SCIENCE OF AGRICULTURE. 



125 



ing, into two parts, soluble and insoluble in water. 

 The average quantity of ashes from 100 parts of dry 

 oak, beech, birch, &c. is, 2.87. 



100 parts of the insoluble 



contain 

 Carbonic acid, 35.80 



Phosphoric acid, 3.40 

 Silica, . . 4.25 

 Oxyd of iron, . .52 



Oxyd of manganese, 2.15 

 Magnesia, . 3.55 



Lime, . . 35.80 

 99.86 



85.47 



The composition of the insoluble part of ashes 

 gives us nearly the constituents of leeched ashes. 

 The soap boiler's process, how^ever, always leaves a 

 portion of potash combined with silica, and he adds 

 more or less lime to render the lye caustic. These 

 add to the value of leeched ashes something more 

 than is indicated in the table. Exposure to air, and 

 the galvanic operations of the roots of plants decom- 

 pose this silicate of potash, (crude glass,) and ren- 

 der the potash soluble in water. This is one great 

 source of the active power of leeched ashes. The 

 course of this wonderful powder, not only in fresh and 

 in leeched ashes, but in some degree, in all salts, is 

 to be found in the action of the bases of these salts 

 on geine and on silicates or granitic sand. 



Peat ashes abounds in carbonate, sulphate, and 

 especially in phosphate of lime. I have always trac- 

 ed free alkali in peat ashes. But alkali exists in it 

 rather as a silicate, as in leeched ashes. Anthracite 

 coal ashes contain carbonate of lime, alumina, oxyd 

 of iron, and, as more or less wood or charcoal is 

 used in kindling it, some potash also — it is good so 

 far as these abound. 



"There is one great, simple principle running 

 through all the classes of soils. It is this, that in all 



