NATURAL HISTORY. 
105 
multiplied by 85 (the present number of furnaces 
now in blast in the neighbourhood) will make the 
weekly consumption 13,600 tons; and the latter 
quantity multiplied by 52, will make the enormous 
total of 707,200 tons a year."' 
The proximity of the basaltic hills of Rowley to 
this coal field seems to indicate former convulsions 
and dislocations of the strata ; nor is this mere con- 
jecture, for at the colliery of Mr. Fereday, near 
Dudley Port, where the workings are carried down 
800 feet perpendicularly, a sudden elevation of the 
coal beds takes place to the extent of 400 feet, the 
measures being precisely correspondent with those 
400 feet lower. On the south-eastern side of the 
castle, the coal takes a declining direction, and is 
supposed to lie at a great depth beneath the basaltic 
rocks, which at some distant period, when some 
powerful volcanic eruption disorganized the primitive 
globe, have broken through the strata. The basaltic 
dykes, or faults, as the miners term them, are common 
to most coal fields, and no doubt exists as to their 
igneous origin, as the coal is charred and converted 
into coke wherever it comes in contact with the basalt. 
To the south of Dudley and the Rowley Hills is the 
Clent range,^ commencing at Hagley, and stretching 
southward to the vicinity of Belbroughton. The hills 
belonging to this range are considered by Mr. Yates to 
consist of porphyritic and amygdaloidal trap, more or 
» Booker, pp. 130—131. 
« Walton Hill is the loftiest of the Clent range, rising 792 feet above tlie Stour, 
and 15 feet higher than Clent Hill, the adjacent eminence. 
P 
