KiNAHAN AND BaILY RspoH 011 Boclis, 8fC. 493 



A very similar change of colour takes place in the section of the Silu- 

 rian rocks of Dingle, Co. Kerry (see PI. XYI). The rocks of group 4 

 are best exposed in the neighbourhood of Lough Grara : but no satis- 

 factory section of group 5 can be seen, although enough is exposed to 

 suggest that they lie in the trough of a shallow synclinal curve, and 

 that they are of greater thicknesses in some places : they seem to 

 be associated with subordinate beds of impure limestone, because, 

 although the latter rock was not found in situ except at Lough Key, 

 yet elsewhere fragments occur associated with the eurites. 



From the sections, it maybe suggested that the rocks of the "Red 

 arenaceous" type were either littoral accumulations, or depositions in 

 shallow water ; while the green beds seem to have been laid down in 

 deeper water, which afterwards became shallow. In two places, viz., 

 at Doon, on the west of Lough Key, and at Moy Gara, to the IST. W. of 

 Lough Grara, tracks, perhaps crustacean, very similar to those found 

 at the Valencia Lighthouse, Co. Kerry, were observed. 



In the Curlew Mountain district, as well as in the Fintona dis- 

 trict, there are remarkable peculiarities in the feldspathic rocks. As 

 mentioned already, those of Fintona have a thin-bedded structure, 

 which looks like the stratification of sedimentary rocks or tuff, 

 although they appear to be eruptive ; here, however, their tuff nature 

 is undeniable. To this subject attention has already been directed by 

 Jukes and Foot {Journ. Roy. Geol. Soc, Ireland, vol. i., p. 247) ; but 

 those observers appeared to be of the opinion that some of these rocks 

 in the country between Loughs Grara and Key might be classed as 

 normal eruptive rocks. In this Report it is pointed out that, to the 

 westward, between Charlestown and Ballaghaderreen, there are roots 

 of the eurites, elvans, and porphyries, occurring in the metamorphic 

 rocks, while in the Lower Old Red Sandstone westward and northward 

 of Ballaghaderreen there are bedded eurites and tuffs ; but eastward 

 in the Curlew Mountains the fragmentary and bedded characters are 

 very decided, the euritoid rocks being breccias, grits, sandstones, and 

 finely-laminated shales, all apparently having been re-arranged and 

 deposited in water. From this it is suggested that the vent of erup- 

 tion was to the westward; a characteristic of the vulcanicity being 

 ' great discharges of tuff, or such-like mechanical products, which were 

 subsecjuently re-arranged and deposited by water over a l^rge area. 

 This eruption must have been considerable, and for some time continu- 

 ous, as otherwise the arenaceous rocks would have been interstratified 

 with the tuffs, which does not seem to be the case. The isolated 

 masses of these tuffose rocks on the Curlew Mountains are portions of 

 the massive beds, separated and detached by breaks and denudation. 

 The suggestion now offered to account for the phenomena just 

 described accords with that proposed by Messrs. Du Noyer and Foot, 

 in explanation of the similar phenomena to be observed in the rocks 

 at Glenflesk, Co. Kerry. 



At Doon, on the west of Lough Key, melaphyres similar to those 

 of ISr. W. Galway occur associated with the euritoid rocks. 



