from  Lightning  at  Purfleet.  295 
very  near,  the  furfaees  of  bodies,  and  extends  only  to 
very  fmall  diftances  from  them. 
It  feems  then,  that  it  is  by  this  kind  of  refiftance  at 
the  furface  of  bodies,  that  the  fluid  is  prevented  from 
efcaping  out  of  the  great  cylinder  and  wire,  whilft  it  is 
accumulating  within  them:  and  therefore,  when  we  be- 
gin to  charge  the  great  apparatus  at  the  nearer  end,  the 
moment  any  part  of  the  charge  arrives  at  the  farther 
end  of  the  wire,  it  is  prevented  (in  fame  degree  at  leaft) 
from  efcaping,  in  confequence  of  the  refiftance  it  meets 
with  at  that  end.  And,  if  we  continue  to  make  the 
charge  greater,  the  charge  itfelf,  during  its  increafe,  muff 
alfo  refill  every  farther  effort  which  any  ways  tends  to 
make  it  greater,  with  a force  probably  proportional  to 
the  quantity  accumulated. 
exp.  xli.  When  the  great  cylinder  and  wire  with  the 
drums  were  fully  charged,,  and  a perfon,  Handing  upon 
the  wire  which  communicated  with  the  well,  fuddenly 
approached  the  brafs  drums  with  his  hand,  an  explofion 
enfued,  which  indeed  was  neither  fo  large,  nor  did  it 
take  place  at  fo  great  a diftance,  as  might  have  been  ex- 
peiled^;  neverthelefs,  the  perfon  received  a violent  fen- 
(d)  The  circumftances  attending  the  explolion  in  this  experiment  were  cer- 
tainly owing  to  the  long  wire  being  not  entire,  but  confifting  of  feveral  pieces 
twilled  together,  the  ends  of  which,  being  very  many,  mull  have  caufed  a con- 
iiderable  part  of  the  fluid  to  efcape,  and  fo  have  weakened  the  general  effe£l. 
7 fatioiv 
