264 MR. GARDINER AND PROF. REYNOLDS ON [May 1902, 
Llandovery Beds are mainly calcareous flags and slates associated 
with a great amount of volcanic material. No pure limestone and no 
black graptolitic shales occur. Volcanic rocks are first met with 
low down in the Wenlock-Llandovery Series, and reach their maxi- 
mum in the Wenlock Series, this being especially noticeable in the 
southern part of the area. Ashes occur interbedded with the lower 
beds of the Ludlow Series, but no lavas; and in the higher Ludlow 
. Beds and the conformably overlying Dingle Series, we have found 
no signs of contemporaneous volcanic action. The volcanic rocks 
are all of the same general character, and include thick beds of 
rhyolitic lava and of coarse and fine ash. 
(3) After the deposition of the Dingle Beds extensive earth- 
movements took place: for, not only is the Old-Red-Sandstone 
(Upper Devonian) Conglomerate now found resting unconformably 
upon the upturned Dingle Beds (Lower Devonian), as, for example, 
along the northern shore of Dingle Bay, but it also rests upon the 
Ludlow Beds on the north side of Clogher Head, and upon the Smerwick 
(? Llandovery) Beds from Sybil Point to Smerwick Harbour. 
During some succeeding age this capping of Old Red Sandstone, 
with its overlying Carboniferous deposits, was bent into an immense 
anticline, the crest of which was over Brandon Mountain, where 
the Old-Red-Sandstone Conglomerate now lies at a height of some 
3000 feet above sea-level. 
(4) The general structure of the Silurian inlier may be defined 
as an S-shaped fold, the middle limb of which is overfolded to the 
north and thrust over the northern limb, the thrust traversing the 
trough of the fold. The arch of the fold between the southern and 
middle limbs is also traversed by a fault. The most marked effect 
of this overfolding is that all the beds exposed along the coast 
appear to dip approximately i in the same direction—south- eastward 
or south-south-eastward. 
(5) This great overfold cannot have occurred in the pre-Old- 
Red-Sandstone and post-Dingle period of earth-movement ; for we 
find the Wenlock Beds of Clogher Head thrust over the Old-Red- 
Sandstone Conglomerate there, which rests with an unfaulted 
unconformable junction upon the Ludlows of Trabaneclogher. 
It is very possible, however, that the overfold and thrusting took 
place during the post-Carboniferous period of earth-movement, which 
brought about the huge anticline of Old Red. Sandstone and Car- 
boniferous rocks reaching right across the Dingle promontory. 
(6) But before this great overfold took place, there had been a 
certain amount of intrusion of igneous rock. This is, in the main, 
a fine-grained diabasic rock, often much altered, and is the ‘green- 
stone’ of the Geological Survey Memoir. It is met with between 
similar beds in the three limbs of the great S-fold, and this points 
to its intrusion before the formation of the fold. 
It is possible that this period of intrusion may have coincided 
with the post-Dingle and pre-Old-Red-Sandstone period of earth- 
movement. And colour is lent to this view, by the occurrence of 
ereenstone, recorded in the Geological Survey Memoir as. intrusive 
