﻿Geological Society. 841 



through a lead plate 4 cm. thick ; in another case, a lead 

 plate, 3 mm. thick, was interposed ; in a third series o£ 

 experiments, a varying number of aluminium foils covered 

 the sensitive plate ; while in a fourth case, the sensitive 

 plate was exposed directly to the rays. All the photographs 

 thus obtained resemble a /3-ray photograph. In cases 3 and 

 4 the grains are apparently equally crowded, in 2 they are 

 less crowded, while in 1 they are much thinner. Fig. 6 

 represents a photograph obtained in the second experiment 

 given above. As expected, the y-ray photographs were 

 found to be similar to the /5-ray photographs of the same 

 magnification, since it is known that all the effects of y rays 

 are due to secondary j3 rays, which they excite. 



The experiments described in this paper were preliminary 

 to the use of the photographic method for determining, with 

 accuracy, the scattering of a particles by gases. 



In conclusion, the writer wishes to express his indebtedness 

 to Dr. W. Makower for suggesting this research, and to him 

 and to Dr. N. Bohr for their continued kind interest and 

 advice during the progress of the experiments described in 

 this paper. He is grateful to the Governing Body of the 

 School of Technology for kindly placing the excellent 

 resources of that institution at his disposal, and to Mr. R. B. 

 Fishenden personally for kind and constant advice through- 

 out the photographic operations. He also wishes to acknow- 

 ledge the kindness of Dr. Hickling, of the Geological 

 Department of this University, who was good enough to 

 allow him the use of his microphotographical apparatus. 



The Physical Laboratory, 



Victoria University, Manchester. 

 March 1915. 



LXXXVIII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 

 [Continued from p. 208.] 



January 6th, 1915.— Dr. A. Smith Woodward, F.U.S., President, 

 in the Chair. 



HPHE following communications were read : — 



1. ' The Silurian Inlierof Usk (Monmouthshire).' By Charles 

 Irving Gardiner, M.A., F.G-.S. 



The Usk inlier lies a few miles north of Newport (Mon.). 



Between the coalfields of South Wales and the Forest of Dean the 

 Old lied Sandstone is "bent into an anticline, the axis of which runs 



