PLATE XLV. 



FIG. 1. 

 SCHISTOSE VOLCANIC BKECCIA. 



LLYN PADAKN, N. WALES. 

 Magnified 30 diameters. Ordinary light. 



The central portion of the figure is occupied by a vesicular lapillum, rendered 

 almost opaque by finely disseminated magnetite. It contains some small felspars. 

 This lapillum was evidently produced by the explosion of a highly basic lava. 

 The ferro-magnesian constituents of the original breccia or tuff are now re- 

 presented by chloritic or serpentinous minerals associated with calcite. The fine 

 grey matrix in which the volcanic fragments lie may represent ordinary sediment. 

 A quartz-grain is seen to the right of the centre. 



The rock has been described by Prof. GKEEN (Q.J.G.S., Vol. XLL, p. 77). 

 It is either of Cambrian or pre-Cambrian age. 



FIG 2. 

 QUAETZITE. 



THE LICKEY HILLS. 



Magnified 55 diameters. Ordinary light. 



This Figure must be examined in connection with Fig. 1 , Plate XLVI. The 

 original grains of quartz are seen to have been well-rounded, probably by sub- 

 aerial attrition. The interspaces between the original grains are occupied by 

 secondary quartz which is somewhat freer from inclusions than the original 

 grains. 



