3H 
VOLCANOES OF THE LOWER OLD RED SANDSTONE book v 
and again succeeded bv coarse brecciated conglomerates of igneous materials, 
which may be inferred to have been due to a renewal of violent eruptions, 
lly degrees the evidence of stratification and of attrition among the 
volcanic materials becomes more pronounced as the ascending section is 
followed; blocks of andesite, even 18 inches or two feet in diameter, assume 
well-rolled, rounded, water-worn forms, like the pebbles of quartzite associ- 
ated with them, and eventually the strata return to the usual aspect of the 
conglomerates of the district. 
I have ner'er seen anywhere better proofs of volcanic explosions, 
contemporaneous with a gi’oup of sti’ata, and of the distribution of volcanic 
fragmentary material round the vents. A further point of much interest is 
the additional evidence furnished by this shore-section of considerable wave- 
action during the accumulation of the coarse conglomerates. To give to 
blocks of porphyrite two feet in diameter a smoothed and rounded form 
must have required the action of water in eonsideralile agitation. 
4. The Ulster Centres 
From the volcanic breccias and conglomerates of the Mull of Cantyre to 
the coast of Antrim in a straight line is a distance of little more than 
twenty miles. On a clear day the Old Tied Sandstone of Cross Slieve, and 
the range of cliffs in which it abruptly descends to the sea between Cushen- 
dall and Cushendun, can be distinctly seen from the Argyllshire shore. The 
geologist who passes from the Scottish to the Irish sections cannot fail to 
be impressed with the resemblance of the rocks in the two countries, and 
with the persistence of the types of conglomei’ate in Lake Caledonia. 
A picturesqrre section has been laid bare between the Coastguard 
Station south of Cushendall and Cushendun T>ay.^ At the south side of the 
little inlet of Cushenchdl, a compact dull quartz-porphyry is exposed in crags 
along the shore. This rock ranges in colour from dark birnvn and purple to 
pale-green and buff. Its texture also varies, as well as the pro]>ortion of its 
felspar-crystals and quartz-blebs. Some parts have a ea-\'eruous structure, 
like that of an amygdaloid, the small globular cavities being filled with 
green decomposition products. 
The stratigraphical relations of this rock are not quite clear, but it is 
certainly older than the Old lied conglomerates which lie to the north of it, 
for these are largely made up of its fragments. The matrix of these detrital 
masses con.sists mainly of the comminuted debris of the porphyry. The 
pebbles include all the varieties of that rock, and are tolerably well- 
rounded. Thei'e is no distinct evidence of volcanic action among these 
conglomerates. They resemble, however, many of the conglomerates in the 
Midland Valley of Scotland, which, as in the case of those on the Forfar- 
shire and Kincardineshire coast, are in great part made of the detritus 
1 For descriptions of tliis district see J. Bryce, Proc. GeoL Soc. i. (1834) p. 396, v. (1837) p. 
69 ; J. Kelly, Proc. Itoy. Irish Acad, x. (1868), p. 239. The area is contained in Sheet 14 of the 
Geological Survey of Ireland, and was mapped by Mr. A. M‘Honry and described by him in the 
accompanying Explanatory Jlemoir (1886), pp. 12, 25. 
