[ 761 ] 



LXX. Proceedings of Learned Societies. 

 GEOLOGICAL SOCIETY. 



[Continued from p. 288.] 



March 13th, 1907. — Aubrey Strahan, Sc.D., F.E.S., Vice-President, 

 in the Chair. 



rPHE following communications were read : — 



1. ' A Silurian Inlier in the Eastern Mendips.' By Prof. Sidney 

 Hugh Eeynolds, M.A., E.G.S. 



An account of the rocks with which the paper mainly deals 

 was brought before the Society on February 7th, 1906 ; but, 

 owing to the discovery just before the meeting of Silurian fossils 

 in material thrown out by moles and rabbits, the paper was 

 withdrawn and further work, including the digging of a series 

 of seven trenches, was carried out. This proved that the frag- 

 mental igneous rock is of two types : — (1) Normal fine-grained 

 tuff, from which in three localities over thirty species of Silurian 

 (probably Llandovery) fossils were obtained and have been iden- 

 tified by Mr. F. B. Cowper Beed : the tuffs are seen at Sunnyhill 

 to underlie the trap. (2) A remarkable coarse ashy conglomerate, 

 the nature and relation of which to the other rocks are both 

 obscure. The following four possibilities with regard to the nature 

 of this rock are discussed in some detail : — (a) That it may be the 

 basement-conglomerate of the Old Bed Sandstone ; (6) that it may 

 be an aqueous deposit of the same general age, and belonging to the 

 same igneous series as the associated trap and normal tuff ; (c) that 

 it may be an old river-gravel, deposited during a terrestrial period 

 subsequent to the fossiliferous Silurian and prior to the Old Eed 

 of the district ; and (d) that it may represent the necks of the 

 volcanoes from which the trap and the normal tuff were ejected. 

 The author is of opinion that the fourth of these possibilities 

 agrees best with the observed facts. The paper concludes with a 

 comparison between the Mefidip Silurian rocks and those of Gower 

 and Tortworth, in both of which localities it appears that the 

 upper beds of the Silurian System are unrepresented. 



2. ' On Changes of Physical Constants which take place in 

 certain Minerals and Igneous Eocks, on the Passage from the 

 Crystalline to the Glassy State ; with a short Note on Eutectic 

 Mixtures/ By James Archibald Douglas, B.A., F.G.S. 



After giving an account of previous experiments in the direction 

 of determining the physical changes accompanying the fusion of 

 rocks and minerals, and their re-solidification into a glassy condition 

 — experiments which are in many cases open to sources of con- 

 siderable error, — the author describes the electrical apparatus 

 employed by himself. Powdered rock of known specific gravity 

 is fused as often as required in a loop of platinum-ribbon. The 



