Vol. 50.] GLACIAL GEOLOGY OF MOUNT KENYA. 525 



land-masses on either side than to have been part of a widespread 

 equal earth-movement. 



There is therefore no evidence on the coast of changes of level 

 sufficiently recent or important to account for the glaeiation. 



The second suggestion, namely, that it was due to local earth- 

 movements, seems much more probable, as in the great rift- valley a 

 few miles to the west there is evidence of very extensive faulting 

 and earth-movements of Pleistocene age ; some of these have cut 

 through the great pile of Settima, the companion volcano that rose 

 opposite Kenya on the western side of the Laikipia plateau. If 

 there were no elevation on the coast or at Kilima Njaro, a differential 

 movement of only 1 in 250 would give the required elevation on 

 Kenya. 



The third cause no doubt contributed something, as not only must 

 the cone once have been very much higher than it is at present, but 

 the slopes would then have been more suitable for collecting snow than 

 the precipitous crags that now form the central summit of the 

 mountain. It is unfortunately impossible to determine from the 

 data at present available the exact height of the original crater, as, 

 until it is known how much the forest-clad slopes have been lowered 

 by denudation, one cannot estimate the height and extent of the 

 base from which the crater rose. Kibo rises about 2000 feet higher 

 than Mawenzi, and the parallel between these, the newer and older 

 eruptive centres of Kilima Njaro, must be very similar to that 

 between Kibo and Kenya. If we assume that the slopes of Kenya 

 in its prime were at the same angle as those of Kibo, then an 

 addition of 2000 feet to the altitude of Kenya would form a peak 

 of almost exactly the right diameter. 



We may thus account for 2000 of the 5400 feet required. But 

 an increase in the size of the snow-fields would lead to an increase 

 in the length of the glaciers, which would thus reach a lower level. 

 To take an illustrative case from the Swiss glaciers. The following 

 glaciers are arranged in pairs, and the members of each pair are 

 closely adjacent and under apparently similar conditions ; thus the 

 two Grindelwald glaciers are parallel, adjacent, flow from the same 

 mountain-axis, and both to the north ; the Aletsch and Fiesch 

 glaciers are also similar, but flow both to the south. The figures 

 are taken from Heim's ' Handbuch der Gletscherkunde,' p. 73 : — 



Name of Glacier. Area of ice- Alt. of snout Depth of snout 

 field in square of glacier in below the neve- 

 kilometres, metres. line in metres. 



/Gorner 69 1840 960 



[Zmutt 27 2100 650 



("Aletsch 



JFiesch 



I Unteraar 



[_ Oberaar 



J Unter Grindelwald.. 

 \ Ober Grindelwald . . 



Area of 







collecting- 







ground. 







99-54 



1353 



1400 



33-57 



1500 



1300 



22-0 



1879 



850 



6-7 



2243 



500 



28 



1080 



1650 



12 



1320 



1400 



