CHARACTERISTICS AND DISTRIBUTION OF LAKES 609 
gauges of a slight intermittent fall of the land during the period from 
1897 to 1906, amounting in all to about feet. The proximity of the 
watershed to the lake (the head- waters of the streams flowing north- 
wards to the Victoria Nile near Lake Choga are distant only from 
16 to 20 miles from the lake shores) suggests the upheaval of a block 
along an approximately east-and-west axis, which cut off the drainage 
lying to the south, and so formed the present lake in the low-lying 
area between the more elevated ground east and west of it. The 
waters of the lake are in most parts shallow, the maximum depth 
being only about 240 feet. 
Owing to the wide expanse of marsh and shallow lake which 
intervenes between the upper and lower portions of the Victoria Nile, 
the fluctuations in the level of Victoria Nyanza have no effect on the 
volume of water passing Foweira. These variations in level are 
divided by Lyons into several classes.^ The first class includes those 
due to climatic changes, which affect the lake over long periods, and of 
which there is much evidence round Victoria Nyanza. Scott Elliot " 
attributes the flat alluvial plains which fill the valleys above the 
present lake-level to the detritus brought down by the tributary 
streams and deposited in the still waters of the lake. The second class 
includes the oscillations due to variations in meteorological conditions 
having a comparatively short period, such as that of about thirty- 
five years detected by Brlickner,^ in which a period of high levels is 
followed by a period of lower levels. Sieger^ gives a table of the 
variations in level of the Central African lakes for different periods. 
Generally speaking, 1850 to 1878 would seem to have been a wet 
period, and 1879 to 1886 a dry one, for the whole of Africa ; but 
from what the gauge readings on Victoria Nyanza teach, it is clear 
that lakes where evaporation is the main controlling factor, and the 
volume discharged is comparatively small, may vary considerably in 
level without any marked change in the average rainfall, since the 
lake-level responds quickly to any temporary increase or decrease of 
supply. The third class includes the annual oscillations which are 
due, in the case of Victoria Nyanza, to April and November rains. 
The fourth class includes the daily oscillations caused by the alterna- 
tion of land and sea breezes, much more noticeable in landlocked 
gulfs like Kavirondo (Kisumu) than in more open situations, as at 
Entebbe. The fifth class includes seiches, of which no precise study 
has yet been made. 
Lake Choga (or Kyoga), 3396 feet above sea-level, is a shallow 
1 OjJ. cit., p. 33. 
2 See A Naturalist m Mid- Africa, p. 40, London, 1896. 
^ Klimaschwa7iJcunge7i seit 1700, Vienna, 1890 ; see also p. 528. 
* Bericht XIII. Vereins-Jahr (1887) Verein Geogr. Univ. IVien. 
39 
