Geological Relations of the East of Ireland. 277 
phyry, and amygdaloid ; but so little of them is exposed, that their 
relations are not easily ascertained. 
. The red iron claystone crops out to the westward, and a quarry 
has been opened upon it to the depth of ten and twenty feet. 
This rock is here in part so thinly stratified as to become almost 
slaty, and it may be raised in flags, which however are not con- 
tinuous, being divided by cross fissures. The strata, which are from 
half an inch to six inches in thickness, are arranged with as much 
regularity as a pile of boards; but in depth they become thicker, 
dipping at an angle of 10° toward the south. The rock of which 
they consist is of a dark brownish red, or even brick red colour, 
very compact in the cross fracture, hard, and heavy, containing 
much iron in its composition. In the direction of the stratified 
structure of the stone, occur spots of calcareous spar, with earthy 
crystals of felspar ; some of the layers consisting wholly of this 
compound. 
About twenty fathoms perpendicularly above the red iron clay- 
stone, limestone crops out to the surface, in strata from one to two 
feet thick, dipping at an angle of 27° toward the south-east into the 
hill ; but little of the rock is exposed to view. From hence up- 
ward we observe only greyish black basalt, amorphous and columnar, 
and containing hornblende. The columnar portions are confined 
to the southern side of the extreme north-western part of the hill, 
appearing as rude projecting pillars, similar in form and composition 
to those of Lin field below, but not so well displayed, rising only a 
few feet above the surface. There are two clusters of these pillars, 
with a slight interval between them. 
The protruding blocks of limestone and limestone conglomerate, 
to which I have already adverted, are to be found in various parts 
of the north-western and south-western arms, and in the exterior 
