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carbon in the original mass, so that after this separating out of the carbon, in the solidifying of the ingot, enough shall remain in the lower part, and too much shall not be found in the upper part, of that portion of the ingot which is used.
After casting the ingot has to be forged.
Now as regards the question of forging, men of my age, when we were boys, did not know of a steam hammer; our knowledge of heavy hammers was confined to double-hand hammers and to helves.
At length the steam hammer in various forms was everywhere to be met with, and it appeared, that in it we possessed, an implement, competent to deal with any such mass of wrought iron, as the arts would ever need. But now forgings of previously unheard-of dimensions, and forgings not of comparatively plastic iron, but of steel, are required. I will ask you to think what is needed in the forging of a mass, say with the object of diminishing its diameter and of adding to its length; is it not clear that the blow in order to be efficacious should make itself felt to the very core of the piece under treatment? Common sense tells us that one might hammer in perpetuity with a carpenter's hammer upon an iron shaft, of comparatively small diameter, with the result, indeed, of bruising and injuring the mere surface, but with no effect upon the centre of the mass.
Similarly, with even large steam hammers, they may, while doing their work of elongation on a large forging, have an injurious effect, by tending to extend the exterior layers more speedily, than the interior can readily follow, and thus there may be set up in the very act of manufacture, injurious internal strains.
To avoid this danger there are now being introduced machines which forge, not by percussion, as hammers do, but by steady pressure.
Assume the forging to be made; it has to be bored, it has to be turned, and then it has to be "oil-hardened," a process requiring special plant, and uncommon care that strains are not set up in the very process which is intended to imp)rove the
