One most important invention or discovery of the nineteenth century was made by William Kelly, who came from Pittsburgh and located near Eddyville, in Lyon County, in 1846. Here he operated both the Union and the Suwanee furnaces, mostly by slave labor, until he conceived the plan of using Chinese workers, which he secured through a New York tea house. As these Celestials, with their pigtails, were the first in this section, they created a great deal of curiosity. Mr. Kelly, having a special knowledge of chemistry and metallurgy, investigated and experimented in the manufacture of iron, and concluded that the crude metal could be converted into steel without fuel; that by placing the fluid metal in a suitable furnace and forcing powerful blasts of air through the molten mass, he could produce the desired result.

His veteran forgemen could not conceive of metal being "boiled" by simply blowing air through it, for it had been their experience that air blown over its surface chilled it. They knew nothing of the affinity of oxygen with carbon for producing heat; they had always consumed quantities of charcoal to secure this greater heat; they had buried bars of wrought iron in charcoal in a furnace, where, the air being shut off, the charcoal was slowly burned for two or more weeks. Then the product was taken out and melted, forming "cast steel." So they were completely surprised when forcing the currents of air through the mass of iron intensified it to incandescence and refined the metal.

The experiment was made in 1851 and used by Mr. Kelly advantageously for many years. Being almost isolated in practically a wilderness, thirty miles from even the nearest country press, the inventor failed to advertise and take proper advantage of his invention. In 1855, however, many of the steamboats plying the Ohio River were using boiler plates made from iron prepared by "Kelly's air-boiling process." The next year Henry Bessemer, an iron manufacturer of England, took out a patent for this pneumatic process, to which his name has been given; but, although Mr. Kelly was delayed in securing his patent by his attorney, when the claim was heard by the commissioner of the Patent Office in this country, it was decided that Mr. Kelly was the inventor and his patent was at once granted. For many years Mr. Kelly received a royalty on his interest in the inventions. In time the patents of Kelly, Bessemer, and Mushet were combined. Prior to this discovery, steel cost five times as much as iron; now steel rails, wearing four times as long as iron, cost only a few dollars more per ton. Thus we see the incalculable importance of another Kentucky invention, for now steel is made directly from pig iron in about thirty minutes, instead of as formerly in almost as many days.