1 88 
Trials  of  Agricultural  Motors. 
per  pound  of  earth  raised  or  moved  is  obtained,  and  this  is  given 
in  the  second  last  column  of  Table  No.  ]. 
The  diagrams  Nos.  1 to  4 (Fig.  9)  show  the  maximum  and  mini- 
mum draw-bar  pull  or  draught  of  the  plough  as  hauled  by  each 
of  the  different  tractors,  but  diagram  No.  5 on  same  page  gives 
the  draw-bar  pull  by  the  McLaren  engine  on  the  heavy  land, 
and,  while  showing  the  enormous  difference  between  the  tough- 
ness of  the  heavy  land  and  of  the  light  land  of  the  field,  it  also 
shows  the  great  variation  in  the  draw-bar  pull  in  different  parts 
at  somewhat  varying  speeds. 
The  wheels  of  all  the  steam  tractors  ran  on  the  land  which 
they  afterwards  ploughed,  but  the  furrow  side  driving-wheel  of 
the  Ivel  tractor  ran  in  the  bottom  of  the  last  ploughed  furrow. 
In  most  cases,  however,  the  weight  of  this  tractor  is  insufficient 
to  do  any  damage  to  the  seed  bed. 
After  the  ploughing  of  the  five-acre  plots,  the  tractors  were 
taken  to  a field  of  wheat  about  half  a mile  from  the  ploughed  land, 
and  there  each  one  was  attached  to  two  Harrison  McGregor  6 ft. 
knife-bar,  sheaf-delivery,  string-binding  reapers,  the  headlands 
and  a lane  having  been  already  cut  by  hand  to  permit  passage 
of  the  tractor.  The  general  lie  of  the  land  was  the  same  for  all 
the  field,  wljich  was  one  of  about  eighty  acres,  with  an  easy  down 
gradient  to  half  its  length  and  slight  upward  gradient  the  other 
half ; but,  on  the  whole,  it  was  what  would  be  considered  fairly 
easy  work,  and  the  land  was  in  nice  condition  as  to  dryness. 
All  the  tractors,  with  the  exception  of  the  two-speed  Ivel, 
were  put  on  to  these  machines.  The  Ivel,  after  a short  period, 
only  hauled  one  machine. 
This  work  was,  as  in  the  case  of  the  light  land  ploughing, 
only  play  for  the  steam  tractors,  especially  the  McLaren  tractor, 
and  the  measure  of  the  ease  or  otherwise  with  which  the  different 
tractors  could  perform  this  work  may  be  gathered  by  reference 
to  the  brake  h.p.  of  the  different  engines  when  tested  on  the 
friction  dynamometer.  A table  of  the  results  of  these  tests  will 
be  found  on  page  197  in  Mr.  Courtney’s  Report.  An  estimate  so 
formed,  however,  can  only  be  approximate,  as  the  difference  in 
the  transmission  efficiency  of  the  different  engines  is  considerable. 
Although  opinions  varied  considerably  as  to  the  ploughing  done 
by  the  different  tractors,  there  was  very  little  difference  of 
opinion  as  to  the  reaping  done,  some  of  which  would  have  been 
done  more  expeditiously  if  the  tractor  drivers  had  been  more 
accustomed  to  the  manoeuvring  of  the  combination  of  tractor 
and  reaping  machine. 
