ago  Papers  relative  to  an  Accident 
over  a building;  it  muft  neverthelefs  be  allowed,  that 
clouds  are  generally  obferved  to  move  with  confiderable 
velocity ; fo  that  when  the  velocity  is  from  three  quar- 
ters of  a mile  or  fomething  lefs,  to  four  or  five  miles  or 
more  in  an  hour,  the  pointed  conductor  is  always  ftruck 
by  the  charge  contained  in  the  great  cylinder.  And  the 
experiments  which  have  been  made  by  the  addition  of 
the  lefs  fubftitute  fliew  alfo,  that  no  fecurity  can  be 
expected  from  a pointed  conductor  when  a thunder- 
cloud is  even  entirely  at  reft. 
UPON  ACCELERATION,  AND  ITS  EFFECTS. 
From  confidering  the  extraordinary  effedts  which  have 
fometimes  been  produced  upon  grofs  matter  by  light- 
ning, and  the  diftance  there  frequently  is  between  thun- 
der-clouds and  the  earth,  when  fuch  effedts  take  place,  I 
fufpedted  that  thofe  effedts  might  in  fome  degree  be 
owing  to  an  increafe  of  the  velocity  of  the  fluid  which 
produced  them. 
To  try  whether  this  was  really  fo,  it  feemed  neceflary 
to  have  an  apparatus  of  a far  greater  length  than  the 
great  cylinder : I therefore  made  ufe  occafionally  of  the 
long  wire  which  has  been  already  defcribed. 
EXP. 
