When kept in the yard, they are still liable to be lost by evaporation. They are here often saturated with water, and this water in its evaporation carries away the ammonia, and carbonic acid which it has obtained from the rotting mass. The evaporation of the water is rapidly carried on, on account of the great extent of surface. The whole mass is spongy, and soaks the liquids up from below (through hollow straws, etc.), to be evaporated at the surface on the same principle as causes the wick of a lamp to draw up the oil to supply fuel for the flame. LIQUID MANURE containing large quantities of nitrogen, and forming much ammonia, is also liable to lose all of its organic part from evaporation (and fermentation), so that it is rendered as much less valuable as is the solid dung.[X] [When does the waste of exposed manure commence? What does economy of manure require? What is the effect of leaching? Give an illustration of leaching.] From these remarks, it may be justly inferred that a very large portion of the _value_ of solid and liquid manure as ordinarily kept is lost by evaporation in a sufficient length of time, depending on circumstances, whether it be three months or several years. The wasting commences as soon as the manure is dropped, and continues, except in very cold weather, until the destruction is complete. Hence we see that true economy requires that the manures of the stable, stye, and poultry-house, should be protected from evaporation (as will be hereafter described), as soon as possible after they are made. LEACHING. The subject of _leaching_ is as important in considering the _inorganic_ parts of manures as evaporation is to the organic, while leaching also affects the organic gases, they being absorbed by water in a great degree. A good illustration of leaching is found in the manufacture of potash. When water is poured over wood-ashes, it dissolves their potash which it carries through in solution, making ley. If ley is boiled to dryness, it leaves the potash in a solid form, proving that this substance had been dissolved by the water and removed from the insoluble parts of the ashes. [How does water affect decomposing manures? Does continued decomposition continue to prepare material to be leached away? How far from the surface of the soil may organic constituents be carried by water?]