230. It is remarked, at § 56, that the shifting of the strata is best observed where the veins make a transverse section of beds of rock, considerably inclined to the horizon. It is also true, that in some cases the near approach of the strata to the level, may make the shifts produced by the veins very easy to be discovered. Thus in Derbyshire, where the mineral veins are in secondary strata, nearly horizontal, there is almost no instance in which the corresponding strata are not observed to be on different levels, on the opposite sides of the same vein. 231. The fact described by De Luc, and referred to at § 55, may, for what we know of it, admit of being explained in two ways. The great wedge of rock which appears to be insulated between two branches of the same vein, may either be a mass that has been broken off, and sustained by the melted matter that flowed all around it; or, it may be a mass of rock contained between two veins that are in reality distinct, and of different formation. Whether this last supposition is the truth, would probably be evident from a careful examination of both parts of the vein; as some difference of character cannot fail to be the consequence of different formation. If no such difference is observed, the two branches must be supposed to belong to the same vein, and the only probable explanation of the insulation of so large a mass of rock will be by the first mentioned supposition. This fact, therefore, notwithstanding the great attention M. De Luc has bestowed on it, still requires further examination, before it can be decided whether it inclines to the Huttonian Theory, as on the first supposition, or is, as on the latter hypothesis, equally balanced between it and the _Wernerian_. 232. Whatever be the case with this fact, the general one of pieces of rock being found insulated in veins, is certainly favourable to the notion of an injected and ponderous fluid having originally sustained them. Where, as happens in some instances, the stones contained in the veins have no affinity to any of the rocks above, they cannot be supposed to have come any how but from below, and to have been carried up by the matter of the vein. The instance from the slip at the Huddersfield Canal has been already mentioned.