The  Tractor  and  Small  Farm 
Horse  Power  and  Mechanical  Power  Compared 
Fundamental  principles.— it  would  seem 
that  the  day  of  tractor  fanning  lias  arrived, 
even  for  the  man  who  owns  a  farm  of  30  acres  or 
so,  hut  before  buying  a  tractor  for  a  farm  of  Ibis 
or  for  that  matter  of  any  size.  it  is  well  to 
a vc  a  slight  knowledge  of  the  fundamental  prin¬ 
ciples  governing  the  successful  operation  of  me- 
horse  exerts  a  pull  equal  to  one-tenth  of  its  own 
weight  for  a  working  day  of  10  hours,  and  it  can 
work  at  the  rate  of  from  1.0  to  two  miles  per  hour; 
thus  wo  find  that  a  horse  of  1200  lbs.  travelling  two 
miles  per  hour  and  pulling  one-tenth  of  its  weight 
would  he  pulling  five-eighths  of  one  mechanical 
horsepower  as  shown  in  table  below. 
Put,  where  animal  horsepower  differs  from  me¬ 
dia  ideal  is  in  its  flexibility,  for  a  horse  may  be  able 
to  exert  for  a  limited  time  an  effort  greatly  in  ex- 
lmrsepower  for  even  a  few  minutes,  whereas  two 
horses  may  develop  eight  or  10  horsepower. 
MECHANICAL  AND  ANIMATE  HORSEPOWER. 
— You  may  think  this  knowledge  not  essential  to 
ihe  successful  operation  of  the  tractor  on  your  farm, 
hut  it  is  and  very  essential,  for  without  it  you  may 
say,  surely  if  two  horses  can  pull  a  plow  over  cer¬ 
tain  grades  a  tractor  developing  five  or  more  horse¬ 
power  should  do  the  same  work.  Put  further  con¬ 
sider  that  the  tractor  loses  approximately  10  per 
? 
7 
-  -:h 
Bringing  in  the  Christmas  Tree  in  Real  Christmas  Weather.  Fig.  603 
ehanieal  power  as  related  to  tractors,  so  as  to  an¬ 
alyze  the  conditions  Under  which  Ihe  I  motor  is  to 
work.  Perhaps  it  would  be  well  first  to  define 
horsepower  as  a  preliminary  step;  .lames  Watt 
after  numerous  experiments  with  heavy  draft- 
horses  established  that  the  average  horse  was 
equivalent  to  33,000  lbs,  raised  one  foot  in  one  min¬ 
ute,  and  this  has  been  adopted  as  the  standard  and 
is  called  a  mechanical  horsepower. 
DIFFERENCES  IN  POWER.— Now  the  horse¬ 
power  delivered  by  a  horse  is  an  entirely  different 
proposition,  as  experiments  tend  to  show  that  a 
short  period  horses  have  exerted  a  pull  equal  to 
cess  of  its  own  weight,  tests  showing  that  for  a 
four  or  five  mechanical  horsepower.  Now  mechan- 
1-10  of  1200=120. 
120X10300  2  miles)  =1207200  ft.  pounds  iu  00  miu- 
utos. 
1267200-5-60=  21120  pounds  per  ft.  minute  or 
52S 
-  or  roughly  %  horsepower. 
S23 
ical  horsepower  is  not  elastic  so  that  the  difference 
for  the  layman’s  purpose  is  this,  that,  for  exam¬ 
ple,  a  two  horsepower  engine  cannot  exceed  two 
cent,  of  its  efficiency  for  every  five  per  cent,  of  up 
grade:  in  other  words  a  tractor  of  five  horsepower 
pulling  up* a  grade  of  10  per  cent,  or  10  ft.  rise, 
in  every  100  ft.  run.  loses  20  per  cent,  or  one-fifth 
of  its  horsepower,  and  would  develop  a  pull  of  only 
four  horsepower  whereas  a  team  of  horses  might 
develop  eight  horsepower  if  necessary.  In  other 
words  the  animate  horsepower  is  elastic,  whereas 
mechanical  horsepower  is  not. 
GRADE  AND  WORK.— Now  with  this  under¬ 
standing  of  the  difference  between  animal  and  me¬ 
chanical  horsepower  the  first  step  iu  determining 
