208 R. R. Walls — The Geology of Portugiiese Nyasaland. 



lack of vegetation and the natural " clearing " in the bush. (See 

 PL VIII, Fig. 2.) But the vast majority of these outcrops all have 

 tbe same appearance and smooth, rounded contours, like petrified 

 whales in a sea of sand. This " whaleback " formation refers to the 

 first three types of Inselberge mentioned above ; the last type is 

 only found in isolated districts, and is by no means common over the 

 country as a whole. The sandy soil is the nursery of the dry bush 

 vegetation, a vegetation which grows with remarkable activity during 

 the short wet season, and covers the whole country. 



With regard to the age of the rocks of Portuguese Nyasaland, it is 

 practically certain that the bulk of the gneiss is Archaean. Yet folded 

 and faulted into this gneiss are possibly rocks of later Paleozoic 

 age. The quartzites of the Lurio valley and their similarity with the 

 quartzites of the Swaziland system of the Transvaal have already 

 been commented upon. It is probable that they lie upon the gneisses, 

 although their line of contact is now more or less obliterated. Again, 

 there are the carbonaceous beds found at Itule on the Lujenda. 

 As coal they have no commercial value, but they are interesting 

 as suggesting that there may be rocks of Carboniferous age in the 

 m.etamorphic complex. Unfortunately none of the numerous 

 prosiDectors have considered it worth while to map out the rocks of 

 this region and so nothing has been added to our knowledge of this 

 area since the time of Thomson. The lines of foliation of the rocks 

 over the north and west of this territory have still to be plotted, and 

 until this is done any statements regarding trough faidting and the 

 possible age of these metamorphic rocks can only be in the nature of 

 vague hazards. The coastal strip of more recent rocks still requires 

 some careful geological scrutiny. Many writers have vaguely 

 mentioned Cretaceous deposits, yet proofs that any of these rocks 

 are of undoubted Cretaceous age have never been produced. The 

 bulk of the deposits are Tertiary and many of them appear of very 

 recent date. Fossils are fairly common in these deposits of the coastal 

 area, though somewhat obliterated in many places by the action of 

 percolating water. Much interesting work might be done in this 

 area by a palaeontologist. 



The minerals of commercial value in this country require very 

 little comment. The beds of impure shale coal and bitumen have 

 already been discussed at length. The graphite in the schist might 

 be worked in a small way in some localities and the mineral after- 

 wards washed in settling tanks to separate out the grit. Iron ores, 

 haematite, magnetite, and ilmenite occur in great quantity foliated 

 in the gneisses and quartzites over the whole country, but the 

 absence of coal and the natural difficulties of extraction render these 

 deposits valueless at present. As with many other countries, before 

 they have been thoroughly explored, wild and fantastic tales of 

 great mineral wealth have spread, gold, silver, precious stones, 

 copper, nickel, zmc, and tin being reported in great abundance. 

 Subsequent investigations have never justified these reports, 



