  The Shi arrangement is an affine arrangement of hyperplanes consisting of the
hyperplanes of the Weyl arrangement and their parallel translations. It was
introduced by J.-Y. Shi in the study of the Kazhdan-Lusztig representation of
the affine Weyl groups. M. Yoshinaga showed that the cone over every Shi
arrangement is free. In this paper, we construct an explicit basis for the
derivation module of the cone over the Shi arrangements of the type $B_{\ell}$
or $C_{\ell}$.
