Geological Society of London. 329 
Prof. Hughes. No fossils have been found in this at Corwen; but 
in a grit occupying a similar position at Glyn Ceiriog numerous 
fossils have been discovered. The Corwen grit is succeeded by grey 
slates with grit-bands; and in Nant Cawrddu near Corwen, and 
Nant Llechog near Pen-y-glog, these slates are followed by banded 
black shales containing numerous graptolites of the Monograptus 
gregarius-zone. Above these are pale bluish slates; and nothing 
further is exposed till we reach the Tarannons. The Corwen Grit 
clearly forms the base of the Llandovery in this area, as suggested 
by Prof. Hughes. 
Il.—May 24th, 1893.—W. H. Hudleston, Esq., M.A., F.R.S., 
President, in the Chair. The following communications were read :— 
1. “Notes on Dartmoor.” By Lieut.-General C. A. McMahon, 
F.G.S. 
The author alludes to Part II. of a memoir on the British Culm 
Measures recently published by Mr. Ussher, F.G.S., in which the 
view is advanced that the granite of Dartmoor resulted from the 
metamorphism of pre-existing rocks which had in a rigid siate 
offered obstruction to a long sustained N. and S. squeeze, and that 
their fusion and consequent consolidation were effected in situ. 
The author gives some of the results of a visit to the western 
borders of Dartmoor. He details some examples of eruptive granite- 
veins intruding into Culm beds in the immediate vicinity of the 
main mass of granite. The latter, in the locality described, is 
porphyritic down to its boundary, and the veins are also porphyritic. 
All the circumstances lead the author to believe that these veins are 
real apophyses from the main mass, and that the view adopted by 
De la Beche regarding the origin of the Dartmoor granite is the true 
one. The author alludes to some features in the Meldon granite- 
dyke not before noted; gives some detailed observations in the bed 
of the River Tavey, and offers an explanation of the way he thinks 
the fine-grained marginal variety of the granite, seen in that locality, 
has been produced. 
The author comments on the improbability that a tremendous 
squeeze sufficient to fuse 225 square miles of a pre-Devonian rock 
into granite should have left the Culm Measures outside the zone of 
marginal contact-metamorphism almost untouched. 
The author, in conclusion, alludes to the often-observed pseudo- 
stratification of the Dartmoor granite, and urges that the cause of 
this is not the one suggested by De la Beche, but that it is due to 
sub-aerial agencies. 
2. “On some Recent Borings through the Lower Cretaceous 
Strata in Hast Lincolnshire.” By A. J. Jukes-Browne, Hsq., B.A., 
F.G.8. 
The borings described in this paper are at Alford, Willoughby, 
and Skegness, and disclose the existence of an unsuspected anticlinal 
axis bringing up Lower Cretaceous rocks beneath the Drift. In the 
- Willoughby boring, beneath the Drift, a brown sand was obtained, 
apparently the ‘ Roach’ division of the Lower Cretaceous, and below 
