CHAPTER VII. 



SOIL AND WATER ELECTRICALLY CONSIDERED 



Soil 



QUITE apart from the chemical character of the soil — 

 and therefore the question of suitable manures — its 

 permeability to water and oxygen and from soil bacteriology 

 we m.ust, in my opinion pay equal attention to its electrical 

 conductivity. 



I am indebted to Dr. Russell's admirable work, Soil 

 Conditions and Plant Growth, for much interesting 

 information. 



Pan Formation. " A pan is a layer of hard impermeable 

 rock that gradually forms at the usual water level below 

 the surface of the soil under certain conditions. Its effect 

 is to cut ofif the soil above from the material below and there- 

 fore to modify profoundly the movements of water and 

 air, leading often to swamp conditions. The effect on 

 vegetation becomes so marked that in agricultural practice 

 the pan has usually to be removed, often at considerable 

 trouble and expense. . . . Pans are best seen when 

 the sand is overlain by a deposit of peat. The sand is then 

 bleached to a depth of 5 to 60 cms. Suddenly there comes 

 a change : a coloured layer of solid rock occurs which may 

 vary in colour from yellow to black and in thickness from 

 10 to 60 cms. . . . This is the pan : underneath it lies 

 the sand proper. . . . But pans are by no means 

 Gonj&ned to peat : they often occur in forests, on heaths and 

 on certain cultivated soils." . . . 



" No method of cultivating these soils has ever been 

 devised, and most of them still remain barren wastes, defying 

 all attempts at reclamation." ..." The bad effect of 

 a layer of Impermeable material near the surface is shown 

 by the Loddington soil . . . typical of an area near 



