CONTENTS. XI 



apocrenates in soil, by transformations of geine ; crenic and apocrenic acids 

 mutually convertible ; all the transformations of geine, worthy of study ; geine 

 is essential to agriculture, Appendix to Chap. iv. p. 100 ; of the chemical his- 

 tory of geine and recent researches of Mulder on this subject ; reasons why geine 

 i» easeniial may be deduced from Mulder's researches. 



CHAPTER V. 



Of the MtrnTAL Acnox or thk Organic and Inorganic Elements of Soil . . . 101 

 Theoretical and practical farmers both aim at the same object ; the action of the 

 elements of soil to be considered in two ways — 1st, the mutual chemical action 

 of the organic and inorganic parts — 2d, the influence of growing plants on this 

 action ; of the importance of salts to this action ; of the action of carbonic acid 

 and the carbonates upon the silicates of soil ; of the modification produced upon 

 this action by the presence of life ; of catalysis or the action of presence, by 

 ■yirhich life acts ; of the action of mineral manures in agriculture ; their earthy or 

 alkaline part always acts one way ; their acid part produces diflerences of ac- 

 tion ; illustration and explanation of the action of salts or mineral manures ; of 

 the action of nitre ; of lime ; of ashes ; of the composition of leached and 

 unleached ashes. 



CHAPTER VI. 



Manure , 131 



Manures contain all the elements which plants want— are divided into three 

 classes ; choice and determination of a standard of value for manures ; nitro- 

 gen, geine, and kind of salts determine the value of manure ; pure cow-dung 

 the type of all other manures ; its composition and analysis ; yearly produce of 

 salts and geine by one cow ; the action of manure referred to the joint effect of 

 all its components ; its action due chiefly to its ammonia ; origin of this in dung ; 

 of the composition and value of horse-dung; fermented horse-dung less valuable 

 than cow-dung ; reasons why ; mode of making good yard manure from horse 

 stable-dung ; of yard 'manure ; importance of kind of litter ; relative value of 

 different straws ; fermentation and age ; its effects on value of yard manure ; 

 long and short, or strong and fat muck ; loss of bulk by age ; statement of com- 

 position of yard manure ; its amount of nitrogen and ammonia ; comparative 

 weights of equal bulks of ox and horse manure ; drainings of manure heaps ; 

 their composition and value ; of the composition and value of human excrement ; 

 analyses of human excrement by Berzelius, and by Fleitmann ; great amount of 

 phosphates found by the last-named chemist ; night-soil, what ; its quality ; how 

 affected by its source ; of hog-manure ; sheep-manure ; of the quantity of manure 

 from 1000 sheep daily ; table of composition of ashes of the excrements of pig, 

 cow, sheep, and horse ; relative effect of these manures, and of night-soil ; on 

 what it chiefly depends ; nitrogen expresses the true value of maniire ; circum- 



