Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/242

 loose roundish stones, properly scoriæ, superincumbent on the respective strata of lava, and belonging to each; but I did not observe any stratum of vegetable mould, properly so called, though I believe there may be some puzzolana and rapilli.”

“ The strata are intersected in many places by walls generally perpendicular to the face of the bank as well as to the direction of the strata, in others inclined somewhat to the latter, and in some to both, and often small ones branching off from the greater perpendicular ones, and inclined to them low down in the substance of the hill itself. These seem evidently to have been fissures or cracks of the whole crust of the hill from top to bottom, into which the lava had flowed and filled them. The lava of which these are composed differs also in the same manner as that of the strata: in some it is compact and almost homogeneous, in which case the joints into which it is divided generally lie across its direction, that is, are nearly horizontal; and it is divided into irregular polygonal parts, in some places assuming a very rude sketch of basaltic columnization; in others it is porous and heterogeneous, particularly in such as are formed of the granitical lava, have a red scorified appearance and an irregularly globular structure.

“ The remarkable analogy between the several circumstances of the face of Somma and of the cliffs of the county of Antrim in Ireland from Bengore head to the river Bush, must strike any one that has seen both. The principal differences between the two are, the constant uniformity of the Antrim strata, the homogeneity of their matter, their basaltic form, and the much greater depth of the strata, which are seldom less than twenty-five or thirty feet, and the less rapid inclination inwards of the strata, which there seems not to exceed an angle of fifteen or twenty degrees, whereas here in Somma the angle is not less than from forty to forty-five degrees,