Xll CONTENTS. 



Page 

 4. Results of experiments with the sulphates of potash and soda, . 109 



5. Functions performed in the soil by the sulphates of potash and 



soda, 113 



6. Suggestions for experiments with the sulphates of potash and soda 



applied alone, . . . . . . .114 



CHAPTER VII. 



EXPERIMENTS WITH GYPSUM, AND WITH THE SULPHATES OF MAGNESIA 

 AND IRON. 



1. Results of experiments on the use of gypsum, applied alone, . 118 



2. Theory of the action of gypsum. Why it does not produce equal 



effects everywhere, and on all crops, . . . .121 



3. Suggestions for comparative experiments with gypsum, applied alone, 126 



4. Results of experiments with sulphate of magnesia, applied alone, 132 



5. Proportion of magnesia contained in our usually cultivated crops. 



Theory of the special action of sulphate of magnesia, . . 134 



6. Suggestions for experiments with sulphate of iron, . . 137 



CHAPTER VIII. 



EXPERIMENTS WITH THE CHLORIDE OF POTASSIUM, AND WITH COMMON 

 SALT, OR CHLORIDE OF SODIUM. 



1. Composition and general properties of the chlorides of potassium, 



sodium, calcium, and magnesium, of the fluoride of calcium, and of 

 muriatic acid, ....... 139 



2. Suggestions for comparative experiments with the chloride of potas- 



sium, applied alone, . . . . . .141 



3. Results of experiments with common salt, applied alone, . .143 



4. Influence of circumstances upon the observed effects of common salt 



when applied directly to the land, . . . .144 



5. Theory of the action of common salt when applied alone, . 1 47 



CHAPTER IX. 



EXPERIMENTS WITH COMMON SALT, Continued, AND WITH THE CHLO- 

 RIDES OF CALCIUM AND MAGNESIUM, WITH MURIATIC ACID, 

 AND WITH THE FLUORIDE OF CALCIUM. 



1. Suggestions for comparative experiments with common salt, applied 



alone, ......' . 149 



2. Experiments with chloride of calcium, and with muriatic acid, applied 



alone, . . . . . . . .153 



3. Experiments with chloride of magnesium suggested, . .155 



4. Suggestions for experiments with the fluoride of calcium (fluorspar,) 156 



