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XLIX. On the Mineral Structure of the South of Ireland^ mth 
correlative matter on Devon and Cornwall^ Belgium^ the 
Eifel^ S^c, By Thomas Weaver, Esq,<i F,R,S,, F.G»S , 
M.Ii.I.A,, ^c. 
Men believe that reason governs their words, but words have often 
power enough to react upon reason.”—jB«cow. 
^ I '’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 was 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: 1st, in a communication made to 
the llritish Association at Newcastle, in August, 1838t; 2nd, 
in a letter addressed to the Rev. Dr. Buckland, Pres. Geol. 
* Geol. Trans., vol. v., second series, 1837. 
t Appendix to the Report of the Irish Railway Commissioners, 1838. 
X Report of the Eighth Meeting of the British Association, 1839. 
