I Have elsewhere pointed out the importance of the two factors —(1) the lateral force which produces the metataxic work (quâ cleavage), (2) the resistance offered to the movement of the constituent particles of a rock-mass in the direction of cleavage-dip (in some cases) by the dead weight of the superincumbent mass; the relative value of the two modifying (in the case of a deep-seated rock-mass) the whole metataxic result. Mr. Harker applies the idea in some criticisms of a paper of General MacMahon's on the “Crumpled Culm-measures of Bude ” (See Geol. Mag. April, 1890).