308 Lakes 



the Danube is 207,000 cubic feet per second. Hence, without 

 taking into account water which would be brought into the 

 lake by tributaries during the two months, we require for 

 outlet a river at least two-thirds of the size of the Danube, 

 and in the Lukuga such a river is found. When Stanley 

 visited it the Lukuga was quite stopped up with dense growth, 

 and no water was issuing; the lake was then rising; when 

 Captain Hore visited it the lake was falling rapidly, and the 

 Lukuga was a rapid river of great volume. One of the chief 

 affluents to the lake was found to be discharging at the rate 

 of 18,750 cubic feet of water per second; a few months later 

 it was dry and the mouth closed with vegetation. During the 

 dry season too the lake, with its 10,000 square miles of surface, 

 is exposed to the evaporating action of the south-east trade 

 wind, and when the supply is so insignificant this must be 

 sufficient of itself to sensibly lower the level. Ordinarily then 

 we might expect the lake to be subject to a yearly ebb and flow 

 corresponding to the periods of drought and rains; and, from 

 what we learn of the great fluctuations of rainfall one year with 

 another, we should expect that during a series of dry years 

 the obstructions to the outflow would gain such a head that 

 the rains of several wet seasons would have to accumulate 

 before forcing a passage. The result would be a tide of a period 

 corresponding to the recurrence of series of wet or dry years. 

 Were the lake situated at or near the level of the ocean, its 

 equatorial position would give it such a preponderance of rain 

 over the whole year as to keep its outlet constantly open ; but 

 its actual position, 2700 feet above the sea, produces an 

 alteration in climate, equivalent to an increase of latitude, 

 which would place it in the trade wind region rather than in 

 that of equatorial calms and rains. That such is actually the 

 effect is shown by the range of temperature, which is moderate 

 (59 to 83 Fahr.), and the rainfall (27 to 30 inches), which is 

 almost exactly that of London. The Central African lakes, 

 from their immense size and from their equatorial position, 

 possess a peculiar interest for the physical geographer, and it 

 is to be hoped that before long we shall have sufficient soundings 

 to give a general idea of the size of their basins, and also tern- 



