Joty—An Estimate of the Geological Age of the Earth. 51 
This brings us face to face with the question as to where and in what form 
this missing potash is to be sought. 
The Glauconite deposits of the deep-sea boundaries and the stratified marine 
sediments undoubtedly must be chiefly made responsible. ‘The composition of 
this substance is given in the Report on the Deep Sea Deposits of the ‘‘ Challenger ” 
Expedition, where it is shown that it contains from 2°52 to 4:21 per cent. of potash 
derived from the sea-water. It may amount to 50 per cent. or 60 per cent. of the 
shallower deposits, or even more. ‘The percentage of soda is from 4 to 7, of the 
potash, and therefore will hardly enter into consideration in this paper. 
The formation of this substance appears dependent on the condition that the 
organic matter in the chambers of Foraminifera should reach the bottom, which, 
if so, will perhaps account for the absence of this body from the deeper deposits. 
The organic matter ‘‘ transforms the iron in the mud into sulphide, which may be 
oxidised into hydrate, sulphur being at the same time liberated: this sulphur 
would become oxidised into sulphuric acid, which would decompose the fine clay,” 
(terrigenous débris), ‘setting free colloid silica, alumina being removed in 
solution; thus we have colloid silica and hydrated oxide of iron in a condition 
most suitable for their combination.” ‘‘ There is always a tendency for potash to 
accumulate in the hydrated silicate formed in this way, and, as we have stated 
before, this potash must have been derived from the sea-water.”* 
The following extract (page 384) will serve to show the opinions of the 
authors (Sir J. Murray and Professor Renard) on the widespread nature of this 
deposit :—— 
‘Tt has already been stated that glauconite is one of the minerals most widely 
distributed in sedimentary rocks. It is found in the primary formations of Russia 
and Sweden among sands and gravels, in the Cambrian sandstone of North 
America, in the Quebec Group of Canada, and in the coarse Silurian sands of 
Bohemia. In the secondary formations its presence is more pronounced ; for 
example, in the Lias, and especially in the middle and upper layers of the 
Jurassic system in Russia, in Franconia, in Swabia, and in England. It has a still 
greater development in the sands, marls, and chalks of the Cretaceous formation. 
It will suffice to recall the glauconitic rocks of the Neocomian, of the Gault, and 
of the Cenomanian in various regions, such as the glauconitic marls of France, 
Germany, England, and several parts of North America. The abundance of 
glauconite is continued into the Tertiary formations, from the lowest up to the 
highest horizons of the series. 
‘From this rapid enumeration, it is seen that glauconite traverses the whole of 
the geological periods, and its formation is continued in modern deposits along 
many continental shores, explored by the ‘ Challenger’ and other expeditions.” 
* Report, p. 389. 
