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VII. — On  the  Accurate  Levelling  of  Drains.  By  Colonel 
Challoner. 
To  Ph.  Pusey. 
Dear  Pusey, — As  complaints  are  very  often  made  of  failures 
in  draining,  in  consequence  of  drains  choking  or  stopping  up, 
especially  where  small  pipes  are  used,  I am  induced  to  address  a 
few  practical  remarks  to  you,  not  with  the  view  of  suggesting 
anything  altogether  new  on  the  subject,  but  rather  of  calling  the 
attention  of  many  of  our  professional  drainers,  as  well  as  the 
landowners  and  farmers,  to  a few  matters  of  practical  detail  in  the 
manner  of  cutting  the  drains  and  laying  in  the  pipes,  which,  if 
attended  to  accurately,  will  greatly  lessen  the  causes  of  complaint 
against  the  (much  abused)  “small  pipe-tiles,”  for  I have  found 
by  experience  that  the  large-bore  pipe-tile  is  equally  subject  to 
stopping  up  or  choking,  from  the  same  cause  as  those  of  a smaller 
diameter. 
It  is  generally  the  custom  for  drainers,  when  cutting  drains,  to 
try  if  they  have  the  proper  fall,  by  pouring  a small  quantity  of  water 
into  the  bottom  of  the  drain,  and  if  that  runs  in  the  direction  they 
wish,  they  rest  satisfied  that  they  have  cut  the  drain  to  a proper 
and  regular  fall ; whereas  if  that  cutting  is  proved  or  tested  by  the 
level,  as  hereafter  described,  it  will  be  found  to  be  anything  but 
what  it  ought  to  be,  especially  where  the  fall  from  the  head  of  the 
drain  to  the  outfall  is  but  trifling  ; and  upon  accurately  testing  it, 
it  will,  in  most  instances,  be  found  that  the  workman  has  con- 
sumed more  than  the  due  proportion  of  the  amount  of  fall  that 
he  has  at  command  in  one  portion  of  the  drain,  while  his  tiles  will 
lie  dead  and  flat  in  another;  and  in  many  instances  I have  found 
the  tiles  lying  in  hollows,  and  following  the  undulations  of  the 
surface , as  if  on  purpose  to  collect  the  sand  or  sediment  which  in 
a short  time  chokes  the  drain.  I will  now  very  briefly  state  how 
this  may  be  avoided  with  little  or  no  additional  expense  or  trouble, 
and  what  I have  myself  practised  with  the  greatest  success  and 
satisfaction  to  my  workmen. 
I first  ascertain  what  amount  of  fall  I can  obtain  from  the  head 
of  my  drain  to  my  outfall : suppose  the  length  of  the  drain  to  be 
96  yards,  and  I find  I have  a fall  of  2 feet,  that  gives  me  a fall  of 
one  quarter  of  an  inch  in  every  yard.  I then  take  a common 
bricklayer’s  level,  12  feet  long,  to  the  bottom  of  which  I attach 
with  screws  a piece  of  wood  the  whole  length — 1 inch  under  at 
