374 TEANSPORT OF GRA]!^ITE AJ?D OTHEE EOCKS NEAR DUBLIN. 



are reefs, after a storm, to be assured of the carrying power of 

 certain seaweeds and the tenacity with which they adhere to 

 rocks at their points of attachment, in order to accept the possibility 

 of the agency in the case under investigation having been some 

 such seaweed as the ' wrack ' or oar-weed of our coasts. In the 

 case of the larger fragments the transporting weeds may have been 

 of a more buoyant character than those of the present day ; while as 

 regards the very minute fragments of granite which we find, they 

 are more likely to have been carried to sea in the grasp of the 

 sucker-like roots of the seaweed than entangled in the roots of a 

 terrestrial plant, which, in the wash, would soon give up the finer 

 particles and only retain the firmly entangled larger fragments. 

 I have recently been informed by the Rev. Wm. S. Green that 

 a sandy beach in the neighbourhood of Toughal, co. Cork, is 

 strewn with fragments of limestone which have been conveyed by 

 seaweeds thrown up after storms from a submarine reef. In this 

 case the rock is much bored by mollusks and other animals, and 

 when the waves beat with violence on the attached seaweed, 

 fragments are broken off which, buoyed by the weed, are driven on 

 shore. 



IS'atural fissures in the rocks and cracks produced by concussions 

 from large masses hurled about by the waves would, I think, 

 sufficiently explain how the fragments might have become freed 

 from the main mass of the reefs, under the stress of the waves. 



I have recently received from Mr. G. H. Kinahan a specimen of 

 a schistose rock from Donegal, containing a sharply angular fragment 

 of red granite, and I cannot but tliink that it may have owed its 

 anomalous position to having been transported by a somewhat 

 similar means to that which is described above. 



Discussiojii. 



Mr. De Eance confirmed the xiuthor's observations, angular frag- 

 ments of limestone being found attached to the roots of Laminaria 

 at the Ormes Head, North Wales. 



Dr. E. Peeceval Weight pointed out that the enormous fucoid 

 seaweeds do not live in tropical, but in the cold and temperate seas. 

 He referred to Anson's mention of the occurrence of seaweeds out 

 at sea with stones attached to them. 



Mr. Ball replied that Dr. Wright's remarks testified strongl}'' to 

 the truth of his theory. There was no evidence of the wide distri- 

 bution of the fragments in the hmestone, they having been observed 

 in only one or two adjacent localities. 



