Mould consists of the following ingredients ; viz. sand, clay, and talcum, or magnesian earth; carbon derived from decayed vegetable and animal substances; the carbonic acid, and water. The good or bad qualities of the soil depend upon a proper mixture of these ingredients ; though, if the carbon, the carbonic acid, and iron, be wanting, the fertility of land will depend on its capacity to retain the quantity of moisture, which is necessary for the nutriment of vegetables.
The relative utility of mould, for the different purposes of the | dener, may be. ascertained by. the sight, smell, and touch. The best is of a light brown or hazle colour; jt cuts easily, and does not adhere to the spade, being light, friable, and crumbling into small clods. The next in quality are the dark-grey and russet-coloured moulds; but the worst are those of a3 very light, or very dark ash-colour, such as are generally found on barren heaths and commons, where they seldom produce any thing except furze and fern.
With respect to smell, Miller observes, that the best time for judging by that sense, is immediately after rain has moistened the soil when the mould, if it be rich and good, will emit an agreeable odour. But the moat accurate criterion is the touch; as it may thus be ascertained whether the would be too sandy, or abound with too much clay ; whether it be fatty and slippery ; or harsh, porous, or friable. The most rer-tile, by this test, holds a medium between the two extremes; being -. easily soluble, consisting of equal parts of sand and clay; and not adhering to the spade, after gentle showers.