( 323 ; 
XVI. — On the Chemical Clianges in the Fermentation of Dung. 
By the Rev. W. R. BOWDITCH, St. Andrew's, Wakefield. 
PnizE Essay. 
An inquiry into the changes undergone by substances in any 
given condition presupposes an acquaintance with them in tlieir 
normal state. The want of this knowledge in the case of manure 
meets every one who attempts to describe its changes in the heap, 
in the soil, or in the plant ; and all that can be done is to use 
the knowledge we possess, and to confess ignorance of what lies 
beyond our means of investigation. 
Analysts tell us for instance, that certain plants contain a con- 
siderable amount of phosphorus, and show in figures the per- 
centage of phosphoric acid in the ashes, indicating the bases with 
which it is supposed to be united in the vegetable : and thus 
people speak of phosphate of lime, magnesia, or ammonia enter- 
ing into the composition of such and such plants. But who will 
venture to assert that the phosphorus is contained in the living 
plant in the same form and combination as in the ash, or even, 
at present, to propose a theory concerning it as more than con- 
jecture?* Again, sulphuric acid may be found duly tabulated 
with every appearance of accurate knowledge, but who will pre- 
sume to limit the sulphur in plants to this particular form of 
combination with oxygen ? 
Unfortunately we are not only ignorant of the combination of 
elements in the living plant, but have yet to devise satisfactory 
methods by which to determine liow much of a given element in 
each case really exists ! 
For example ; Messrs. Way and Ogston have published a 
series of determinations of the sulphur contained by some of our 
cultivated crops which bears the impress of labour and com- 
petency. We might tlierefore reasonably expect the results to 
be reliable. But Mr. Sorby has another series relating to the 
same element which differs so widely that hotli cannot be right ; 
nor can the differences be mere errors of analysis. Prof. Johnston 
again differs from both the series, and in the article of cabbage 
multiplies Mr. Sorby's figures by four (nearly) ! and expresses his 
opinion upon the whole matter thus ; " I do not quote more of 
these results, as I believe further experiments will show the 
numbers obtained by these expei'imenters to be all below the truth."^ 
* " One source of difficulty in these analyses (i. e. of albumen) is the presenee 
of inorganic matter, such as phosphates, which does not, perhaps, exist in tite 
albumen in the same form as that in tvhich it is found in the ashes." — Tiirnei's 
' Chemistr)-,' by Liebig and Gregory, vol. ii. p. 1200. 
t 'Experimental Agriculture,' p. 103. 
