820 Geological Society. 



we have seen. The author is very clear in the way in which he 

 demonstrates the insufficiency of the Maxwell-Hertz equations for 

 moving media, and outlines the electronic theory of Lorentz. 

 Perhaps it is mainly a question of taste, but we do not like the 

 use of the term polarisation instead of induction. We are in the 

 habit of regarding the term 4ttI as standing for polarisation. 



LXXX. Proceedings of Learned Societies,. 



GEOLOGICAL SOCIETY. 



April 26th, 19.11.— Prof. W. W. Watts, Sc.D., M.Sc, F.R.S., 

 President, in the Chair. 



[Continued from p. 468.] 



Dr. J. D. Falconer, M.A., F.G.S., gave an account of the 

 Geology of Northern Nigeria, illustrating his remarks by means 

 of lantern-slides. He pointed out that the Protectorate of 

 Northern Nigeria covers an area of about 255,000 square miles, 

 over half of which crystalline rocks are exposed at the surface. A 

 series of hard banded gneisses of an Archaean type is intermingled 

 with a series of quartzites, phyllites, schists, and gneisses of sedi- 

 mentary origin, in such a way as to suggest that the two series, 

 while originally unconformable, have been at a later period affected 

 by a common folding and foliation along axes which are predo- 

 minantly meridional in direction. The two series have also been 

 pierced by numerous igneous intrusions of a granitic type, which 

 are subdivided into (1) an older, wholly or partly foliated group, 

 and (2) a younger non-foliated group, characterized by the pre- 

 dominance of soda-bearing types. 



Folded and faulted rocks of Cretaceous age are found in the 

 valleys of the Benue and the Gongola. They consist of a lower 

 series of sandstones and grits, in places salt-bearing, and an upper 

 series of limestones and shales with numerous fossils of Turonian 

 age. These Cretaceous rocks are overlain un conformably by a 

 horizontal series of sandstones, grits, conglomerates, and ironstones, 

 which in Sokoto province contains intercalations of Middle Eocene 

 limestone. Considerable volcanic activity occurred during Tertiary 

 times, and gave rise to extensive fields of basaltic lava in Bauchi 

 and Pornu, as also to numerous puys of trachyte, phonolite, olivine- 

 basalt, and nepheline-basalt throughout Southern Pauchi, Muri, 

 and Yola. Repeated minor oscillations of the crust occurred during 

 the latter part of the Tertiary Era, and culminated in the elevation 

 of the Bauchi plateau, the depression of the Chad area, and the 

 establishment of the present river-system. 



