The new process was received with astonishment by all the iron-working world. It was approved by many, but scoffed at by others. As trials went on, however, the feeling against it increased. The iron so made was often "rotten," and no one could tell exactly why. Bessemer, however, continued to investigate everything for himself, regardless of all suggestions. Some ideas of permanent value were offered to him, but were set at nought. It was not till another series of independent experiments were made that he himself discovered the secret of failure. It then appeared that, by mere chance, the iron used in his first experiments was Blaenavon pig, which is exceptionally free from phosphorus; and consequently, when other sorts of iron were thrown at random into the converter, the phosphorus manifested its refractory nature in the unworkable character of the metal produced. Analyses made by Professor Abel for Sir Henry showed that this was the real cause of failure. Once convinced of this fact, Sir Henry set to work for the purpose of removing this hostile element. He saw how phosphorus was removed in the puddling-furnace, and he now tried to do the same thing in his converter. Another series of costly and laborious experiments was conducted; and first one patent and then another was taken out, tried, and abandoned. His last idea was to make a vessel in which the converting process did not take place, but into which he could put the pig iron as soon as it was melted, along with the same kind of materials that were used in the puddling-furnace. He was then of opinion that he must come as near to puddling as possible, in order to get the phosphorus out of the iron. Just as he was preparing to put this plan into operation, there arrived in England some pig iron which he had ordered from Sweden some months previously. When this iron, which was free from phosphorus, was put into the converter, it yielded, in the very first experiment, a metal of so high a quality that he at once abandoned his efforts to dephosphorize ordinary iron. The Sheffield manufacturers were then selling steel at £60 a ton; and he thought that as he could buy pig iron at £7 a ton, and by blowing it a few minutes in the converter could make it into what was being sold at such a high price, the problem was solved. But there was yet one thing wanting. He had now succeeded in producing the purest malleable iron ever made, and that, too, by a quicker and less expensive process than was ever known before. But what he wanted was to make steel. The former is iron in its greatest possible purity; the latter is pure iron containing a small percentage of carbon to harden it. There has been an almost endless controversy in trying to make a definition that will fix the dividing line that separates the one metal from the other.[24]