622 TRANSACTIONS OF SECTION E 



Of tlie land thus destroyed part is washed into deep water and lost, but much 

 of the coarser material is rolled into shingle-beaches, or forms sand-banks and duues. 

 These form our best protection against farther inroads. If the coast-erosion is 

 stopped, shingle, beach, and sandbank will themselves wear out and disappear, ana 

 valuable lowlands behind may be spoilt by the sea. 



Another compensation for the loss on the coast will be found in the great gain 

 of alluvial land in the sheltered estuaries ; but against this must be set the rapid 

 silting-up of our harbours, even of those into which no streams flow. 



Before we take for granted the desirability of attempting to stop the erosion 

 of our coasts (except near towns) we must strike a balance between loss and gain. 

 If the loss exceeds the gain there will still remain the question. Shall we obtain 

 any sufficient compensation for the enormous cost of an}' works put up to protect 

 agricultural land ? 



Some curious problems are suggested by this inquiry. Many may think them 

 of no practical importance, but to the geographer and geologist they are of great 

 interest. If what is said above is coiTect, and since civilised man has lived in 

 Britain there has been a rapid change of sea-level followed by a long rest — what 

 are the prospects of a similar period of rapid change again setting in ? A new rise 

 or fall to the extent of a few feet would have most disastrous efi"ects on all our 

 coasts and harbours, and would also seriously affect our inland drainage until 

 things were adjusted to the new conditions. 



2. The Study of Social Geograiihy. By Professor G. W. Hoke, 



The author discussed the following theses: — 



1. Geography is the science of distribution. 



2. Geographic science is best served by a study of the causes rather than by a 

 study of the effects of distribution. 



3. Geographic factors need notbe/«cfs of distribution. 



4. The factors of social distribution are Jdstoric and psychic, as well as 

 environmental, 



5. The student of geography must have a clear-cut notion of the limitations of 

 the field, and to prevent hopeless confusion it is essential that he keep constantly 

 in mind the relation of the special subject of investigation to the field of geography 

 as a whole. 



3, The Structure of Southern Nigeria. 5?/ John Parkinson, B.A.,F.G.S. 



After remarking on the tentative nature of this communication, owing to so 

 large a part of the colony having been unvisited by him, the author defined as of 

 fundamental importance the boundaries of the crystalline rocks. 



The southern boundary of these rocks, which are by far the oldest member of 

 the rather limited series found in the colony, forms a rude semiellipse, indented on 

 the east by the complex of the Oban Hills, and crossing the Niger in lat. 7° 19' N. 

 (Giirich). As far as Southern Nigeria is concerned outliers of the sedimentary 

 series do not occur, or have not yet been found. The researches of Esch and Solger 

 have proved the occurrence of Cretaceous rocks in the Ivamerun, and during the 

 past three years these have been traced westward, by the Mineral Survey of Southern 

 Nigeria, round the base of the Oban Hills, up the Gross River to Abakalliki, the 

 most northerly point yet reached in the eastern province. The appearance of the 

 country as seen from Abakalliki suggests that the Cretaceous strata extend 

 northward for another thirty miles. Their westward extension, whether of 

 surface or sub-surface, remains to be definitely fixed, though they probably 

 extend from Afikpo to within fifty miles of the Niger as the dominant formation. 

 Westward from Asaba to Benin City and Ifon, and through the Ijebu country to 

 Abeokuta, the country is an undulating plain, consisting entirely of rocks later 

 than Cretaceous in age. From geological considerations which are foreign to this . 



