CONTENTS. Xlll 



Explanation of dew ....... 77 



Heat of soils 78 



Heat in rotting farmyard manure 78 



Causes of heat of fermentation . . . . .79 

 Influence of colour on heat-retaining power ... 80 



Power of soils for absorbing gases 81 



Gases found in soils . . . . . . .81 



Variation in gas-absorbing power of soils ... 82 

 Absorption of nitrogen by soils ..... 82 



Requirements of plant-roots in a soil . . . .83 



Influence of tillage on number of plants in a certain area 86 



Comparison of English and American farming . . 86 



II. Chemical composition of a soil ...... 87 



Fertilising ingredients of a soil . . . . . . 87 



Importance of nitrogen, phosphoric acid, and potash in a 



soil 88 



Chemical condition of fertilising ingredients in soils . 89 

 Amount of soluble fertilising ingredients in soils . . 90 

 Value of chemical analysis of soils . . . . .90 



III. Biological properties of a soil ... 92 



Bacteria of the soil . .... 92 



Recapitulation of Chapter I , .96 



APPENDIX TO CHAPTER I. 



NOTE 



I. Table of absorptive power of soil substances by Schiibler . 98 

 II. Table of rate of evaporation of water in different soils by 



Schiibler 99 



III. Table of hygroscopic power of soils dried at 212 F. 



(Davy) 99 



IV. Gases present in soil . . . . . . .100 



V. Amount of plant-food in soils . . . . . .100 



VI. Chemical composition of the soil 101 



VII. Forms in which plant-foods are present in the soil . . 107 



CHAPTER II. FUNCTIONS PERFORMED BY MANURES. 



Etymological meaning of word manure 109 



Definition of manures .... 



Different classes of manures ... .111 



Action of different classes of manures 113 



