169 



In the foregoing table are several terms, which, being provincial 

 expressions, may not be generally comprehended. They will, how- 

 ever, be understood, probably, sufficiently well for the present in- 

 tention : it, however, may not be amiss to observe that clunch, in 

 that part of the country to which the above table refers, represents 

 the firm blue clay of Wallerius (argilla plastica particulis subtiliori- 

 bus), which is generally used for tiles: and in Cambridgeshire the 

 same term is employed to describe a white hard clay, containing 



sand and small stones. *. 



/ 



The line formed by the bearing, or laying of one stratum upon 

 another, is termed THE PARTING, and according to the facility of 

 separation it is named a good parting or a bad parting. Sometimes 

 the two strata are so closely conjoined as to render their separation 

 very difficult, this is termed a bad parting. On the other hand, a 

 thin dusky laminated matter is sometimes interposed between the 

 two masses, whereby a good parting is formed. 



Besides these partings of one stratum of coal from another, each 

 stratum will be found disposed to part, at numerous secondary di- 

 visions er partings, which run parallel to the former, but are neces- 

 sarily not so visible nor so strong. Other divisions or lines of 

 separation occur, which cross the former horizontal ones in nearly 

 a perpendicular direction ; these are called BACKS. These are crossed 

 too by others, at right angles, also in a direction approaching to 

 perpendicular: these are called CUTTERS. The facility of separa- 

 tion at these lesser lines of partings will often be found to be pro- 

 moted by a film of pyritous, earthy, and even stony matter having 

 formed the substance which is interposed at these partings. 



In the parting between the superior part of the mass of coal, 

 and the impending stratum or roof of the mine, very considerable 

 differences occur. Sometimes the parting is very difficult and bad, 

 from the closeness of their union. At other times the head of the 

 mass is sprinkled with a powder like soot, or powdered charcoal 



VOL. i. z 



