"Third. The gas for heating the stoves is supplied from gas-producers, similar to those commonly used by Mr. Siemens for his regenerating furnaces, and which have already been described before this Association. They consist of a simple brick en closure or fireplace, with bars near the bottom, for the admission of a very small quan tity of air. The gas is formed by slow combustion of a very thick fire, supplied with poor coal, or slack, down a slope, or hopper, the gas passing off from above the'fuel through pipes to the hot-blast stoves. Gas may, however, be taken from the top of the blast-furnace for heating the stoves, provided proper arrangements are made to separate it from the dust which comes over from the blast-furnace with it; and, judging from recent practical experiments, it is certain that there are several ways in which this may be done with perfect success.
"The late James Beaumont Neilson, who did so very much for the iron manufacture by his original invention of the hot-blast in 1829, was sufficiently long-sighted to predict the advantages that would flow from the use of blast of a very high temperature, though, as it happened, he was limited to what could be obtained from passing the air through iron pipes exposed to a fire, as in common stoves.
"Mr. Neilson said, 'In the new regenerator ovens that had just been described, the great capacity of fire-brick for heat had been well taken advantage of, and a very im portant step in advance had been by giving the means of raising the temperature of blast much above the extreme limit practicable with the old ovens; and he considered this would be productive of the greatest benefit in the working of blast-furnaces. lie had no doubt the make of iron would be considerably increased by the higher temper ature of blast given by the regenerator ovens.' "These anticipations have been fully borne out in practice during upwards of four years' regular working of the stoves. The high temperature of the blast produces such
an improved effect in the furnace that the 'burden' is increased so as to save fully five hundred-weight of coke per ton of iron made; and as there is less fuel supplied, so there are less impurities taken in, and the quality of the iron is improved, the tweer breasts' do not 'work hot' or burn, or give more trouble than usual, as the burden is increased as just stated. The same furnace is, of course, enabled to do more work, the 'make' being increased fully one-fifth: so that a given 'plant' produces 20 per cent. more iron per annum, besides saving nearly 3s. per ton for coke.
"There is less friction or loss of pressure of blast in these stoves than in common ones, and there is no loss of blast by leakage through cracked or burned cast-iron pipes or joints. More stoves are now being erected on the same plan." Every practical iron-master will comprehend at once the economy and benefits of the foregoing plan of hot-blast apparatus. It is not only commended by the great increase of temperature produced, but by its simplicity, cheapness, and reliability.
Those who have had the most experience with the common hot-blast ovens, or "stoves," formed with cast-iron pipes, are familiar with their imperfections. It is impossible to construct a cast-iron heater that will give much over half the temperature of blast obtainable from the regenerator described.
But we are far behind our cousins across the water in the manufacture of iron and in the use of the new and wonderful inventions perfected within the last ten years. It is true, Siemens's regenerators are in use at Pittsburg; yet but few of our iron manu facturers know much or any thing about them. Their application to the production of bar iron direct from the ore will be considered further on.