Vol. 50.] THE GLACIAL GEOLOGY OF MOUNT KENYA. 515 



33. Contributions to the Geology of British East Africa. — 

 Part I. The Glacial Geology of Mount Kenya. By J. W. 

 Gregory, D.Sa., F.G.S. (Read May 23rd, 1894.) 



Contents. 



Page 



I. Introduction 515 



II. The former Glaciation 518 



III The Nature and Age of the Glaciation 520 



IV. The Causes of the Grlaciation 522 



V. Climaric Conditions during the Period of Maximum Glaciation ... 527 



VI. Summary of Conclusions 530 



Map of the S.VV. slopes of Mount Kenya 517 



I. Introduction. 



In the discussion as to the respective merits of the rival theories 

 concerning the causes of former glaciation, lew lines of work seem 

 likely to yield better results than the study of the originally 

 greater extension of glaciers in tropical regions. When therefore, 

 on emerging from the dense forests of the lower slopes of Mount 

 Kenya, I came upon a series of old moraines, not 10 miles from 

 the Equator and far below the level of the existing glaciers, my 

 interest was at once aroused in the additional problems presented 

 for solution. 



Mount Kenya is situated in long. 37° 20' E. and lat. 0° 6' S. ; it 

 rises to the height of approximately 19,500 feet, and covers an 

 area of about TOO square miles. It consists in its lower part of 

 a huge pile of volcanic ash and debris, with a low gradient, rising 

 from 7200 to 10,200 feet, densely covered whh forest ant bamboo- 

 jungle. Above this frowu steep craggy slopes of coarse agglome- 

 rates, ash, and lava, while the whole is surmounted by a rugged 

 pyramidal peak which is part of the central core of the old volcano. 



The central peak is of such excessive steepness that the snow is 

 scattered irregularly over it, instead of forming a ' calotte ' or snow- 

 cap, similar to those on Kibo (the higher summit of Kilima iNjaro) 

 and Chimborazo. The snow accumulates in the hollows and on 

 the slopes with lower gradients ; from these snow-fields a series of 

 glaciers flow down into the valleys. 



The existing glaciers occur mainly on the western and south- 

 western slopes of the mountain. The three principal classes of 

 glaciers are represented ; there are the normal valley-glaciers, of 

 which the largest is the Lewis glacier, named after the late Prof. J. 

 Carvell Lewis, whose premature death cut short a career of such 

 brilliant work on glacial geology. This, and two similar valley- 

 glaciers to the north-west of it, flow from neve-fields to below the 

 snow-line. Their lower courses are bordered by moraines. The 

 glaciers are crevassed, especially in the steeper portions of their 

 coarse, and are separated from the neve-fields by fairly large herq- 

 schrunds. The second type consists of the ' corrie ' or ' hanging 



Q. J. G. S. No. 200. 2 o 



