Henry Bessemer invents an elongated artillery shell…

Henry Bessemer invents an elongated artillery shell that is rotated by the powder gases.

The French authorities with whom he is negotiating, however, point out that their cast-iron cannon would not be strong enough for this kind of shell.

He thereupon attempts to produce a stronger cast iron.

In his experiments he discovers that the excess oxygen in the hot gases of his furnace appears to have removed the carbon from the iron pigs that were being preheated—much as the carbon is removed in a puddling furnace—leaving a skin of pure iron.

Bessemer next finds that blowing air through melted cast iron not only purifies the iron but also heats it further, allowing the purified iron to be easily poured.

This heating effect is caused by the reaction of oxygen with the carbon and silicon in the iron.