The Origin of the Nitrates in Griqualand West 123 
THE ORIGIN OF THE NITRATES IN GRIQUALAND 
WEST. 
By R. Marwortu, Pu.D., M.A. 
READ MARCH 27, 1895. 
The occurrence of nitrate of potash in South Africa has been known 
for many years, as the farmers in some districts are in the habit of 
preparing it for their own use from materials occurring in the mountains. 
Samples of such crystallized saltpetre were received from time to time 
from the districts of Calvinia, Victoria West, Prieska, Marico, Griqua- 
town, Cradock, and others, but they remained samples only in spite of 
an eager demand for more. 
In the year 1893, considerable excitement was created by the report 
that extensive deposits of nitrates had been discovered in the Doorn- 
bergen, near Prieska, and in the Asbestos Mountains on the other side 
of the Orange River. 
At the request of the Colonial Government, I visited the farm 
Doornbergfontein, at the south-eastern extremity of the Doornbergen, 
and subsequently a large number of farms between Prieska and Griqua- 
town on behalf of private enterprise. During my visits to these regions, 
I had ample time to study the question of the origin of the nitrates, 
and as the results of my observations and subsequent experiments 
appear to me to be of some interest, I venture to lay them before you 
to-night. 
The Doornbergen and the Asbestos Mountains form one range of low 
hills extending from the north of Griquatown to the south-west of 
Prieska, and are separated from each other by the valley of the Orange 
River. The slates and quartzites of probably Devonian age, of which 
they consist, are highly ferruginous, and often so finely laminated that, 
on exposure to the action of atmosphere, they cleave into large sheets, 
as thin as window-glass, or even writing-paper. Other portions are more 
solid and compact, and if pieces are struck against each other they ring 
like glass, owing to the large amount of silicates of iron and lime which 
they contain. 
A peculiar feature of these hills is that the numerous valleys and 
gorges which traverse them, and branch out in all directions, are lined 
