Xi/ri


in  which  v  equals  the  velocity  in  feet  per  second  ;
t  is  the  sine  of  the  inclination  of  the  slope  or  the


fall  of  the  water  surface  in  a  given  distance  di-
vided by  that  distance ;  r  is  the  area  of  the  cross-
section  in  square  feet  divided  by  the  wet  perimeter
in  lineal  feet ;  n  equals  the  coefficient  of  friction
for  different  sized  channels  and  channels  of  differ-
ent surfaces.  The  values  of  n,  as  determined  by
recent  investigations  on  American  canals,  are
approximately  as  follows :

71=0.0175  for  canals  in  earth  in  excellent
condition,  well-coated  with  sediment,  regular  in
cross-section,  and  free  from  vegetation,  loose
pebbles  and  cobbles.
71=0.020  for  canals  in  earth,  in  good  condi-
tion, lined  with  well-packed  gravel,  partly  cov-
ered with  sediment,  and  free  from  vegetation.
71=0.0225  for  canals  in  earth,  in  fair  condi-
tion, the  wetted  surface  being  lined  with  sedi-
ment, with  an  occasional  patch  of  minute  algae,
or  composed  of  loose  gravel  without  vegetation.
71=0.035  for  small  ditches  having  a  rough,
uneven  bed,  and  for  canals  in  earth  in  fairly
good  condition,  but  partially  filled  with  aquatic
plants.
The  location  of  canals  in  the  arid  region  of  the
United  States  is  a  comparatively  simple  matter.
The  mountain  ranges  give  a  general  direction  to
the  slopes  which  lie  at  their  base.  The  rivers  that
water  the  plains  east  of  the  Rocky  mountains  have
falls  varying  from  seven  to  fifty  feet  to  the  mile.
The  trend  of  the  country  is  in  two  directions —
away  from  the  mountains,  and  toward  the  streams.
