﻿576 Geological Society. 



2. « The Bargate Beds of Surrey, and their Microscopic Contents.' 

 By Frederic Chapman, Esq., F.R.M.S. 



3. ' On Deposits from Snowdrifts, with Special Reference to the 

 Origin of the Loess and the Preservation of Mammoth-remains.' 

 By Charles Davison, Esq., M.A., F.G.S. 



4. ' Additions to the Eauna of the Olenellus-zone of the North- 

 west Highlands.' By B. N. Peach, Esq., F.R.S., F.G.S. 



5. 4 Questions relating to the Formation of Coal-Seams, including 

 a New Theory of them : suggested by Field and other Observations 

 made during the past decade on both sides of the Atlantic' By 

 W. S. Gresley, Esq., F.G.S. 



6. ' Observations regarding the Occurrence of Anthracite generally, 

 with a New Theory as to its Origin.' By W. S. Gresley, Esq., 

 F.G.S. 



After discussing Dr. J. J. Stevenson's theory of the origin of 

 anthracite, the author describes the nature and mode of occurrence 

 of the anthracites of Pennsylvania, and gives his reasons for con- 

 cluding that the de-bituminization of coal was not produced by 

 dynamic metamorphism during mountain-building, but rather by 

 previously applied hydrothermal action. He further discusses the 

 applicability of his theory to other cases of anthracite, including 

 that of South Wales and Ireland. 



7. ' The Igneous Rocks of the Neighbourhood of Builth.' By 

 Henry Woods, Esq., M.A., F.G.S. 



In south-west Radnorshire (just north of Builth) there is an area 

 of Ordovician and associated igneous rocks, surrounded on all sides 

 except the north-west by Silurian beds ; this is shown on Sheets 56 

 S.W. and S.E. of the Geological Survey map, and was described by 

 Murchison. In this paper the author gives a map of the southern 

 half of this area, and a description of the igneous rocks — andesites, 

 andesitic ash, rhyolites, diabase-porphyrite, and diabase. The 

 diabase-porphyrite is intrusive in the andesite, and the diabase in 

 the Llandeilo Shales. The andesitic ash rests on the andesite, and 

 is overlain by the Llandeilo Shales. The author concludes that the 

 andesites, andesitic ash, rhyolites, and diabase-porphyrite are of 

 Lower Llandeilo age ; and that the diabases are post-Llandeilo and 

 pre -Llandovery. 



8. ' On the Relations of some of the Older Fragmental Rocks in 

 North-west Caernarvonshire.' By Prof. T. G. Bonney, D.Sc, LL.D., 

 F.R.S., F.G.S., and Miss Catherine A. Raisin, B.Sc. 



In a recent paper on ' The Felsites and Conglomerates between 

 Bethesda and Llanllyfni, North Wales,' it is argued that, in the 

 well-known sections on either side of Iiyn Padarn, a great uncon- 

 formity separates the rocks into two totally distinct groups. 



The authors of the present communication discuss at the outset 

 the great physical difficulties involved in this hypothesis ; a subject 





