Bones may be made fine enough for this operation, either by grinding, etc., or by boiling under pressure, as previously described; indeed, by whatever method bones are pulverized, they should always be treated with sulphuric acid before being applied to the soil, as this will more than double their value for immediate use. Bone-black is chiefly used by manufacturers of super-phosphate of lime, who treat it with acid the same as has been directed above, only that they grind the black very finely before applying the acid. [What other forms of bones may be used in making super-phosphate of lime? Why is super-phosphate of lime a better fertilizer than phosphate of lime? What can you say of the _lasting manures_?] _Bone ashes_, or bones burned to whiteness, may be similarly treated. Indeed, in all of the forms of bones here described, the phosphate of lime remains unaltered, as it is indestructible by heat; the differences of composition are only in the admixture of organic constituents. _The reason why super-phosphate of lime is so much better than phosphate_, may be easily explained. The _phosphate_ is very _slowly_ soluble in water, and consequently furnishes food to plants slowly. A piece of bone as large as a pea may lie in the soil for years without being all consumed; consequently, it will be years before its value is returned, and it pays no interest on its cost while lying there. The _super-phosphate_ dissolves very _rapidly_ and furnishes food for plants with equal facility; hence its much greater value as a manure. It is true that the _phosphate_ is the most _lasting_ manure; but, once for all, let us caution farmers against considering this a virtue in mineral manures, or in organic manures either, when used on soils containing the proper absorbents of ammonia. They are _lasting_, only in proportion as they are _lazy_. Manures are worthless unless they are in condition to be immediately used. The farmer who wishes his manures to _last_ in the soil, and to lose their use, may be justly compared with the _miser_, who buries his gold and silver in the ground for the satisfaction of knowing that he owns it. It is an old and a true saying that "a nimble sixpence is better than a slow shilling." IMPROVED SUPER-PHOSPHATE OF LIME. [What are the ingredients of the _improved_ super-phosphate of lime?] To show the manner in which super-phosphate of lime is perfected, and rendered the best manure for general uses, which has yet been made, containing large quantities of phosphoric acid and a good supply of ammonia,--hereby covering the two leading deficiencies in a majority of soils, it may be well to explain the composition of the _improved super-phosphate of lime_ invented by Prof. Mapes. This manure consists of the following ingredients in the proportions named:-- 100 lbs. bone-black (phosphate of lime and carbon). 56 " sulphuric acid. 36 " guano. 20 " sulphate of ammonia.