COMPOSITION OF WOOD ASHES. 121 



ran be obtained, it is better to employ it in the fresh 

 state, so as to add its organic matter also. 



Wood ashes are very commonly used, and form a 

 manure of great value. Below is the composition, 

 from Johnston's Lectures, of ash from the oak and the 

 beech : these are merely given as illustrating thf 

 general character of wood ashes. 



TABLE IX. 



Percentage of Oak. 



Potash, 8-43 



Soda, 5-64 



Common salt, 0-02 



Lime, 74-63 



Sulphate of lime, .... 1-98 



Magnesia, 4'49 



Oxide of iron, 0-57 



Phosphoric acid, .... 3-46 



Silica, 0-78 



100-00 100-00 



The substances composing these ashes, are seen at a 

 glance to be of a valuable character for applying to 

 the soil. Even without an analysis, we might con 

 fidently have asserted that this would be the case, from 

 the fact that they had already been found proper for 

 the support of vegetation. It will be noticed that the 

 proportion of potash and soda is very considerable, 

 being in fact more in the above ashes than in most 

 others. Beside these there is quite an appreciable 

 proportion of phosphoric acid, and a very large quan 

 tity of lime : part of this was in combination with the 

 phosphoric acid. The potash, soda, lime and mag 

 nesia, were doubtless for the most part combined with 

 carbonic acid, forming carbonates. The potash, soda 

 and common salt, being soluble in water, of course 

 act first and disappear first; the lime and other con- 



