Inventors at Work, with Chapters on Discovery

by George Iles

“All being thus arranged, and a blast of 10 or 15 pounds’ pressure turned on, about seven hundred-weight of molten pig iron was run into the hopper provided on one side of the converter for that purpose. All went on quietly for about ten minutes; sparks such as are commonly seen when tapping a cupola, accompanied by hot gases, ascended through an opening on the top of the converter, just as I had supposed would be the case. But soon after a rapid change took place; in fact, the silicon had been quietly consumed, and the oxygen, next uniting with the carbon, sent up an ever-increasing stream of sparks and a voluminous white flame. Then followed a succession of mild explosions, throwing molten slags and splashes of metal high up into the air, the apparatus becoming a veritable volcano in a state of active eruption. No one could approach the converter to turn off the blast, and some low, flat, zinc-covered roofs, close at hand, were in danger of being set on fire by the shower of red-hot matter falling on them. All this was a revelation to me, as I had in no way anticipated such violent results. However, in ten minutes more the eruption had ceased, the flame died down, and the process was complete. On tapping the converter into a shallow pan or ladle, and forming the metal into an ingot, it was found to be wholly decarburized malleable iron. Such were the conditions under which the first charge of pig iron was converted in a vessel neither internally nor externally heated by fire.”

First Bessemer Converter and Ladle.
A, external elevation. B, vertical section during an in-pour of metal. C, during a blow. F, E, ladle with discharge valve at bottom. H, tuyères. G, bottom with tuyères.
From “Sir Henry Bessemer: an Autobiography,” by permission of Engineering, London.

The narrative continues with details of further masterly experiments until the new process was turning out steels of excellent quality, containing any desired fraction of carbon, at a cost of but six to seven pounds sterling per ton as against fifty to sixty pounds by the methods which Bessemer laid upon the shelf. His predecessors had made forty to fifty pounds of steel at a time in small crucibles, he made five tons in twenty minutes. In his magnificent simplification Bessemer at a stroke dismissed a long series of troublesome processes long believed to be as unavoidable as winter’s cold. He did away with the smelting of pig iron, the rolling, shearing and piling of bars, and the heating furnace. From the beginning of the Bessemer manufacture to the present hour, its main output has been rails for railroads. In this single service the debt due to Bessemer surpasses computation, for his steel has as least six-fold the durability of the iron it has replaced. A rail laid at Crewe Station in 1863, weighing twenty pounds to the yard, was turned in 1866 and taken up in 1875; it was estimated that 72,000,000 tons had passed over it, while the greatest wear of its tables was but .85 inch.

Bessemer did not at once enter upon success in the practical application of his process. British pig iron, with which he dealt, abounded in phosphorus, an element which he could not drive out, and which made his steels faulty. It was only when, at length, he obtained pure pig iron from Sweden that he was able to supply the market with pure, soft malleable iron, and with steels of various degrees of hardness. In a sequel, full of interest, he sketches the shrewd means by which he secured a handsome fortune from his great invention, for Bessemer had remarkable business ability as well as inventive genius. His labors in steel-making obliged him to neglect his devices in the plate-glass manufacture which, despite their merit, were also neglected by the producers of plate-glass. He remarks: “The simple fact is that an invention must be nursed and tended as a mother nurses her baby, or it inevitably perishes.”

Bessemer’s Versatility.

So far from finding it gainful to concentrate his mind on a single problem, ignoring every other, Bessemer delighted in pursuing a wide variety of experiments, especially before his engrossing responsibilities in the manufacture of steel. In glass-making he introduced some notable improvements. He tells us: “In going over a glass-works I had noticed what I, at the moment, thought was a great oversight in the mode of proceeding. The materials employed, namely, sand, lime and soda in ascertained quantities, were laid in heaps upon the paved floor of the glasshouse, and a laborer proceeded to shovel them into one large heap, turning over the powdered materials, and mixing them together; a certain quantity of oxide of manganese was added during the general mixing operation, for the purpose of neutralizing the green color given to glass by the small amount of oxide of iron contained in the sand. The materials were then thrown into the large glass pots, which were already red-hot inside the furnace. What appeared to me to be wanting in this rough-and-ready operation was a far more intimate blending of these dry materials. A grain of sand lying by itself is infusible at the highest temperature attainable in a glass pot, and the same may be said of a small lump of lime; but both are soluble in alkali, if it be within their reach. These dry powders do not make excursions in a glass pot and look about for each other, and if they lie separated the time required for the whole to pass into a state of solution will greatly depend on their mutual contact. In such matters I always reason by analogy, and look for confirmation of my views to other manufactures or processes with which I may happen to have become more or less acquainted. I may here remark that I have always adopted a different reading of the old proverb, ‘A little knowledge is a dangerous thing’; this may indeed be true, if your knowledge is equally small on all subjects; but I have found a little knowledge on a great many different things of infinite service to me. From my early youth I had a strong desire to know something of any and all the varied manufactures to which I have been able to gain access, and I have always felt a sort of annoyance whenever any subject connected with manufacture was mooted of which I knew absolutely nothing. The result of this feeling, acting for a great many years on a powerful memory, has been that I have really come to know this dangerous little of a great many industrial processes. I have been led to say this so as to illustrate my observations on the extreme slowness of the fusion of glass by an analogy in the manufacture of gunpowder. I have shown it impossible for the dry powdered materials employed in the manufacture of glass to react chemically upon each other when they are lying far apart. Now if I take the three substances, charcoal, nitre and sulphur, of which gunpowder is composed, and break them into small fragments, then shake them loosely together, and put a pound or two of this mixture on a stone floor and apply a match, the nitre will fizzle briskly, the sulphur will burn fitfully or go out, and the charcoal will last several minutes before it is consumed. If, instead of this crude and imperfect mixture, we take the trouble to grind these ingredients under edge-stones into a fine paste with water, and then dry and granulate it, we have still the precise chemical elements to deal with which we ignited on the stone floor; but they now exist in such close and intimate contact as instantly to act upon each other, and a ton or two of these otherwise slow-burning materials will be converted into gas in the fraction of a second. The inference was simple enough, namely, to grind together the materials required to form glass, and when the heat of the furnace arrives at the point where decomposition takes place, the whole will pass into the fluid state much more quickly, and will yield a much more homogeneous glass than is obtained in the usual manner.”

Improves the Drying of Oils.

Bessemer one day paid a visit to the works of his friends, Hayward and Company, London, manufacturers of paints and varnishes. He was struck with the wastefulness and imperfection of the time-honored process of drying oils in an iron pot over an open fire; a crude method always attended with danger, and not seldom with a complete loss of the heated oil. As he walked through the works there occurred to him a much better plan which he at once embodied in a sketch. His ideas were put into practice by his friends, to their lasting profit. Instead of a small charge of two or three gallons heated over an open fire, he suggested that fifty or sixty gallons should be run into a tank, in the bottom of which was a pipe terminating in a large rose-head. Connected with this pipe was a coil that could be heated to any desired temperature, and air could be forced through this coil, escaping through the rose-head into the oil. The exact degree of heat required could be thus maintained, and the process completed with certainty and safety, without waste, and, above all, with no discoloration of the oil. This method, carried to a further degree of oxidation, is the foundation of the vast linoleum industry throughout the world.