occurring near Knockmahon in the County of Waterford. 13 



The composition of this rock, as obtained by analysis, is as 

 follows : — 



Water* . . 

 Silica . . 

 Alumina 

 Peroxide of irot 

 Protoxide of iro 

 Lime . . . 

 Magnesia 

 Potassa . . 

 Soda . . . 



I. 



II. 



1-86 



1-80 



72-33 



72-33 



8-97 



9-07 



6-40 



6-27 



1-06 



1-06 



1-98 



1-86 



trace 



trace 



1-46 



1-46 



5-83 



5-83 



99-89 



9968 



Felsite, spec. grav. = 2*64. — A section was cut from a speci- 

 men of flesh-coloured felsite obtained from a very broad band of 

 this rock seen in the cliff near the village of Annestown, and 

 immediately west of a copper vein on which some explorations 

 are being made. 



Under the microscope this was found to consist of a colourless 

 and generally amorphous matrix enclosing a few dodecahedral 

 crystals of quartz and some small crystals of felspar. 



Other portions of the matrix appear to be indistinctly crystal- 

 line, and to enclose a few laminae of a greenish mineral, probably 

 chlorite. A chemical analysis of this rock afforded results as 

 under : — 



Waterf 138 



Silica 80-50 



Alumina .... 

 Peroxide of iron 

 Protoxide of iron . 

 Oxide of manganese 



Lime 



Magnesia . . . 

 Potassa .... 

 Soda 



8-33 

 3-44 

 •96 

 trace 

 1-21 

 trace 

 1-89 

 2-12 



9983 



Columnar Slate, spec. grav. =2'66. — A specimen from a band 

 of highly metamorphosed slate, which makes its appearance a 

 little to the east of the Stage lode, was next selected for exami- 

 nation. 



This rock, which is of a bluish-grey colour, is compact and 

 cherty in its structure, and is divided by a double cleavage into 

 a series of columnar masses, the planes of division of which are 



* Of which '35 was lost in the water-bath. 

 t Of which '37 was lost in the water-bath. 



