ON MANURES. I59 



divested by the process of boiling-, not only of every particle 

 of flesh, but also of a material portion of oil which is also ex- 

 tracted ; and it is only in that state that they can be brought 

 to the condition of fine powder. In this state it is only rea- 

 sonable to suppose that they cannot be so beneficial to the land 

 as when fresh and unboiled; yet we find, by the report of the 

 Doncaster Association "on bone manure," — to which we shall 

 presently refer, — that they have been found more effectual 

 after having- passed through the manufactories. When not 

 ground completely into powder; they are, however, broken in 

 the machines, by cast-iron rollers, formed with deeply indented 

 rims, by which they are first partially bruised, and then falling- 

 down upon other sets of rollers, each with the teeth more 

 closely fixed, they are in this manner reduced to various sizes, 

 from one inch to half an inch in thickness, and a considerable 

 quantity of coarse dust is also procured by the process. These 

 bones are usually sold under the respective designations of 

 inch, three-quarters inch, half-inch, or dust; but the greatest 

 demand is for those of the half-inch size, which contain all the 

 dust which has been formed in crushing them. The "dust" 

 is collected in great measure by riddling the inch and three- 

 quarter inch bones. 



When the bones are not boiled, each pair of rollers is fur- 

 nished with a set of malleable iron scrapers attached below, 

 in order to clear the teeth of any animal matter which may 

 adhere to them, and thus the oily substance contained in the 

 bones is saved. As bone mills have been now very generally 

 erected, there are few parts of the country where the manure 

 cannot be procured in a prepared state; but when the bones 

 are only to be had raw, and it is an object with the farmer to 

 reduce them to a small size, they can be easily broken to 

 pieces by his own labourers. [The value of bones being so 

 generally admitted, we cut out a number of experiments which 

 only tended to make assurance doubly sure.] 

 , Effects of Bone-Dust and Bones. — Bone-dust is the fittest 

 state in which to lay it upon grass, for it will not only take 

 more immediate effect upon the crop, but if laid in pieces, it 

 would interrupt the progress of the scythe. It should, how- 

 ever, be recollected, that fine powder can only be obtained 

 from spent bone which has undergone the process of manufac- 

 ture. It is therefore spread, as a top-dressing, by hand ; but it 

 is also very commonly laid in the drills for turnips, tor which 

 purpose many ingenious machines have been contrived for 



