THE LUMBWA AND ELGON CAVES 
283 
but nothing of this nature has as yet come to light. The 
above theory also premises that the outlet of the lake sea- 
wards was to the north-east, possibly through the Rudolph 
trough, or if not, into the Pibor flats and so on into the Sobat 
valley. 
The lowest line of caves on Mount Elgon must be at a 
height of nearly 6000 feet, and some, I think, occur up to 
the 7000 feet level, and the caves in Lumbwa are stated by 
Mr. Knight-Bruce to occur at the following heights : Bagau 
cave 7000 feet, Gitoi cave 6000 feet, Kibipiten cave 6000 
feet, Kiptoit 6900 feet, Sausit 6100 feet, a total range in 
altitude of 1000 feet. Now if the caves on Elgon are 
attributable to excavation by water action we must adopt 
one of two hypotheses : either that there was a vast inland 
sea extending up to the Mau Escarpment on the east, 
and (if at an altitude of 6000 feet to 7000 feet) bounded by 
mountain ranges of still greater altitude on all other sides, 
which is somewhat inconceivable ; or we must fall back on 
the theory that in comparatively recent times the mountain- 
mass of Elgon was vastly lower, and at that time in contact 
with the inland sea, and that it has since been raised by earth 
movements to its present level. 
With regard to the second proposition, viz. the elevation 
of the mountain : this problem is not an easy one, for great 
mountain masses like Elgon would not, as a rule, be likely 
to be raised to any great extent, for after the occurrence of a 
vent in the earth’s crust through which volcanic activity is 
manifested and a vast amount of material ejected, there comes 
a period of quiescence, and the tendency would be for the 
mass of ejecta to settle and arrive at a position of equilibrium 
as regards the surrounding area, for the piling up of an enormous 
mass of material cannot fail to produce a local stress, which 
has to be slowly adjusted. If this adjustment occurs very 
gradually nothing happens ; if it occurs near a great line of 
weakness, such as a big fault plane, and abundant water is 
present, further eruptions probably take place. 
With regard to Elgon our knowledge of the sequence of 
events is faulty, but, as before remarked, there appears to be 
little doubt that at one period early in the history of the moun- 
