616 Mr. J. Beete Jukes and the Rev. Samuel Hadghton on the 



Description of the foregoing Fdstones — continued. 



No. 3. Bonmahon, county ofWaterford ; pale greenish felstone, stratified; in other localities 

 in this neighbourhood the felstone is found in columnar masses, sometimes almost 

 translucent on the edges, like the hornstone of the German geologists. 



No. 4. Benaunmore, near Glenflesk, county of Kerry; occurs in columnar masses, 200 feet 

 long; it is massive, fine-grained, with rounded specks of quartz (globuliferous) 

 and small occasional facets of felspar, brittle, of conchoidal fracture, somewhat 

 lamellar, and translucent on the edges, with a ringing clink, and striking fire freely 

 when struck with the hammer. 



No. 5. Near Pitt's Head, half-way between Caernarvon and Beddgelert, at the summit level 

 of the road, caused by a band of translucent greenish felstone; pale green, semi- 

 translucent, with facets of felspar. 



The first three of the foregoing analyses are of rocks from the district under 

 our consideration, — 



No. 1. Ballymurtagh, from the north-east extremity of the southern band 

 of felstones. 



No. 2. Carrickburn, from the centre of the same band. 



No. 3. Bonmahon, from the south-west extremity of the same southern 

 band. 



The other two analyses are of rocks similar to the foregoing, but from very 

 difierent districts: — 



No. 4. Benaunmore, near Killarney, associated with beds of the Old Red 

 Sandstone epoch. 



No. 5. Pitt's Head, Caernarvonshire ; from the lowest Silurians, but above 

 the Lingula beds and magnetico-phosphatic bands of the same county. 



The difference between these felstones and the bastard granites associated 

 with them is evident in the relative proportions of potash and soda. The 

 cause was absent, whatever it was (sea water or other cause), that produced 

 the excess of soda above potash, and the felstones of Wicklow, Wexford, 

 Waterford, Kerry, and Caernarvon, are simply potash granites of the ordinary 

 type, that by rapid cooling acquired a stony instead of a crystalline structure, 

 and that appear to be contemporaneous with the beds with which they are 

 associated. The following Table exhibits the true character of these stony 

 granites : — 



