16 CONTENTS. 



soil ; the Saxon fields considered in this respect ; the power of absorption con- 

 sidered in manuring Change produced in the composition of the soil by the 

 system of farm-yard manuring ; the different stages of this system, the fina 1 

 result Examples of these stages in the Saxon experimental fields Cause of 

 the growth of weeds ; remedies The history of husbandry, what is taught by 

 it Present condition of European husbandry Present production ot the land 

 compared with the earlier ; conclusions Continuation of production regulated 

 by a natural law Law of restoration ; defective practice of it Agricul-.ure in 

 the time of Charlemagne Agriculture in the Palatinate Corn fields in the 

 valleys of the Nile and Ganges ; nature provides in them for the restoration of 

 food of plants Practical agriculture and the law of restoration The sta- 

 tistical returns of average crops afford an explanation of the condition of corn 

 fields, . * 184 



CHAPTER VI. 



GUANO. 



Composition compared with that of seeds ; small amount of potash in it ; its ac- 

 tionGuano and bone-earth, similarity of their active ingredients Guano 

 acts quicker than bone-earth, or a mixture of the latter and ammoniacal salts , 

 reason of this Oxalic acid in Peruvian guano ; the phosphoric acid rendered 

 soluble by its means Peruvian guano, its effect on the cultivation of corn- 

 Moist guano loses ammonia Moistening guano with water acidulated with 

 sulphuric acid ; effect Inactivity of guano in dry and very wet weather- 

 Rapidity of its action as a manure, on what dependent Comparison of the 

 effect of farm-yard manure and guano ; effect produced by mixing the two- 

 Guano on a field rich in ammonia Increased produce by guano, what it pre- 

 supposesExhaustion of the soil by continuous use of guano Mixture of 

 guano with gypsum and with sulphuric acid The Saxon agricultural experi- 

 ments; their results, ... 245 



CHAPTER VII. 



POUDRETTE HUMAN EXCREMENTS. 



Poudrette, nature of ; small amount of the food of plants in it Human excrement, 

 its value Construction of the privies in the barracks at Rastadt Calculation 

 of the amount of corn produced by the excrement collected ; importance to the 

 neighbourhood Its effect not impaired by deodorising with sulphate of iron 

 The excrement of the inhabitants of towns as manure Its importance, . 258 



CHAPTER VIII. 



EARTHY PHOSPHATES. 



High agricultural value of phosphates Phosphates of commerce ; selection of the 

 kind to be used dependent on the object in view, and on the nature of the soil 

 The rapidity and the duration of the effect of the neutral and of the soluble 

 phosphate (superphosphate) of lime The Saxon manuring experiments, 262 



