Rags, hair, etc., thus treated, will in a short time be reduced to such a condition that they may be immediately used by plants instead of lying in the soil to be slowly taken up. It is better in all cases to have manures act _quickly_ and give an immediate return for their cost, than to lie for a long time in the soil before their influence is felt. [What is their value compared with that of farm-yard manure? How should old leather be treated? Describe the manurial properties of tanners' refuse. How should they be treated? Are horn piths, etc. valuable?] A pound of woollen rags is worth, as a manure, twice as much as is paid for good linen shreds for paper making; still, while the latter are always preserved, the former are thrown away, although considered by good judges to be worth forty times as much as barn-yard manure. Old leather should not be thrown away. It decomposes very slowly, and consequently is of but a little value; but, if put at the roots of young trees, it will in time produce appreciable effects. _Tanners' and curriers' refuse_, and all other animal offal, including that of the slaughter-house, is well worth attention, as it contains more or less of those two most important ingredients of manures, nitrogen and phosphate of lime. It is unnecessary to add that, in common with all other animal manures, these substances must be either composted, or immediately plowed under the soil. Horn piths, and horn shavings, if decomposed in compost, with substances which ferment rapidly, make very good manure, and are worth fully the price charged for them. ORGANIC MANURES OF VEGETABLE ORIGIN. _Muck_, the most important of the purely vegetable manures, has been already sufficiently described. It should be particularly borne in mind that, when first taken from the swamp it is often _sour_, or _cold_, but that if exposed for a long time to the air, or if well treated with lime, unleached ashes, the lime and salt mixture, or any other alkali, its acids will be _neutralized_ (or overcome), and it becomes a good application to any soil, except peat or other soils already containing large quantities of organic matter. In applying muck to the soil (as has been before stated), it should be made a vehicle for carrying ammoniacal manures. SPENT TAN BARK. [Why is decomposed bark more fertilizing than that of decayed wood?] _Spent tan bark_, if previously decomposed by the use of the lime and salt mixture, or potash, answers all the purposes of prepared muck, but is more difficult of decomposition. [How may bark be decomposed? Why should tan bark be composted with an alkali? Why is it good for mulching? Is sawdust of any value?]