A HISTORY OF NOTTINGHAMSHIRE 



and the openings for clay near Wollaton and for stone on Trowell Moor; 

 though some of these are now poor. The alternations of sandstone and 

 shale give rise, by their different ways of weathering, to very undulating 

 country, usually well clothed with vegetation. The fresh exposures of 

 the harder rocks are of peculiar art 'shades with a predominant neutral 



tint. 



The Nottinghamshire coals burn to an ash and have a composition 

 exemplified by one from Shireoaks, analyzed by C. Tookey :' 



Carbon 77'4 



Hydrogen 4'9& 



Oxygen and Nitrogen 9^32 



Sulphur 0-92 



Ash 3-90 



Water and loss 3'5o 



lOO'OO 



Some varieties called ' splint ' coal show a very bright ' face ' when split, 

 and, in others, extra bright bands may be seen standing out from the parts 

 which consists of loose dust. The bright bands are cross sections of the 

 broken tree stems of Sigillaria, etc., the surface markings of which are 

 sometimes seen when the fracture lies in a suitable direction. The 

 loose dust, often called ' mother-of-coal,' if carefully handled and suit- 

 ably examined under the microscope, is seen to consist of the disc-bearing 

 cells of some kind of gymnospermous tree, probably of Cordaites. 



In Clifton Colliery a bed of ' Cannel ' coal is found between the 

 ' Waterloo ' and ' Deep Soft ' seams. This kind of coal has no definite 

 structure in it and is supposed to be the result of the decomposition of 

 the material of ordinary coal, and its deposition as a water-borne sedi- 

 ment. It contains, instead of plant stems, the spines, scales, vertebras 

 and teeth of ganoid fishes referred to the genera Ctenacantbus, Gyracan- 

 thus and Megalichthys. It is also more gaseous than ordinary coal, as its 

 name implies. 



Clunch and gannister are materials which form the bed next below 

 any coal seam. In the case of all the coal seams of Nottinghamshire, as 

 far as known, it is clunch that is found. This is a kind of kneaded up 

 clay, without internal stratification, and often showing the remains of 

 the roots of the plants which have made the overlying coal. It is also 

 called ' underclay ' and ' seat-earth.' The clunch is often valuable as a 

 fireclay, but is little worked in Nottinghamshire, less than 9,000 tons of 

 it being raised in 1901, against nearly 68,000 tons from Derbyshire. 

 Gannister is a hard siliceous band found in the same position beneath 

 certain coals with which marine remains are associated, but it has not 

 been definitely recognized in Nottinghamshire. 



The largest of the roots found associated with the underclay is the 

 Stigmaria. This usually stands upright and has a diameter of 1 8 inches 

 and upwards. In a downward direction it branches into four parts, each 



1 Percy, Metallurgy, vol. i. 

 4 



