I. I ntroduction . A mong the slates of the Isle of Man some strata have been found which represent, in the opinion of Mr. G. W. Lamplugh, so distinct a type of phenomenon that he assigned thereto a special name—that of a ‘crush-conglomerate.’ In the earlier announcement of this result in 1895, he defined the rock as ‘made up of scattered fragments set in a slaty matrix,’ and considered it ‘due to the breaking-up under pressure of alternations of flaggy slate and thin grit-bands’ ( op. cit. p. 565). So far as this general statement goes, we shall find it included in the description, of many fragmental rocks; but when we seek further information, and enquire concerning the fragments whether they be angular or round, scattered or crowded, uniform or various, composed of neighbouring rocks or of remote ones, and of the pressure, whether it be shearing or otherwise, metamorphosing or not—then our troubles begin. The paper in the Quarterly Journal was only a preliminary account of what had been observed, and a full statement was promised when the Geological Survey-Memoir on the island should: be published, which took place in 1903. I had early, however, taken an interest in the question, owing to the inclusion by Sir Archibald Geikie of some rocks in Anglesey in the same category. But I had not to wait so long as 1903, for, with the greatest kindness, Mr. Lamplugh lent me some advance-proofs of the principal passages involved, and thereby enabled me to spend portions of