92 THE SOIL. 



summer months takes up from the surface soil and carries 

 down into the deeper layers. 



In lysimeters^ or underground rain-gauges specially con- 

 structed for the purpose, a collection was made of the 

 rain-water, which trickled through a layer of earth, 

 6 inches deep by 1 square foot in transverse section, from 

 the 6th April to the 7th October. The rain-gauge kept 

 at a neighbouring observatory indicated, up to the 1st 

 October, a fall of rain amounting to 480*7 millimetres 

 (18-75 inches).* 



Four lysimeters were filled with the same earth taken 

 from the subsoil of the stiff clay at Bogenhausen ; in two 

 of them (in. and IV.) the earth was manured with 

 2 pounds of cow's dung ; the other two were left un- 

 manured. Nos. II. and IV. were sown with barley. 



Calculated upon a square metre (10-75 square feet) of 

 ground, the following were found to be the quantities of 

 water that had passed through. Dr. Zoeller determined 

 the amount of soluble substances contained in the water ; 

 the quantities of phosphoric acid and ammonia were too 

 smaU to be appreciable : — 



* The lysimeter consisted of a square box, open at the top, closed 

 at the bottom ; at a depth of six inches from the open top a sieve -was 

 inserted, from which, up to the rim, the box was filled with earth. 

 The rain falling upon a square foot of surface, and trickling through 



