part 1] AXD ASSOCIATED BOCKS OF MOZAMBIQUE. 



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The marine erosion theory, which Uas never found favour, 

 scarcely requires mention, for it Avas only temporarily suggested by 

 Bornhardt. According to the later views of that writer, the 

 inselberg landscape is regarded as a product of repeated cycles 



of pluvial erosion. 

 "| Dr. J. D. Falconer 

 has developed this 

 conception, and 

 in his book on 

 Northern Nigeria 

 (pp. 245-46) he 

 makes the state- 

 ment that 



" there is no reason, 

 however, to believe 

 that this peculiar to- 

 pography cannot arise 

 simply through an 

 alternation of periods 

 of weathering and 

 periods of erosion, 

 brought about either 

 by a gentle oscilla- 

 tion of the crust, or 

 by a repeated base- 

 levelling of the plains 

 and rejuvenation of 

 the drainage system. 

 A plane surface of 

 granite and gneiss 

 subjected to long- 

 continued weathering 

 at base-level would be 

 decomposed to un- 

 equal depths, mainly 

 according to the com- 

 position and texture 

 of the various rocks. 

 When elevation and 

 erosion ensued, the 

 weathered crust 



would be removed, 

 and an irregular sur- 

 face would be pro- 

 duced, from which 

 the more resistant 

 rocks would project.' 



This theory 

 might be consi- 

 dered satisfactory 

 if. in addition, it 

 could be shown that there are internal structures and differences 

 of composition in the rocks of the inselberge adequate to explain 

 the superior resistance offered by them as compared with those of 

 the surrounding plain or plateau. In Nigeria such a difference 



