No. 673. 



Vol. LVII of Whole Series. 



Price 2s. 6d. 



The 



Geological Magazine 



riDontblv^ Soninal of (Beologt* 



WITH WHICH IS INCORPORATED 



THE GEOLOG 



EDITED BY 



HENEY WOODWAED, LL 



AND ^"•^iJODS,! 



E. H. EASTALL, M.A. 



ASSISTED BY 



Prop. J. W. GREGORY. D.Sc. F.R.S. Sir JETHRo" J. H. TEALL, Sc.D., F.R.S. 



i\ H. HATCH, Ph.D., M.Inst.M.M. Prof. W. W. WATTS, Sc.D., F R S 



Prof. J. E. MARR, Sc.D., F.R.S. HENRY WOODS, M.A., F.R.S. 



Dr. A. SMITH WOODWARD, F.R.S. 



JULY, 1920. 



CONTENTS :— 



Page 

 EDITORIAIi NOTES 289 



Original Articles. 



Differentiation and Ore-deposits. 



By E.H.Eastall 290 



Notes on the Fauna of the Lower 



Devonian Beds of Torquay. 



Parti. ByP. R. CowperKeed. 



(Plate IV.) 299 



Hornblendite at Vavasour Mine, 



Cantley, Quebec. By J. Stans- 



FIELD 307 



On an Exposure of Sands and 



Gravels containing Marine Shells 



at Easington, Co. Durham. By 



D .WOOLACOTT 307 



On Jurassic Ammonites from East 



Africa, collected by Prof. J. W. 



Articles {continuedj. Page 

 Gregory. By L. F. SPATH. 



(Plate V.) 311 



Investigation of the Mechanical 

 Constitution of Loose Arenaceous 

 Sediments by the method of 

 Elutriation. By H. A. Baker... 321 



Reviews. 

 Geology of the Yangtse Estuary 

 below Wuhu 333 



Diagnostic Characteristics of Marine 



elastics 334 



The Mineral Deposits of South 



America 334 



Special Reports on the Mineral 



Resources of Great Britain. 



Vol. VI 336 



Earthquakes in Oregon 336 



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