HONE STONES, &C. 
39 
Hone Slates are slaty stones used in straight pieces for 
sharpening tools after they have been ground on revolving 
.grindstones. The more important varieties are the following : — 
The Norway ragstone , which is the coarsest variety of hone 
slate, is imported in large quantities from Norway. In Charn- 
wood Forest, near Mount Sorrel, in Leicestershire, particularly 
from the Whittle Hill quarry, is obtained the Charley Forest 
stone , said to be one of the best substitutes for the Turkey oilstone, 
and it is much in request by joiners and others. Ayr stone , 
snake stone , and Scotch stone are used especially for polishing 
copper plates. The Welsh oilstone is almost in equal repute 
with the Charley Forest stone ; it is obtained from the vicinity 
of Llyn Idwal, near Snowdon, and hence it is sometimes called 
Idwal stone. From Snowdon is also obtained the cutler’s green 
stone. The Devonshire oilstones , obtained near Tavistock, which 
were introduced by Mr. John Taylor, are of excellent quality, 
but the supply being irregular, they have fallen into disuse. 
The German razor hone , which has been long celebrated, is 
obtained from the neighbourhood of Ratisbon, where it occurs 
as a vein running through blue slate, varying in thickness 
from one to eighteen inches. When quarried it is sawn into 
thin slabs, and these are generally cemented to slices of 
slate which serve as a support.. The Washita and Arkansas 
oil-stones are made from the fine siliceous rock called 'novaculite* 
The Turkey, oilstone is said to surpass in its way every other 
known substance, and it possesses in an eminent degree the pro- 
perty of abrading the hardest steel : it is, at the same time, of 
so compact and close a nature as to resist the pressure necessary 
for sharpening a graver, or any instrument of that description. 
There are black and white varieties of the Turkey oilstone, the 
black being the harder, and it is imported in somewhat larger 
pieces than the white ; they are found in the interior of Asia 
Minor, and brought down to Smyrna for sale. 
Among the examples of mineral substances employed as 
burnishers and here exhibited, will be found a specimen of agate 
(p. 54), and a piece of haematite or red iron ore (p. 75). 
The corundum and emery exhibited in this case are varieties 
of alumina , a mineral which is presented in its purest form in 
the ruby and sapphire. Emery is obtained from the N.E. part of 
the island of Naxos, and from near Ephesus in Asia Minor; 
it occurs also in many localities in the United States. From 
its excessive hardness it is used as an abrasive agent ; and is 
also employed for polishing, for which purpose it is prepared by 
grinding and washing, and the finest is sold under the name 
of flour of emery. Emery is largely used in the arts, principally 
in the convenient form of emery-wheels, emery-cloth, &c, 
In addition to the stones which have been already mentioned, 
there will be found in this case a series from France showing the 
celebrated “ Burr Stones ” of La Ferte-sous-Jouarre (Seine et 
Marne). The combined roughness and hardness of this tertiary 
