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XLIX. On the Mineral Structure of the South of Ireland ^ *a.nth 

 correlative matter on Devon and Cornwall, Belgium, the 

 Eifel, Sfc. By Thomas Weaver, ^5^., F.R.S., F.G.S, 

 M.R.I. J., 8^c. Src. 



" Men believe that reason governs their words, but words have often 

 power enough to react upon reason." — Bacon. 



T^HE following remarks, bearing on the mineral structure 

 -■- of a considerable portion of the south of Ireland, are 

 drawn from me by certain representations made by Mr. 

 Griffith on the same subject, respecting which my first im-- 

 pression was that I might be content to suffer them to pass 

 without public comment, persuaded that no intelligent geolo- 

 gist, who would duly sift and weigh the evidence adduced on 

 both sides, could be at a loss in coming to a correct decision. 

 But as it is not every reader who will take this trouble, and 

 as unquestioned assertions not unfrequently pass as established 

 truths with the unwary, further reflection has taught me that 

 I owe it both to the Geological Society and to myself not to 

 remain silent. However adverse to controversy, and how- 

 ever irksome the task of entering upon it, a man should always 

 be ready to give a reason for the faith that is in him. 



It has so happened that my Memoir on the Geological Re- 

 lations of the south of Ireland* (which in its more material 

 points M'as communicated to the Geological Society in the year 

 1830), and Mr. Griffith's Outline of the Geology of Ireland, 

 with its accompanying Geological Mapf, were brought before 

 the public eye much about the same time, namely, in the early 

 part of 1838. The marked discrepancies observable not 

 only between our respective maps of the south of Ireland, but 

 also in Mr. Griffith's own map itself, could not fail to strike 

 other geologists as well as myself; while, on referring to the 

 written outline, so far from finding an elucidation of the dis- 

 cordances, the outline itself appeared at variance with the 

 map. I have reason to know that other geologists felt equally 

 unable to discover the precise purport and extent of Mr. 

 Griffith's meaning, and hence some explanation seemed ne- 

 cessary. Doubtless, aware of such an impression, Mr. Grif- 

 fith has been led to give that explanation, accompanied by 

 many changes in his views: Ist, in a communication made to 

 the British Association at Newcastle, in August, 1838 J; 2nd, 

 in a letter addressed to the Rev. Dr. Buckland, Pres. Geo]. 



* Geol. Trans., vol. v., second series, 1837. 



t Appendix to the Report of the Irish Railway Commissioners, 1838. 



\ Report of the Eighth Meeting of the British Association, 1839. 



