GEOLOGICAL SOCIETY OF DUBLIN. 
23 
downward. The stratification of this conglomerate appeared to coincide 
with that of the country generally, the strike being H. 1ST. E., and the 
bedding at a high angle. 
Just behind George Prestwich’s the porphyry is quarried, and it was 
here that I procured the specimens, in one of which you will perceive 
an embedded pebble of felstone of the size of a nut, notwithstanding 
the crystalline porphyritic and apparently molten character of the rock. 
East of this band there extends another band parallel to it, and 
about 100 yards in width, right across the hill, composed of felstone 
varying from a rather dark-gray through a pale green to a nearly pure 
white, having the compact smooth texture usual with this rock, but 
exhibiting every here and there small glittering facets of crystals of 
feldspar. 
Over, or to the eastward of this, there appear to be some beds of a 
kind of ash, either felstone or greenstone, or having both characters 
intermingled, containing at one place on the coast veins of felstone, 
which are probably the ends of small contemporaneous flows of that 
rock. 
East of these again at the Hanging Stone, and at all places ET. H. E. 
and S. S. W. of it, is a band of greenstone about 80 or 100 yards wide, 
and very well exhibited along the cliffs. This greenstone is of a finer 
grain than that before mentioned, but is a well-characterized greenstone. 
It is remarkable that both in this and in other rocks of the district 
there is a much greater proportion of iron pyrites in small detached 
cubical crystals than is usual in such rocks. 
Proceeding along the cliffs south of the Hanging Stone, when about 
a quarter of a mile south of it, the greenstone gradually becomes 
earthy and friable, and passes into a flaky sort of greenish or yellow¬ 
ish ash, which shortly becomes distinctly stratified, and passes up into 
thin beds of fine-grained slate and gritstone, and these are shortly 
overlaid by a bed of coarse conglomerate, twenty or thirty feet thick, 
over which is more thick, massive ash, and then a small exposure of 
dark gray compact felstone terminates the section. 
These clearly stratified rocks dip E. S. E. at 70° or 80°. The con¬ 
glomerate is full of well-rounded pebbles of trap and fragments of slate, 
some of the traps being compact felstone, others quite vesicular, almost 
pumiceous in appearance, such as I did not see in situ anywhere. It 
had very much the aspect, except from its highly inclined position, 
of one of the beds of volcanic breccia and conglomerate one so often 
sees about recent and active volcanoes; and it occurred to me that in 
these pebbles of vesicular trap we might have preserved the only frag¬ 
ments of the more superficial parts of the flows of molten matter which 
were produced at the time of the igneous outburst, the compact fel- 
stones being the lower part of those molten streams. 
As a general result, then, of this description, we may state that here, 
as in many other localities of the Cambro-Silurian district of the south¬ 
east of Ireland and the opposite coast of Wales, volcanic outbursts and 
eruptions were taking place in the bed of the sea, in which those muds 
