Correspondence — Professor J. F. Blake. 569 



of the value of the brilliant discoveries of our days" made by the 

 eminent palaeontologists cited by Beecher, or by that distinguished 

 inve.-tigaior himself. Sv. Leonk. Toknquist. 



Lund, September, 1896. 



ANGLESEY AGGLOMERATES. 



Sir, — In his short paper in your current (November) x number, 

 Sir A. Geikie is very ready to give up his opinion as to the 

 agglomeratic character of certain fragmental rocks in Anglesey, but 

 I hope my own opinion was based on too solid a foundation to be 

 so easily overthrown. After reading this retractation, I turned to 

 Sir A. Geikie's and my own original description of these 

 agglomerates, quoted below, and it appeared to me at once that if 

 the phenomena in the Isle of Man were the same as in Anglesey, 

 the rocks in the former locality could not be " crush-conglomerates." 

 1 therefore turned again to the description of these "crush- 

 conglomerates" as given by Mr. Watts, and this is what he says : — 

 "The fragments exhibit a great uniformity in composition, and 

 nothing has hitherto been found in them but grits and slates," 

 which "could all be matched either in the transition series or else 

 in the main grits and slates" (between which the crush has taken 

 place). " Although Mr. Lamplugh was alive to the importance of 

 looking out for the existence of fragments of igneous rocks and 

 other strangers, and collected a number of specimens to be tested 

 with this point in view, not a single fragment of any other rock 

 has up to the present been detected." 2 



We cannot doubt that Sir A. Geikie is equally alive to the 

 importance of this feature, and, indeed, his new descriptions of the 

 rocks in Anglesey indicate as much, but I think in his enthusiasm 

 he must have forgotten his older, fuller, and, 1 think, more accurate 

 account of them. This is what he first said about the rocks at 

 Llangefni: "The agglomerates . . . contain abundant blocks of 

 reddish quartzite, pieces of various felsites and of finely 

 amygdaloidal andesites." 3 My own statement is practically 

 identical : " They contain huge masses of quartzite and igneous 

 rocks." 4 These are certainly not descriptions of the rocks of the 

 neighbourhood between which the crushing could have taken place. 

 Sir A. Geikie noio writes : " The strata affected appear to have been 

 originally shales or mudstones (with possibly some fine felsitic 

 tuffs), alternating with bands of hard siliceous grit." 5 These two 

 descriptions are very different. Can Sir A. Geikie reconcile them ? 



Of the rocks near Cemmaes he originally wrote (of the vent on 

 Mynydd Wylfa) : " It is filled with a coarse agglomerate, among the 

 large blocks in which fragments of quartzite, limestone, felsite, grit, 

 and shale may be noticed " (five varieties of rock) ; and the vent on 

 the west side of Cemmaes harbour " appears to have been drilled 



1 Geol. Mag., Dec. IV, Vol. Ill, p. 481. 



2 Q.J.G.S., vol. li, p. 591. 



3 Ibid., vol. xlvii, p. 130. 



4 Ibid , vol. xliv. p. 487. 



5 Geol. Mag., Ike 1Y, Vol. Ill, p. 481. 



