292 Mr. Weaver oti the Struchire of the South of Ireland, 



described at Riversville on the right bank of the Maine *, a 

 low ridge crosses that river and extends some distance be- 

 yond it, in which I could discover traces only of the grey- 

 wacke formation, and around which the carboniferous lime- 

 stone of the vale appears to sweep on the north, east, and 

 south, in nearly horizontal position, wherever exposed in 

 the adjacent quarries +. For these several reasons my view 

 necessarily differs from that taken by Mr. Griffith. 



From the preceding it will be inferred that I do not con- 

 sider Mr. Griffith's representations as in any respect invalida- 

 ting the conclusions to which I have been led, as exhibited in 

 my memoir on the south of Ireland. The day is past when 

 it might be authoritatively pronounced that such and such a 

 limestone is carboniferous merely because it contains some 

 fossils that are common to the latter. I have entered at some 

 length into this subject in my memoir on the south of Ireland 

 and in the Lond. and Edin. Phil. Mag. for August 1 839, to 

 which I beg to refer. But I cannot avoid noticing in this 

 place, as a case in point, the communication made by Mr. 

 Austen to the British Association, at Birmingham, in August, 

 1839, respecting the fossil remains of the limestones and 

 slates of South Devon:}:, which in its general views so well 

 corresponds with the tenor of my publication in the Lond. 

 and Edin. Phil. Mag. of the same month, although our re- 

 spective observations and inferences were made independently 

 of each other. Mr. Austen conceives that a great identity 

 of species can be established between the Radiaria, Mollusca, 

 and Crustacea, of a portion of the Rhine and those of South 

 Devon ; and he states that both districts present many forms 

 of animal structure, such as in this country we should call 

 carboniferous, and that o{ forty species which were enume- 

 rated, some were hardl}', and some not at all, to be distin- 

 guished from those of our mountain or carboniferous limestone. 

 Mr. Austen considers as the geological equivalents of the 

 slates and limestones of Souih Devon those of the Rhine and 

 Eifel, and that strata in the south of Ireland are of the same 

 age ; observing also that many of the same fossils occur at 

 Nehou and St. Sauveur in Lower Normandy. He remarks 

 also that oW red sandstone is an unfit name to designate the 

 limestones and roofing slates of South Devon, or the white 

 sandstones of Lower Normandy and Brittany. To which I 

 may add, that it is also inapplicable to the older stratified 

 rocks of Ireland. 



* Memoir on the South of Ireland, § 13. f Ibid., § 51. 

 J See AtheuEeuni of August 3], 1839, p. 661. 



