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typically that which is known as equatorial ; two rainy seasons and two 
dry seasons make up the year, the rains coinciding more or less with 
the equinoxes and the dry seasons with the solstices, except that the 
second minor lains are delayed about 1 to 2 months after the autumn 
equinox. As Capt. Lyons hopes soon to publish a monograph on the 
meteorology of the Nile valley, I shall say little about the details of 
rainfall of the different catchment basins, contenting myself with broad 
principles and main features. March, April and May form the greater 
rainy season, and October, November and December the lesser. The 
rainfall of the former season may be considered twice as heavy as that 
of the latter, but it is the latter which practically decides the height 
of the lake in the following year. This, according to Capt. Lyons, is 
due to the fact that in the summer months, when the rainbelt lies to the 
north of the lake, the dry south winds must blow across the lake basin 
even though the diurnal reversal of winds on the lake is not mastered 
by them. These dry winds greatly increase the evaporation, and there 
is a marked diminution of the water between July and November, 
which must be primarily due to the increased evaporation. 
The rainfall in the catchment basin may be taken as 1250 millimetres 
per annum on the average. As the evaporation off the lake is probably 
the same, the area of the lake may be left out of the catchment alto- 
gether. The balance of the catchment basin amounts to 184,000 square 
kilometres, on which there is a mean annual rainfall of 230 cubic kilo- 
metres. The mean discharge of the Victoria Nile over the Ripon Falls 
appears to the approximately 580 cubic metres per second or 18 cubic 
kilometres per annum. This represents about fVth the mean rainfall. 
The greatest discharge of the lake seems to be about 850 cubic metres per 
second and the lowest 450. As the lake has risen in a single year 80 
centimetres, which represents an increase of water of 48 cubic kilometres, 
and has fallen 60 centimetres which represents a decrease of water of 
36 cubic kilometres, it will be seen that the discharges from the lake 
are factors of less importance in determining the level of the lake than 
the heavier rainfall and diminished evaporation in a year of good rain, 
and the lighter rainfall and increased evaporation in a year of poor rain. 
The great function of Lake Victoria in the economy of the Nile supply 
is the insuring of a nearly constant discharge of water into the Victoria 
Nile, and providing much of the evaporation which comes down in the 
catchment basin itself in the shape of rain. 
