liament was passed in 1769 for discontinuing, upon the exportation of iron in foreign ships, the drawbacks of such parts of the duties payable thereon as exceeded the duties payable upon iron imported in British ships. In this year the importation of iron from Russia alone amounted to upwards of 34,000 tons. To such an extent, through the fostering care first given by Peter the Great, had the iron mines arrived in Russia, that they materially injured the sale of the Swedish iron, from whence, much less than a century before, they used to import considerable quantities into Russia. Such are the effects to be produced when governments wisely patronise national objects of improvement and industry.

The American war breaking out in 1775, a formidable rival, as then considered, to our iron trade was removed, and soon after the close of that war the increase of our trade, and the extension of our manufactures, created an additional consumption of iron in the country; and although we had powerful competitors in Russia and Sweden, yet our furnaces, with the agency of the steam-engine, were producing an annual increase, by manufacturing iron with pit-coal instead of charcoal.

CHAP. V.

GREAT BRITAIN.

BEFORE we proceed to detail the vast results in the iron trade, consequent upon the use of pit-coal, aided by the powerful assistance of the steam-engine, it will be desirable to take a retrospective view of the means hitherto employed for blowing the furnaces.

The machine first employed for this purpose was a pair of leather bellows, worked by the hand; but when it became necessary to smelt iron in large quantities, the size and number of the bellows were increased. Two pairs of bellows were so connected, by means of a lever, that the one pair shut when the other opened. The handle of each pair was successively moved by two cogs, placed at right angles to each other on the horizontal axis of a water-wheel, so that, during the revolution of the wheel, one of the cogs shut one pair of bellows, and forced the included air into the furnace, while the other, which at this instant opened, was shut by the action of the other cog, and thus discharged its contents into the furnace. By this means a continued blast was kept up, excepting a trifling pause when the motion was changed.

Another engine, called the water blowing machine, has been used for producing a strong blast. It has been pretty generally adopted on the Continent, but does not seem to have come into use in this country. A current of water is made to pass through a kind of cullender, placed in the open air, and perforated with a number of triangular holes. The water descends through these apertures in many small streams, and by exposing a great surface to the atmosphere, it drags along with it an immense quantity of air, and is conveyed

through a tube till it dashes against a stone pedestal inclosed in a large vessel. The mixture of air and water which falls upon the pedestal is dispersed in every direction - the air is separated from the water—it ascends to the upper part of the vessel, and rushes through a pipe to the furnace, while the water descends through apertures at the bottom of the vessel.* It is proper to observe, however, that, as by this method the air was loaded with moisture, it was necessary to make the condensing vessel as high as conveniently could be, that the air might arrive at the furnace in as dry a state as possible.

Machines of such a description might have been sufficient for smelting iron, when charcoal was used for fuel; when, from the small quantity of air that was then requisite for blast, whether from the great inflammability of the fuel, or the smallness of its capacity, the manufacturer had more frequently felt the effects of over-blowing than under-blowing his furnace; but now, when coal began to be used, it became necessary to construct machines formed of the most durable materials, and capable of affording a powerful and constant blast.

The earliest contrivance of this kind was a forcing pump, worked by a water-wheel or a steam-engine; and it would appear that the first cylinders - at least, of any magnitude were erected at the celebrated Carron Iron Works, in the year 1760, by Mr. John Smeaton, soon after these works (which, in a few years, became amongst the most famous in Europe †) had been established by the projector, Dr. Roebuck, and other parties.

* Franciscus Tertius de Lanis ("Magister Nat. et Artis," lib. 5. cap. iii.) observes, that he has seen a greater wind generated by a machine of this kind than could be produced by bellows ten or twelve feet long.

†The Carron Works consist of five blast furnaces, sixteen air furnaces, a clay mill for grinding clay and making fire bricks for the use of the said furnaces, an engine that raises four tons and a half of water at one stroke, and, on an average, draws seven strokes in a minute. This engine goes in time of drought, and consumes sixteen tons of coal in twenty-four hours. Besides the coals consumed by this engine, there are 120 tons burnt every day in the works, and by the inhabitants belonging to them. Besides the air furnaces there are three cupola furnaces, that go by virtue of the blast furnaces, by pipes conveyed from the machinery of the blasts: their business is much the same with the air furnaces. There are also four boring mills for boring

According to the custom of the times, the operation of blowing was at first performed by large bellows, moved by means of a water-wheel. Pit-coal was the stable fuel in use, it having been very generally applied, since the year 1750, as a substitute for charcoal in the blast furnace, but the scanty supply of air, and its want of density, seldom permitted the produce of the furnace to exceed ten or twelve tons weekly; and frequently, in summer, the quantity was reduced even below this. The Carron Company collected immense quantities of charcoal, and they found that their blast was much better calculated for the operation of smelting with it, than with the uninflammable pit-coal obtained in their neighbourhood. Experience, however, gradually unfolded means of adapting machinery better calculated to the nature of the coal fuel; more powerful wheels were constructed, the bellows were abandoned, and, in their place, large iron cylinders were introduced.

These cylinders were four feet six inches diameter, exactly fitted with a piston, moved up and down by means of a waterwheel. In the bottom of the cylinder is a large valve, like that of a bellows, which rises as the piston is lifted up, and

guns, pipes, cylinders, &c. One of the boring mills is adapted for turning the guns on the outside--they have likewise smiths' forges, for making the largest anchors and anvils, as well as small work of various kinds; besides a forge for making malleable iron, and a plating forge, also a forge for stamping iron, the hammer of which, with the helve, are both of cast metal, and weigh a ton and a half.-Sir J. Sinclair's Statistical Account of Scotland, 1792.

Nobody is admitted to view the works on Sundays, except those who are properly recommended, or known to be worthy of attention. Mr. Burns, the Ayrshire poet, not knowing, or not attending to, this regulation, made an attempt to be admitted, without discovering who he was, but was refused by the porter. Upon returning to the inn at Carron, he wrote the following lines upon a pane of glass, in a window of the parlour into which he was shown:

thus admits the air into the cavity of the cylinder below. Immediately above the bottom is a tube which goes to the furnace, and as it proceeds from the cylinder, is furnished with a valve opening outwards. Thus, when the piston is drawn up, the valve in the bottom rises, and admits the air that way into the cylinder, while the lateral valve shuts, and prevents any air from getting into it through the pipe. When the piston is thrust down, the valve in the bottom shuts, while the air being compressed in the cavity of the cylinder, is violently forced out through the lateral tube into the furnace.

There were four of these large cylinders applied to blow the furnace, and so contrived that the strokes of the pistons, being made alternately, produced an almost uninterrupted blast. The pumps being worked alternately by a water-wheel having four cranks upon its axis, each of which moved the piston of a cylinder, which had a stroke of four feet six inches, some little intermission could indeed be perceived, but it was too trifling to produce any sensible effect on the furnace. Even this could have been prevented by means of a large reservoir, into which all the four cylinders might discharge their blast.*

*The situation and singular construction of the Devon Iron Works, begun in July, 1792, merit the attention of the curious in mechanics and architecture. A steep bank rises more than fifty feet above the level of the river, and is composed of a rock, or very thick stratum of freestone, very dry, and uniform in its texture, and almost free from cracks and fissures. Instead of the usual method of building with stone and lime, the several parts of the works have been formed in this bank by excavations made in the rock. Two furnaces, which are each above forty feet high and fourteen feet diameter, and also the spacious arches which give access to the workmen, at the bottom of the furnace, to draw off the liquid metal and slag, are cut out of the rock. The roof which covers the casting-house, a room seventy feet long, fifty feet wide, and twenty-three feet high, is supported by the sides of the quarry and the solid pillars of the rock, that were left for this purpose in making the excavation. In like manner is formed the engine-house and its apparatus, which is intended to supply the two furnaces with wind, by throwing, at each vibration of the engine, a sufficient quantity of air out of a large cylinder into a long gallery, or close mine, formed in the rock. This magazine of wind will contain above 10,000 cubic feet of air, much condensed by the power of the engine, as the gallery is very closely shut up, and made air-tight, having only two apertures,