THE VICTORIA NYANZA 
7 
far away from the land as only to permit of the inclusion of 
chambered shells capable of floating and drifting for a con- 
siderable distance before becoming waterlogged and sinking 
to the bottom. Whilst sailing on the Victoria Nyanza 
gasteropod shells may be frequently observed floating at a 
considerable distance from the land, and they may be driven 
by winds and currents for many miles before they finally sink. 
As Dr. Andrews has pointed out, the vertebrate fauna of 
these Miocene beds is closely similar to that occurring at 
Mogara in the Libyan Desert and presents affinities to the 
fauna of beds of similar age in Beluchistan. 
At all the outcrops, from Nira to Kikongo, the dip of the 
Miocene beds is constant, viz. 8° N. by W. This up tilting may 
be due to the sagging down of the earth’s crust in this region 
by the enormous weight of the thousands of feet of lava which 
have been poured out and piled up by the volcanic vents of 
Gwasi. It is true that Captain H. G. Lyons has come to the 
conclusion that the northern coast of the Victoria Nyanza is 
gradually sinking — to the extent of 80 cm. in nine years at 
Entebbe — but this depression can hardly be connected with 
the uptilting of the Miocene beds near Karungu, or else we 
should expect to find the Kavirondo Gulf increasing in depth. 
It is, however, well known to be steadily becoming shallower. 
Owing to this northerly dip the Miocene beds soon disappear 
completely beneath the basalt plateau of Gwasi. No trace of 
them was visible even in the deep and wide meridional valleys 
of Kitama and Kikongo, which must have been excavated in 
the soft deposits prior to the outflow of the nepheline-basalt. 
To the south the uptilted beds are thinning out rapidly, and, 
moreover, in this direction they would naturally occur at a 
higher and higher level, but they have been completely denuded 
away when the lake stood higher than at present, and there 
was not the smallest trace of them in the hills of granitic 
gneiss to the south of the wide Kuja valley. The only chance 
of finding any further outcrops lay in my searching along 
their line of strike, viz. to E. by N., but to the east of Kikongo 
the basalt no longer rested on the Miocene deposits, but on 
an ancient augite-andesite, from which the Miocene strata 
had previously been denuded away excepting for a small 
