The very extensive round of experiments to which I have submitted mixtures of this nature, clearly establishes all the conclusions I have formed on these points. The strength of the mixture, three parts steel to one of stubs, gives a resistance in the rod of 6-16ths broad by 5-16ths thick, and 12 inches long, containing 1·40625 solid inches, equal to 10,295 lbs. before separating; thus being equal, in a barrel of the dimensions before mentioned, to an internal pressure of 5,555 lbs. to the inch of tube. The proportions mentioned in my previous work are 25 lbs. of stubs to 15 lbs. of steel; the strength of this mixture in the rod is equal to a tension of 8,960 lbs., and the barrel is capable of restraining a pressure internally of 4,818 lbs., making full 15 per cent. dissimilarity in favour of the larger proportion of steel: indeed, all experience points to the great advantage, that steel, properly worked, possesses over iron alone. Great good can be effected by condensing iron by hammer-hardening; greater than I have shown steel to be capable of receiving additionally: as, already having it naturally, there is no necessity for using artificial means to obtain it. Nor is steel so liable to depreciation in the hands of an inexperienced artisan; as the degree of expansion is not more, in the large proportion of steel mixture, than a loss of strength equal to 4-1/2 per cent, by heating and cooling gradually. The loss in the mixture containing less steel is 7-1/2 per cent. The specific gravity of the two is in proportion. The frequent welding and re-rolling of iron is of the most beneficial tendency, the elongation of the fibres being highly advantageous; for, a fibrous piece of iron may be compared to a wire rope, the more strands the greater tenacity; and the smaller the strands, even up to a proximity of fineness to the human hair, the greater the weight they will bear in tension. One large wire which, when single, will suspend 500 lbs., will, when drawn down to six small ones, suspend 600 lbs.; and so on to the greatest extreme. Another great advantage received by the repeated reworking of iron, is obtaining an increased density; for when this is secured to a certain extent, you have closed in proportion the pores of the metal; and in this state it is not liable to that degree of expansion or contraction, or that fluctuation in strength, which arises from softening the iron. Nor can you gain, save to a limited extent, any improvement by hammering,--hammer-hardening, for instance,--simply because it is already improved to the utmost extent we are at present acquainted with.