  We have defined a slowness, s, as the reciprocal conjugate of velocity, v. s
= -ih/v. We have shown that Einstein's postulate (v has an upper limit) implies
that s is discrete. A velocity operator is defined as the derivative with
respect to s. Superposition of corresponding Eigenfunctions give Galilean law
of addition of velocities. We have replaced the differential operator by the
corresponding finite difference symmetric operator. We have shown that
superposition of corresponding discrete Eigenfunctions give relativistic law of
addition of velocities. A reciprocal symmetric number system is developed and
with the help of this number system we have shown the relation between
superposition and relativistic law of addition of velocities.
