316 THE STRUCTURE AND SUCCESSION AT 



Cranberry Head is about forty feet high, standing upon a 

 sandstone base. Since water level on either side finds soft 

 shales, these have worn away, leaving the outstanding firmer 

 sandstone. The front of the head, too, is parallel with the 

 strike, and the dip is directly seaward. These conditions give 

 less chance for wave attack than would otherwise exist. Not- 

 withstanding this, the head musv eventually wear away. 

 Brown, writing in 1871, said : " A block, 20 yards square and 

 15 j^ards high slipped off from Cranberry Head, forming an 

 island." Although this was not very many years ago, no trace 

 of the " island " now remains. Moreover, as the sea works 

 landward, the cliffs are becoming lower ; for here the land 

 surface slopes away from the sea. 



Black point. — -Around Cranberry Head no new measures 

 are exposed, for the shore either follows the strike or cuts back 

 into beds already seen. At Black point, about a mile from 

 Cranberry Head, are good exposures of coal and strata. The 

 point is sandstone, much broken into cubical blocks, which aids 

 the sea action in rapidly eroding it back. Three coal beds crop 

 here. The lower is one and one-half feet thick, with a foot of 

 fire-clay, resting upon sandstone. Above are six inches of fine 

 clay and marl, then coarser shale ten feet to the middle seam, 

 which is one foot thick. Sixteen feet higher is the third seam, 

 three feet thick, with coarse sandstone above and clay and shale 

 below. All these clays contain Stigmiria rootlets, while the 

 sandstone contains Sigillaria and Calamites. Mr. Charles Robb 

 says these Black Point seams are the same as those cropping at 

 Chapel point. Their enclosing strata go far towards proving 

 his conclusion to be correct. This is especially true of the 

 coarse gritty limestone overlying a coal bed at each point. I 

 have found no other coal seam without clay or shale immediately 

 above. In default of this evidence, however, one would be 

 disposed to call the Black Point beds new ones, owing to the 

 increase in their thickness and in that of the intervening strata 



