  Four propositions are considered concerning the relationship between the
zeros of two combinations of the Riemann zeta function and the function itself.
The first is the Riemann hypothesis, while the second relates to the zeros of a
derivative function. It is proved that these are equivalent, and that, if the
Riemann hypothesis holds, then all zeros of the zeta function on the critical
line are simple. The Riemann hypothesis is then shown to imply the third
proposition holds, this being a new necessary condition for the Riemann
hypothesis. The third proposition is shown to be equivalent to the fourth, and
either is shown to yield the result that the distribution of zeros on the
critical line of $\zeta (s)$ is that given by the Riemann hypothesis. The
results given are obtained from a combination of analytic arguments,
experimental mathematical techniques and graphical reasoning.
