MINERALOGY OF THE REDHEAD. 357 



iriass of gravelstone, upwards of thirty feet in 

 thickness, and extending in length a considerable 

 way along the coast. The gravelstone is divided 

 into horizontal strata, and contains numerous 

 partial beds of sandstone. In one place, I ob- 

 served in the gravelstone an angular mass of sand- 

 stone, precisely similar to the beds of sandstone 

 below the gravelstone, which mass Vv^as surround-^ 

 ed on all sides by calcareous-spar, or limespar, and 

 the spar also fdled up a small linear vein which 

 penetrated to its centre. This fact incontestibly 

 proves, that the sandstone below was formed some 

 time before the gravelstone, and had even ac- 

 quired a sufficient degree of induration to admit 

 of fragments being detached, while the sharp edges 

 of the fragments shew, that it had not travelled 

 far from its original situation. The two rocks of 

 gravelstone and sandstone, are separated by a well 

 defined line, which also proves the posterior for- 

 mation of the incumbent mass. 



In one. place, there is a small perpendicular rent 

 in the inferior sandstone, wide towards the top, 

 but becoming narrow, and at last terminating 

 about four feet from the separating line, which 

 divides the two rocks. Into the mouth of this 

 rent, the smaller balls of the gravelstone have de- 

 scended, and filled up the superior portion of the 

 cavity, and the finer particles of sand have filled 

 up the inferior narrow portion. And it is re- 

 markable, that the slaty fracture of the sandstone 



