1^8 ON THE BASALTIC COUNTRY IN IRELAND. 



along with the others across the fagades, it displays its whole 

 thickness, above fifty feet. 

 Irregular rris* This stratum is of that variety of basalt T have on different 

 matic basa.t. occasions distinguished by the name irregular prismatic; it 

 resembles the columnar basalt in grain, but differs from it 

 totally in principle of internal construction, foi ts prisms are 

 small, not articulated, and indifferent as to the position of 

 their axes, which is perpetually changing. 



The irregular prismatic basalt accompanies the columnar 

 in most countries, as at Pont du Baume, at Trezza, at Bol- 

 sena in the Sound of Mull, and at Stqff'a. In Antrim it is 

 very common; and here is a striking resemblance between 

 the rock crowning the celebrated columns at Stqffa, and a 

 stratum covering a very neat colonnade at Craigahulhir, 

 near Portrush, 



This stratum (as is well exhibited in the view of Port- 

 moon) is scolloped off irregularly from the point where it 

 becomes superficial (x), until it completely disappears at 

 (z) ; a thin stripe of its lower edge alone is ever resumed 

 again. 



Fourth Stratum j (A). 



4th stratum. The next three strata will require only very short descrip- 

 tions; the fourth is about seven feet thick, entirely columnar, 

 the pillars small, but not neat; they appear very white from 

 a thick covering of byssus saxatilis, which shows a great 

 predilection for this stratum. 



Fifth Stratum, (g). 



5th stratum. This stratum is ochreous, and more of a slate colour than 



any of the other red strata; as it is friable, it soon acquires 

 a grassy coat, through which it is only in spots that it shows 

 its proper colour; it is about eight feet thick. 



Sixth Stratum, (/). 



6th stratum. This stratum is composed of rude massive pillars so 



coarsely formed, that on the least abatement of perpendicu- 

 larity the columnar form can scarcely be traced. 1 his stra- 

 tum is about ten feet thick, it forms the vertex of the 



beautiful 



