The blast for the furnace is driven by two enormous engines, each of three hundred horse-power. The blast used here is, as we have said, a hot one, the air being heated by the consumption of the gases evolved from the material itself. The gradual steps by which these successive modifications were introduced is an evidence of how slowly industrial processes have been perfected by the collective experience of generations, and shows us how much we of the present day owe to our predecessors. From the earliest times, as among the native smiths of Africa to-day, the blast of a bellows has been used in working iron to increase the heat of the combustion by a more plentiful supply of oxygen. The blast-furnace is supposed to have been first used in Belgium, and to have been introduced into England in 1558. Next came the use of bituminous coal, urged with a blast of cold air. But it was not until 1829 that Neilson, an Englishman, conceived the idea of heating the air of the blast, and carried it out at the Muirkirk furnaces. In that year he obtained a patent for this process, and found that he could from the same quantity of fuel make three times as much iron. His patent made him very rich: in one single case of infringement he received a cheque for damages for one hundred and fifty thousand pounds. In his method, however, he used an extra fire for heating the air of his blast. In 1837 the idea of heating the air for the blast by the gases generated in the process was first practically introduced by M. Faber Dufour at Wasseralfingen in the kingdom of Würtemberg. In this country, charcoal was at first used universally for smelting iron, anthracite coal being considered unfit for the purpose. In 1820 an unsuccessful attempt to use it was made at Mauch Chunk. In 1833, Frederick W. Geisenhainer of Schuylkill obtained a patent for the use of the hot blast with anthracite, and in 1835 produced the first iron made with this process. In 1841, C.E. Detmold adapted the consumption of the gases produced by the smelting to the use of anthracite; and since then it has become quite general, and has caused an almost incalculable saving to the community in the price of iron. The view of the engines which pump the blast will give an idea of the immense power which the Phoenix company has at command. Twice every day the furnace is tapped, and the stream of liquid iron flows out into moulds formed in the sand, making the iron into pigs--so called from a fancied resemblance to the form of these animals. This makes the first process, and in many smelting-establishments this is all that is done, the iron in this form being sold and entering into the general consumption.