The number of blast furnaces in the parish of Merthyr-Tydvil amounts to upwards of 30. The cast iron produced is, however, seldom brought into the market, but is almost entirely converted into bar iron, of which, at Mr. Crawshay’s works, 600 tons are manufactured in a week. Numerous iron railways, extending through a length of 220 miles, facilitate the transport of the materials and the exportation of the products. That concurrence of favourable circumstances, which we have noticed as occurring at Dudley, prevails in an equal degree in South Wales.
The same economy which the use of coal has introduced into the smelting of cast iron from the ore, also extends to its refinery into bars. And this process would supersede in every iron work the use of wood charcoal, were not the iron produced by the latter combustible, better for many purposes, particularly the manufacture of steel. In some English smelting works, indeed, where sheet iron is prepared for making tin plate, a mixed refining process is employed, where the cast iron is made into bar iron by wood charcoal, and laminated by the aid of a coal fire.
Till 1740, the smelting of iron ores in England was executed entirely with wood charcoal; and the ores employed were principally brown and red hematites. Earthy iron ores were also smelted; but it does not appear that the clay iron-stones of the coal-basins were then used, though they constitute almost the sole smelting material at the present day. At that era, there were 59 blast furnaces, whose annual product was 17,350 tons of cast iron; that is, for each furnace, 294 tons per annum, and 51⁄8 tons per week. By the year 1788, several attempts had been made to reduce iron ore with coaked coal; and there remained only 24 charcoal blast furnaces, which produced altogether 13,000 tons of cast iron in the year; being at the rate of 546 tons for each per annum, or nearly 11 tons per week. This remarkable increase of 11 tons for 51⁄8, was due chiefly to the substitution of cylinder blowing machines worked with pistons, for the common wooden bellows. Already 53 blast furnaces fired with coke were in activity; which furnished in toto 48,800 tons of iron in a year; which raises the annual product of each furnace to 907 tons, and the weekly product to about 171⁄2 tons. The quantity of cast iron produced that year (1788)
| by means of coal, was | 48,800 | tons, |
| and that by wood charcoal, was | 13,100 | |
| constituting a total quantity of | 61,900 | tons. |
In 1796, the wood charcoal process was almost entirely given up; when the returns of the iron trade made by desire of Mr. Pitt, for establishing taxes on the manufacture, afforded the following results:—
121 blast furnaces, furnishing in whole per annum 124,879 tons, constituting an average amount for each furnace of 1032 tons.
In 1802, Great Britain possessed 168 blast furnaces, yielding a product of about 170,000 tons; and this product amounted, in 1806, to 250,000 tons, derived from 227 coke furnaces, of which only 159 were in activity at once. These blast furnaces were distributed as follows:—
| In the principality of Wales | 52 |
| In Staffordshire | 42 |
| In Shropshire | 42 |
| In Derbyshire | 17 |
| In Yorkshire | 28 |
| In the counties of Gloucester, Monmouth, Leicester, Lancaster, Cumberland, and Northumberland | 18 |
| In Scotland | 28 |
| 227 |
In 1820, the iron trade had risen to the amount shewn in the following table:—
| Tons. | |
|---|---|
| Wales manufactured, per annum | 150,000 |
| Shropshire and Staffordshire | 180,000 |
| Yorkshire and Derbyshire | 50,000 |
| Scotland, with some places in England | 20,000 |
| Total | 400,000 |