Of the various theories that have been advanced from time to time to account for the origin of jointed structure in rocks, the one that seems to find greatest favour amongst geologists of the present day is that put forth in M. Daubrée’s Etudes Synthétiques de Géologie Expérimental, vol. i. p. 300, et seq., wherein their formation is ascribed to the effects produced by torsion. No one can read the account of M. Daubrée’s experiments without feeling convinced that the deductions he has drawn will enable us to account for the origin of many forms of joints in a manner that leaves little or nothing to be desired. The mere fact that some of the foremost leaders of geological science at the present day hold views on this subject practically identical with his, will, doubtless, be generally regarded as a sufficient reason for accepting M. Daubrée’s theory as one that has supplied a definite and satisfactory answer to the much-vexed question of the origin of joints in general.