Or,  nothing  whatever  may  be  known  concerning  the  formula,  in
which  case  it  is  necessary  to  assume  a  form  for  the  equation  and
then  determine  the  constants  by  an  adjustment  of  the  observa-
tions. In  any  event,  the  problem  is,  to  ascertain  those  constants
which  will  make  the  given  expression,  whether  of  previously  known
or  assumed  form,  represent  the  observations  as  nearly  as  possible.
Should  there  be  uncertainty  as  between  different  forms  which
could  be  assumed,  or  should  the  residuals  resulting  from  a  solution
be  unsatisfactorily  large,  one  or  more  other  forms  may  be  assumed
and  the  constants  be  determined  for  each  of  them,  that  one  being
finally  adopted  for  which  the  sum  of  the  squares  of  the  residuals
is  the  least.
