A further proof of the late age of these southern patches of volcanic material is shown by two bands of vesicular toadstone in the Yoredale series, a little south from the village of Kniveton. These rocks are traced on the Survey Map, and are shown in a diagram in the Memoir, where their position is sought to be explained by a system of parallel faulting.[37] I was able to trace the actual contact of the western band with the strata underneath it, and satisfied myself that there is no fault at the junction. The igneous material is regularly bedded with the Yoredale shales and limestones. Either, therefore, these bands are intercalated lava-streams or intrusive sills. If mere vesicular structure were enough to distinguish true outflowing lavas, then there could be no doubt about these Kniveton rocks. But this structure is found in so many Carboniferous sills, particularly in those thin sheets which have been injected into coals and black shales, that its presence is far from decisive. The vesicles in the Kniveton rocks are small and pea-like, tolerably uniform in size and shape, and crowded together. They are thus not at all like the irregular cavities in the ordinary cellular and scoriaceous lavas of the toadstone series. [Footnote 37: _Op. cit._ p. 87.] Whether or not the question of their true relations be ever satisfactorily settled, these Kniveton bands are certainly younger than the lower portion of the Yoredale group. Their evidence thus agrees with that of the southern agglomerates in showing that the volcanic activity of this region was continued even after the thick calcareous masses of the Carboniferous Limestone series had ceased to be deposited. Besides the six necks to which I have referred, a rock in Ember Lane, above Bonsall, probably belongs to another vent.[38] It is particularly interesting from the great preponderance of limestone fragments in it. The volcanic explosions at this locality broke up the already solidified limestones on the floor of the Carboniferous Limestone sea, and strewed them around, mingled with volcanic blocks and dust of the prevailing type. [Footnote 38: This is outcrop No. 39 of Mr. Bemrose's paper, p. 632.] When the district has been more carefully searched, other centres of eruption will no doubt be discovered. It may then be possible to depict the distribution of the active vents, and to connect with them the outflow of the bedded lavas. So far as I have been able to ascertain, there are no necks of dolerite or basalt, though, as I have shown, dykes or veins of molten rock are occasionally to be found in the agglomerates of the necks.