200 VIGNETTES FROM NATURE. 



a megalithic structure, piled up of four large 

 boulders from the neighbouring hillside, and 

 but little squared or hewn by artificial means. 

 The boulders do not belong to the same 

 Cambrian rock as the underlying hill ; they 

 are fragments of Snowdonian granite, trans- 

 ported hither by the glaciers of the great ice 

 age, which scratched the grooves and furrows 

 on the naked limestone of the mountain 

 itself. I can trace these grooves all around 

 me on every hand ; and indeed the bossed 

 and rounded surface of all the shoulders 

 would in itself suffice to suggest glacial action 

 immediately to any geological eye. Similar 

 markings occur on the sides of the three 

 upright stones in the cromlech, and on the 

 under front of the table-stone which lies 

 across them ; but here and there the original 

 striated surface has been cut away by the 

 rude tools of the primitive cromlech builders, 

 in order roughly to shape the irregular 

 masses for their present position. For of 

 course cromlechs, though very ancient from 



