Exceedingly slag-like lavas are to be seen among the amygdaloids, immediately preceded and followed by beds of compact black basalt with few or no vesicles. From the manner in which such rocks yield to the weather, they often assume a singularly deceptive resemblance to agglomerates. One of the best examples of this resemblance which have come under my notice is that of the rock on which stands Dunluce Castle, on the north coast of Antrim. Huge rounded blocks of a harder consistency than the rest of the rock project from the surface of the cliffs, like the bombs of a true volcanic agglomerate, while the matrix in which they are wrapped has decayed from around them. But an examination of this matrix will soon convince the observer that it is strongly amygdaloidal, and that the apparent "bombs" are only harder and less cellular portions of it. The contrast between the weathering of the two parts of the rocks seems to have arisen from an original variety in the relative abundance of steam-cavities. The origin of such nodular or pillow-like blocks has been already referred to at pp. 26 and 193. Another singular instance occurs at the foot of the outlier of Fionn Chro (Fig. 360), in the island of Rum. A conspicuous band underlying the basalts there might readily be taken for a basalt-conglomerate. But in this case, also, the apparent matrix is found to be amygdaloidal, and the rounded blocks are really amygdales, sometimes a foot in length, filled or lined with quartz, chalcedony, &c. A somewhat different structure, in which, however, the appearance of volcanic breccia or agglomerate due to explosion from a vent is simulated, may be alluded to here. The best instance which I have observed of it occurs at the south end of Loch-na-Mna, in the island of Eigg, within a basalt which is remarkable for a streaky flow-structure. On the weathered faces the streaky layers may be observed to have been broken up, and their disconnected fragments have been involved in ordinary basalt wherein this flow-structure is not developed, while large blocks and irregular masses are wrapped round in a more decomposing matrix. There can be no doubt that in such cases we see the effects of the disruption of chilled crusts, and the entanglement of the broken pieces in the still fluid lava.