I may here state that steel was used for crank shafts in this service in 1863, as then manufactured in Prussia by Messrs. Krupp, and generally known as Krupp’s steel, the tensile strength of which was about 40 tons per square inch, and though free from flaws, it was unable to stand the fatigue, and broke, giving little warning.  It was of too brittle a nature, more resembling chisel steel.  It was broken again under a falling weight of 10 cwt. with a 10 ft. drop = 121/2 tons.

The mild steel now used was first tried in 1880.  It possessed tensile strength of 24 to 25 tons per square inch.  It was then considered advisable not to exceed this, and err rather on the safe side.  This shaft has been in use eight years, and no sign of any flaw has been observed.  Since then the tensile strength of mild steel has gradually been increased by Messrs. Vickers, the steel still retaining the elasticity and toughness to endure fatigue.  This has only been arrived at by improvements in the manufacture and more powerful and better adapted hammers to forge it down from the large ingots to the size required.  The amount of work they are now able to subject the steel to renders it more fit to sustain the fatigue such as that to be endured by a crank shaft.  These ingots of steel can be cast up to 100 tons weight, and require powerful machines to deal with them.  For shafts say of 20 inches diameter, the diameter of the ingot would be about 52 inches.  This allows sufficient work to be put on the couplings, as well as the shaft.  To make solid crank shafts of this material, say of 19 inches diameter, the ingot would weigh 42 tons, the forging, when completed, 17 tons, and the finished shaft 113/4 tons; so that you see there is 25 tons wasted before any machining is done, and 51/4 tons between the forging and finished shaft.  This makes it very expensive for solid shafts of large size, and it is found better to make what is termed a built shaft; the cranks are a little heavier, and engine framings necessarily a little wider, a matter comparatively of little moment.  I give you a rough drawing of the hydraulic hammer, or strictly speaking a press, used by Messrs. Vickers in forging down the ingots in shafts, guns, or other large work.  This hammer can give a squeeze of 3,000 tons.  The steel seems to yield under it like tough putty, and, unlike the steam hammer, there is no jarring on the material, and it is manipulated with the same ease as a small hammer by hydraulics.

The tensile strength of steel used for shafts having increased from 24 to 30 tons, and in some cases 31 tons, considering that this was 2 tons above that specified, and that we were approaching what may be termed hard steel, I proposed to the makers to test this material beyond the usual tests, viz., tensile, extension, and cold bending test.  The latter, I considered, was much too easy for this fine material, as a piece of fair iron will bend cold to