494 Dr. C. Callaway — The MetamorpMc and 



five appearance of the scales wlien found in an isolated, or detached 

 condition. 



Geological Position and Locality. — In the Blackband Ironstone of 

 the Middle Carboniferous Limestone Series, worked at Borough Lee, 

 near Edinburgh. 



VI. — The Metamorphic and Associated Eocks South of Wexford. 

 By C. Callaway, M.A., D.Sc. Lond., F.G.S. 



IRISH land, which has so long puzzled our statesmen, proves to be 

 equally perplexing to our geologists. The metamorphic rocks 

 have excited much controversy, and new problems are emerging. 

 Prof. Hull ^ claims to have found Laurentians in Donegal, Gal way, 

 and intermediate localities, while Mr. Kinahan, in this Magazine,- 

 sums up the evidence for the old opinions. As I have recently 

 studied one of the areas referred to by the latter, I submit a few 

 comments on a part of his paper. I am much indebted to him for 

 the very kind and courteous manner in which he abridged my 

 work by indicating the most important sections, and regret that I 

 must ungratefully repay the obligation by differing widely from his 

 conclusions. 



Mr. Kinahan utters a very just caution against attaching undue 

 importance to lithological characters. Lithology must undoubtedly 

 be subordinate to petrology. But the Archsean geologists are quite 

 justified in accepting, with due precautions, the guidance of lithology, 

 when petrology is not available. 



The paragraph (p. 427) in Mr. Kinahan's paper which I venture 

 to criticize runs thus : — " The rocks of the Carnsore or S.E. Wexford 

 district I have very carefully worked out, and to me it appears that 

 northward and westward they gradually merge into unmetamorphic 

 rocks ; and in the latter are found Oldhamia, a Cambrian fossil." 

 These words call for special comment, because, as it appears to me, 

 they express a fallacy of observation which has led to very erroneous 

 conclusions. The argument mainly runs upon the words " gradually 

 merge." I shall endeavour to show that the facts of the case can 

 only be met by inserting " do not " before " gradually." 



It has been frequently assumed that, if a metamorphic rock lies 

 near unaltered beds whose age is determined by fossils, the former 

 must be an altered portion of the latter series. The possibility that 

 the two rocks were brought together by faults has not received due 

 attention. In the Survey Map of Anglesey, as I have shown in this 

 Magazine and elsewhere, the same beds are in one place coloured 

 " Cambrian " and in another " Silurian," simply because they were 

 locally associated with those groups ; whereas, on a closer examina- 

 tion, the junctions between the altered and unaltered series were 

 invariably seen to be faults. I contend that the same oversight has 

 vitiated the published work on the geology of Wexford. 



The Survey Map of the Carnsore area represents three parallel 



1 Britisli Association, 1881 ; and previously in Nature. 

 "^ September, 1881 ; also British Association, 1881. 



