CONTENTS. 



CHAPTEE Xl.—contimied 



wanting — Progress in agriculture impossible if dependent on a supply 

 of ammoniacal compounds; results of Lawes' experiments with salts of 

 ammonia — The artificial supply of ammonical manures contrasted with 

 the crops produced and the increase of population — Increase of nitro- 

 genous food by natural means ; formation of nitrite of ammonia by oxi- 

 dation in the air according to Schonbeim — Supply of food in excess neces- 

 sary to produce corn-crops ; reasons — How the necessary excess of nitro- 

 genous food for corn may be obtained from natural sources — The supply 

 of nitrogen in farm-yard manure in the Saxon experiments corresponded 

 to the crop of clover-hay — Loss of nitrogen in lime soils by oxidation ; 

 utility of a supply of nitrogen to such soils — Effect of nitrogenous food 

 on the aspect of young plants ; on potatoes — Empirical and rational 

 systems of agriculture ..... PAGE 289 



CHAPTER XII. 



COMMON SALT, NITRATE OF SODA, SALTS OF AMMONIA, 

 GYPSUM, LIME. 



Effect of these substances as elements of food ; their effect on the condition 

 of the soil — Kuhlmann's experiments with common salt, nitrate of soda, 

 and salts of ammonia; experiments with the same substances in Bavaria ; 

 conclusions : these matters are elements of food ; they are chemical 

 means for preparing the soil ; they cause the distribution of the food in 

 the soil in the form proper for the growth of plants — Experiments by 

 Pincus with gj^DSum and sulphate of magnesia on clover ; decrease of 

 flowers and increase of stem and leaves of clover by sulphates ; the crop 

 is not in proportion to the quantity of sulphates used — Effect of gypsum 

 not yet explained ; indication in the comportment of clover soils with 

 solution of gypsum ; such solution disperses potash and magnesia in the 

 soil — Manures, their effect not explained by the composition of plants 

 produced by them— Composition of the ash of clover manured with dif- 

 ferent substances — Effect of lime ; experiments of Kuhlmann and Trager ; 

 comportment of lime-water with soils .... 335 



APPENDICES. 



Beech leaves and asparagus, their ash-constituents at different periods of 

 growth — The amylum of the palm — Motion of sap in plants — Drain, 

 lysimeter, river, and bog water, their constituents — Fontiualis antipja-etica 

 from two different waters, ash-constituents — Vegetation of maize in 

 solutions of its food — Experiments on the growth of beans in pure and 

 prepared turf, results — Japanese agriculture — The cultivated soil of 

 the torrid zone, its exhaustibility, its manure — Analysis of clover by 

 Pincus — Clover sickness, its causes ..... 353 



