Notes and Comments. 59 



hearing our leader's views on the spot, we were satisfied that 

 Tiddeman's theory was the correct one. On the second day, 

 unfortunately, Tiddeman was indisposed, but Prof. Marr led 

 the party, and on that date we were equally convinced that 

 Prof. Marr's views were correct ! During the discussion which 

 subsequently took place in Section C, it was stated that a 

 careful examination had been made of the Draughton quarry, but 

 no trace could be found of the miniature reef-knoll. 'No,' 

 replied Prof. Marr, ' because I brought it away in my bag ! ' 

 So that probably a Yorkshire reef -knoll reposes somewhere in 

 a Museum at Cambridge. 



FENLAND SILT. 



In The Geological Magazine for December Mr. F. Hardy 

 has a paper on ' The Mineral Composition of the Modern 

 Fenland Silt, with special reference to the Carbonate Minerals.' 

 A detailed microscopic examination shows that the generally 

 accepted ideas as to the origin of the fenland silt are correct. 

 Mr. Hardy concludes ' A sample of modern Fenland silt con- 

 taining 8.98 per cent, of carbonate was found on mineralogical 

 examination to include dolomite as well as aragonite in its 

 mineral assemblage. The dolomite is present in fresh angular 

 crystal grains, which suggest a secondary and recent origin 

 of the mineral. It has possibly been deposited from sea- 

 water which periodically covers the foreshore of the Fenland 

 border of the Wash. The general mineral composition 

 of the silt resembles closely that of certain geologically 

 recent deposits of Cambridgeshire, and points to the boulder- 

 clay left by the North Sea glacier as the chief source of the 

 material of which the silt is composed. The silt has mainly 

 been deposited by sea-currents which carry southwards the 

 eroded glacial deposits of the South Yorkshire and North 

 Lincolnshire coasts. An attempt is made to interpret the 

 results of a chemical analysis of the silt in the light of its 

 mineralogical composition, chiefly with regard to carbonate, 

 potash, and phosphate. Muscovite is found to be the main 

 source of potash, and apatite of phosphate in the silt.' 



LIVERPOOL GEOLOGISTS. 



The Liverpool Geological Society continues to publish 

 its familiar pink-covered Proceedings, part i of Vol. XIII. 

 having been recently received. The papers on China and the 

 weight of Mountains are not of especial interest to the Liverpool 

 Society, but the publication contains the Presidential Address 

 of Dr. J. C. M. Given on ' The Divisions of the Pleistocene 

 Period ' ; ' Marl and Marling in Cheshire,' and ' The Contribu- 

 tion of a local Geological Society to a Regional Survey,' both 

 by Mr. W. Hewitt ; and ' Coastal Changes at the mouth of 

 the Alt.' There are too many misprints, and we think it 



1921 Feb. 1 



