PHYSICAL GEOGRAPHY 
39 
Similar fluctuations are recorded of Tanganyika; while in the case of 
Bangweolo and Mweru fluctuations of level would also seem to occur in cycles. 
The differences between Livingstone’s map of Bangweolo and the map made by 
Giraud, the observations of Mr. Joseph Thomson, Mr. Alfred Sharpe, and 
Mr. Poulett Weatherley of the same lake may all be reconciled by this theory 
of a few feet fluctuation in its rise and fall. A few feet, more or less, would 
make the vast lake of M. Giraud the “ restricted open water ” of Livingstone, and 
the wide marsh with a few open pools conjectured by Sharpe and Thomson. 1 
Of course the average rainfall I have quoted must not be taken as the 
rainfall of each part of British Central Africa. So far as our observations 
go some districts receive no more than 35 inches per annum. 2 These again, 
especially if they contain mountains of great height like Mlanje, may record 
a rainfall exceeding 100 inches. A rainfall of 60 inches is common. 
V' 
PIN DA MOUNTAIN AND PINDA MARSH, LOWER SHIRE 
In consequence of this fairly good supply of rain the country is well watered 
by perennial streams and rivers. At the extreme end of the dry season there 
are streams which dry up though water can almost always be found a short 
distance below the surface. Still compared to other parts of East Central 
Africa the bulk of our rivers and rivulets may be described as perennial, that is 
to say containing running water all the year round. This is not suprising as so 
much of the country is mountainous and in these highlands the rain is spread a 
little less unequally over the area. It may safely be said that above altitudes 
of 4000 feet (and a large proportion of the land is above 4000 feet) no month 
passes without a fall of rain. Even at Zomba where the altitude is only 3000 
feet it is a rare occurrence for no rain to fall in any given month. 
But the year is clearly divided into seasons of rain and drought. The 
rainy season generally begins at the end of the month of November and heavy 
rains fall in December. There is often a short lull about Christmas time, but 
1 Since this passage was penned Mr. Poulelt Weatherley, the explorer and sportsman, has thoroughly 
circumnavigated and mapped it. His observations concur rather with those of Livingstone than of Giraud. 
2 A small patch at the south end of Lake Nyasa in one year only received 26’62 inches of rain. 
