On  the  Accurate  Levelling  of  Drains. 
115 
one  end  than  at  the  other — thereby  throwing  the  level  1 inch  out 
of  the  true  horizontal  line;  when  the  drain  has  got  to  its  proper 
depth  at  the  outfall,  1 apply  the  broadest  end  of  the  level  to  the 
mouth,  and  when  the  plumb-bob  indicates  the  level  to  be  correct 
the  1-inch  fall  has  been  gained  in  the  4 yards;  and  so  on  I keep 
testing  the  drain  as  it  is  dug  quite  up  to  the  head,  when  an 
unbroken,  even,  and  continuous  fall  of  2 feet  in  the  whole 
96  yards  has  been  obtained.  The  pipes  are  then  laid  in,  and  the 
level  proved  again  on  the  pipes,  which  regulates  any  little  ine- 
qualities in  laying  them  in  : this  I have  found  that  the  men  do 
willingly  without  any  additional  charge  per  rod  ; but  even  sup- 
posing that  the  men  were  to  fancy  that  it  was  any  additional 
trouble,  a very  slight  increase  in  the  pay  per  rod  would  be  amply 
and  fully  compensated  by  avoiding,  in  many  instances,  the  vex- 
ations attendant  upon  draining. 
Believe  me,  truly  yours, 
C.  B.  Challonkr. 
Charles-street,  Berkeley -square, 
29 tli  April,  1850. 
Bricklayers  I evel  on  a large  scale.  The  false  bottom  may  be  made  with  a hinge,  so  as  to  answer 
for  any  fall. 
A — Undulating  surface  of  Land. 
B — The  line  shows  the  position  of  very  many  drains  when  accurately  examined  by 
means  of  the  level. 
C — The  plain  line  shows  the  position  of  a drain  put  in  as  recommended. 
