484 Rev. T. G. Bonney — Burrows in Limestone Rock. 



cropping strata, and in the level sea-stripped scars, I submit that we 

 have final and irrefragable proof that the surface of these anciently 

 submarine hills had not been touched by the iceberg or glacier for 

 some time before, nor at any time since, they respectively emerged 

 from the waves." 



I have recently had an opportunity of examining the neighbour- 

 hood of Llandudno, with the aid of Mr. Darbishire's very interesting 

 and valuable paper, and will endeavour to state why on this point I 

 see no reason for altering my conclusion. If I rightly understand 

 him, we are agreed that the district shows signs of both marine 

 denudation and glacial action ; the debate, therefore, is narrowed to 

 this one point, whether or not these hills have been capped by ice 

 since they were covered by the sea. Mr. Darbishire argues for the 

 negative answer from the presence of (1) sea-beach and beach 

 marks ; (2), Pholas burrows. 



(1). Among these he enumerates certain large blocks lying on 

 the upper plateau of the Great Ormeshead, " the remains of the play 

 or rage of the waves about the head of the new-born island, and as 

 such emphatically a raised beach of the grandest kind," and several 

 nearly horizontal surfaces of limestone in the same neighbourhood, 

 ■' cut and furrowed, and worn in fissures, potholes and other forms, 

 very similar to those of the like beds in like positions in the inter- 

 tidal spaces below." These blocks I had described, figuring one of 

 the largest (Plate XII. Vol. IV. p. 289) as most probably hlocs 

 percJiees. That this is a gigantic stranded boulder is placed beyond 

 dispute by a very brief examination of the locality. Its base is 

 flat, and rests upon three slight projections in the rough shelving 

 scar of limestone, upon which it lies. The only question is by 

 what agency it has been conveyed to its present position. This may 

 have been done : 



(a). By the force of the waves, as suggested by Mr. Darbishire. 

 No doubt the position of this, and the numerous other similarly 

 situated blocks, might be accounted for iu this way ; but in that 

 case, I think, we might fairly expect to see a more beach-like 

 arrangement of the boulders, a larger quantity of rounded pebbles, 

 and (as the elevation of the Head can hardly be more recent than the 

 deposition of the lowland ' till' with its numerous boulders of trap 

 and foreign rocks — often ice-scratched) a considerable sprinkling of 

 boulders from the neighbourhood of Conway. Mr. Darbishire 

 himself acknowledges that he has " not found anywhere at the 

 higher level one block of any other rock than Mountain Limestone." 

 The weathering of the limestone scars in the neighbourhood, which 

 he brings forward, with some reserve, as a proof of marine denuda- 

 tion, does not differ from what may be seen on most horizontal 

 surfaces of limestone, and may be produced by the action of the 

 atmosphere and of freshwater impregnated with carbonic acid gas. 

 I am familiar with similar markings in many limestone districts 

 far away from the sea, among others in parts of the higher Alps.^ 



^ During my examination of the large boulder mentioned above, I was led, in a 

 search for ' Pholas ' burrows, to look narrowly into a crack about an inch and a 



