HONE SLATES. - A mineralogical distinction for various slaty stones that are used in straight pieces or slabs for whetting or sharpening the edges of tools subsequently to their having been ground on revolving grindstones. The following quotations are from Mr. Knight's paper in the Trans. of the Society of Arts, vol. 50, page 233.

1. - "Norway Ragstone. - This is the coarsest variety of the hone slates. It is imported in very considerable quantities from Norway in the form of square prisms, from nine to twelve inches long, and one to two inches diameter, gives a finer edge than the sandstones, and is in very general use."

2. - "Charnley Forest Stone is one of the best substitutes for the Turkey oilstone, and much in request by joiners and others, for giving a fine edge to various tools and also penknives. It has hitherto been found only on Charnwood Forest, near Mount Sorrel, in Leicestershire." The best Charnley Forest Stone, is by some considered to come only from the Whittle Hill Quarry, the other stones from the neighbourhood are more pinny, or present hard places.

3. - "Ayr-stone, Scotch-stone, or Snake-stone, is most in request as a polishing stone for marble and copper-plates; but the harder varieties have of late been employed as whetstones." These stones should always be kept damp or even wet, to prevent their becoming hard.

4. - "Idwall or Welsh Oil-stone is generally harder, but in other respects differs but little as a whetstone from the Charnley Forest. It is obtained from the vicinity of Llyn Idwall, in the Snowdon district of North Wales," and is now in more general use for small articles of cutlery than the Charnley Forest Stone.

5 - "Devonshire Oil-stone is an excellent variety for sharpening all kinds of thin edged broad instruments, as plane-irons, chisels, etc, and deserves to be better known. This stone was first brought into notice by Mr John Taylor, who met with it in the neighbourhood of Tavistock, and sent a small parcel to London for distribution; but for want of a constant and regular supply, it is entirely out of use here."

6. - "Cutlers' Green Hone is of so hard and close a nature, that it is only applicable to the purposes of cutlers and instrument makers, for giving the last edge to the lancet and other delicate surgical instruments. It has hitherto been only found in the Snowdon mountains of North Wales."

7. - " German Razor Hone. - This is universally known throughout Europe, and generally esteemed as the best whetstone for all kinds of the finer descriptions of cutlery. It is obtained from the slate mountains in the neighbourhood of Ratisbon, where it occurs in the form of a yellow vein running virtually into the blue slate, sometimes not more than an inch in thickness, and varying to twelve and sometimes eighteen inches, from whence it is quarried, and then sawed into thin slabs, which are usually cemented into a similar slab of the slate to serve as a support, and in that state sold for use. That which is obtained from the lowest part of the vein is esteemed the best and termed old rock." The German Hone is now used almost exclusively for razors, as being very soft, it is cut by any instrument applied at an angle, and not laid fiat down as a razor invariably is.

8. - " Blue Polishing Stone is a dark slate of very uniform character; in appearance not at all laminated; is in considerable use among jewellers, clock-makers, and other workers in silver and metal, for polishing off their work, and for whose greater convenience it is cut into lengths of about six inches, and from a quarter of an inch to an inch or more wide, and packed up in small bundles of from six to sixteen in each, and secured by means of withes of osier, and in that state imported for use."

9. - "Grey Polishing Stone is a stone of very similar properties to the blue, but of a somewhat coarser texture and paler colours. Its uses are the same and both kinds are manufactured near Ratisbon."

10. - " Welsh Clearing-stone is a soft variety of hone-slate, the use of which is confined to curriers, and by them employed to give a fine smooth edge to their broad and straight-edged knives for dressing leather. They are always cut of a circular form."

11. - Peruvian Hone has been recently introduced as a whetstone, and is said to be imported from South America. It cuts freely with either oil or water, and is suitable for sharpening large tools that do not require a very fine edge.

12. - Welsh Hone. See article 4.

13. - Oilstone White and Black. These are varieties of the Turkey-stone. See Oilstone.

14. - Arkansas Stone, from N. America is of unequal texture and cuts slowly.

15. - Bohemian Stones are imported from Germany, and are used by jewellers in the same manner as the blue and grey polishing stones for polishing small works, such as the settings around gems. The Bohemian stones cut well, and keep a good point for small work.