IX. 
Penistone, to 1,859 feet ; and at Bradfield Point, N. W. of Sheffield, to 
1,246 feet. From this high ridge the whole coal district slopes to the 
eastward, and finally loses itself beneath the low terrace of magnesian 
limestone, which margins the southern part of the great central vale of 
Yorkshire. From this Tract, the Aire, Calder, and Dun receive their 
principal branches, and almost all these numerous streams run in valleys 
originally of great beauty and interest, and not wholly deprived of their 
charms by the wonderful extension of manufacturing industry and 
machinery from Leeds, Wakefield, Bradford, Halifax, Huddersfield, and 
Sheffield. 
Internal Structure. — The component strata of the coal tract are 
sandstone, (some of the lowest beds on the northern and western border 
correspond to the. millstone grit noticed in the preceding pages,) argil- 
laceous shales, often full of fossil plants, ironstone, and beds of coal. 
There is no limestone more than a few inches thick in the whole district ; 
the soil is generally argillaceous, in places a mere sand. 
Aspect of Vegetation. — This is still the woody district of York- 
shire, though in all the valleys the ironworks of former days and the 
thousand uses for timber generated by the industry of the present age, 
have swept away whole forests of oak. Within the memory of man, 
great destruction of this nature occurred at and near Sheffield, and yet 
at this moment within a small circle of that theatre of fire, are many of 
the grandest woods in the north of England. These chiefly occupy and 
often fill the valleys, but the highest summits are generally covered with 
heath and peat. 
DISTRIBUTION OF PARTICULAR PLANTS. 
The following plants, found in this district, have not been noticed 
in other parts of Yorkshire. 
Cotyledon umbilicus, Circaea alpina. 
Of these. Cotyledon umbilicus is supposed to attain its northern 
limit in Yorkshire. 
Hebden Valley, a branch from the great vale of the Calder near 
Halifax, is one of the most productive parts of this district for the 
Botanist. 
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