Vol. 56.] IGNEOUS KOCKS OF COUNTY WATERFOKD. 679 



analysis is of a boulder of dark-grey banded felsite from the coast 

 near Annestown, and is grouped with the potash-soda felsite s. 

 The rock which Haughton analysed was from the neighbourhood of 

 Bunmahon, while Phillips's first analysis is of the Knockmahon 

 quartz-porphyry, and his second is of a flesh-coloured soda-felsite 

 near Annestown. Dr. Hatch compares these Waterford felsites 

 with others from the counties of Wicklow and Wexford, 1 where 

 rocks of the same general age are largely developed. 



The analyses of the four felsites by Haughton, Phillips, and 

 Hatch are appended, together with an analysis of the grey 

 felsite from Garrarus made for me by Messrs. H. 0. Jones & E. 

 Eobinson, of Clare College, in the Cambridge University Laboratory. 



SiCX, 



I. 



Per cent. 

 .. 7720 

 ... 6-54 



.. 5-82 



'" 1-81 

 •60 

 ,.. 3-69 

 ... 303 

 ... 112 



II. 



Per cent. 

 80-50 

 8-33 

 3-44 

 •96 

 1-21 

 trace 

 1-89 

 2-12 

 1-38 



99-83 



III. 



Per cent. 

 710 

 14-2 



•8 

 '( 



trace 



11 



96 



•7 



1-5 



996 



2-626 



IV. 



Per cent. 

 75-6 

 12-8 



1-9 



1 



•4 

 5-6 

 30 



•5 



99-9 

 2-606 



V. 



Per cent, 

 80-55 



A1 2 3 



Fe (X 



9-87 

 213 



PeO 





CaO 



MgO 



KX) 



2-21 



•81 

 2-43 



Na 2 



BLO 



•42 

 1-06 





99-81 







99-48 



Specific gravity 



2-64 



— 



I. ' Pale greenish felstone, stratified,' Bunmahon (Haughton). 



II. Flesh-coloured felsite from cliff near Annestown (Phillips). 

 III. Compact brown felsite, 1 mile west of Great Newtown Head (Hatch). 

 IV. Compact dark-grey banded felsite, boulder near Annestown (Hatch). 



V. Grey felsite intrusive in black slates, Garrarus Strand (see p. 661). 



Prom the foregoing analyses it will be seen that only No. II can 

 be classed as a soda-felsite, all the others being potash-soda felsites 

 (Nos. I & IV) or potash-felsites (Nos. Ill & V). Prom microscopical 

 characters it is, however, apparent that soda-felsites (keratophyres) 

 of several types are represented in this area as in Wicklow (see 

 p. 683, Type G, etc.). 



Microscopically, the felsites are divisible into several groups 

 according to the characters of their groundmass. This is a 

 convenient method of grouping them, but perhaps not entirely 

 natural, as some of the t\pes of groundmass are due to secondary 

 changes. A complete series of chemical analyses would probably 

 enable us to distinguish the three groups of potash-felsites, potash- 

 soda-felsites, and soda-felsites which Hatch discovered in this petro- 

 graphical province. The extinction-angles of the majority of the 

 plagioclase-phenocrysts indicate albite. 



The first type (Type A) to be mentioned is the microcrys- 



1 Geol. Mag. 1889, p. 70, & Mem. Geol. Surv. Irel. 1888, Explan. Sheets 

 138 & 139, p. 50. 



