Murchisons Silurian System. 231 



guarantee for its absolute necessity in all researches under- 

 taken for the discovery, and ultimate working of new coal 

 beds. 



Of the Brown Clee Hill coal field, Mr. Murchison ob- 

 serves, these carboniferous tracts, the loftiest in Great Bri- 

 tain, are surrounded on all sides, and separated from each 

 other by the old red sandstone ; and as it rises to a consi- 

 derable height above the flanks of these hills, the thick- 

 ness of the overlying coal measures can at once be read 

 off by any geologist. Their dimensions are further proved 

 by numerous works which penetrate them, and in conse- 

 quence of the old red sandstone dipping inwards from the 

 sides of each of the hills, the coal is seen to lie in broken 

 basins of shallow depth. 



In some parts of the field there are three beds of coal, 

 " the uppermost being about two feet, and the second, called 

 batty coal, about three feet thick, and the third, or single 

 coal, about two feet and six inches in thickness. 



The two upper coals, usually pyritous and of a very infe- 

 rior quality, are separated from each other by only about 

 nine feet of clod shale. The batty coal indeed is frequent- 

 ly near the surface, the uppermost bed being often wanting. 

 The only seam worth extracting is the single or bottom 

 coal, which lies in some places twelve feet beneath the batty 

 coal; but this depth varies in different parts of the hill. 

 The intervening strata consist of clod and shale, known by 

 the workmen as petticoat measures, horse-flesh measures, 

 &c. and of one band of sandstone, about nine feet thick, 

 called level rock. Muck of this coal, particularly that of the 

 upper beds, is in a half-consolidated state, the vegetable 

 fibres appearing prominently in the mass, and giving to it 

 the appearance of charcoal. Coals of similar character are 

 much less frequent in the Titterstone Clee field, where 

 they are termed mother, but they often occur in the poor 

 and thin coal tracts of Shropshire. Now the variety of 

 coal described in italics has been found to characterise the 



