Velocities  of  Cannon  Ralls,  See. 
53 
Of  the  nature  of  the  experiment ,-  and  of  the  machinery 
ufed  in  it. 
The  intention  of  the  experiment  is  to  difeover  the 
axftual  velocity  with  which  a ball  iffues  from  a piece,  in 
the  ufual  practice  of  artillery.  This  velocity  is  very 
great ; from  one  thoufand  to  two  thoufand  feet  in  a fe- 
cond  of  time.  For  conveniently  efiimating.  fo  great  a 
velocity,  the  firft  thing. neceffary  is- to  reduce  it,  in  fome 
known  proportion,,  to  a.  fmall.  one.  This  we  may  con- 
ceive to  be  effected  thus : fuppofe  the  ball,  with  a great 
velocity,,  to.  ftrike  fome  very  heavy  body,  as  a large 
block  of  wood,  from  which  it  will  not  rebound,  fo  that 
they  may  proceed  forward  together  after  the  ftroke.  By 
this  means  it  is  obvious,  that  the  original  velocity  of 
the  ball  may  be  reduced  in  any  proportion,  or  to  any 
flow  velocity  which  may  conveniently  be  meafured,  by 
making  the  body  ftruck  to  be  fufficiently  large ; for  it  is 
well  known,  that  the  common  velocity,  with  which  the 
ball  and  block  of  wood  would  move  forward  after 
the  ftroke,  bears  to  the  original  velocity  of  the  ball  only, 
the  fame  ratio  which  the  weight  of  the  ball  hath  to 
that  of  the  ball  and  block  together.  Thus  then  veloci- 
tiesof  one  thoufand  feet  in  a fecond  are  eafily  reduced  to 
thofe. 
