185 MINERALOGY OF THE FENTLAND HlLL^a/ 



Clinkstone, Clinkstone-Porphyry, Amygdaloidal 

 Clinkstone-Porphyry, Greenstone, Compact Fel- 

 spar, Claystone, Claystone-TufF, and Porphyry, 



I. Conglomerate, 



This rock is composed of roundish, angular, andt 

 other shaped portions of quartz, grey-wacke, grey- 

 wacke-slate, porphyry, felspar, flinty- slate, com- 

 mon jasper, hornstone, and mica. The portions 

 are from the size of a man's head and upwards^ 

 to that of a pea, and the larger masses are con- 

 nected together by a basis or paste of the smaller 

 pieces, and these again are joined together without 

 any basis, just as stones are which have been de- 

 posited from a state of chemical solution. It varies 

 in hardness ; two principal varieties may be dis- 

 tinguished, a hard and soft. In the hard variety^ 

 the basis and the included portions run into each 

 other, and are so crystalline and firmly joined to- 

 gether, that it is only by means of violence that 

 we can break off masses. This variety generally 

 forms the mass of entire strata ; at other times we 

 find it intermixed in cotemporaneous portions in 

 the softer variety. The softer variety is so loose 

 in its texture, that we can readily break it with 

 the hammer, and even extract the imbedded por- 

 tions with the fingers. It occurs, in general, more 

 abundantly, than the hard vai'iety. 



