152 Intelligence and Miscellaneous Articles. 



resulting in the formation of coral-reefs and their final uplift to 

 different levels above the sea. 



2. ' The Whitehaven Sandstone Series.'* By J. D. Kendall, Esq., 

 F.G.S. 



The Whitehaven Sandstone, with its associated shales, is a 

 purple-grey deposit sometimes having a thickness of 500 or 600 feet. 

 The author gives details of a large number of sections of the series, 

 which also contains thin coal-seams and occasionally Spirorbis- 

 limestone. 



He combats the view that it is stained Middle Coal-measure 

 deposit, and gives his reasons for believing that it rests uncon- 

 formably upon the Middle Coal-measures, and also that it has not 

 received its colour by abstraction of colouring-matter from the 

 Permian beds, but that the colour actually belongs to the deposit. 

 He describes sections which lead him to suppose that the deposit 

 has a wider distribution over the Cumbrian district than is allowed 

 by previous writers. 



3. ' Notes on the Genus Murchisonia and its Allies, with a 

 Revision of the British Carboniferous Species, and Descriptions of 

 some New Forms.' By Miss J. Donald. 



IX. Intelligence and Miscellaneous Articles. 



ON THE DOUBLE REFRACTION OF ELECTRICAL RAYS. 

 BY K. MACH. 



r *PHE experiments show that plates of wood cut parallel to the 

 -*- fibres behave towards electrical rays in just the same manner 

 as plates of crystal cut parallel to the optical axis do towards the 

 rays of light. The inquiry naturally suggests itself whether plates 

 of wood which are cut at right angles to the fibres are singly 

 reflecting in the direction of the latter, as the optical analogy 

 suggests. The forestry collection of the Hohenheim Agricultural 

 Academy provided me with materials for experiments in this 

 direction : experiment confirmed the accuracy of the supposition. 

 A plate of Scotch fir (Pinus sylvestris) almost a metre in diameter 

 and 16 centim. in thickness, cut at right angles to the axis of the 

 tree, being placed between the crossed mirrors, the path of the 

 sparks remained dark even when the adjustment was most sen- 

 sitive. The same result was obtained when a smaller plate of the 

 same material, 70 centim. in diameter and 14 centim. thick, was 

 introduced into the path of the rays, and even when both plates 

 were joined so as to form one 30 centim. in thickness. A third 

 plate of a dense and heavy kind of wood (JSophora japonica) was 

 investigated, and in this case also the path remained dark. — 

 Wiedemann's Anncden, No. 2, 1895. 



