A  French  writer,  Poncelet,  gives  the  traction  on  "oak
planks  not  dressed"  at  21  lbs.  Another  French  writer
gives  the  traction  of  carts  on  an  "'o^iken  platform"  at  less
than  29  lbs.,  but  of  "trucks  of  two  tons"  on  the  same
platform  at  nearly  44  lbs.  Taking  the  average  of  various
experiments,  and  correcting  this  by  the  opinion  of  those
who  have  experience  in  the  matter,  I  place  the  traction  on
a.  dead  level  plank  road,  well  constructed  of  hard  wood,
the  load  being  on  a  common  four-wheeled  wagon,  with
good  iron  axles,  the  wheels  in  good  order  and  the  pace
being  a  walk,  at  forty  pounds  io  the  ton ;  or  four  times  the
iraction  on  the  best  railroad.  On  a  macadamized  road,
well  made  and  in  good  order,  the  iraction  will  exceed  sixty
pounds;  while  on  our  ordinary  earth  roads,  take  the  aver-
age of  the  year,  the  traction  may  be  set  down  at  not  less
than  a  hundred  and  twenty  pounds;  or  three  times  the
traction  on  a  plank  road.
To  express  in  different  terms  the  same  results,  the  trac-
tion on  a  level,  is,  on  the  plank  road,  two  per  cent,  of  the
entire  load;  on  a  macadamized  road,  more  than  three  per
cent.;  and  on  a  common  earth  roAd  six  per  cent.o^  the
same.
Where  the  surface  is  perfectly  level,  then  a  horse  at  a
walk,  can,  with  the  same  exertion,  draw,  on  a  good  plank
road,  three  thousand  pounds,  as  on  the  average  of  our  pre-
sent roads,  he  can  draw  one  thousand  pounds.
