228 Scientific Proceedings, Royal Dublin Society. 
miles), and from the latter to the centre of Bantry Bay (14 miles). 
There is a distance of about sixteen miles from the outcrop of the 
“Old Red Sandstone” south of Dingle Bay to the outcrop of the 
“Old Red Sandstone” on the north of the Kenmare river. 
In the diagram it is shown that near Ding!e there is a thickness 
of “Dingle Beds” represented by the strata a, b, c, and d, which are 
also repeated in the country to the south; but to the south, in 
addition to these, are the strata marked e, on which the “Old 
Red Sandstone” Jies conformably. We have therefore now to 
account for the fact, that while the strata e were accumulating in 
the country south of Dingle Bay, no contemporaneous beds were 
laid down on the other side of that bay in the western portion 
of the Dingle Promontory. 
It would appear that, for a time after the deposition of the 
marine or typical Silurians, there were successive accumulations 
of matter, represented by the strata a, b, c, d, over the whole of 
this portion of §.W. Ireland ; but that after the beds d were de- 
posited a great disturbance took place in the region N. of Dingle 
Bay, the southward boundary of which ran along what is now 
the valley of Dingle Bay, or there may have been a fault along 
that line, with an upthrow to the north.* This would cause the 
rocks in said region to be upraised, and brought under the in- 
fluence of the denuding agencies; but whilst this was taking 
place on the northward side of what is now Dingle Bay, rocks 
were still being continuously deposited on the southward side, 
and the strata represented by e were accumulating. 
But after the rocks e were deposited in the south country, the 
denudation of the strata in the north country ceased, and then 
the “Old Red Sandstones” began to be deposited and gradually 
spread over the whole region, and upon it again were laid down, 
ever conformable deposits, up to the coal measures. In support 
of this hypothesis we find in the sections published by Jukes, that 
the “Old Red Sandstone” to the south is thicker than that to the 
north ; also that on the Silurian and Dingle Beds the “Old Red 
Sandstone ” is of unequal thickness, while still farther northward 
it gradually thins away. 
At the beginning of this communication attention was directed 
to Geikie’s observations as to the different basins of the Scotch 
* See note in Press, 
