310 REY. J. F. BLAKE ON THE 
more scattered Archzean foci, we have the few volcanic areas which 
now mark the globe, whose limits appear to have forsaken for ever 
the British Isles. 
This is what we might expect if the sedimentary deposits form a 
damper to the heat within. In the early stages of the earth’s history 
but a slight concentration of explosive force would suffice to break 
through the external coat and pour the contents of the interior on 
the surface, where they would be degraded by the atmosphere and 
increase the thickness of the coat. As this thickening progressed, it 
would require a greater force to break through, and points or lines 
of weakness would be more remote from each other; thus the violence, 
the infrequency, and the circumscription of volcanic outbursts would 
increase together, though the total sum of the forces in action might 
at the same time decrease. 
One other general question is suggested. The absence of ordinary 
sediments of Archzean date in these Welsh areas is as remarkable as 
the rarity of volcanic rocks in the Highland gneiss. 
Is this due to a difference in age? or do we see in the one the 
area occupied by land, in the other that occupied by the sea in that 
remote, long-extended, but at present little-studied epoch ? 
Discussion. 
Mr. Torrey called attention to the discrepancy between the views 
of Prof. Blake and Dr. Hicks as to the consecutiveness or the separa- 
bility of the series below the Cambrian conglomerate; also to the 
difference between their views as to Ogof Llesugn, and as to the 
character of the Dimetian of Dr. Hicks. 
Dr. Hicks said that diversity of opinion among progressive writers 
did not prove that the stationary party was correct. He appreciated 
the value of Prof. Blake’s paper as regards the stratigraphy, though 
he could not accept his views as regarded some points in the petrology. 
Prof. Blake entirely agreed with him that the rocks he had classed 
as Dimetian, Arvonian, and Pebidian at St. David’s were of Pre- 
Cambrian Age, and also as to the separation of the Pre-Cambrian 
series from the Cambrian conglomerate. Prof. Blake, he thought, 
had not succeeded in proving the connexion between the granitoid 
(Dimetian) and the overlying volcanic series. He observed also that 
Prof. Blake’s map was wrong in that it omitted the Clegyr-Bridge 
breccias and others near Nun’s Well. He pointed out that Prof. 
Blake was distinctly opposed to the principal tenets of Dr. Geikie, 
including the evidence of intrusion of the granitoid series and the 
great fold of the volcanic series. 
Mr. T. Davies said that the Dimetian differed mineralogically 
from typical granites; the quartz and felspar constituents had very 
different relations from what they had in ordinary granites. Also 
the behaviour of the rock under the hammer was different. 
Mr. F. Drew said that Dr. Hicks had not taken up in detail the 
differences between his views and those of Prof. Blake, to which 
