The  fuel  cost  is  based  on  the  following  assumption :

For  the  Diesel,  the  consumption  has  been  taken  in  each  case
as  the  mean  between  full  and  half-load  rates.  These  rates  were
actually  determined  by  tests.
For  the  Crossley,  1.5  to  1.25  pounds  of  coal  per  B.  H.  P.  hour
plus  an  allowance  for  stand-by  losses.
For  the  steam  engine,  4  to  3.5  pounds  of  coal  per  B.  H.  P.  hour
for  the  lowest  and  highest  powers,  assuming  an  evaporation  of
8  pounds  of  water  per  pound  of  coal.
The  cost  figures  in  the  original  table  have  all  been  transposed
to  dollars  and  cents.  The  computations  are  based  on  a  year  of
2700  working  hours.
In  the  discussion  on  Clark's  paper,  the  cost  computations
were  rather  severely  criticised,  mainly  on  account  of  the  fuel
costs  assumed.  The  claim  was  made  that  both  the  coal  consump-
tion for  the  steam  engine  and  the  cost  of  the  steam  coal  was
assumed  too  high,  and  that  the  cost  of  oil  at  3.8  c.  per  gallon  could
only  apply  to  seaboard  towns.  As  far  as  American  conditions
are  concerned,  the  assumption  regarding  the  steam  engine  would
seem  to  be  about  right,  while  the  cost  of  anthracite  at  $5.70  per
ton  for  the  gas  engine  is  certainly  not  too  low.  On  the  other
hand,  the  prijce  of  3.8  c.  per  gallon  for  the  crude  oil  would  seem  to
favor  the  Diesel  engine.  It  all  comes  to  the  point  that  applies
to  all  computations  of  this  kind,  and  that  is  that  the  results  are
strictly  applicable  only  to  the  locality  for  which  they  are  com-
puted. Allowing  for  possible  difference  in  the  labor  costs,  how-
ever, -it  seems  to  the  writer  that  the  comparison  is  quite  fair  as
between  the  steam  and  the  gas  engine.
