from  Lightning  at  Purfleet.  30  r 
fion  perceptible  to  the  fenfe  of  feeling,,  as  well  as  to  that 
of  fight. 
Now,  before  the  great  explofion  was  caufed,  the  fluid 
accumulated  in  the  apparatus  muft  have  been  diffufed 
equally  through  it,  in  confequence  of  its  elaftic  princi- 
ple ; and,  being  fo  circumft anced,  a fudden  application  of 
the  hand,  or  any  other  fubftance,  which  would  open  a 
door  for  the  paflage  of  the  fluid  into  the  earth,  was 
found  to  difcharge  the  greater  part  of  that  fluid  : and 
whatever  part  thereof  was  fo  difcharged,  the  moft  diftant 
particles  feemed  to  have  arrived  at  the  point  where  the 
explofion  took  place,  at  the  fame  time  with  thofe  that 
were  the  neareft  to  it;  becaufe,  immediately  after  the  ex- 
plofion, there  was  very  little  of  the  fluid  remaining  in 
the  apparatus. 
If  then  the  difcharge  of  the  fluid  be,  as  it  feems  to  be, 
very  nearly  inftantaneous,  the  particles  of  it  muft  move 
with  velocities,  and  confequently  with  forces,  very  nearly 
proportional  to  thofe  diftances. 
From  this  confideration  I apprehend  it  will  appear, 
why  the  fenfation  upon  the  difcharge  from  the  long  wire 
in  the  forty- fixth  experiment  was  more  violent:  and 
upon  recollecting  the  thirty-feventh,  thirty-eighth,  and 
thirty-ninth  experiments,  and  the  obfervations  I made 
upon  them,  I am  inclined  to  believe,  that  the  effeCl 
Qq  2 depends 
