C w 3 



at Holyhead, and has for the moft part thick lay- 

 ers of quartz intercepted between it's laminae. 



g. Hornblende Slate with Quartz; colour ochre 

 yetlaw, with black mining ftreaks of hornblende ; 

 fra&ure fchiftofe ; feels landy ; refembles gneifs* 

 the yellow colour feems to proceed from a ferru- 

 ginous quartz. 



h. Trap with Hornblende; colour bluifh, or 

 greenifh black; fracture fine fplintery; contains 

 fome grains of magnetic ironftone. 



i. Trap with Mullen; colour greyifh black, with 

 a made of red, fra&ure uneven and fine fplintery. 



f ■ ft ■ 



k. Trap with Krag ; colour greyifh black, with 

 a fhade of red; fracture uneven and fine fplintery. 



1. Siliciferous Trap ; colour blackifh grey, or 

 dark iron grey, with numerous rounded white 

 fpecks, as fmall as the point of a pin ; it is alfo 

 full of rifts, and thefe exhibit a bluifc or reddifb 

 ferruginous illinition ; fra&ure uneven and fplin- 

 tery. 



m. Ferruginous Clays ; fome are fo penetrated 

 with calces of iron, as fearcely to indicate a flaty 

 texture; colour bluifh brown; externally fome 

 luftre; internally none; readily imbibes water. 



n. Mullen with Asbestinite ; colour of a red- 

 dim grey when firft broken, with very little luf- 

 tre ; fraCture uneven and earthy. 



S a D. Sill- 



