One kind was being made by an English firm, and another by a French company.
The English plan was to make what is called compound armor. This was hard steel welded on to a back of softer metal, the idea being that the soft back would act as a sort of cushion, and save the front part of the plate from being cracked by the blows of the shot.
The French system was to make a mixture of steel and nickel. They claimed that the nickel alloy would give greater strength to the plate.
Secretary Tracy was so anxious that we should have the best possible armor for our battleships that he ordered a plate from both companies, and sent them to the Naval Academy at Annapolis to be tested.
The big guns were tried on first one and then the other; the English armor cracked in four pieces, but on the nickel steel the shot were shattered into fragments.
Congress immediately voted that the new battleships should be supplied with nickel-steel armor, and an appropriation was made for this purpose.
Before the new contract could be carried out, President Harrison learned that a man named Harvey had invented a process for hardening the surface of the steel used in making tools. This process was found to be so excellent that it revolutionized the making of tools, which were thereafter made from the hardened or "Harveyized steel."
This process had never been applied to any large surface, but it was thought that if Harvey's method could be used for the nickel-steel plates, a perfect armor would be the result.
The experiment was therefore tried. A large nickel-steel plate was subjected to the process and then tested at Annapolis.
The result was highly satisfactory; all the projectiles sent against the plate were shattered, while the plate remained comparatively uninjured.