The various processes by which the iron is prepared to be used in bridge-building are many of them as new as is the use of this material for this purpose, and it will not be amiss to spend a few moments in examining them before presenting to our readers illustrations of some of the most remarkable structures of this kind. Taking a train by the Reading Railroad from Philadelphia, we arrive, in about an hour, at Phoenixville, in the Schuylkill Valley, where the Phoenix Iron-and Bridge-works are situated. In this establishment we can follow the iron from its original condition of ore to a finished bridge, and it is the only establishment in this country, and most probably in the world, where this can be seen. [Illustration: THE ENGINE-ROOM.] These works were established in 1790. In 1827 they came into the possession of the late David Reeves, who by his energy and enterprise increased their capacity to meet the growing demands of the time, until they reached their present extent, employing constantly over fifteen hundred hands. [Illustration: RUNNING METAL INTO PIGS.] The first process is melting the ore in the blast-furnace. Here the ore, with coal and a flux of limestone, is piled in and subjected to the heat of the fires, driven by a hot blast and kept burning night and day. The iron, as it becomes melted, flows to the bottom of the furnace, and is drawn off below in a glowing stream. Into the top of the blast-furnaces the ore and coal are dumped, having been raised to the top by an elevator worked by a blast of air. It is curious to notice how slowly the experience was gathered from which has re suited the ability to work iron as it is done here. Though even at the first settlement of this country the forests of England had been so much thinned by their consumption in the form of charcoal in her iron industry as to make a demand for timber from this country a flourishing trade for the new settlers, yet it was not until 1612 that a patent was granted to Simon Sturtevant for smelting iron by the consumption of bituminous coal. Another patent for the same invention was granted to John Ravenson the next year, and in 1619 another to Lord Dudley; yet the process did not come into general use until nearly a hundred years later. [Illustration: CARRYING THE IRON BALLS.]