Vol. 55.] BEDDEB ROCKS OF COXTJTTY WATEEPOED. 765 



the groundmass. These clear areas, representing sections of the 

 nodules, frequently coalesce [502] [22 w], and are often crowded 

 with clear transparent felspar-microlites and a few needles of apatite. 

 A micropoikilitic or granophyric structure [14 w] [502] [15 w] 

 [22 w] is not uncommon in the groundmass, and occasionally 

 [22 w] is of coarser texture in the nodules. The latter are also 

 sometimes [22 w] marked by a central, clear, rounded quartz-grain 

 which does not seem to be of secondary origin. In one case [21 w] 

 the nodules are outlined by a distinct narrow ring of clear angular 

 quartz-grains. 



The analysis of one of these nodular felsites [22 w] was carried 

 out for me in the University Laboratory, Cambridge, by Messrs. 

 H. 0. Jones & C. Eobinson : — 



Per cent. 



SiO., Silica 75-70 



AI2O3 Alumina 12-58 



FcgOg Iron Sesquioxide 1-72 



CaO Lime 1-55 



MgO Magnesia '70 



K.,0 Potash , 4-50 



Na^O Soda I'SO 



HoO Water 1'23 



This analysis bears a remarkable resemblance to that of the 

 Tardree rhyolite quoted by Teall,^ which is as follows, differing 

 chiefly by the smaller amount of alumina and lime, and the absence 



of magnesia : — 



Per cent. 



SiO^ Silica 76-4 



AI2O3 Alumina 14-2 



Fe^Oj Iron Sesquioxide 1-6 



CaO Lime 'Q 



K^O Potash 42 



Na.O Soda 1-8 



H2O Water 1-5 



100-3 



The Tramore felsites belonging to the Carrigaghalia Series mostly 

 contain porphyritic felspars [13] [626], probably of andesine ; but 

 in some cases [54 w] [80] phenocrysts are almost absent. Mono- 

 clinic felspars are occasionally present [626], and porphyritic 

 quartz-crystals as well [13]. The groundmass is generally micro- 

 crystalline, with varying degrees of coarseness, and rarely [567] is 

 it cryptocrystalline. Granophyric and porphyritic quartz-pheno- 

 crysts, similar to those described in the Fishguard felsites,^ are 

 noticeable in some slides [626], and microperthitic structure in 

 the felspar-crystals is occasionally visible [13]. Lines of flow and 

 banding are also present in some cases [54]. 



The tuffs in the Raheen Series are composed mostly of fragments 



^ • Brit. Petrogr.' 1888, p. 348. 



^ Quart. Journ. Geol. Soc. vol. li (1895) p. 165. 



