Bones and Sulphuric Acid as Manures. 
453 
grease. It was soon found, however, that boiled bones were as good 
manure as those that were unboiled. There still remained in the boiled 
bones two substances either of which might be their active principle. 
But Sprengel states that he found bones which had been burnt still act 
as manure; and Mr. Hannam has tried the same experiment with the 
same result. Now, as fire drives out of the bone the solid jelly which 
holds it together, there remains only the earthy matter behind, thus 
proved to be the manuring substance. This being phosphate of lime, 
chemistry suggested that, since lime was in so small a quantity, the 
phosphoric acid united with it must be the true manure contained in 
bones, and that if that lime was taken from it by sulphuric acid the phos- 
phoric acid, thus set free, would be greatly strengthened in its immediate 
activity." 
This view of the theory of the application should be taken with 
certain limitations ; in fact, it only refers to a solution of burnt 
bones, as it depends on the assumption that the earthy part of 
bones is their only manuring substance. This, it is true, is 
asserted by Sprengel, and followed by Liebig, and certain of 
my own experiments seem to bear out the assumption. Thus in 
one case I found 1 6 bushels of bones, burnt to whiteness, give a 
better crop than 16 bushels of fresh bones. In two other cases, 
where the tillage was assisted by a half-dressing of farm manure, 
burnt bones did not act so beneficially ; and in one, upon very 
poor soil, they completely failed. In all the cases, however, 
burnt bones acted more quickly than the fresh ones, and fresh 
bones the more efficiently when reduced to a fine powder. Prom 
which facts we may infer that the superiority of burnt over fresh 
bones, in certain cases, is owing to the former being more access- 
ible to the plant. And other evidence sanctions this. Thus we 
know that burnt bones absorb large quantities of water, by which 
means the organic acids in the soil the more easily act upon the 
phosphates and render them soluble ; that, in fact, thev speedily 
decompose, while fresh bones, if not ground very small, are very 
slowly acted upon by any acid, and remain for a length of time 
in the soil unchanged. In the above trials, too, it will be seen 
that where the land was partially manured, so as to give the 
young plant a start, the fresh bones were, if anything, superior to 
the calcined ones, and that, when the land was very poor, though 
the burnt bones took the lead, they could not maintain it ; a proof 
that though the phosphate of the bone may be the chief fertilizing 
element, it cannot of itself supply all the wants of the crop. 
The only conclusion which facts warrant is that the phosphates 
are the chief fertilizers in bones; that they are more accessible 
to the plant when the fat is removed from the bone; and hence, 
in many cases, where the soil is not deficient in organic food, such 
is the necessity of a supply of these phosphates, that the removal 
of the animal matter from the bone has a beneficial effect. 
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