LUMBWA CAVES 
485 
the true original forest has nothing to do with altitude or 
climate, but is due to the intervention of man. 
Thanks are accorded to Mr. C. M. Dobbs, District Com- 
missioner, Kericho, for the great assistance he rendered in 
these investigations. 
NOTE ON THE COMPOSITION OF THE EOCK OF 
THE LUMBWA CAVES 
By V. H. Kirkham and W. Colet Birch 
Specimens of the soft, earthy rock from the workings of 
the Lumbwa have shown up to about 18 per cent, phosphate 
of lime, and it was thought that this constituent was probably 
the reason for its use. 
Subsequent analyses seem to disprove this theory. A 
sample of the crushed rock, actually taken by the natives, 
was obtained, and gave the following analysis : — 
Per cent. 
Water 18-95 
Silica ...... 47-76 
Calcium oxide . . . .2-97 
Magnesium oxide . . . .1-08 
Sodium oxide .... 4-87 
Potassium oxide . . . .2-88 
Ferric oxide ..... 4-98 
Manganese oxide . . . .0-82 
Aluminium oxide . . . .22-08 
Phosphoric oxide . . . . 0-13 
Carbon dioxide .... trace 
100-97 
It will be seen the rock consists very largely of a hydrated 
aluminium silicate, and that the amount of phosphate present 
is too small to have any importance. 
