easily and cheaply mined, and works easily of iron to that from the hematite and magin the blast furnace. On account of its de- netic ores, and better adapted for castings ficiency in silica it is necessary to use a lime- than for converting into malleable iron. The stone containing this ingredient, that the pure, rich ores, however, are many of them elements of a glassy cinder may be provided, unsurpassed. It is found in beds of all diwhich is the first requisite in smelting iron; mensions, and though in the eastern part of or the same end may be more advantageously the United States they prove of limited exattained by adding a portion of magnetic tent, those of Missouri and Lake Superior ore, which is almost always mixed with are inexhaustible. Magnetic and specular silica in the form of quartz; and these two ores are associated together in the same disores are consequently very generally worked trict, and sometimes are accompanied by together the hematites making two-thirds hematite beds; and it is also the case, that or three-quarters of the charge, and the mag-iron districts are characterized by the prevanetic ores the remainder. lence of one kind only of these ores, to the exclusion of the others.

Magnetic ore is the richest possible combination of iron, the proportion of which cannot exceed 72.4 per cent., combined with 27.6 per cent of oxygen. It is a heavy, black ore, compact or in coarse crystalline grains, and commonly mixed with quartz and other minerals. It affects the magnetic needle, and pieces of it often support small bits of iron, as nails. Such ore is the loadstone. It is obtained of various qualities; some sorts work with great difficulty in the blast furnace, and others are more easily managed and make excellent iron for any use; but all do better mixed with hematite. The magnetic ores have been largely employed in the ancient processes of making malleable iron direct from the ore in the open forge, the Catalan forge, etc., and at the present time they are so used in the bloomary fires. They are found in inexhaustible beds of all dimensions lying among the micaceous slates and gneiss rocks. These beds are sometimes so extensive that they appear to make up the greater part of the mountains in which they lie, and in common language the mountains are said to be all

ore.

The red oxides of the secondary rocks consist, for the most part, of the red fossiliferous and oolitic ores that accompany the so-called Clinton group of calcareous shales, sandstones, and argillaceous limestones of the upper silurian along their lines of outcrop in Pennsylvania, Maryland, and eastern Tennessee, and from Oneida county, N. Y., westward past Niagara Falls, and through Canada even to Wisconsin. The ore is found in one or two bands, rarely more than one or two feet thick, and the sandstone strata with which they are associated are sometimes so ferruginous as to be themselves workable ores. The true ores are sometimes entirely made up of the forms of fossil marine shells, the original material of which has been gradually replaced by peroxide of iron. The oolitic variety is composed of fine globular particles, united together like the roe of a fish. The ore is also found in compact forms, and in Wisconsin it is in the condition of fine sand or seed. Its composition is very variable, and its per-centage of iron ranges from 40 to 60. By reason of the carbonate of lime diffused through some of the varieties, these work in the blast furnace very freely, and serve extremely well to mix with the silicious ores.

Specular ore, or specular iron, is so named from the shining, mirror-like plates in which it is often found. The common ore is sometimes red, steel gray, or iron black, and all Of the varieties of carbonate of iron, the these varieties are distinguished by the only ones of practical importance in the bright red color of the powder of the ore, United States are the silicious and argillawhich is that of peroxide of iron. Mag-ceous carbonates of the coal formation, and netic ore gives a black powder, which is that of a less oxidized combination. The specular ore thus contains less iron and more oxygen than the magnetic; the proportions of its ingredients are 70 parts in 100 of iron, and 30 of oxygen. Though the difference seems slight, the qualities of the two ores are quite distinct. The peroxide makes iron fast, but some sorts of it produce an inferior quality

the similar ores of purer character found among the tertiary clays on the western shores of Chesapeake Bay. The former varieties are the chief dependence of the iron furnaces of Great Britain, where they abundantly occur in layers among the shales of the coal formation, interstratified with the beds of coal-the shafts that are sunk for the exploration of one also penetrating beds

inferior, brittle quality of cast iron. They are chiefly found near the coast, and being easily dug, and also reduced to metal with great facility, they proved very convenient for temporary use before the great bodies of ore in the interior were reached. Some furnaces are still running on these ores in the south-west part of New Jersey, and at Snowhill, on the eastern shore of Maryland, and the iron they make is used to advantage in mixing at the great stove foundries in Albany and Troy with other varieties of cast iron. It increases the fluidity of these, and produces with them a mixture that will flow into and take the forms of the minutest markings of the mould.

of the other. The layers of ore are in flattened blocks, balls, and kidney-shaped lumps, which are picked out from the shales as the beds of these are excavated. The ore is lean, affording from 30 to 40 per cent. of iron; but it is of easy reduction, and makes, when properly treated, iron of fair quality. In Pennsylvania, Ohio, western Virginia, Kentucky, and Tennessee, the ores occur with the same associations as in England; but the supply is, for the most part, very precarious, and many furnaces that have depended upon them are now kept in operation only by drawing a considerable portion of their supplies from the mines of Lake Superior, more than one thousand miles off. Among the horizontally stratified rocks west of the Alleghanies, the same bands of ore are traced over extensive districts, and are even recognized in several of the different states named. One of the most important of these bands is the buhrstone ore, so called from a cellular, flinty accompaniment which usually underlies it, the whole contained in a bed of peculiar fossiliferous limestone. So much carbonate of lime is sometimes present in the ore, that it requires no other flux in the blast furnace. Its per-centage of iron is from 25 to 35. from 25 to 35. Along the line of outcrop of some of the carbonates are found deposits of hematite ores, the result of superficial changes in the former, due to atmospheric agencies long continued. In coal furnaces are of small size compared southern Ohio, at Hanging Rock particularly, numerous furnaces have been supported by these ores, and have furnished much of the best iron produced at the west.

Charcoal has been the only fuel employed in the manufacture of iron until anthracite was applied to this purpose, about the year 1840, and still later in the United Statescoke and bituminous coal. So long as wood continued abundant in the iron districts, it was preferred to the mineral fuel, as in the early experience of the use of the latter the quality of the iron it produced was inferior to that made from the same ores with charcoal, and even at the present time, most of the highest-priced irons are made with charcoal. The hard woods make the best coal, and after these, the yellow pine. Hemlock and chestnut are largely used, because of their abundance and cheapness. The char

with those using the denser mineral coal, and their capacity rarely exceeds a production of ten or twelve tons of pig iron in twenty-four hours. In 1840 they seldom The carbonates of the tertiary are found made more than four tons a day; the differin blocks and lumps among the clays along ence is owing to larger furnaces, the use of the shores of the Chesapeake at Baltimore, hot blast, and much more efficient blowing and its vicinity. The ores are of excellent machinery. The consumption of charcoal character, work easily in the furnace, make a to the ton of iron is one hundred bushels of kind of iron highly esteemed-particularly hard-wood coal at a minimum, and from this for the manufacture of nails-and are so abundant that they have long sustained a considerable number of furnaces. They lie near the surface, and are collected by excavating the clay beds and sorting out the balls of ore. The excavations have been carried out in some places on the shore below the level of tide, the water being kept back by coffer dams and steam pumps.

Bog ores, with which the earliest furnaces in the country were supplied, are now little used. They are rarely found in quantities sufficient for running the large furnaces of the present day, and, moreover, make but an

running up to one hundred and fifty bushels or more, according to the quality of the coal and the skill of the manager. The economy of the business depends, in great part, upon the convenience of the supplies of fuel and of ores, of each of which rather more than two tons weight are consumed to every ton of pig iron. As the woods are cut off in the vicinity of the furnaces, the supplies are gradually drawn from greater distances, till at last they are sometimes hauled from ten to fourteen miles. The furnaces near Baltimore have been supplied with pine wood discharged from vessels at the coaling kilns