Ashes and Soot 



15 per cent., and furze the richest with about 30 

 per cent. Broom and furze contain as well a cer- 

 tain quantity of phosphoric acid. The presence of 

 broom shows phosphoric acid in the soil. Bracken is 

 relatively poor in phosphoric acid. When the plants 

 are young and not too strong, instead of burning, 

 it is better to bury them where they grow by 

 ploughing in. 



Soot. 



Soot is the deposit on the sides of chimneys 

 of unburnt particles, driven out by the smoke of 

 our hearths. The more incomplete the combustion 

 the more abundant is the formation of soot — as is 

 easily proved by looking at a lamp. Soot contains 

 potash, and phosphoric acid ; but above all ammonia 

 and sulphuric acid (that is to say sulphate of 

 ammonia) are formed. The composition of soot 

 is very variable, depending upon its origin ; its 

 action on vegetation is due in some cases to sulphate 

 of ammonia, or equally in the case of leguminosae 

 to free sulphuric acid. 



Some soot contains great quantities of potash, 

 and then is suitable for clovers. It also contains 

 from I to 3 per cent, of nitrogen. As the quality 

 varies very much, however, it ought to be bought 

 cheaply, or on analysis. It is used for various 

 crops, wheat, and pasture, but above all it is recom- 

 mended for vegetable culture. It can be used 

 freely in the garden, where, as with coal ashes, its 

 black colour tends to make the soil earlier. 



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