from  Lightning  at  Purfleet.  291 
exp.  xxxvii.  Upon  connecting  one  end  of  this  long 
Wire -with  the  farther  end  of  the  great  cylinder,  and  the 
other  with  one  end  of  the  brafs  drums  ; I found,  that 
about  fix  uniform  turns  of  the  wheel,  with  a moderate 
velocity,  were  required  to  caufe  the  appearance  of  a fmall 
ft  ream  of  light  at  the  top  of  the  fpout  defcribed  in  the 
firft  experiment,  when  the  model,  with  the  pointed  con- 
ductor upon  it,  flood  direCtly  under  the  great  cylinder, 
but  at  the  diftance  of  five  inches. 
exp.  xxxviii.  When  the  great  cylinder  was  uncon- 
nected with  the  long  wire  and  brafs  drums,  and  whilft  the 
model,  with  the  fame  conductor  upon  it,  remained  in  its 
place ; about  two  turns,  with  the  fame  velocity,  were  fuf- 
ficient  to  charge  the  great  cylinder,  fo  as  to  caufe  a fimi- 
lar  appearance  at  the  fpout. 
exp.  xxxix.  On  feparating  the  great  cylinder  from  a 
fourteenth  part  of  it  (which  fourteenth  part  for  the  pre- 
sent I call  the  little  cylinder)  the  model  and  machine  con- 
tinuing in  their  places,  it  was  found,  that  half  a turn  of 
the  wheel  was  fufficient  to  Charge  the  little  cylinder,  fo 
as  to  caufe  the  like  appearance  at  the  fpout, 
fifteenth  observation.  Now  thefe  differences  in 
the  numbers  of  turns  required  for  caufing  limilar  ap- 
pearances, when  the  feveral  charges  were  given  in  the 
thirty-feventh  and  thirty-eighth  experiments,  could  not 
Vol.  LXVIII.  Pp  arife 
