  The set of Salem numbers is proved to be bounded from below by
$\theta_{31}^{-1}= 1.08544\ldots$ where $\theta_{n}$, $ n \geq 2$, is the
unique root in $(0,1)$ of the trinomial $-1+x+x^n$. Lehmer's number
$1.176280\ldots$ belongs to the interval $(\theta_{12}^{-1},
\theta_{11}^{-1})$. We conjecture that there is no Salem number in
$(\theta_{31}^{-1}, \theta_{12}^{-1}) = (1.08544\ldots, 1.17295\ldots)$. For
proving the Main Theorem, the algebraic and analytic properties of the
dynamical zeta function of the R\'enyi-Parry numeration system are used, with
real bases running over the set of real reciprocal algebraic integers, and
variable tending to 1.
