KARIANDUSS DEPOSITS OF RIFT VALLEY 55 
diatomaceous clay are now in many cases exposed high above 
the present lake levels. 
It may be asked why the soda-laden water did not redissolve 
the dead skeletons of the diatoms, but this is probably due 
to the organic material which helps to cement together the 
skeleton, and also to the presence of an admixture of aluminous 
matter which continually washed down into the lakes and 
helped to bury the siliceous fragments. 
A few remarks as to the economic aspects of these deposits 
may not be amiss. 
Diatomite is used for various industrial purposes, amongst 
others to mix with nitro-glycerine to form dynamite ; the 
kind used for this purpose usually comes from Prussia, 
and is called Kieselguhr. Owing, however, to the invention 
of more powerful and safer explosives this is a decreasing 
need. 
One of its greatest uses is as a polishing material for metal 
work ; it is known under the commercial name of Tripoli, 
from the country whence it was originally introduced. Some 
of the polishing soaps also contain diatomaceous earth. It 
is also used for making the so-called ‘ candles ’ of the more 
modern filters. It is a first-class non-conductor of heat, and 
mixed with a modicum of clay is made into bricks for lining 
fireproof rooms, as a lining for stoves, furnaces, &c. It might 
also be used to great advantage to make tiles for houses in 
tropical countries. It is also used in the manufacture of 
water glass or silicate of soda and artificial meerschaum. 
Its value commercially depends on the amount of silica it 
contains, its white colour, its absorbent qualities, and the 
fineness with which it is ground. 
The analyses of samples from different parts of the world 
give results varying from 75 per cent, to 90 per cent, of silica 
and 3 per cent, to 10 per cent, of alumina, the balance being 
made up of small percentages of iron, potash, soda, and organic 
matter. Its value commercially in its crude state is only 
£3 to £4 per ton, but if properly sifted and ground, and of 
uniform high quality, it would be worth three or four times this 
amount. The present consumption in England is said to be 
about 3000 tons per annum. The great difficulty in shipping 
