FABT ZIX. 



ON THE IMPROVEMENT OF THE SOIL BY MECHANICAL AND 

 CHEMICAL MEANS. 



LECTURE XIV. 



THE QUALITIES OF THE SOIL MAY BE CHANGED BY ART. 



Connection between the kind of soil and 

 the kind of plants that grow ujion it. p. 304 



Of draining, and its effects 300 



Practical effects of draining 311 



Of the theory of springs p. 312 



Of ploushinii'and subsoiling 318 



Of deep-ploughing and trenching 321 



Improvement of the soil by mixing 323 



LECTURE XV. 



IMPROVEMENT OP THE SOIL BY CHEMICAL MEANS. 



Of saline manures 327 



Theory of the action of potash and soda.328 

 Sulphates of potash, soda, magnesia, and 



lime (gypsum) 331 



Theory of the action of these sulphaies .332 



Nitrates of potash and soda 335 



Effect of these nitrates on the quantity 



of various crops 336 



Effect of the nitrates on the quality of 



the crop 3.39 



Cases in which they have failed .341 



Theory of the action of these nitrates... 343 

 Special effects of the nitrates of potash 



and soda 344 



Use of common salt 345 



Chlorides of calcium and magnesium.,. 347 

 Phosphate of Hme and earth of bones... 348 



Silicates of potash and soda 349 



Salts of ammonia ib. 



Of mixed saline manures 352 



Wood ashes ib. 



Use of kelp 355 



Straw a.«!hes 356 



Turf-peat or Dutch-ashes 350 



Crushed granites and lavas 361 



Results of experiments with mixed ma- 

 nures 362 



LECTURE XVI. 



OF THE USE OF LIME AS A MANURE. 



Of the composition of common and 

 magnesian limestones 364 



Of the burning and slaking of lime 366 



Changes which the hydrates of lime 

 and magnesia undergo by prolonged 

 exposure to the air 367 



States of chemical combination in which 

 lime may be applied to the land 369 



Of the various natural forms in which 

 cor6ona/e of lime is applied to the land. 370 



Effects of marl, and of (he coral, shell, 

 and lime-stone sands upon the soil 374 



Of the use of chalks, as a manure 375 



Is lime indispensable to the fertility of 

 the soill 377 



States of combination in which lime ex- 

 ists in the soil 379 



Of the quantity of lime which ought to 

 be added to the soil 381 



Ought lime to be applied In large doses 

 at distant intervals, or in smaller quan- 

 tities more frequently repeated! 383 



Form and state of combination in which 



lime ought to be applied to the land. , .386 

 Use and advantage of the compost form. 383 



When ought lime to be applied 1 389 



Of the effects produced by lime upon 



the land and upon the crops 390 



Circumstances by which the effects of 



lime are modified 393 



Effects of an overdose of lime 395 



Length of time during which lime acts.. 396 



Of the sinking of lime into the soil 397. 



Why liming must be repeated 398 



Theory of the action of lime 400 



Of lime as the food of plants ib. 



The chemical action of lime is exerted 

 chiefly on the organic matter of the soil.401 



