594 
Report oil the Analysis of the Ashes of Plants. 
})hosphoric acid, sulphuric acid, and common salt, with very fre- 
quently carbonic acid, and sometimes oxide of manganese. 
The general laws which we have above mentioned have been 
deduced from a number of ash-analyses made by various chemists 
at different periods. 
But of the numerous analyses of ashes of plants which have 
been published, a very large portion has been considered by 
chemists of the present day as unworthy of confidence from want 
of correctness in the methods employed ; whilst others of un- 
questionable accuracy are either too limited in number or not suf- 
ficiently systematic to afford the full information which it is so 
desirable to possess on this head. 
The present investigation was set on foot to supply this de- 
ficiency ; and we will now proceed to mention the points which we 
consider require elucidation. 
In the first place, it is necessary to ascertain by the analy sis of 
as many specimens of each as the time and labour involved will 
admit of, the quantity and chemical composition of the mineral 
matter contained in all plants which are the objects of English 
agriculture, and of the important parts of such plants. 
This knowledge is a most essential element in the construction 
of any rational system of agriculture, and upon it alone can we 
hope to select our crops for the soils upon which they are to 
grow, and judiciously to supply the manure suited to their wants. 
Precise information upon this point would in all probability 
explain to us the advantage of certain rotations which have re- 
ceived the sanction of experience, at the same time suggesting 
modifications and alterations to suit the mineral peculiarities of 
each crop. 
We should then know what are the crops that, from the large 
quantity, as well as the valuable character, of the materials they 
remove from the soil, are really deserving of the name of " ex- 
hausting crops." If such plants happened to be consumed for 
the most part in large towns, or that from any cause their inor- 
ganic matter could not be returned to the soil, their cultivation 
\^ould of course require the employment of artificial manures of 
composition analogous to that of the ash. 
On the other hand, crops of this exhausting character, if fed off 
on the land or in stalls (the manure, solid and liquid, being 
studiously preserved and returned to the soil), would be amongst 
our most efficient agents for the improvement of the land, by 
bringing to the surface a large portion of valuable salts suited to 
the necessities of the next crop. 
Thus, of two green crops equally valuable in other respects, 
we should select the one whose ash most resembled in quantity and 
composition that which the succeeding corn crop would require. 
