At  1250  thermal-imits,  the  curve  of  constant-heat  begins  to  waver,
but  is  almost  straight,  and  at  higher  values  the  curves  turn  down  at
the  high  pressure  ends,  tending  to  depart  more  and  more  from  the
family  characteristic.  This  is  largely  due  to  the  fact  that  the  curves
of  specific  heat  as  determined  by  these  investigators  show  a  decrease
of  the  specific  heat  with  increasing  temperature  imtil  a  minimum  is
reached,  for  each  pressure,  after  which  the  specific  heat  increcLses  with
increase  of  temperature.  An  increase  in  the  value  given  to  the  specific
heat  tends  to  lower  the  curves  of  constant-heat,  because  the  greater
the  specific  heat,  the  smaller  will  be  the  temperature  range  through
which  it  is  necessary  to  heat  the  steam  in  order  to  give  it  a  certain
increase  in  heat-contents.
