In dissolving the salt, it is well to hang it in a basket in the upper part of the water, as the salt water will immediately settle towards the bottom (being heavier), and allow the freshest water to be nearest to the salt. In this way, the salt may be all dissolved, and thus make the brine used to slake the lime. It may be necessary to apply the brine at intervals of a day or two, and to stir the mass often, as the amount of water is too great to be readily absorbed. This mixture should be made under cover, as, if exposed, it would obtain moisture from rain or dew, which would prevent the use of all the brine. Another objection to its exposure to the weather is its great liability to be washed away by rains. It should be at least ten days old before being used, and would probably be improved by an age of three or four months, as the chemical changes it undergoes will require some time to be completed. [Explain the character of this mixture as represented in the diagram. (Black board.)] The character of this mixture may be best described by the following diagram:-- We have originally-- +----------------------------------+ | | Lime-+ Salt | consisting of | +---Chlorine } Chloride | | and } of | | +-Sodium. } Sodium. | | | --Carbonic acid | | | and | | | --Oxygen in the air. +-Chloride of lime.-+ | +-Carbonate of Soda. [Y] The lime unites with the chlorine of the salt and forms _chloride of lime_. The sodium, after being freed from the chlorine, unites with the oxygen of the air and forms soda, which, combining with the carbonic acid of the atmosphere, forms carbonate of soda. Chloride of lime and carbonate of soda are better agents in the decomposition of muck than pure salt and lime; and, as these compounds are the result of the mixture, much benefit ensues from the operation. When _shell_ lime cannot be obtained, Thomaston, or any other very pure lime, will answer, though care must be taken that it do not contain much magnesia. LIME. [What effect has lime on muck? On what does the energy of this effect depend? Why should a compost of muck and lime be protected from rain?] Muck may be decomposed by the aid of other materials. _Lime_ is very efficient, though not as much so as when combined with salt. The action of lime, when applied to the muck, depends very much on its condition. Air-slaked lime (carbonate of lime), and hydrate of lime, slaked with water, have but a limited effect compared with lime freshly burned and applied in a caustic (or pure) form. When so used, however, the compost should not be exposed to rains, as this would have a tendency to make _mortar_ which would harden it. POTASH.