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PROCEEDINGS OF THE GEOLOGICAL SOCIETT. [vol. l xx ii> 



an interesting sequel to that of Mi\ Charles Dawson's Piltdown 

 skull, in which the canine teeth are even more ape-like. 



The cordial thanks of the Fellows present were conveyed to 

 Prof. Gr. Elliot Smith. 



Dr. J. W. Evans discussed the different methods of obtaining 

 the directions-image ('interference-figures') of a small 

 mineral in a rock-slice, unaffected by the light from neigh- 

 bouring minerals. He preferred the use of a diaphragm in the 

 focus of the eye-piece, in conjunction with a Becke lens. 



He also described the inferences that might be drawn from the 

 form, position, and movement on the rotation of the stage of 

 the isogyres (dark bars or bushes) in the directions-images, both 

 of chance sections and of those cut parallel to planes of optical 

 symmetry or at right-angles to optical axes. He showed how 

 the character or sign of the crystal and its approximate optic 

 axial angle might be determined. 



Lantern -slides, petrological microscopes, and accessories were 

 exhibited ; and the cordial thanks of the Fellows present were 

 expressed to Dr. Evans for his lecture. 



December 15th, 1915. 



Dr. A. Smith Woodward, F.E.S., President, 

 in the Chair. 



The List of Donations to the Library was read. 



Dr. Aubrey StrahajST, F.R.S., gave an account of a deep 

 boring which was made in 1913 in search of coal, in the parish of 

 Little Missenden, at an elevation of 459 feet above sea-level. 

 The collection of specimens and the identification of fossils were 

 carried out by Mr. J. Pringle. For the first 1200 feet the hole 

 was punched, and nothing is known of the strata traversed down 

 to that depth — beyond the fact that the boring started in the top 

 of the Middle Chalk, passed through some Oxford Clay, and, below 

 that, some oolitic limestones which presumably belong to the Great 

 Oolite Series. From 1200 feet the hole was drilled for 64 feet, and 

 cores were preserved. The cores consisted of alternations of lime- 

 stone and mudstone, with a rich and characteristic Upper Ludlow 

 fauna. Among the fossils was OrtJioceras dame si Roeiner, 

 [? Krause], which had not previously been obtained in this 

 country. 



The boring served to fix part of the northern boundary of the 

 tract of Old Red Sandstones which underlie London. It was 

 intended to publish a full account in the next issue of the 

 Summary of Progress of the Geological Survey. 



