112 THE SOIL. 



jointly by Professor Nageli and Dr. Zoeller, in the 

 Botanic Garden at Munich, most strikingly prove the 

 correctness of the conclusions to which the analysis of 

 drainage and other waters has led. Instead of growing 

 plants in solutions of the mineral elements of their food, 

 as had been done in all previous experiments, they pur- 

 sued the very opposite course ; they placed the -seeds 

 of the plants in a soil containing all the elements of 

 their food in an insoluble state. 



In such experiments, it is not easy to find a material 

 which can be used as a substitute for arable soil, and 

 possessing all its properties ; and the difficulty is proved 

 by the fact, that none of the plants grown by Boussin- 

 gault and others, in an artificial soil, abundantly pro- 

 vided with all the elements of food, could even remotely 

 bear comparison with a plant grown in a fertile arable 

 soil. Pulverised charcoal or pumice-stone have the 

 power of extracting many elements of the food of plants 

 from their solutions, and physically fixing them ; but 

 they have not, in the moist state, that soft, plastic, and 

 yielding condition of the -clay in arable soil, which per- 

 mits the intimate contact of the roots with the earthy 

 particles. The best substitute for the purpose is coarse- 

 ly-powdered turf, which, in the moist state, forms a 

 plastic mass, bearing a remote resemblance to clay, and, 

 like arable soil, absorbs all elements of the food of 

 plants from their solutions. Accordingly Nageli and 

 Zoeller used in their experiments coarsely-powdered 

 turf as the vehicle of the nutritive substances, after hav- 

 ing ascertained its absorptive power for the several ele- 

 ments of food. 



A litre (1*76 pint) of turf, weighing 324 grammes 

 (4 987 '6 grs.), was found to absorb from solutions of car- 

 bonate of potash, carbonate of ammonia, carbonate of 

 soda, and phosphate of lime 1*45 grammes (22*4 grs.) 

 of potash, 1*227 grammes (19 grs.) of ammonia, 0*205 

 gramme (3*2 grs.) of soda, and 0*890 gramme (13*7 grs.) 

 of phosphate of lime equal to 0*410 gramme (6*3 grs.) 

 of phosphoric acid. 



The quantities of potash and ammonia here given do 



