o2 Joty—An Hstimate of the Geological Age of the Earth. 
The analyses show that the mineral may vary in composition. ‘‘ All that can 
be said is that the glauconite now forming at the bottom of the sea is, like the 
glauconite of geological formations, a hydrous silicate of potash and of ferric oxide, 
containing always variable quantities of alumina, ferrous oxide, magnesia, and 
often lime” (p. 386). 
Merrill gives analyses, showing that the glauconitic marls of New Jersey 
contain up to 7 per cent. of potash, and remarks on the extent of such beds in 
the Cretaceous formation of New Jersey.* 
Potash is also taken up by organisms in the sea, more especially by the sea- 
weeds. A very considerable amount must exist in the immense masses of vegeta- 
tion in the shallower waters of the sea. 
There is further a very interesting manner in which potash is abstracted from 
the sea, and returned to the land, which must, in its extension over Geological 
Time, have served to return immense quantities to the soils of coastal regions. 
This is by means of rain-water. 
In Dr. Angus Smith’s work on ‘‘ Air and Rain” it is recorded that, near Caen 
in France, it has been estimated (by M. J. Pierre), that a hectare of land annually 
receives from the atmosphere, by means of rain, 8°2 kilogrammes of KCl, and 
8:0 kilogrammes of K,SO,, amounting to a total of 7:9 kilogrammes of potassium. 
This is 1:23 tons of potassium per square mile per annum, or 1°48 tons of K,O. 
Now it is a well-known fact that, whereas sodium salts so brought to the land, 
are again freely yielded up by the soils, potash salts are retained. Vegetation 
also requires these salts as an essential constituent, sodium salts are not essential to 
vegetation.T 
In connexion with this, the relative losses of the alkalies as shown in the 
table (ante), compiled from Mr. Merrill’s work on ‘‘ Rock Weathering” should 
be considered. It appears from that table that the average loss of potash, in the 
soils taken as examples, was 56°3 per cent., the soda loss being 69°7. According 
to this, the rivers are not carrying sufficient potash into the sea relatively to soda 
to account for what is goimg on under the decomposing effects of subaerial 
agencies. 
We can see, too, that the revelations of the soil analyses are at variance with 
the broad facts of rock-chemistry to which we have been frequently referring. 
Thus, if we effect for potash a similar calculation to that carried out for soda, and 
estimate from the average potash percentages in the sedimentary detrital rocks, 
and of the primary crust-rock, the amount of potash lost and saved (assuming as 
before the alumina as the constant factor), we find the K,O lost to be 15 per 
* Loe. cit., p. 184. 
+ See Roscoe’s and Schorlemmer’s Chemistry, u., Part 1., p. 57; also Mendeleeff’s Chemistry, 1897, 
I, p. 546, 
