A 
On the Old Red Sandstone of Ireland. 137 
The question remained in abeyance while the officers of the 
Geological Survey were examining the rocks of north-east Mun- 
ster ; until about 1864, when Foot declared that he suspected the 
rocks of the Curlew Mountains to be “ Dingle Beds.” The fol- 
lowing year Jukes examined these rocks for himself, and subse- 
quently announced his belief that the lower portion of the so- 
styled Old Red Sandstone near Ballaghaderreen, a dozen miles 
or more W.S.W. of the Curlew Mountains was probably of the 
same age as the Dingle Beds; since it seemed to lie conformably 
on similar fossiliferous Silurians, as previously stated by Kelly, 
while it was similarly capped unconformably by what all would 
regard as true Old Red Sandstone [Carboniferous]. 
Still it was premature to say what itsage might be, until it and 
all the tracts mentioned by Griffith had been systematically ex- 
amined. 
At thistime I began the work in West Galway and Mayo; 
and after seven years careful examination I came to the conclusion 
that the oldest rocks there are Cambrians. 
These are partially covered, as it would seem, conformably, by 
Cambro-Silurians. 1 found that resting unconformably on both of 
these are newer rocks; some of which, years ago, were proved by 
their fossils to be Silurians, but others of which for atime were con- 
sidered to be Old Red Sandstone. All of these are capped uncon- 
formably by the acknowledged Old Red Sandstone [Carboniferous]. 
The rocks extending from Loughs Corrib and Mask, by Maum, 
to the Atlantic, on the south of Killary Harbour, had for years 
been known co be Silurians ; but the rocks between Toormakeady, 
on Lough Mask, and Mweelrea, north of the mouth of Killary 
Harbour, as also an isolated tract farther north near Louisburgh, 
were at one time supposed, on account of their lithological cha- 
racter, to be Old Red Sandstone. Griffith, however, found Silu- 
rian fossils at Toormakeady, while subsequently I found such, in 
somewhat similar rocks, in the Mweelrea Mountains. It was 
either during the exploration in which Griffith found the fossils at 
Toormakeady, or on a subsequent occasion, that he came to the 
conclusion that all were of Silurian age; the Louisburgh beds being 
the newest, and representatives of a portion of the Dingle Beds.” 
To the northward of Toormakeady, in the neighbourhood of 
Croaghmoyle, there is a large tract of rocks that Jukes, Symes 
Scren. Proc. R.D.S., Vou. 11., Pt. 1. TL 
