THEIIl SOtlROE AND ORIOJN. 



.263 



might well be excused for calling some of these rock massos 

 " a composition of pebbles, grit and other concrete matter " 

 and doubting that they were " ever hewn fi-om the rock." 

 1 sliall Hj)oak of the rock of wliich these stones are com- 

 posed as iSilicious Breccia. 



Besides the stones which are composed of tliis Silicions 

 Breccia, there are others, five in number, which are com- 

 posed of a Dolomitic Breccia, in which comparatively 

 small fragments of (Mountain) Limestone are embedded 

 in a reddish matrix, containing iron and carbonate of lime. 

 This has, so far as I know, never been differentiated from 

 the Silicions Breccia by previous observers. It is, however 

 a distinct rock; and the fact that all three stones of the 

 (^ovo are composed of it is, I think, noteworthy. 



The two small stones in the Lower Tyning, as well as 

 one, perhaps two, in the Great Circle, and one in the 

 North-east Circle Avenue, are a yellowish Limestone. The 

 presence of an Echinoid in one of the stones in the Lower 

 Tyning marks this rock as belonging to the Oolite series of 

 geologists. 



Tour stones are composed of Sandstone: the Quoit, two 

 in the Great Circle, and one in the South-west Circle. I 

 think it not unlikely that the Sandstones in the circles are 

 of PaliBOzoic age, perhaps Old Red Sandstone. But that 

 of the Quoit is of a different and closer character. 



Thus, if we separate these Sandstones, there are five dis- 

 tinct kinds of rocks — Silicions Breccia, Dolomitic Breccia, 

 Oolitic Ijimestono, coarser Sandstone, and the close fine- 

 grained cherty Sandstone of the Quoit. 



Whence were these severally bi-ought ? 



The Sources of the Stanton Drew Stones.— 1. TLe 

 Silicious Breccia. — Although the variable nature of this rock 

 makes it impossible to say, for certain, from what exact spot 



