462 ON THE EEFPTIVE EOCKS OF SAEN, CAEENAEVONSHIKE. 



Prof. Blake had already committed himself as regards these 

 particular rocks. His views and those of the Author in the main 

 agreed and were adverse to Dr. Hicks's interpretation, hut he had 

 not previously known of the evidence of their being intrusive into 

 the later formations. He doubted if the difference between the 

 granite and the diorite was well made out. The " granite " becomes 

 a hornblende-gneiss near the ashy series, where he thought the 

 junction was not a faulted one. He also had his doubts as to the 

 diabase being strictly intrusive. On the whole his conclusions were 

 not very different from those of the Author. 



Mr. Watts regarded the paper as a description of a petrographical 

 complex, of the nature required by modern theories of meta- 

 morphism. He agreed in the making use of cleavage to ascertain 

 the age of the rocks. As regards structural relations, he rather 

 doubted the analogy with laccolites, which generally occur in 

 the main anticlines of strata. The question of segregation towards 

 the bottom of the mass was interesting if the same intrusion is 

 really more basic towards the bottom, but there may have been 

 distinct intrusions. Judging from recent experience in Shropshire, 

 there appeared to be evidence of a sequence in rock-series with a 

 regular fall in the percentage of silica. 



Prof. Hfohes referred to the protrusion of solid granite in ex- 

 planation of some marginal faults, and to certain fossiliferous zones 

 which defined the stratigraphical position of the sedimentary series 

 in which the rocks described by Mr. Harker occuiTed. He spoke of 

 the intermixing of the hornblende-diabase and the picrite, and 

 thought that the boulders of hornblende-picrite of North Wales 

 represented only portions of the well-known hornblende-diabase- 

 dykes of the district. 



Mr. Rtitlet said that the comparison with laccolite rather 

 troubled him. These might be lenticular patches rather than 

 laccolites. 



The Atjthoe was disposed to accept Mr. Teall's suggestion with 

 respect to nomenclature. The schistose granite mentioned by Prof. 

 Blake he had not seen ; he thought it might be simply fluxion-struc- 

 ture, deferring to the stratified appearance in the hornblende-diabase 

 and hornblende-picrite, he thought there was no great division in 

 time. Some small masses resembling laccolites do occur in relation to 

 earth-movements elsewhere in Wales. His section was an ideal 

 one ; the pipes were not always laid down even in exposed lacco- 

 lites. The Anglesey rocks were only locally picrites. 



