GEOLOGICAL SOCIETY OF DUBLIN. 211 



tains to the westward stretching to the south of Kenmare Bay ; and it 

 is not at all improhable hut that these remarkable felspathic rocks may 

 in this district be associated with the copper lodes, which have proved 

 so productive in the Berehaven or Allihies Mine. These rocks have a 

 general resemblance to each other in all these districts, and when once 

 seen and recognised, cannot be easily mistaken for any other description 

 of rock ; they are of a pale-bluish or greenish- gray colour, weathering 

 white to the depth of several inches, slightly translucent on the edges, 

 of conchoidal fracture, and sharp metallic ring under the hammer. 



The Cornish miners who are acquainted with the mining districts of 

 Wicklow and Waterford consider these rocks as the equivalents of their 

 own Elvans, to which they bear no external resemblance, though it 

 cannot be denied that they appear to exert an equally favourable influ- 

 ence on the productiveness of the metallic lodes with which they are 

 associated; and the results of my analyses prove that they have an inti- 

 mate relation to the granitic rocks in their chemical and mineralogical 

 composition. The resemblance in composition to some varieties of gra- 

 nite is, indeed, so striking, that it requires but a slight effort of the 

 imagination to conceive them as granites cooled under peculiar circum- 

 stances, which prevented the development of the usual crystalline 

 structure. 



In some cases, however, these siliceo-felspathic rocks appear to be , 

 deposited in stratified beds, conformable to the slates and felspathic ash- 

 beds with which they are found associated. This is particularly the 

 case in the Ovoca district, where the mass of felspathic rock is found to 

 lie between dark soft slates of the Silurian age, and has never been ob- 

 served to penetrate these slates in dykes. 



I shall now proceed to the discussion of the analyses of these rocks 

 from the Wicklow, Waterford, and Killarney districts respectively : — 



1. Siliceo-felspathic Rocks of the Vale of Ovoca, county of Wicklow. 



The cupriferous and pyritous lodes of this district have aN.E. and 

 S. W. bearing, and an underlay to the S. E. They appear to be nearly 

 conformable to the planes of bedding of the slate in which they occur ; 

 and they are overlaid to the S. E. by a thick mass of siliceo-felspathic 

 rock, which rises into the remarkable hill called the Bell Bock, on the 

 west side of the Ovoca. The lodes are all dislocated by a left-handed 

 heave, coinciding apparently with the direction of the Ovoca Valley, 

 and the felspathic rock partakes of this movement of the lodes. It has 

 a stratified character throughout, and in places, as near the Tigroney 

 Mine, it assumes completely the character of an ashy-slate, weathering 

 perfectly white. 



I obtained specimens of the Bell Bock from Mr. Edward Barnes, 

 Besident Director of the "Wicklow Copper-Mine Company, which were 

 procured by blasting two or three feet into the rock, so as to obtain a 

 portion quite free from the action of the weather. The specimens are 



