Superphosphate of Lime. 
145 
be absent, however rich the manure may otherwise be, the crop 
will be a failure. Not that we must tlierefore draw the con- 
clusion that the organic manures are of little or no importance 
to root-crops ; — they are of value, and particularly to the grain- 
crops which succeed. 
The organic matter which composes about one-third the sub- 
stance of bones is, however, so intimately combined with the 
earthy portion, and their disunion is accomj)iished with such diffi- 
culty, that the good effects of either are to a certain extent neutral- 
ized, at least so far as the first crop is considered ; and we are con- 
sequently obliged to supply five or six times as much as the crop 
actually requires, and to render them available by means of pul- 
verization. It is on this principle that the assistance of sulphuric 
acid is sought for and obtained — it serves by its chemical affinities 
to separate the component parts of the bones, and render them more 
soluble and available as food for plants. In the excellent and 
accurate experiments of Mr. Hannam, related in a former Number 
of the Journal, it was clearly proved that fresh bones when 
ground were superior to boiled ones, from which the fat was ex- 
tracted ; and the latter were superior to burnt bones, from which 
the gelatine « as also removed. This result was, however, far more 
striking when the bones were dissolved in sulphuric acid, a dif- 
ference of nearly 2 tons of turnips being observed, whilst with the 
bones merely ground a difference of 17 cwt. only was exhibited. 
From the same experiment we likewise learn that the beneficial 
effects derived from the earthy part of bones are 4| times 
greater than that derived from tue organic parts. I refer to 
the Journal for the particulars of these experiments, and to the 
previous Number for other statements, from which, if we had no 
other evidence, we should be justified in drawing the conclusion 
that 20s. laid out in bones and acid will go much further than 
40s. expended in bones alone, so far as the turnip crop is con- 
cerned. 
These experiments, however, appear to have been made with the 
addition of a very considerable quantity of water, so as to apply the 
manure to the land in a liquid state, which, without denying its 
superiority, is yet attended with such difficulty, trouble, and incon- 
venience, that it is vain to expect that farmers generally would incur 
it. The expense of a proper cart for the application of this manure 
in a liquid state is very considerable, and sufficient to prevent its 
general adoption. And although it was in this form that the 
public were first made acquainted with its valuable properties, 
yet its general adoption must be attributed to the additional dis- 
covery that it can readilv be applied in the state of compost by 
means of the common drill. Having directed my attention to the 
preparation and employment of this valuable manure in the form 
VOL. VII. L 
