546 Transactions of the Canadian Institute. [Vol. VII. 



The capacity to abstract the potassium is increased if the silicates are 

 mixed with organic matter. Consequently the potassium which rain 

 water may contain is in great part removed when the latter filters 

 through soils, and, therefore, the water discharge from alluvial areas is 

 always richer in sodium than potassium. This capacity of soils to 

 abstract potassium is a matter of direct demonstration, and it " explains 

 the presence of so small an amount of potassium salts in the waters of 

 rivers, lakes, streams, and oceans where the lime and soda have accumu- 

 lated."* This cause of deficiency acts not only in the case of the potas- 

 sium leached out of disintegrating rock by rain water, but also on the 

 potassium carried from the sea to the land areas by rain water. The 

 potassium thus carried is not inconsiderable, for, according to M. J. 

 Pierre,-]- the rain water in the neighbourhood of Caen (France) annually 

 carries to each hectare of land, about 7.9 kilograms of this element, or 

 about 1.23 tons per square mile. 



This mode of elimination also operates in the ocean, where, how- 

 ever, the organic matter responsible for the removal, is derived from 

 plankton organisms, which, on dying, fall to the sea bottom and their 

 remains decomposing, the potassium they hold reacts with the argil- 

 laceous material on which the deposits rest and forms the mineral 

 known as glauconite, containing as low as 0.95 per cent, of oxide of 

 potassium, but other estimates range from 2.52 to 4.21 per cent. The 

 sodium present is very much less in quantity.^ This mineral is now 

 being formed, as it has been formed in the past, on the ocean bottom 

 over the areas which fringe the continental coasts and it constitutes as 

 much as, or more than, half of the deposits in shallower waters. Consider- 

 ing the extent of these areas as well as the fact that they cover the sea 

 bottom of those localities into which river discharge takes place, it will 

 be recognized what a very important factor the constant formation of 

 glauconite is in eliminating potassium from sea water and thus prevent- 

 ing an increase in the amount of that element in the ocean. This 

 formation has been going on in the past geological periods, for it is to be 

 found§ in the primary formations of Russia and Sweden, in the sands 



* Mendeleef s Chemistry, Vol. i, p. S47, '897. 



t The reference is gfiven in Dr. Angus Smith's " Air and Rain," which is quoted by Joly {loc. cit.) 



X The analysis of five specimens as given by Murray & Renaud (Challenger Report, Deep Sea Deposits, 



p. 389) gave: 



/. //. ///. IV. V. 



Ca 1.69 1.26 1.27 1.34 1. 19 



Mg 2.49 3.13 3.04 2.83 4.62 



K-2 O 2.52 4.21 3.86 3,36 0.95 



Na2 0.90 0.25 0.25 0.27 0.62 



Other analyses quoted by Roth, (Allgemeine and Chemische Geologic, Vol. i, p. 559, 1879) gave a per- 

 centage of potassium (not K2 O) varying from 2.8 to 7.3. 



§ Murray & Renaud, op. cit., p. 384. 



