215 
of the Counties of Derry and Antrim. 
often indeed sinking below the surface, but never raising its 
lower edge above it ; but when at Solomon s Porch, the boun- 
dary of our basaltic area begins to deflect to the south-west, 
and then to the south, the ascent of the stratum to the south- 
ward begins to operate, and we perceive the dotted line of its 
quarries gradually to rise along the face of the mountain from 
the shore to Monyneeny and Seafin, where it has attained the 
height of 1 500 feet : it is true, the actual stratum has not 
been opened at these two great elevations, but the white 
rubble immediately below the basaltic fa£ade proves incon- 
testably that it is close at hand. 
An accumulation of basaltic strata, had in this southern 
course, as well as on the northern shore, covered the lime- 
stone up to the summits of the hills or mountains. 
I have already stated how the ridge of mountain is suddenly 
interrupted by the valley of the Mayola, from 1600 to 1700 
feet deep, but if we look to the southward, in the rectilineal 
course of the strata (the positions of which we have been able 
to ascertain with so much accuracy ) , we shall find near the 
summit of the mountain Slievegallon a similar white limestone 
stratum crowned with basalt, cutting it in the very direction 
the former ought to have reached it, that is perhaps two 
hundred feet higher, the ascent of the strata to the southward 
having elevated their planes so much in a distance of four 
miles, the probable interval between the summits of these 
mountains. 
We are now to decide whether this calcareous and basaltic 
fragment, on the summit of Slievegallon mountain, be the 
last remnant of the old arrangement we have been tracing, 
and ascertaining with so much precision, for seventeen or 
