Dr. C. Callaway — Geology of Anglesey. 55 



III. — Some Points in the Geology of Anglesey. 

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



I DO not hesitate to say that Dr. Roberts could not have written 

 the letter which appears in this Magazine for December, 1881, 

 if he had read my papers on Anglesey with care. Not onlj' does 

 he confound together things which I have expressly made to differ, 

 but be attributes to me opinions which never existed in either my 

 thoughts or my writings. I must remove some of these misappre- 

 hensions, before discussing the real questions in dispute. 



1. Dr. Roberts refers to the grit in the quarries near Nebo, 

 " which," he says, "Dr. Callaway has mistaken for granitoidite." I 

 do not think that any selection of words in our language could more 

 emphatically contradict this singular misstatement than the following 

 quotation from one of the very papers from which my critic is sup- 

 posed to have derived his information : — " I could find no granitoid 

 rock in these quarries, but the ordinary granitoidite occurs on about 

 the same horizon, one-third of a mile to the north-east." ^ On the 

 same page, I refer to the rock as " quartzose grit" and "quartzose 

 conglomerate," descriptions which Dr. Roberts himself adopts. 



2. Dr. Roberts discusses the contorted rocks of Northern Anglesey, 

 "which," he aifirms, "Dr. Callaway has included under the head 

 metamorphic." Again we have : — " This area of so-called metamor- 

 phic rock." And that his readers may be thoroughly impressed with 

 my error, he further on reiterates, " which Dr. Callaway has included 

 under the head metamorphic," and more to the same effect. All this 

 is pure error. Referring to one of my papers on Anglesey, my 

 critic will see that over a page - is occupied in showing that the 

 rocks in question are, on the whole, not metamorphic, but sometimes 

 unaltered, sometimes partially altered, sometimes metamorphic. On 

 the next page, they are summarized thus: — "The northern area is 

 thus seen to consist of chloritic schists, felspatho-quartzose grits, 

 felspathic shales, chloritic slates, quartz-conglomerates, and grey 

 limestones, with some hornstone ^ bands at more than one horizon." 

 Out of these seven types, only one (chloritic schist) has undergone 

 thorough metamorphism. A little further on (p. 229), I include 

 these strata in my " Slaty Series," which I describe as " hypometa- 

 morphic, a term used to express a partial change." 



It is more satisfactory to come to genuine criticism. Dr. Roberts 

 objects to my statement " that in no case are there any signs of a 

 transition between altered and unaltered beds." He " imagines " 

 that I refer to Northern Anglesey only, but a writer's own words are 

 a safer guide than his critic's imagination. I made no such limit. 

 I used such phrases as "the altered rocks of Anglesey," and "many 

 parts of Anglesey." But I will confine myself to the northern area, 

 since Dr. Roberts finds it more convenient. In opposition to mj'- 

 views, he announces that he is " in a position to state that ... at 



1 Geol. Mag. March, 1880, p. 118. 



^ Quart. Journ. Geol. Soc. vol. xxxvii. p. 223. 



2 Incorrectly printed " Umestone." 



