598 MESSES. G. W. LAMPLUGH AND W. W. "WATTS ON [Nov. 1 895, 



attention. In the references to previous descriptions some important 

 papers by Profs. Hughes and Bonney seemed to have been over- 

 looked. The breccia with large rounded masses in the Dimetian at 

 St. David's was described by Prof. Hughes in the Geol. Mag. in 

 1883, and in a paper by himself to the Society in 1884, as the 

 ' result of crushings.' Prof. Bonney and he had also come to the 

 conclusion some years ago that many of the augen-gneisses in the 

 North-west of Scotland were produced by the breaking-up and 

 crushing of a massive felspar-rock near lines of fault. The paper 

 by the Author was, in Dr. Hicks's opinion, a very valuable one ; 

 for not only did it describe a very marked case, but it also entered 

 more fully into the mode of production than had hitherto been 

 done. He did not like to see the term ' conglomerate,' which has 

 hitherto been confined to a rock with water-borne pebbles, used for 

 this breccia ; and would prefer to keep the old term ' fault-breccia.' 



Gen. McMahon remarked that the finding of a trilobite in the 

 conglomerate - was unfortunate for the Author. Earth-movements 

 had been credited with many wonderful achievements, but that they 

 should produce, as the Author seemed to think, structures so like a 

 trilobite as to deceive the very elect was, if true, a disturbing fact. 

 On the other hand, if we believed the evidence of competent palaeon- 

 tologists, and accepted the trilobite as a clearly recognizable fossil, 

 he was unable to understand how the pressure which had converted 

 -slates into breccia, and had subsequently ground the angular frag- 

 ments into a well-rounded conglomerate, had failed to grind the 

 trilobite out of existence. 



Prof. Hughes thought that the peculiar character of the rock was 

 more due to the nature of the ' intermediate ' beds, which consisted, 

 where undisturbed, of alternations of thin layers of grit in shale, 

 than to the near contact of the great mass of shale above with the 

 grit below, and that it was an example of the protrusion of an 

 immense number of small pieces of solid rock through a matrix 

 yielding under crush. 



Mr. McHeney pointed out that he had recently detected similar 

 conglomerates in the Portraine and Balbriggan areas, which lie 

 along the continuation of the line joining Cumbria with the Isle of 

 Man. These conglomerates are about 500 feet thick, and contain 

 fossiliferous pebbles of the adjacent Silurian limestone, which is 

 also in places partly brecciated. The conglomerates have been 

 considered to be of volcanic origin by Jukes and others, and appear 

 to correspond to those described by the Author in all important 

 particulars. 



Mr. H. B. Woodwaed remarked that beds somewhat analogous to 

 those described by the Author occurred in the Isle of Purbeck. 

 Above the hard Portland Stone and Purbeck ' Caps,' there was a 

 well-known belt of ' Broken Beds,' and in his opinion this was pro- 

 duced by crushing and irregular movements of the strata during 

 uptilting — a view supported by the fact that the layers were dis- 

 rupted on slightly varying horizons, and that slickensides occurred 

 on surfaces of the Purbeck limestones. 



