CONTENTS. XIU 



of the value of different straws for this purpose ; of the principles of irrigation ; of 

 the action of pure and impure water ; of tlie composition of the deposits from 

 freshets ; the nature, action, and value of rain and snow, in agriculture ; " snow 

 the poor man's manure," — how far this is true ; of paring and burning ; of turn- 

 ing in green and dry crops. 



CHAPTER VIII. 



Physical Propkrths of Soil, 242 



Great differences in soil depend upon physical not upon chemical properties ; physi- 

 sical properties independent of chemical constitution ; opinion of Liebig on this 

 subject ; physical characters of soil are dependent on its relation to heat, moist- 

 ure, consistency, and electrical state ; in all these relations, geine acts the chief 

 part ; of the quantity of water produced by the decomposition and waste of geine ; 

 the amount evaporated per acre from this source ; the quantity evaporated from 

 woodland, exceeds the amount of rain which falls ; of the waste of geine caused 

 by this evaporation of water ; of the proportion of carbon which is derived from 

 the soil, and from the air by forest trees. 



CHAPTER IX. 



BoNBS, SCPERPHOSPHATE OF Lime, AND ITS Preparation, 251 



Of the composition of bones ; consist of an animal and of a mineral part ; bones 

 act as forcing vegetation or as developing and forming seed ; the first depends on 

 the fermentation of the animal part of bone, producing ammonia ; the second 

 action depends on the mineral part of bone ; bones seed formers, or root, leaf, 

 and stem I'ormers ; bones to be studied as entire, or partially, or wholly deprived 

 of their gelatinous parts ; composition of entire bone ; no practical use to be 

 made of bone by the farmer, till the bone is reduced to powder ; of the composi- 

 tion of bone partially deprived of its animal parts ; how this is to be effected ; of 

 boiling and steaming bones ; how such bones are best used ; of bone ash, or bone 

 deprived of all its animal matter ; of sugar-house refuse, and animal black ; of 

 the treatment of l>one8 and bone ash by acids, as oil of vitriol, to produce super- 

 phosphate of lime ; no solution of bone in this case, is rather a pap-forming pro- 

 cess ; explanation and illustration of the process ; account of the properties of 

 phosphoric acid ; final result of the action of oil of vitriol on bones, in the right 

 proportion, is the formation of plaster, and superphosphate of lime with free oil 

 of vitriol ; of the quantity of oil of vitriol required by raw bones ; by bones 

 partly cooked ; by bone ash ; of the composition of superphosphate of lime ; of 

 its solubility in water ; of the process to be followed to prepare superphosphate 

 of lime, and of the cost of that product ; it should contain all the phosphoric acid 

 of bone in a soluble state ; great importance of this point ; how best effected ; 

 phosphoric acid must hot be free ; soluble alkaline phosphates most desirable for 



