Nine years ago (in 1904) I described a diagram—the moriogram, as I called it—which served for the graphical determin.stion of angles and indices in the case of zones in which the principal poles included a right angle. It was, therefore, restricted in its application to zones in the cubic, tetragonal, orthorhombic, hexagonal, and rhombohedral systems, and to zones in the monoclinic system passing through the pole of symmetry. Although the moriogram may be used with sufficient accuracy for practical purposes in the case of many substances with triclinic symmetry, in which the angles between the principal poles differ little from right angles, there necessarily remain many instances in which it cannot be applied with any approximation to accuracy.