of the Counties of Deny and Antrim. 195 
tween high and low water mark, but when it ascends along 
with the others across the faqades, it displays its whole thick- 
ness, above fifty feet. 
This stratum is of that variety of basalt, I have on different 
occasions distinguished by the name irregular prismatic ; it 
resembles the columnar basalt in grain, but differs from it 
totally in principle of internal construction, for its 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 Bolsena in 
the Sound of Mull , and at Staff'd. In Antrim , it is very com- 
mon; and here is a striking resemblance between the rock 
crowning the celebrated columns at Staffa, and a stratum 
covering a very neat colonnade at Craigahullur, near For trash. 
This stratum ( as is well exhibited in the view of Portmoon ) 
is scolloped off irregularly from the point where it becomes 
superficial (jc), until it completely disappears at (%) ; a thin 
stripe of its lower edge alone is ever resumed again. 
Fourth Stratum, (h). 
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 shews a great 
predilection for this stratum. 
Fifth Stratum , (g ) . 
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 
C c 2 
