  We give a geometric interpretation of the group law for Jacobian varieties by
extending the geometric construction of chords and tangents on an elliptic
curve. For any given algebraic curve $\mathcal X$ and reduced divisors $D_1,
D_2 \in \mbox{Jac } \mathcal X$, we define curves $\mathcal X^\prime$ and
$\mathcal X^{"}$ such that the intersection $\mathcal X \cap \mathcal X^\prime$
determines precisely the divisor $-(D_1+D_2)$ and the intersection $\mathcal
X\cap \mathcal X^{"}$ determines $D_1+D_2$. For superelliptic curves such
formulas are made explicit.
