Lower Palceozoic Rocks of the South-East of Ireland. 615 



there is some reason to thmk that the central point of the erupt.ve forces that 

 have operated on the south-east of Ireland was situated somewhere in the wes 

 of the county of Waterford. 



3. Felstones of the South-East of Ireland.-Th^ felspathic traps which are 

 associated w.th the Cambro-Silurian slates of Wicklow, Wexford, and Water- 



tLZ7^ '/ S'' ^°'^^^"^P°—^ -^^^ the slates, in which they occur 

 inte stratified. They resemble the granite of the main axis in chemical com- 

 position, although quite dissimilar in appearance. This resemblance and 

 dissimilarity may be seen from a study of the following Table, and the descrip- 

 tion ot the rocks that accompanies it :- 



Table XV. 



Analysts of Felstones. 



Silica, .... 

 Alumina, . . . 

 Peroxide of iron, 



Lime 



Magnesia, . . . 

 Potash, . . . 

 Soda, .... 

 Protoxide of iron, 

 Loss by ignition, 



Totals 



Ballymurtagh. 

 1 



81-36 

 7-86 

 3-32 

 0-99 

 0-45 

 3'09 

 2-63 



CamckbnrD. 

 2 



78-40 

 11-32 

 0-92 

 0-45 

 0-48 

 4-83 

 309 



6-56 



Bonmahon. BeDaunmore. 



77-20 

 6-54 

 5-82 

 Carb. 1-81 

 0-60 

 3-69 

 3-03 



1-12 



99-70 



100-05 



99-81 



71-52 

 12-24 

 3-16 

 0-84 

 0-39 

 5-65 

 3-36 



1-20 



98-36 



Pitt'3 Head. 

 5 



74-88 

 12-00 

 3-50 

 0-34 

 1-28 

 4-77 

 2-49 

 0-20 

 1-20 



100-66 



No. 2. 



Description of the foregoing Felstones. 

 No. 1. BeU Rock, Ballymurtagh Mine, Vale of Ovoca, county of Wicklow; from a depth of 

 two or three feet mthe rock, obtained by blasting; it weathers white to the depth 

 of a few inches owing to the kaolinization of its felspar, but the natural colour of 

 the rock is a pale grayish-green; it is exceedingly hard, striking fire freely under 

 the hammer, but, when subjected to the long-continued action of the reducing 

 flame of the blow-pipe, it melts slightly on the ed^es. ° 



Carrickburn, county of Wexford ; pale grayish-green°feIstone, with occasional facets 

 of felspar; weathers quite white; passes in some parts of the mountain into a rock 

 of a nodular, siliceous, concretionary structure, the concretions being 1-3 inches 

 in diameter, and, when broken open, often hollow, or filled with pure quartz and 



4l2 



