the situation two courses were open to us, either to discover in 
Australia a supply of easily utilised salts of the German type or to 
locate other potash minerals and devise means for their economic 
utilisation. 
To the monumental work of several scientists, particularly 
J. Usiglio, C. Ochsenius and ,T. H. Van’t Hoff, is due the thorough 
understanding of the origin of the famous German potash deposits 
through the evaporation under normal conditions of temperature 
and pressure of a completely or almost completely land locked 
mass of ocean water. The complete details of the whole process 
have been so thoroughly investigated that the exact order of de- 
position of the various simple and complex; salts of sodium potas- 
siiim, magnesium and calcium, and their conditions of stability 
are so wel l known that should a. similar basin be met with elsewhere, 
tlie prospecting of it could be carried out in the most scientific and 
least expensive fashion. Although the conditions favourable to the 
concentration of these minerals in commercial quantities are known 
to exist in several localities at the present day, e.g., in the Dead 
Sea, the. Caspian Sea, etc., and although similar conditions must 
have frequently prevailed in past geological ages, the chances of 
finding other Workable deposits of this kind appear every year to 
be more remote, the ready solubility in water of the valuable 
minerals rendering them too liable to be dispersed again in succeed- 
ing ages and returned to the ocean, or by interaction with kaolin 
and hall oy site converted into insoluble and valueless mica. Certain 
it is that in Australia no discovery of such beds was made, and 
supplies of potash to meet this and other emergencies had to be 
sought elsewhere. This search was eminently successful. 
At that time only two other minerals were receiving serious 
attention as possible sources of potash, viz., felspar and alunite. 
Potassium is estimated to form 2-46 per cent.* of the whole litho- 
sphere, and the average potassium in the earth’s crust within the 
Australian Continent is beyond doubt very close to the average 
tor the whole earth, so that a surface slice of Australia 10 feet deep 
contains about 1 o bifiion tons of potassium or, on the average, 
half-amillion tons to the square mile. It seems almost incredible 
at first sight therefore that we should ever be faced in Australia 
with a potash famine. The difficulties of course are that this 
potash is irregularly distributed and even where plentiful is almost 
wholly present as felspar or mica and thus not readily available 
as plant food either in its widely distributed form or in its known 
concentrations, It. should be borne in mind, however, that the 
Darling Ranges wit hin a few miles of Perth are composed of granite 
with an average content of five per cent, of potash, i.e., two cwt. 
of potash in every cubic yard, or one million tons of potash per 
square mile 10 feet thick. Not only is there this huge amount of 
* F. W. Clarke, data of Geochemistry, 4tli edition (1020). 
