Reviews — A. P. Colevian — Dry Land in Geology. 333 



the TJnited States one of three things must occur : either a great 

 improvement in metallurgical processes, rendering the employment 

 of low-grade ores remunerative, or some change of economic con- 

 ditions leading to a similar result, or the great development of foreign 

 sources of supply accompanied by cheap transport. In conclusion, 

 some attention is paid to the amount of coke likely to be available in 

 the future for iron-smelting ; no apprehension is felt of any failure 

 in this quarter, since apparently the fuel will last longer than the 

 iron-ore. 



E. H. R. 



IV. — Dky Land in Geology. By A. P. Coleman. Smithsonian 

 Eeport for 1916, pp. 255-72, 



rpHIS is a reprint from the Bulletin of the Geological Society of 

 JL America of the Presidential Address for 1915. It is pointed 

 out that all the earlier geologists confined their attention almost 

 exclusively to marine dej^osits, because these contain abundant 

 fossils, whereas in terrestrial deposits they are scarce or wanting. 

 It is only of recent years that the importance of the latter group has 

 been recognized. The chief types are arid and glacial respectively ; 

 arid deposits have now been found or imagined in all systems except 

 the Ordovician and Jurassic, and it is possible that the idea has been 

 overdone, since it is not proved that all red sandstones were 

 necessarily formed in deserts. A careful study also shows a remark- 

 ably close association between arid and glacial deposits ; at first sight 

 this seems improbable, but it is actually occurring in the world 

 to-day: The primary question of the origin of the land remains 

 unanswered ; we can only suppose it to be due on isostatic principles 

 to an accidentally uneven distribution of density in the globe, and 

 unless we are prepared to admit flow of rock-material below the 

 crust on a gigantic scale it seems to follow that continents and ocean 

 basins must be on the whole permanent features, and adjustments of 

 the boundaries of sea and land have been confined to the margins of 

 continental masses. 



R. H. R. 



E,E!:E»0RTS .A^lSTTD IPI^OCEEIDinSTGrS. 



Geological Societt of London. 



May 1, 1918.— G. W. Lamplugh, F.R.S., President, in the Chair. 

 Dr. A. Hubert Cox, M.Sc, F.G.S., delivered a lecture on the 

 Relationship between Geological Structure and Magnetic Dis- 

 turbance, with especial reference to Leicestershire and the Con- 

 cealed Coalfield of J^^ottinghamshire. 



Before the lecture, at the request of the President, Dr. A. Strahan, 

 r.R.S., Director of the Geological Survey, briefly outlined the 

 circumstances that had led to an investigation into a possible 

 connexion between geological structure and magnetic disturbances. 

 The magnetic surveys conducted by Riicker and Thorpe in 1886 and 



