part 1] PROCEEDINGS OF THE GEOLOGICAL SOCIETY. lxxxi 



February 20th, 1918. 



Mr. G. W. Lamplugh, F.R.S., President, 

 in the Chair. 



The List of Donations to the Library was read. 



The following communication was read : — 



k The Geological Aspects of the Coral-Reef Problem.' By Prof. 

 William Morris Davis, For.Corr.G.S. 



March 6th, 1918. 



Mr. G. W. Laveplugh, F.R.S., President, 

 in the Chair. 



Harold Downes, M.B., F.L.S., F.R.M.S., Ditton Lea, Ilminster 

 (Somerset) ; Thomas Wilson Ogilvie, 44 Irish Street, Whitehaven 

 (Cumberland i ; and Joti Parshad, B.A., care of the Geological 

 Surrey of India, Calcutta, were elected Fellows of the Society. 



The List of Donations to the Library was read. 



Mr. John Frederick Norman Green delivered a Lecture on 



the Io-neous Rocks of the Lake District. He first drew 

 attention to some of the manuscript 6-inch maps of the Lake 

 District, prepared nearly fifty years ago, by the Geological Survey. 

 and pointed out that, although undoubtedly most accurate, they 

 appeared to differ greatly in the volcanic area from his own. He 

 suggested that the reason was, that there was a fundamental dif- 

 ference in the classification of tuffs and lavas. A large proportion 

 of the Lake-District rocks were brecciated. and had been supposed 

 to be altered tuffs : with the unbrecciated rocks into which they 

 passed they had been mapped as ashes. A number of specimens 

 and photographs were shown, indicating that the brecciation and 

 apparent bedding were due to flow. Specimens were also shown of 

 explosion-breccias, of the normal tuffs (which the Lecturer believed 

 to be mainly the result of erosion between eruptions), and of rocks 

 simulating true tuffs, but actually sandstones and conglomerates, 

 composed of detrital igneous material. Attention was drawn to 

 the criteria for distinguishing the various types. Manuscripts in 

 the possession of the Geological Survey proved that W. T. Aveline, 

 whose maps were extraordinarily accurate and detailed, had anti- 

 cipated by thirty years the Lecturer's separation from the volcanic 

 rocks of the basal beds of the Coniston Limestone Series. 



When re-mapped on this basis, the Borrowdale Series appeared 

 as a simple and regular sequence, strongly folded and cronping out 



VOL. lxxiv. f 



