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stances which unite with the calcareous matter of which it is chiefly 
formed. 
Free-stone, so called from its breaking or working in all direc- 
tions with the same degree of freedom, is a compact lime-stone 
of an earthy fracture, and is often met with in the search for coal. 
When it is of a very considerable degree of thickness, it obtains, in 
many coal countries, the name of post-stone, of which four varieties 
occur, named, according to their colour, white, grey, hrown or yellow, 
and red post. These are sometimes called by the colliers, hands ; 
thus they will say, grey free-stone hands, but the Scotch colliers term 
them grey fekes. 
Whin-stone, Basaltes, and other stones whose hardness is 
such that their angular parts will scratch glass, and whose fracture 
exhibits an appearance so much resembling that which might be ex- 
pected from sand half vitrified, as to have induced many to suspect them 
to be of volcanic origin, also form strata of considerable importance, 
from their hardness and quality, in most coal mines. These are com- 
monly called cockle in Cornwall, and skurdy in the north of Scotland. 
Iron-stone, called also metal stone, and by the Scotch colliers 
dogger hand, is a stratum, which is generally next above the roof of 
the coal. It is very hard, compact, and solid, and of considerable 
weight. Its colours are various shades of brown and grey, and 
sometimes it is nearly black. It evidently consists of argillaceous 
earth, impregnated with iron. Nodules of a richer ore of the same 
metal are frequently contained in it. These are called hall iron- 
stone, cat's-head, and doggers. Masses of pyrites are also fre- 
quently found in this stratum. 
Shale, or slate-clay, called also shiver. Mack metal, and hleas, 
and by the northern colliers Mae or till, often also forms the roof of 
coal mines. It is generally bluish, blackish, or of a reddish grey. 
It is frequently marked with impressions of vegetables. It breaks 
into long thin shivery lamina, and is very friable. It readily re- 
