s on which our information
regarding it is less complete than might be desired. Its investigation
is surrounded with peculiar difficulties, not merely on account of its
complexity, but because its properties render it exceedingly difficult
to obtain a sample which fairly represents its average composition. In
the case of long dung, these difficulties are so great that it is
scarcely possible to overcome them; and hence, discrepancies are
occasionally to be met with in the analyses of the most careful
experimenters. The most minute and careful analyses yet made are those
of Voelcker, who has compared the composition of fresh and rotten dung,
and studied the changes which the former undergoes when preserved in
different ways. He employed in his experiments both fresh and rotten
dung, and subjected them to different methods of treatment. His analyses
are given in the accompanying table, in which column 1 gives the
composition of fresh long dung, composed of cow and pig dung. 2. Is dung
of the same kind, after having lain in a heap against a wall, but
otherwise unprotected from the weather for three months and eleven days
in winter, during which time little rain fell. 3. The same manure, kept
for the same time under a shed. 4. Well rotten dung, which had been kept
in the manure heap upwards of six months. 5. The same, after having lain
against a wall for two months and nine days longer.

+-------------------------------+-------------+-------------+--------------+
| | 1 | 2 | 3 |
+-------------------------------+-------------+-------------+--------------+
| Water | 66.17 | 69.86 | 67.32 |
| Soluble organic matters | 2.48 | 3.86 | 2.63 |
| Soluble inorganic matters. | | | |
| Silica | 0.237 | 0.279 | 0.239 |
| Phosphate of lime | 0.299 | 0.300 | 0.331 |
| Lime | 0.066 | 0.048 | 0.056 |
| Magnesia | 0.011 | 0.019 | 0.004 |
| Potash | 0.573 | 1.096 | 0.676 |
| Soda | 0.051 | 0.187 | 0.192 |
| Chloride of sodium | 0.030 | 0.106 | 0.058 |
| Sulphuric acid | 0.055 | 0.160