X CONTENTS. 



Page 

 4. Importance of local climatic knowledge, .... 26 



5. Composition of the several parts of animal bodies, and how they are 



built up and sustained, . . . . . .27 



6. General functions of the animal body, .... 30 



7. Special structure of the digestive organs of different animals, . 33 



8. General relations between the soil, the plant, and the animal, . 34 



9. How analyses are corrected through the perception of such relations, 



and how we arrive at an exact knowledge of the composition of the 

 plant, the soil, or the animal, . . . . .36 



CHAPTER III. 



HOW EXPERIMENTS ARE TO BE MADE AND JUDGED OF. 



1. Of the form, extent, kind, and condition of the land on which experi- 

 ments ought to be made, . . . .38 



2. Precautions to be adopted in making experiments in husbandry, . 41 



3. What observations ought to be made, and how, . . . 42 



4. Quantity of land required for a continuous series of field experi- 



ments, ........ 43 



5. Experiments should be made with a view to a definite object or end. 



Evils arising from badly conducted experiments, . . 45 



6. Why the results of analogous field experiments are often so discordant, 47 



7. Importance of ascertaining the limits of natural variation in the pro- 



ductiveness of an experimental field. Necessity of double experi- 

 ments, ........ 48 



8. Ought the mean of the natural produce of different parts of a field to 



be taken as the standard with which to compare the produce of 

 experimental manured portions ? .... 52 



CHAPTER IV. 



INFLUENCE OF CIRCUMSTANCES ON THE RESULTS OF EXPERIMENTS. 



1. Influence of the varying quality of farm-yard manure on the results 



of experiments in which it is one of the substances employed, . 54 



2. Influence of the previous treatment of land upon the results of field 



experiments. Long-continued action of bones, ... 56 



3. Influence of one substance in counteracting the beneficial action of 



another, ........ 59 



4. Influence of the time, manner, and form of its application on the 



apparent effect of a manure ; also of the period at which a root 

 crop is lifted, ....... 60 



5. Influence of the physical condition of a substance, its state of chemi- 



cal combination, and its tendency to decompose in a given soil, 



on the immediate effects it produces, . . . .66 



6. Influence of different varieties of seed in causing discordances in the 



observed effects of different manures, .... 68 



