332 Reviews — J. F. Kemp — The Outlook for Iron. 



ridge is its terminal moraine at some stage of the retreat. But when 

 we come to consider the higher members of the glacial series the 

 question is not quite so simple. It is quite clear that in East Anglia 

 there are two boulder-clays, divided by sands and gravels ; the most 

 notable feature of the upper one, which is equivalent to the Chalky 

 Boulder-clay of the Midlands, is the presence of enormous quantities 

 of Kimeridgian material, which can only have come from the north- 

 west, that is in a direction more or less at right angles to the flow of 

 the North Sea Glacier. Mr. Harmer considers that this ice, his 

 Great Eastern Glacier, originated in the mountains of the North of 

 England and flowed down the Yale of York, across Lincolnshire, and 

 over the Fenland, being reinforced by lateral glaciers descending 

 from the Pennine valleys and by ice coming up the Humber gap 

 from the North Sea. Hence it contains a great varietj' of Jurassic 

 and Cretaceous erratics, especially Kimeridge Clay, Neocomian sand- 

 stones, hard Chalk, and characteristic tabular flints from Lincoln- 

 shire, the latter being very abundant and easy to recognize. This 

 second glacier ploughed up and incorporated in its own deposits 

 much of the North Sea Drift, so that the westward extension of the 

 latter is ill-defined. This hypothesis explains in a satisfactory 

 manner the abundance of Kimeridgian material in Norfolk and 

 Suffolk, which is difficult or impossible to account for in any other 

 way. Granting the fundamental assumption tliat land ice can move 

 in any direction for any distance over a more or less flat surface, the 

 rest is easJ^ It is also shown by a study of the relation of the drifts 

 to the valleys of Norfolk that great denudation took place between 

 the deposition of the two boulder-clays, and this fact is of much 

 interest in connexion with the question of the occurrence of inter- 

 glacial periods, since a long interval of time is indicated, which may 

 correspond to one of tlie warm periods of Penck and Briickner. The 

 origin of the plateau gravels and valley gravels of the area may also 

 be ascribed to the torrential waters set free during the later stages 

 of the melting and retreat of the ice. 



It will thus be seen that this book contains in a very condensed 

 form a summarj- of an enormous amount of work and presents 

 problems of absorbing interest, which will probably continue to 

 occupj'Jhe attention of geologists for a long time to come. 



II. H. E. 



III. — The Odxlook foe Ieon. By J. P. Kemp. Prom the Smith- 

 sonian Report for 1916, pp. 2*89-309. Washington, 1917. 



IN these few pages the author gives a resume of our present 

 knowledge of the reserves of iron-ore still available, with special 

 reference to the United States. The general conclusion is that while 

 the supplies of high-grade ore are distinctly limited, the reserves 

 of low-grade ore are practically inexhaustible. The output of ore 

 from the Lake Superior region, for example, cannot be kept up to the 

 present production with a minimum of 50 per cent of iron for more 

 than fifty years, while on a similar basis the Clinton ores of Alabama, 

 Tennessee, and Georgia can be considered as assured for a little over 

 100 years. Hence for a successful continuance of iron-smelting in 



