It is admitted that the data, from which the author draws his conclusions are, taken piecemeal, scanty, hazy, and often ambiguous. The main purpose of the investigation was to examine the contention of Bonney that the phenomena of Bardon Hill might possibly be explained by assuming flow-brecciation, and also to satisfy the author's own observation of a not irregular distribution of enclaves, which seemed to him to warrant a revision of the ideas held on the relative age of the units, that go to the building of the hill. Perhaps the main quest may be summarized into—whether the Bardon Rock is to be regarded as merely compacted agglomerate or whether it is truly igneous ? With these purposes in view the groups of data given in this paper rank in order of value: 1, Field Data; 2, Macroscopic Data; 3, Microscopic Data; 4, Chemical Data. This order iolds good, because the more searching the investigation the more obscure the real issues become—befogged by the increasing insistence of metamorphic phenomena. Any conclusions drawn must satisfactorily explain the bulk phenomena of the Bardon Hill rocks and must depend on converging evidence. Where two opposing explanations are possible, the author has adopted the simpler as the more likely.