234 Dr. Berger on the Dykes 



loose roundish stones, properly scoiise, 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 perpen- 

 dicular 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 generallv lie across its 

 direction, that is, are nearly horizontal ; and it is divided into ir- 

 regular 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 

 im Somma the angle is not less than from forty to forty-five degrees, 



