52 KAEIANDUSS DEPOSITS OF EIFT VALLEY 
THE KAEIANDUSS DEPOSITS OF THE EIFT VALLEY 
By C. W. Hobley. 
One of the most marked features of the geology of the Eift 
Valley is the occurrence of thick beds of a mealy friable rock 
varying in colour from pure white to light brown. The place 
where they first attracted attention was on the east side of 
Elmentaita Lake, where a small stream has carved its way 
through those deposits, and the Masai name this place 01 
Karianduss, from the presence of this white rock. A little 
search will, however, demonstrate the existence of such deposits 
at many places both on the east and west flanks of the Eift 
Valley between Nakuru and the south extremity of the Kodong 
Valley. There are, for instance, large beds in the valley of 
the Endorit Eiver, north-west of Eburu Mountain, and also 
in the valleys between Ngong Mountain and the Kodong Eiver. 
Its occurrence is also reported from the vicinity of Sugeta, north 
of Baringo. Altogether, the deposits of this material in the 
Eift Valley must amount to millions of tons. 
The proper name of this substance is Diatomite, and it is 
a siliceous deposit principally of organic origin, which is found 
in many other parts of the world, and is mainly composed of 
the skeletons, technically called frustules, of minute lowly 
plants called Diatoms, belonging to the order Diatomaceae or 
Bacillariaceae. These plants are among the most rudimentary 
form of life and rarely measure more than -^oth of an inch 
in length. They consist of single cells of grey and brown 
protoplasm enclosed in a flinty casing formed of two portions, 
which fit together like a box and its lid. They are to be found 
in most fresh-water ponds, and especially flourish in mossy 
marshes such as one finds on the Aberdare Eange, and they 
form a kind of scum on the water. With the flinty casing it 
may be a matter of surprise that such tiny atoms manage to 
float, but it is believed that they are able to do this by means 
of a certain amount of oil contained in their structure. Diatoms 
multiply with great rapidity and in spite of the flint envelope 
conjugation takes place, which in these lowly organisms brings 
new vigour to the stock. At death the shells sink to the bottom 
