130 Correspondence — Dr. C. Callaway. 



Thames, at higbest 407 feet above the sea. The author compares 

 it with the rubble-beds overlying the raised beaches of Sangatte and 

 Brighton, It is unconnected vpith any river-course, is not of marine 

 origin, and its materials, where not local, are derived from the 

 southward. 



coiais-ssiPOi^nDEniTaiE!. 



DR. CALLAWAY versus MR. G. H. KINAHAN. 



SiE, — Mr. Kinahan, in his observations in your current issue on 

 my paper, "On the Rocks South of Wexford," which appeared in 

 your November Number, is, I think, a little too sweeping in his 

 assertions. It is incorrect to say that I pronounced his work wrong 

 without first seeing it. I examined carefully all the localities he 

 was kind enough to point out, and others which seemed likely to 

 throw light upon my special investigation, except the Saltee Islands, 

 which, from their isolation, could have no bearing on the question, 

 and the Crossfarnoge section, which I had not time to visit. It was 

 the less necessary to study the latter, since Mr. Du Noyer's Map 

 favoured my views, and Mr. Kinahan's own descriptions appeared 

 to me to admit of a similar interpretation. I believe the difference 

 between us may be fairly stated thus : Mr. Kinahan argues that 

 there is a passage between the metamorphic rocks and the series 

 which he calls Cambrian (my Pebidian), because these are inter- 

 stratified with the granitoid and gneissic bands of the former beds 

 of schist similar to the adjoining beds of the latter. I hold that 

 there in no passage, not only because there is a distinct break, but 

 also because the schists associated with the gneiss difi'er widely 

 from the so-called Cambrians, in mineral characters and degree of 

 alteration ; the schists being truly metamorphic (crystalline and 

 foliated), while the "Cambrians" are merely felspathio shales, slates, 

 and grits, which, having undergone some alteration, often bear a 

 superficial resemblance to the true schists. If this statement of the 

 case is coriect, the issue between us is largely one of lithology, and 

 the value of our observations will depend upon our respective 

 competence to distinguish between difi"erent kinds of rocks. I can- 

 not but think that the loose views which have prevailed, as to what 

 constitutes a true passage between formations, have seriously vitiated 

 much of our current geology. 



I am rather surprised that Mr. Kinahan should recommend me to 

 visit Yar-Connaught with a view of ascertaining whether there is 

 a passage between metamorphic and unaltered Cambrian in the ai'ea 

 Bouth of Wexford ; especially since in the former district, according 

 to Mr. Kinahan himself (Geology of Ireland, p. 190), the meta- 

 morphic rocks graduate, not into Cambrian, but into " Cambro- 

 Silurian." 



I owe Mr. Kinahan an apology for attributing to him a change of 

 front in describing as "Cambrian " rocks which he had, as I thought, 

 previously regarded as " Cambi'o-Silurian." As he is the author of 



