from  Lightning  <w  Purfleet.  307 
to  be  in  contadi  with  the  powder.  After  having  charged 
a fmall  phial,  which  did  not  exceed  a pint  in  meafure, 
with  only  a few  turns  of  the  wheel,  he  made  the  dif- 
charge,  and  fired  the  gun-powder.  The  advantage  he 
gained  by  having  fo  fmall  a thread  of  metal  in  this  ex- 
periment was,  that  it  could  be  made  red-hot  with  ale fs 
charge  than  what  is  necefiary  when  a thicker  wire  is 
made  ufe  of;  and  the  fmallnefs  of  the  charge  he  em- 
ployed to  fire  the  powder  was  a certain  proof  that  the 
Heel  thread  had  been  made  red-hot. 
Upon  the  whole  we  find,  that  this  method  of  firing 
gun-powder  is  totally  different  from  the  other,  where  the 
great  apparatus  was  employed ; becaufe  the  faint  lumi- 
nous ftream,  obferved  at  the  brafs  drums  where  the  gun- 
powder was  applied,  I found  was  abfolutely  incapable  of 
making  the  point  of  metal  within  the  cartridge  red-hot* 
Befides,  there  did  not  appear  to  be  any  explofion  what- 
foever  between  the  apparatus  and  the  powder  at  the  in- 
flant  it  was  fired. 
Before  I conclude  this  paper,  it  may  not  be  amifs  if  I 
take  notice  of  certain  atmofpheres,  which  bodies  have 
round  them  when  they  are  properly  charged  with  this 
elaflic  fluid ; becaufe  the  nature  of  them  may  not  per- 
haps be  perfectly  underflood  by  every  one  who  attends 
to  enquiries  of  this  kind. 
Vo  l.  LXVIII.  R r Every 
