which  descends  outside  the  spire  and  tower  as  far  as  the  level  of 
the  roof.  The  conductor  then  enters  a  large  iron  down-spout, 
and  is  carried  into  the  same  drain  as  that  in  which  the 
spout  discharges  itself.  Immediately  under  the  roof  of  the 
nave  and  against  the  wall,  a  line  of  iron  gas-pipe  extended  par- 
allel with  the  horizontal  lead  gutter  which  conveyed  the  water 
from  the  roof  to  the  iron  spout  in  which  the  conductor  was  en- 
closed. This  line  of  gas-piping,  though  not  in  use  for  some 
time  previous  to  the  fire,  was  in  contact  with  the  pipes  connected 
with  the  meter  in  the  vestry,  where  the  fire  originated,  and  was 
not  more  than  three  feet  distant  from  the  lead  gutter  on  the 
roof.  As  no  indications  of  the  electric  discharge  having  taken 
place  through  the  masonry  were  found,  as  in  the  case  of  the 
church  at  Kersal  Moor,  it  seems  highly  probable  that  the  light- 
ning left  the  conductor  at  the  point  where  the  latter  entered  the 
iron  spout,  and  by  traversing  the  space  between  the  leaden  gutter 
and  the  line  of  gas-piping  in  the  roof  found  a  more  easy  path  to 
the  earth  by  the  gas-mains  than  was  provided  for  it  in  the  drain. 
In  my  experiments  on  the  electrical  condition  of  the  terrestrial 
globe*,  I  have  already  directed  attention  to  the  powerful  influ- 
ence which  lines  of  metal,  extended  in  contact  with  moist  ground, 
exercise  in  promoting  the  discharge  of  electric  currents  of  com- 
paratively low  tension  into  the  earth's  substance,  and  also  that 
the  amount  of  the  discharge  from  an  electromotor  into  the  earth 
increases  conjointly  with  the  tension  of  the  current  and  the 
length  of  the  conductor  extended  in  contact  with  the  earth.  It 
is  not,  therefore,  surprising  that  atmospheric  electricity,  of  a  ten- 
sion sufficient  to  strike  through  a  stratum  of  air  several  hundred 
yards  thick,  should  find  an  easier  path  to  the  earth  by  leaping 
*  Philosophical  Magazine,  August  1868. 
