ch material. Sifted coal ashes are also
very useful for this purpose.

CHAPTER XVII.

SOLUBLE PHOSPHATES IN FARMYARD MANURE.

There is one thing in these experiments of Dr. Voelcker's which deserves
special attention, and that is the comparatively large amount of
_soluble phosphate of lime_ in the ash of farm-yard manure. I do not
think the fact is generally known. In estimating the value of animal
manures, as compared with artificial manures, it is usually assumed that
the phosphates in the former are insoluble, and, therefore, of less
value than the soluble phosphates in superphosphate of lime and other
artificial manures.

Dr. Voelcker found in the ash of _fresh_ farm-yard manure, phosphoric
acid equal to 12.23 per cent of phosphate of lime, and of this 5.35 was
_soluble_ phosphate of lime.

In the ash of well-rotted manure, he found phosphoric acid equal to
12.11 per cent of phosphate of lime, and of this, 4.75 was soluble
phosphate of lime.

"That is, indeed, an important fact," said the Doctor, "but I thought
Professor Voelcker claimed that 'during the fermentation of dung, the
phosphate of lime which it contains is rendered more soluble than in
fresh manure.'"

"He did say so," I replied, "and it may be true, but the above figures
do not seem to prove it. When he wrote the sentence you have quoted, he
probably had reference to the fact that he found more soluble phosphate
of lime in rotted manure than in fresh manure. Thus, he found in 5 tons
of fresh and 5 tons of rotted, manure, the following ingredients:

SP: Soluble Phosphate of Lime.
IP: Insoluble phosphates.
TP: Total Phosphates.
TSA: Total Soluble Ash.
TIA: Total Insoluble Ash.
TA: Total Ash.

--------------+-----+-----+-----+-------------+-----+-----+-----
| | | | Potash | | |
5 Tons. | SP | IP | TP +------+------+ TSA | TIA | TA
(10,000 LBS.) | | | | Sol. |Insol.| | |
--------------+-----+-----+-----+------+------+-----+-----+-----
Fresh manure | 29.9| 38.6| 68.5| 57.3 | 9.9 | 154 | 405 | 559
Rotted manure | 38.2|57.3 |95.5 | 44.6 | 4.5 | 147 | 658 | 805
--------------+-----+-----+-----+------+------+-----+-----+-----

"It will be seen from the above figures that _rotted manure contains
more soluble phosphate of lime than fresh manure_.

"But it does not follow from this fact that any of the insoluble
phosphates in fresh manure