tals. If the fracture of a bar of steel appears crystaline, the steel may be considered imperfect-as, in fact, a kind of strong, coldshort iron. It will harden, of course, but it will not retain a sound edge, certainly not a point, and it is brittle, like excellent cast iron. In good steel, we are not able to detect, by means of the strongest lens or microscope, any indications of a geometrical form of the grain. The grains of the fracture may be large, and the fracture itself may appear like that of bright gray cast iron. But this is a matter of little consequence, for the size of the grain can be reduced by refining, even in the blacksmith's fire, and by hammering. By melting it in a crucible, we can make cast steel of it. But the grains of steel must be round, however small or large they may be. This, of course, applies to steel which is not too much hardened. If too much heated and hardened, the best steel will be crystaline in its fracture.

Several years ago, various experiments were made by English, French, and German scientific men, to make steel by artificial alloys, that is, by combining iron with other metals. Experiments were also made to impregnate iron with carbon by a different method than that usually employed, namely, by means of cement in the chest. But none of these experiments resulted in any practical advantage. Time, and iron of good quality, are indispensable conditions of success in the manufacture of steel. Slight alterations in the cement may prove advantageous; but there is no rational probability that we shall ever succeed in manufacturing good steel from bad iron. As we have stated once before, pure iron is perfectly useless for any other practical purpose. Steel is made of iron which, generally speaking, contains a smaller amount of impurities than other iron. Still, there may be bar iron which contains less foreign matter than steel; but it is the form in which foreign matter is present which distinguishes the one from the other. A theoretical investigation of this subject, however interesting, would lead us too far beyond our limits. Nevertheless, we shall observe that white plate iron, of the best quality, containing generally from three to four per cent. of carbon, is the hardest kind of iron, harder even than the best cast steel. Still, it is brittle, and is not susceptible of being drawn out by the hammer. Steel contains all the impurities of the iron from which it is made, while the iron generally contains the impurities existing in the ore from which it was made, and in the coal and fluxes employed in smelting it. Steel contains carbon, sulphur, phosphorus, silicon, arsenic, antimony,

copper, tin, and manganium; and the best English cast steel contains nitrogen. The latter, of course, cannot be present in any other form than in combination with carbon, thus forming a cyanide of iron. Among these impurities, carbon and silicon hold the first rank; then follow sulphur, arsenic, and manganium. The elasticity and strength of the Solingen steel result from the presence of nearly 0.4 per cent. of copper; and the excessive hardness of some French steel results from the presence of manganium. The hardest, though not the strongest, kind of steel is the finer quality of Styrian steel. This is pure iron, containing 1.13 per cent. of carbon. In order better to elucidate this subject, we shall insert the following table, exhibiting the various compositions of steel:—

No. 1 is Styrian steel, celebrated for hardness and elasticity. It is called Brescia steel, and is principally sold in Italy, where quality is made an object of special attention by the cutler and blacksmith. No. 2, common English cast steel, and No. 3, the best razor steel from Sheffield. No. 4, Solingen, or Siegen steel, known to be very tough. No. 5, very hard Styrian steel. No. 6, inferior Styrian steel. A critical examination of this table will enable us to see clearly what is necessary to constitute good steel. The steel which contains most impurities is No. 3. It is generally uniform and hard, but very fusible; it cannot bear heat. No. 5 may be considered harder than No. 3; but it is brittle, and will not receive a fine edge. No. 1 is less hard than No. 5, but it is better adapted for cutlery and weapons. No. 4 is, of all others, most suitable for swords; indeed, for this purpose, it is very little inferior to Damascus steel. It is not so well adapted as No. 3 for cutlery, nor equal to No. 5 for mint stamps.

We misapply words when we appropriate the term impurities to

the matter which, independently of iron, steel contains. These impurities are essential elements in its constitution; and, it appears, the greater the variety, the better the steel. In what way these admixtures are brought into the iron, we are unable to say; but a careful examination of the ores from which the iron is made will enable us faintly to approximate towards the solution of this question. The ore from which No. 1 was derived is a very pure carbonate of iron and manganese. No. 2 was derived from common Swedish or Russian iron, both of which were smelted from magnetic ore. This ore frequently contains sulphur, silex, titanic acid, and copper. No. 3 was made from Danemora iron, the latter smelted from magnetic ore. The Danemora ore contains, in addition to iron, a variety of matter. We may thus, in some measure, account for the presence of so large an amount of foreign matter in the steel. The ore whence No. 4 was obtained contains a large amount of manganese, always a little copper, sulphur, silex, and often a small amount of spar of lime and clay. It is a crystallized carbonate, or spathic ore. Nos. 5 and 6, like No. 1, were obtained from a very pure carbonate of iron and manganese. Some of the admixtures may enter into combination with the iron in the cement box; but this is not the case with others. Carbon, sulphur, phosphorus, nitrogen, and probably arsenic, may be united with the rods during the process of cementation; but silicon, antimony, copper, tin, and manganium are present in the iron before it is exposed to this operation. These investigations show more clearly than any we have yet presented, the advantages resulting from mixing ores, if a given variety of admixtures is not already contained in the ore. Where wrought and cast iron are strong and fine, and contain, besides a variety of matter, carbon and silicon, the steel which is made from them will be of the same character. It has been proposed to manufacture steel by melting cast iron along with those materials which would purify it, and still leave carbonsuch as alkaline matter, wrought iron, and iron ore; or by melting wrought iron or pure oxide of iron along with carbon, in a crucible. No such experiments amount to anything. Though they should be successful, their expensiveness is so great that they will never be productive of any practical result.

The hardening of steel may be perfectly understood by studying its nature. In endeavoring to arrive at the temperature best adapted to a particular case-a case, for instance, in which we have to deal with a strange kind of steel—a practical test, namely, drawing the

bar into a tapered point, or chisel, is applied. This wedge-shaped chisel will, of course, be more warm towards the point than at the thick part; and it is evident that this part will, when cooled in the same cold medium, be harder than the thick part. By breaking, and continuing to break off the point, the difference of grain will show the different temperatures which have been applied. The finest and closest grain is considered the best. In hardening such steel, it is heated with due relation to the degree of the test heat. Though this manipulation is very imperfect, careful and intelligent workmen are generally quite successful in arriving at a knowledge of what degree is favorable. The degree of hardness depends, in some measure, upon the heat of the steel, but mainly upon the difference between the heat of the steel and that of the water or medium in which it is cooled. The coldest water will make the hardest steel. Mercury is better adapted to harden steel than water; so is water, acidulated with any kind of acid, or containing any kind of salt in solution.

The process of hardening is performed with due relation to the quality of the steel and the purposes for which it is designed. In most instances, the hardening is effected in water, or brine. Saw blades are thus hardened, after being heated in melted lead. Sabres are heated in a suffocated fire of charcoal, and then swung rapidly through the air. Mint stamps are hardened in oil, or metallic compositions. The common method of procedure in hardening is this: The steel is overheated, cooled in cold water, and then annealed or tempered by being so far reheated that oil and tallow will burn on its surface; or the surface is ground and polished, and the steel reheated until it assumes a certain color. The gradations of color consecutively follow: a light straw yellow, violet, blue, and finally gray or black, when the steel again becomes as soft as though it had never been hardened.

CONCLUSION.

It is evident that the quality and quantity of iron we are enabled to produce depend, in a great measure, upon the nature and qualities of the ore at our disposal. By means of science and industry, great difficulties can be overcome. But the only condition upon which we can rationally base any hope for the future relative to iron manufacture and its collateral branches, consists in the union of natural advantages with skill, activity, and intellectual cultivation. The conditions which favor the manufacture of iron, in this country, are so superior to those which exist in Europe, that any comparison between them would be useless, if not inadmissible. Our immense ore deposits are unparalleled in the known world. Our hills are covered with a rich growth of timber; and the bowels of the earth abound in stone coal of the most advantageous quality. True, we are excluded from foreign markets by the high price which labor commands; but this obstacle will, in time, we have no doubt, be effectually removed by the energy and perseverance of our countrymen. The application of science and machinery, in the manufacture of iron, does not exhibit so high a state of cultivation as we find in other departments of labor, such as the manufacture of calico prints and silks; but, when the principles involved in this interesting and highly important branch of industry are once thoroughly understood by our artisans, results will show that the low price of labor will prove of no advantage over a skillful and inventive intellect.

This branch of industry presents a wide field for the exhibition of skill and enterprise. After an advantageous location for an establishment is selected, the fundamental object which the intelligent manufacturer should seek to secure is the improvement of the quality of iron. We repeat, to this object every other should be regarded as subordinate. He who best understands what is necessary to improve its quality, is most competent to work cheaply. We have an abundance of inferior iron already in the market;