Geological Society of London. 287 
The classification of the Malvern schists originally proposed was 
somewhat enlarged, the injection schists being subdivided into 
(1) Schists of Primary Injection, in which one rock was injected 
into another, and (2) Schists of Secondary Injection, formed by the 
infiltration of secondary minerals along shear-planes. 
One of the most important of the chemical changes produced in 
the conversion of a diorite into an acidic schist was the elimination 
of magnesia. ‘This was proved by analyses. The recent researches 
of Mr. Alexander Johnstone had shown that even in the laboratory, 
and at the ordinary temperatures, carbonated waters were able to 
remove magnesia from certain of its combinations with silica. 
2. “Supplementary Notes on the Metamorphic Rocks around the 
Shap Granite.” By Alfred Harker, Hsq., M.A., F.G.S., and J. HE. 
Marr, Esq., M.A., F.R.S., Sec.G.S. 
This paper contains some additions and corrections to the work 
submitted to the Society by the authors on a previous occasion 
(see Quart. Journ. Geol. Soc. vol. xlvii. p. 266). In the present 
communication special attention is paid to the alteration of a group 
of basic volcanic rocks by the granite. 
IIJ.—May 10th, 1893.—W. H. Hudleston, Esq., M.A., F.R.S., 
President, in the Chair. The following communications were read : 
1.—“The Felsites and Conglomerates between Bethesda and 
Llanllyfni, North Wales.” By Prof. J. F. Blake, M.A., F.G.S. 
The author brought forward fresh evidence in support of the 
views he had previously expressed as to the Cambrian age of these 
felsites, and as to the unconformity of the conglomerates on the 
Purple Slates. 
A new Tunnel Section at Penrhyn Quarry was described, in which 
felsite was followed by St. Ann’s Grit with a Conglomerate-band, 
and there lying in the midst of the Cambrian Series. After a word 
or two on the conglomerate on Moel Rhiw-wen, the sections on either 
side of Llyn Padarn were discussed in detail, and it was shown that 
the distribution of the rocks on the surface of the country could 
only be explained by the unconformable position of the conglomerates 
and grits, which, moreover, lie nearly horizontal. 
After a discussion of the conglomerates of Bettws-Garmon, a 
detailed section of the adit at Moel Tryfaen was given, in which it 
was shown that there was only a 3ft. 6in. band of conglomerate 
next the Purple Slates, followed by 1850 feet of Banded Slates and 
Laminated Grits with four distinct intercalated bands of felsite; 
and it was argued that the conglomerate on the summit, 55 yards 
across, could scarcely be represented by this thin band. Finally, 
the distribution of rocks on Mynydd-y-Celgwyn was shown to be 
satisfactorily explained by unconformity. 
Incidentally it was mentioned that a band of rock in the felsite 
at Llyn Padarn, which had been considered to be a deposited slate, 
was in reality an intrusive igneous rock. 
The conglomerates described were considered to be an overlap of 
the Bronllwyd Grit. 
