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NA TURE 



[Feb. 



merged in the Masai plain. As to the geological story of 

 the mountain, Mr. Thomson works it out thus : — 



" Let me try to trace the sequence of events which have 

 produced Kilimanjaro. An examination tells us that in 

 the serrated peak and rugged sides of Kimawenzi we see 

 the original volcano, which, without doubt, existed long 

 before there was a trace of its neighbour Kibo. Kima- 

 wenzi, after the imprisoned earth-forces found vent, rose 

 in size and grandeur, added layer after layer to its height 

 and circumference by a continual alternation of lava 

 sheets and beds of agglomerate and tuff. It appears 

 probable that it welled or belched out its contents without 

 any of those terrific outbursts by which whole mountains 

 are blown into the air or enormous areas submerged 

 under a molten flood ; for, curiously enough, we find no 

 evidence that any of its lava-flows ever extended beyond 

 the base of the mountain, or ashes accumulated to any 



depth in the surrounding country. At the present day 

 the metamorphic rocks are seen to crop out at its very 

 base on the east and south-east, and we have no reason 

 to suppose that they ever were covered by lava rocks. As 

 this — for a volcano — gentle accumulation went on, the 

 hypogene agents would have more and difficulty in forcing 

 the lava up the now elongated vent or orifice, and a time 

 would come when the weight of the column would, in 

 the end, balance the strength of the forces below. We 

 can now imagine the terrible struggle that would ensue 

 as the pent-up gases laboured mightily to relieve the 

 pressure. Doubtless for a time they would succeed oc- 

 casionally in clearing off the incubus and getting tempo- 

 rary outlet. At last even that would fail, and the 

 volcano was doomed either to become extinct or find 

 another vent. After some grand convulsions the latter 

 was effected, and a new volcano began its existence to 



-Mount Kenia fro: 



the west of Kimawenzi. In process of time it soon 

 rivalled its neighbour in size, and finally towered above 

 it, battering Kimawenzi's hoary head — probably then 

 snow-capped — with showers of stones, and even threaten- 

 ing to obliterate it under the volcanic ejections. Mean- 

 while Kimawenzi, now no longer under a reign of fire, 

 with its volcanic life-work finished, began, like all things 

 earthly, to crumble away before the slow-boring influence 

 of apparently puny agents. Rain, snow, and frost worked 

 on insidiously but steadily, and soon told their usual tale 

 of denudation as they gradually loosened and washed 

 away the loose ashes which formed the crater, under- 

 mined the more compact lavas, and hurled them to the 

 bottom of the mountain : until finally the solid core which 

 had originally choked the orifice stood out a shattered, 

 weather-beaten pinnacle with only a slight indentation to 

 mark the line of the original crater The beautiful con- 

 cave curve, so characteristic of large volcanoes, is still to 



be seen from the east, and speaks of the once handsome 

 proportions of Kimawenzi. 



" The fate which befell Kimawenzi soon came upon 

 Kibo. A height was reached which baffled all the at- 

 tempts of Vulcan to raise the lava to the surface, and, 

 like the other, it became extinct. Evidently, however, 

 the imprisoned forces had either spent their original 

 strength, or they frittered away their terrible energies in 

 the production ot numerous parasitic or secondary cones, 

 instead of uniting in another grand effort and producing 

 a third great volcano. 



" These cones were spread in great numbers all along 

 the southern side of Kibo and Kimawenzi, and set them- 

 selves to the task of strengthening or buttressing them 

 up. An enormous mass of lavas and agglomerates was 

 belched forth, resulting eventually in the formation of 

 what I have called the Chaga terrace or platform, and the 

 long ridge which penetrates far into the Masai country. 



