  Let $n\geq 2$ be any integer. We study the optimal lower bound $v_{n, n-i}$
of the canonical volume and the optimal upper bound $r_{n,n-i}$ of the
canonical stability index for minimal projective $n$-folds of general type,
which are canonically fibered by $i$-folds ($i=0,1$). The results for $i = 0$,
$v_{n,n}=2$ and $r_{n, n}=n+2$, are known to experts. In this article, we show
that $v_{n,n-1}=\frac{6}{2n+(n \bmod 3)}$ and $r_{n,n-1}=\frac{1}{3}(5n+ 3 + (n
\bmod 3))$. The machinery is applicable to all canonical dimensions $n-i$.
