  Let $\scriptstyle K$ be a number field and $\scriptstyle X_1$ and
$\scriptstyle X_2$ two smooth projective curves defined over it. In this paper
we prove an analogue of the Dyson Theorem for the product $\scriptstyle X_1
\times X_2$. If $\scriptstyle X_i = {\bb P}_1$ we find the classical Dyson
theorem. In general, it will imply a self contained and easy proof of Siegel
theorem on integral points on hyperbolic curves and it will give some insight
on effectiveness. This proof is new and avoids the use of Roth and Mordell-Weil
theorems, the theory of Linear Forms in Logarithms and the Schmidt subspace
theorem.
