Geological Society. 131 



spirals A and B ; these are arranged so as to be easily replaced in case of 

 accidental melting or damage. For this purpose the thumb-screws L and 

 M are removed, and the whole instrument turned half round upon the 

 screws and P ; the plugs being in this position released, can be replaced 

 by fresh ones, two small springs making the requisite contacts without 

 trouble. The path of the current is shown by arrows. 



There are two small entrance-tubes, through which a breath is taken to 

 fill the instrument with the air to be examined. These are not shown in 

 the figure, not being in the plane of section. 



Q is the magneto-electrical machine, the dimensions of which are 

 8x5x If inches. 



XXI. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from p. 67.] 



June 23, 1880.— Robert Etheridge, Esq., E.E.S., 



President, in the Chair. 



HPHE following communications were read : — 

 J- 1. " On the Skull of an Ichthyosaurus from the Lias of Whitby, 

 apparently indicating a new species (I. zetlandicus, Seeley), pre- 

 served in the Woodwardian Museum of the University of Cam- 

 bridge." By Prof. H. G. Seeley, E.B.S., E.G.S. 



2. " Note on the Cranial Characters of a large Teleosaur from 

 the Whitby Lias, preserved in the Woodwardian Museum of the 

 University of Cambridge." By Prof. H. G. Seeley, E.B,S., P.G.S. 



3. "On the Discovery of the Place where Palaeolithic Imple- 

 ments were made at Crayford." By E. C. J. Spurrell, Esq., E.G.S. 



The Brickearths of Crayford lie in a channel excavated from the 

 Thanet Sand and subjacent Chalk. The flakes here described were 

 found below the level of the top of the Chalk, on a sort of slope of 

 sand. They form a layer, about 10 feet from N. to S., and 15 

 feet (perhaps more), from E. to W., which is at one end 36 feet, 

 at another about 42 feet, below the present surface. The flakes lay 

 touching each other, the larger sometimes being several inches 

 thick ; they are new and clean, though sometimes studded with 

 calcareous concretions. Some were broken across, evidently before 

 being covered. The author had been enabled to piece many together, 

 and show that the manufacture of hachcs was the purpose for which 

 they were fractured. Also he had found two pieces of a hache. 

 Fragments of bone were found associated with the flints ; among 

 them was part of the lower jaw of Rhinoceros tichorhinus. The 

 author regards these Brickearths as slightly newer than the Dart- 

 ford gravel, which here caps the Thanet Sand, and in which flint 

 implements have also been found. 



4. "The Geology of Central Wales." By Walter Keeping, Esq., 

 M.A., E.G.S. With an Appendix by C. Lapworth, Esq., E.G.S., on 

 a new species of Cladophora. 



The district described by the author is much contorted and dis- 



