  Let $\Gamma$ be a chart, and we denote by $\Gamma_m$ the union of all the
edges of label $m$. A chart $\Gamma$ is of type $(7)$ if there exists a label
$m$ such that $w(\Gamma)=7$, $w(\Gamma_m\cap\Gamma_{m+1})=7$ where $w(G)$ is
the number of white vertices in $G$. In this paper, we prove that there is no
minimal chart of type $(7)$.
