78 A PRACTICAL TREATISE 



Fish- Shells. — The shells of fish, when burnt, produce the 

 purest species of lime, but they are more commonly employed 

 in a pounded state, in which they may be so advantag-eously 

 used, that oyster-shells, when crusiied and drilled upon 27-inch 

 ridg-es, at the rate of 40 bushels per acre, produced as fine a 

 crop of turnips as another field of the same land, manured, for 

 the sake of the experiment, at Mr. Coke's, at Holkham, with 

 farm-dung- at the rate of 8 tons per acre ; nor was there any 

 apparent difference in the succeeding crops of barley and clo- 

 ver. The powder has also been tried at the same farm, for 

 wheat, in competition with rape-dust — both powder and dust 

 at the rate of 4 cwt. per acre, each drilled on a light gravelly 

 loam, in both spring and autumn. The crop was not, in either 

 case, measured, but there was no perceptible difference in 

 either. The field was afterwards sown with turnips, and the 

 produce proved a good crop. Yet, notwithstanding the result 

 of these experiments, no fair conclusion- can be drawn from 

 them regarding their respective effects, as manure, in that 

 sense in which it is understood to mean nutriment; for, 

 although lime may excite the powers of other nutritive matter 

 in the soil, and thus promote vegetation, it possesses no sub- 

 stance, within it-self, which can impart nourishment. 



In some places these shells are found in large beds almost 

 entire, and they may be then either ground by passing them 

 through the oil-cake crusher, or broken into pieces by repeatedly 

 drawing a heavy stone or iron roller over them when spread 

 upon a floor of flags or clinkers. There is, however, a more 

 economical mode of attaining the same object, which is by 

 merely making them the lower tier of a dung-hill, or by 

 spreading them at the bottom of the farm-yard, in which the 

 drainage of the urine will decompose them, and in that state 

 the manure will possess all the advantage of a compost with 

 lime. They may also be used whole on stiff land or clay, on 

 which they act mechanically, opening and loosening the clods, 

 and by that means making way for the roots to penetrate their 

 fibres. To such land they will be found very serviceable, and 

 as they moulder gradually, every year a little, until they are 

 quite spent, they wear down slowly, and their effects, when 

 laid on in sufficient quantity, are long perceptible; but they 

 sliould not be applied to sandy ground. 



On many parts of our coast, shell-sand also forms a valuable 

 species of manure, for the shells which are deposited at the 

 bottom of the sea become there in time decomposed, and the 



