a century ago.
It is most beneficial on sandy or peaty soil, and by its means large
tracts of worthless land have been brought under profitable cultivation.
It requires that the land to be so treated shall be under the level of
the river at full tide, and it is managed by providing a sluice through
which the river water is allowed to flood the land at high tide, and
again to escape at ebb, leaving a layer of mud generally about a tenth
of an inch in thickness, which it brought along with it. By the
repetition of this process, a layer of several feet in thickness, of an
excellent soil, is accumulated on the surface. Herapath, who has
carefully examined this subject chemically, has shown that in one
experiment where the water used contained 233 grains of mud per gallon,
210 were deposited during the warping. The following analyses will show
the general nature of the matters deposited, and the change which they
produce on the soil:--No. 1 is the mud from the Humber in its natural
state, No. 2 a specimen of warp of average quality artificially dried,
No. 3 a sandy soil before warping, and No. 4, the same fifteen years
after having received a coating of 11 inches of mud.

+---------------------------------+---------+--------+---------+--------+
| | 1 | 2 | 3 | 4 |
| +---------+--------+---------+--------+
| Water | 47.49 | ... | 1.06 | 2.00 |
| Organic matter | 5.94 | 6.93 | 2.20 | 7.61 |
| Chloride of Calcium | ... | ... | } ... | ... |
| Magnesium | } ... | 0.10 | } ... | ... |
| Sodium | } 1.66 | } 0.94 | } 0.14 | 0.16 |
| Potassium | } | } | } | |
| Sulphate of Soda | } ... | 0.31 | } ... | ... |
| Magnesia | } ... | 1.18 | } ... | ... |
| Lime | trace | 1.10 | trace | trace |
| Carbonate of Magnesia | 2.60 | 0.31 | trace | 0.29 |
| Lime | 3.59 | 8.18 | trace | 0.46 |
| Potash and Soda | 0.18 | 0.47 | trace | 0.17 |
| Magnesia | 1.69 | 2.60 | trace | 0.26 |
| Lime | 0.39 | 0.68 | trace | 0.14 |
| Peroxide of Iron