from  Lightning  at  Purfleet.  287 
ftance  continued  the  fame,  there  was  no  fuch  ap- 
pearance. 
exp.  xxxvi.  But  when  the  rounded  end  was  moved 
confiderably  nearer,  that  is,  within  fix-tenths  of  an  inch, 
alight  was  vifible;  but  then  it  was  faint,  and  not  more 
than  one-tenth  of  an  inch  in  diameter,  even  at  the  in- 
ftant  before  the  explofion  happened. 
thirteenth  observation.  By  the  firft  of  thefe  ex- 
periments it  appears,  that  the  influence  which  the  point 
had  upon  the  whole  of  the  fluid  contained  in  the  great 
cylinder,  was  fuch  as  to  caufe  a general  tendency  of  it 
towards  the  lefs  fubftitute ; but,,  on  account  of  the  re- 
finance which  feemed  to  operate  at  the  furface  of  the 
brafs  ball,  it  was  there  flopped,  and  by  degrees  accumu- 
lated, till  fuch  time  as  the  accumulation  was  great 
enough  to  overcome  that  reliftance.  Now,  according  to 
this  manner  of  reafoning,  the  point  did  not  draw  the  fluid 
out  of  the  great  cylinder  filently ; but  when  the  accumu- 
lation had  got  to  a fufficient  degree,  a fudden  explofion 
enfued,  more  or  lefs  violent,,  according  to  the  circum- 
ftances  which  accompanied  the  experiment, 
fourteenth  observation*  From  the  other  experi- 
ment it  appears,  that  the  rounded  end  had  not  fo  great 
an  influence  as  the  point  upon  the  charge  in  the  cylin- 
der; becaufe  we  were,  obliged  to  bring  it  five  times 
nearer. 
