COAL ASHES. 116 



getables, merely for the sake of the potash they 

 contain, to help to form the compost heap be- 

 fore mentioned. 



The ashes of beech seem to possess a pecu- 

 liar quality in addition to the salts of potash, 

 viz. phosphates; and it is calculated that 100 

 lbs. of the lixiviated ashes of the beech, would 

 yield as much phosphate as 400 lbs. of fresh 

 human excrement, or enough to supply suffi- 

 cient phosphoric acid for the production of 

 3S20 lbs. of straw, or from 15 to 18,000 lbs. 

 of corn. 



Coal ashes — yield, on analysis, a small por- 

 tion of sulphate of lime (gypsum,) charcoal 

 and lime. The beneficial results arising from 

 the use of these ashes are generally attributed 

 to the sulphate of lime they contain ; but as 

 these results are so much greater, than are 

 produced by an equal proportion of the sul- 

 phate, when applied in its pure state (that of 

 gypsum,) the cause must be sought for in 

 some other ingredient they contain ; and with 

 deference to those who have previously written 

 on this subject, the greater portion of the good 

 effect attending the use of coal ashes, may be 

 attributed to the presence of the charcoal they 

 contain. Elsewhere, the power possessed by 

 charcoal of absorbing other gases, and again 

 yielding them to the soil, will be alluded to, 

 and it is to this power and the presence of car- 

 bon and nitrogen thus absorbed, that the bene- 

 fit is supposed to be due. The lime which 

 exists, independently of the gypsum, may 

 also produce its effect, but the quantity con- 

 tained in coal ashes is too small for it to be 



