4 8 
BRITISH CENTRAL AFRICA 
the Chambezi, the Luangwa) contain an upper stratum of alluvial deposit where 
the valleys are broad and the rocks do not strike through. The principal 
mountain ranges are mostly granite ; and granite with its upper layers often 
rotten and even turned into red ferruginous clay constitutes the formation of 
much of the Shire Highlands. There is an outcrop of sandstone on the north¬ 
west and north-east coasts of Lake Nyasa (Mount Waller and the hills of 
Amelia Bay are examples); a little way back from the lake shore at the north 
end (in German territory); to the west of the River Shire near the Portuguese 
frontier ; at the south end of Tanganyika ; and all round about Lake Mweru 
and in the countries adjoining the River Luapula. Volcanic lavas and tuffs are 
present on parts of the upper plateau of Mlanje and at the north end of Lake 
OX LAKE NYASA 
Nyasa. There is a good deal of quartz in the mountains to the west of Lake 
Nyasa, especially to the south-west, and in parts of the Shire Highlands (such 
as Mlanje). The low flat hills in the Upper Shire district are composed of 
marble which yields a very good building lime. Much the same lime is also 
obtained from places on the west coast of Lake Nyasa, where there must be 
likewise a kind of limestone amongst the low hills near the lake shore. The 
surface of much of the low-lying country on the banks of the Upper Shire is 
little else than a deposit of the shells of molluscs mixed with black vegetable 
earth. 
This black “ cotton” soil, which is usually extremely rich for cultivation, and 
is so much valued in India, is found plentifully in many stream valleys and 
depressions, especially in the Nyasaland provinces, and is classed by me as 
alluvium. 
On the east coast of Lake Nyasa, a few miles inland from Msumbo and 
Chisanga (Stations of the Universities Mission), a soap stone has been found by 
! 
