Had the invention been patented, it would have become public property in fourteen years from the date of the patent, after which period the public would have been able to buy bronze powder at its present [i.e., ca. 1890] market price, viz. from two shillings and three pence to two shillings and nine pence per pound. But this important secret was kept for about thirty-five years and the public had to pay excessively high prices for twenty-one years longer than they would have done had the invention become public property in fourteen years, as it would have been if patented. Even this does not represent all the disadvantages resulting from secret manufacture. While every detail of production was a profound secret, there were no improvements made by the outside public in any one of the machines employed during the whole thirty-five years; whereas during the fourteen years, if the invention had been patented, there would, in all probability have been many improved machines invented and many novel features applied to totally different manufactures.
While these words, to some extent, were the rationalizations of an old man, Bessemer's career showed that his philosophy had a practical foundation; and, if this was indeed his belief, the episode explains in large measure Bessemer's later insistence on the legal niceties of the patent procedure. The effect of this will be seen.
Bessemer's intervention in the field of iron and steel was preceded by a period of experiments in the manufacture of glass. Here Bessemer claims to have made glass for the first time in the open hearth of a reverberatory furnace.[11 ] His work in glass manufacture at least gave him considerable experience in the problems of fusion under high temperatures and provided some support for his later claim that in applying the reverberatory furnace to the manufacture of malleable iron as described in his first patent of January 1855, he had in some manner anticipated the work of C. W. Siemens and Emil Martin.[12 ]
The general interest in problems of ordnance and armor, stimulated by the Crimean War (1854-1856), was shared by Bessemer, whose ingenuity soon produced a design for a projectile which could provide its own rotation when fired from a smooth-bore gun.[13 ] Bessemer's failure to interest the British War Office in the idea led him to submit his design to the Emperor Napoleon III. Trials made with the encouragement of the Emperor showed the inadequacy of the cast-iron guns of the period to deal with the heavier shot; and Bessemer was presented with a new problem which, with "the open mind which derived from a limited knowledge of the metallurgy of war," he attacked with impetuosity. Within three weeks of his experiments in France, he had applied for a patent for "Improvements in the Manufacture of Iron and Steel."[14 ] This covered the fusion of steel with pig or cast iron and, though this must be regarded as only the first practical step toward the Bessemer process,[15 ] it was his experiments with the furnace which provided Bessemer with the idea for his later developments.
These were described in his patent dated October 17, 1855 (British patent 2321). This patent is significant to the present study because his application for an American patent, based on similar specifications, led to the interference of William Kelly and to the subsequent denial of the American patent.[16 ] In British patent 2321 Bessemer proposed to convert his steel in crucibles, arranged in a suitable furnace and each having a vertical tuyère, through which air under pressure was forced through the molten metal. As Dredge[17 ] points out, Bessemer's association of the air blast with the increase in the temperature of the metal "showed his appreciation of the end in view, and the general way of attaining it, though his mechanical details were still crude and imperfect."
Figure 1.—Bessemer's Design for a Converter, as Shown in U.S. Patent 16082. This patent, dated November 11, 1856, corresponds with British patent 356, dated February 12, 1856. The more familiar design of converter appeared first in British patent 578, March 1, 1860. The contrast with Kelly's schematic drawing in Fig. 2 (p. 42) is noticeable.
Experiments were continued and several more British patents were applied for before Bessemer made his appearance before the British Association on August 13, 1856.[18 ] Bessemer described his first converter and its operation in some detail. Although he was soon to realize that he "too readily allowed myself to bring my inventions under public notice,"[19 ] Bessemer had now thrown out a challenge which eventually had to be taken up, regardless of the strength of the vested interests involved. The provocation came from his claims that the product of the first stage of the conversion was the equivalent of charcoal iron, the processes following the smelting being conducted without contact with, or the use of, any mineral fuel; and that further blowing could be used to produce any quality of metal, that is, a steel with any desired percentage of carbon. Yet, the principal irritant to the complacency of the ironmaster must have been Bessemer's attack on an industry which had gone on increasing the size of its smelting furnaces, thus improving the uniformity of its pig-iron, without modifying the puddling process, which at best could handle no more than 400 to 500 pounds of iron at a time, divided into the "homeopathic doses" of 70 or 80 pounds capable of being handled by human labor.[20 ] Bessemer's claim to "do" 800 pounds of metal in 30 minutes against the puddling furnace's output of 500 pounds in two hours was calculated to arouse the opposition of those who feared the loss of capital invested in puddling furnaces and of those who suspected that their jobs might be in jeopardy. The ensuing criticism of Bessemer has to be interpreted, therefore, with this in mind; not by any means was it entirely based on objective consideration of the method or the product.[21 ]
Within a month of his address, Bessemer had sold licenses to several ironmasters (outside Sheffield) and so provided himself with capital with which to continue his development work; but he refused to sell his patents outright to the Ebbw Vale Iron Works and by this action, as will be seen, he created an enemy for himself.
The three years between 1856 and 1859, when Bessemer opened his own steel works in Sheffield, were occupied in tracing the causes of his initial difficulties. There was continued controversy in the technical press. Bessemer (unless he used a nom-de-plume) took no part in it and remained silent until he made another public appearance before the Institution of Civil Engineers in London (May 1859). By this time Bessemer's process was accepted as a practical one, and the claims of Robert Mushet to share in his achievement was becoming clamorous.