This dry mud is one great source of plant food for the farm, but it is largely supplemented by what the Egyptians term _coufri_, or _sabbakh_. This is not always available, and depends upon the position of the farm; but there are parts of the Delta where, to all appearance, the tract being reclaimed or taken up for bringing into cultivation is so much level, or nearly level, land, with a mound or slight elevation here and there where the winds have drifted the sand apparently to a considerable depth. Except to the eye of the experienced there is nothing to show that flourishing cities and villages have existed there in the past; but many of these slight elevations are the sites where teeming populations once existed, and all has gone back, with some few exceptions--dust to dust. The exceptions are where the spade of the fellah comes upon the remains of a tomb or priestly edifice, these, as is well-known, being the lasting part of man's work, which are being discovered constantly even now, with their builders', sculptors', and painters' handiwork looking, when the sand has been removed, almost as fresh and uninjured as if they were the traces of two or three generations back instead of having been buried many centuries ago. These solid remains, or ruins, may be comparatively few; but in all probability have been surrounded by an enormous population, whose houses, originally built of the sun-dried Egyptian brick, have in the course of time gone back, like everything animal that surrounded them, to a rough earth ready for the worker's spade, which digs up from an almost inexhaustible mine--with nothing to tell of the past but a few broken shards--a splendid fertiliser for the farm. But this _coufri_ manure requires discrimination in its use, too strong an application being likely to prove hurtful to a crop, seeing that analysis shows that its plant-feeding qualities are due to the salts it contains--sometimes as much as 12 per cent, of salt, soda, ammonia, saltpetre, phosphates, and the like. The value to an English farmer of such a mine of artificial chemical manure as this may be conceived, and it would make the eyes brighten of one here who strengthens his land by applications of marl, or else has to content himself with a top dressing of chalk from some pit sunk in a corner of his holding.