from  Lightning  at  Purfleet.  305 
When  the  Leyden  phial  is  charged  we  find’  by  expe- 
riment, that  the  charge  is  confined  in  a firiaU  compafs, 
or  very  much  condenfed,  near  one  furface  of  the  glafs. 
It  is  alfo  true,  that  the  oppofite  furface  of  the  fame  glafs 
is  as  much  ratified,  or  (according  to  Dr.  franklin,  who 
was  the  firft  that  obferved  it)  in  a minus  ftate.  Now,  ac- 
cording to  this  rule,  the  greater  the  furface  of  the  glafs  is, 
and  of  an  even  and  limited  thicknefs,  the  greater  charge 
may  be  given ; arid  the  greater  the  charge,  the  greater  muft 
be  the  effect  (whenever  the  difch arge  is  properly  made)  to 
reftore  the  natural  ftate  of  the  glafs  on  the  two  oppofite 
fides.  In  order  therefore  to  fire  gun-powder  with  this 
kind  of  apparatus,  experience  hath  taught  us  hitherto, 
that  the  powder  fhould  be  confined,  for  example,  in  a 
tube  or  cartridge ; and  that  this  cartridge  fhould  be  placed 
in  fuch  a manner  as  to  make  part  of  the  circuit  neceffary 
for  the  difcharge  of  the  fluid  from  one  furface  of  the 
glafs,  and  carry  it  through  the  cartridge  to  the  other  fur- 
face. But  it  is  alfo  neceffary,  before  the  powder  can  be 
fired,  to  have  part  of  the  wire  which  forms  the  circuit  in 
contact  with  the  powder ; or,  to  have  one  end  of  the  wire, 
which  makes  part  of  the  circuit,  forced  a little  way  into 
one  end  of  the  cartridge;  and  another  end  of  a wire, 
which  alfo  makes  part  of  the  circuit,  forced  a little  way 
into  the  other  end  of  the  cartridge ; but  fo  as  that  the 
two 
