dust has long been
employed as a manure, and the success which has attended its use has led
to the introduction of the refuse cake from some other oil seeds, such
as those of mustard and castor-oil, which cannot be employed for
feeding. Like the seeds of all plants, these substances are rich in
nitrogen, and their ash, containing of course all the constituents of
the plant, supplies the necessary inorganic elements. The following are
analyses of these substances, which, in addition to the amount of
nitrogen and phosphates, shew also that of water and oil, to which
reference will be made in a future chapter, in relation to the feeding
value of some of them. The detailed composition of their ash may be
judged of from that of the seeds from which they are made, and which
have been given under that head.

+--------------------+------------+-------------+-------------+---------+
| | Rape-Cake. | Poppy-Cake. | Cotton-seed | Castor- |
| | | | Cake. | Cake. |
| +------------+-------------+-------------+---------+
| Water | 10.68 | 11.63 | 11.19 | 12.31 |
| Oil | 11.10 | 5.95 | 9.08 | 24.32 |
| Albuminious } | 29.53 | 31.16 | 25.16 | 21.91 |
| compounds } | | | | |
| Ash | 7.79 | 12.98 | 5.64 | 6.08 |
| Other constituents | 40.90 | 38.18 | 48.93 | 35.38 |
| +------------+-------------+-------------+---------+
| | 100.00 | 100.00 | 100.00 | 100.00 |
| Nitrogen | 4.38 | 4.94 | 3.95 | 3.20 |
| Silica | 1.18 | 3.36 | 1.32 | 1.96 |
| Phosphates | 3.87 | 69.3 | 2.19 | 2.81 |
| Phosphoric acid } | | | | |
| in combination } | 0.39 | 3.27 | 0.15 | 0.64 |
| with alkalies } | | | | |
+--------------------+------------+-------------+-------------+---------+

A general similarity may be observed in the composition of all these
substances; they are rich in nitrogen, and contain as much of that
element as is found in six or seven times their weight of farm-yard
manure, and a somewhat similar proporti