Velocities  of  Cannon  Balls,  See.  7 5 
every  inconvenience,  giving  juit  the  neceffary  degree  of 
friilion  to  the  tape,  without  ever  flopping  its  motion;  fo 
that  of  the  real  quantity  drawn  out  by  the  vibration  of 
the  pendulum  there  could  not  poffibly  be  the  leaft  doubt. 
This  Ample  contrivance  confifted  barely  of  about  flx  or 
eight  inches  of  the  lift  of  woollen  cloth  fattened  upon 
the  arch  of  a fmall  piece  of  wood,  which  was  fhaped 
into  the  form  of  the  fegment  of  a circle  thus  the 
tape  being  made  to  pafs  through  between  the  curved  flde 
and  the  lift,  which  was  moderately  ftretched  and  fattened 
by  its  two  ends  to  thofe  of  the  little  arch. 
Upon  the  whole,  the  machinery  was  all  fo  perfect, 
and  every  circumftance  attending  the  experiments  of 
the  two  enfuing  days  fo  carefully  obferved,  that  I can. 
with  great  fafety  rely  on  the  conclufions  refulting  from 
them.  And  as  thofe  of  the  one  day  were  made  with 
leaden  balls,  and  thofe  of  the  other  with  iron  ones, 
which  differ  greatly  in  weight,  every  other  circumftance 
being  the  fame,  they  afford  very  good  means  for  difeo- 
vering  the  law  of  the  different  weights  of  Ihot,  while 
the  variations  in  the  powder  from  two  to  four  and 
eight  ounces  furnifh  us  with  the  rule  for  the  different 
quantities  of  it. 
L % 
The 
