Motion  by  Impact  and  Gravity.  373 
We  have  fhewn,  that  in  this  cafe  at  leaft  Bernoulli’s 
hypothecs  is  founded  upon,  and  coincides  with,  the  com- 
monly received  doctrine  of  motion,  and  therefore  we  can 
hardly  entertain  a doubt  of  the  fuccefs  of  the  experi- 
ment, fuppofing  it  had  never  been  tried.  The  author 
himfelf,  in  the  pafiage  above  quoted,  tells  us,  that  he 
found  it  fo;  but  we  need  not  reft  upon  his  authority  : a 
fimilar  experiment  has  been  lately  made  by  Mr.  sm Ea- 
ton, and  is  defcribed  at  length  in  the  Philofophical 
Tranfaftions,  vol.  LXVI. 
It  does  not  appear,  that  d.  Bernoulli  attempted  to 
meafure  any  thing  but  the  time  of  c£s  defcent  through 
any  particular  fpace:  Mr.  smeaton  has  given  us  both 
the  times  of  oh  defcent,  and  the  proportions  of  the  velo- 
cities acquired,  in  a variety  of  cafes.  By  moving  the 
weights  he  makes  ufe  of  nearer  to,  or  farther  from,  the 
center  d,  he  alters  the  lengths  of  the  levers  at  which  the 
particles  a£t,  without  increafe  or  diminution  of  their 
number : he  does  the  fame  with  the  circle  or  axis  n m p, 
and  confequently  the  lever  m d ; and  in  every  cafe,  from 
the  known  character  of  that  ingenious  gentleman,  we 
may  prefume  that  his  numbers  are  fafely  to  be  relied 
upon. 
His  conclufions  may  receive  fome  illuftration  from  the 
preceding  theory. 
Bbb  2 
From 
