in the Counties of Monmouth, Glamorgan, &c. 345 
earth, without going to the expence and labour of sinking 
deep pits, and erecting powerful fire-engines. However, 
in process of time, in situations where the coal and iron ore 
that are above the level of these natural drains, become ex- 
hausted, it will be found necessary to sink shallow pits, and 
erect fire-engines for the draining and working of the coal 
and iron ore, and at a future period, pits of greater depths, 
must be sunk for the same purposes. 
10. There are 12 veins or strata of coal in this mineral 
depository, from 3 feet to 9 feet thick each ; which together 
make 70^ feet: and there are 11 more, from 18 inches to 3 
feet, which make 24^ feet, making in all 95 feet ; besides a 
number of smaller veins from 12 to 18 inches, and from 6 to 
12 inches in thickness, not calculated upon. 
11. By taking the average length and breadth of the fore- 
going different strata of coal, the amount is about 1000 square 
miles, containing 95 feet of coal in 23 distinct strata, which 
will produce in the common way of working 100,000 tons 
per acre, or 64,000,000 tons per square mile. 
12. If the whole extent of this mineral country was an 
even plain, the border or outbreak of each stratum would 
appear regular and true ; but owing to the interposition of 
hills and valleys, the edges of the strata, if nicely measured 
and planned, would seem indented and uneven, yet in many 
instances the due range is totally thrown out of course, 
in consequence of knots, dikes, or faults; 
13. These faults or irregularities are not confined to the 
edges of the strata, but they take grand ranges, through the 
interior of the bason, generally i ~ a north ana south direction, 
and often throw the whole of the strata, for hundreds of acres 
Yy 2 
