192 
Trials  of  Agricultural  Motors. 
furrow  ploughs  and  placed  three  ploughmen  thoroughly  ex- 
perienced in  their  use  at  the  disposal  of  the  Society.  This 
arrangement  was  generally  welcomed  by  the  several  competitors. 
It  was  further  essential  that  there  should  be  as  little  difference 
as  possible  between  any  of  the  plots  which  the  motors  would 
have  to  work.  The  field  in  which  the  trials  took  place  was 
carefully  measured  up  and  levelled,  and  it  was  fortunately 
possible  to  set  out  five-acre  plots  for  each  which  were  to  all 
intents  and  purposes  exactly  similar.  (See  Figs.  1 and  8.) 
The  depth  of  ploughing  had  to  be  regulated  by  the  nature 
of  the  ground,  and  this  was  fixed  at  5 inches  for  all  competitors, 
so  as  not  to  disturb  the  chalk  subsoil. 
As  the  three  ploughs  used  were  identical,  and  as  we  were 
not  testing  the  ploughs  themselves,  it  was  obviously  unnecessary 
to  make  a dynamometer  test  of  each,  but  in  order  to  ascertain 
whether  there  was  any  material  difference  in  the  nature  of  the 
ground,  tests  were  made  with  the  same  plough  and  engine  on 
the  land  left  unploughed  between  the  plots.  The  results 
obtained  are  shown  in  the  dynamometer  chart  (Fig.  9),  which  is 
a reproduction  of  the  actual  diagrams  recorded  by  the  dynamo- 
meter. 
If  the  first  four  diagrams  are  compared,  it  will  be  noticed  that 
Nos.  1 and  3 present  a slightly  increasing  draught  from  left  to 
right,  while  in  Nos.  2 and  4 the  reverse  takes  place  to  a very 
similar  degree.  This  corresponds  with  the  undulation  of  the 
land  and  is  incidentally  evidence  of  the  correctness  of  the  record. 
Comparing  these  four  diagrams  it  will  be  noticed  that  the 
draught  in  the  lower  portion  of  the  field  is  more  than  on  the 
upper  part,  the  ground  being  caked  harder,  though  as  compared 
with  diagram  No.  5,  which  was  taken  subsequently  in  heavy 
land,  the  differences  are  relatively  small. 
For  further  comparison,  the  weight  of  ground  actually  moved 
by  the  motor  during  the  trial  was  ascertained  by  weighing  two 
or  more  samples  of  earth  one  yard  square  on  each  plot,  the 
mean  of  these  weights  is  given  in  Table  1.  The  difference  in 
these  weights  is  to  a considerable  extent  due  to  the  way  in  which 
the  ploughing  had  been  effected.  Owing  to  the  difference  of 
level  of  the  draw-bar  adopted  by  different  competitors  and  to 
other  causes,  it  was  found  more  difficult  to  maintain  a uniform 
depth  of  furrow  and  level  pan  in  some  instances  than  in  others. 
The  trials  were  to  have  been  commenced  at  9 a.m.  on  the 
Tuesday  morning,  but  it  was  11  o’clock  before  a start  could  be 
made.  The  delay  was  in  no  way  due  to  want  of  preparation  or 
