A friend, assured of his success, put fifty thousand dollars into the business. Immediately Bessemer made plans of all the machinery required, sent various parts to as many different establishments, lest his secret be found out, and then put the pieces of his self-acting machines together. Five assistants were engaged at high wages, under pledge of secrecy. At first he made one thousand per cent profit; and now, in these later years, the profit is three hundred per cent. Three of the assistants have died; and Mr. Bessemer has turned over the business and the factory to the other two. The secret of making the bronze powder has never been told. Even Mr. Bessemer's oldest son had reached manhood before he ever entered the locked room where it was made. For ten years the inventor now turned his attention to the construction of railway carriages, centrifugal pumps, etc. His busy brain could not rest. When frequent explosions in coal-mines occasioned discussion throughout the country, he made, at large expense, a working model for ventilating mines, and offered to explain it to a committee of the House of Commons. His offer was declined with thanks. A little investigation on the part of great statesmen would have been scarcely out of place. At the great exhibition in London in 1851, he exhibited several machines,--one for grinding and polishing plate glass, and another for draining, in an hour, an acre of land covered with water a foot deep. The crowd looked at them, called the inventor "the ingenious Mr. Bessemer," and passed on. Two years later he made some improvements in war implements, and submitted his plans to the Woolwich Arsenal; but they were declined, without thanks even. Some other men might have become discouraged; but Mr. Bessemer knew that obstacles only strengthen and develop men. The improved ordnance having been brought to the knowledge of Napoleon III., he encouraged the inventor, and furnished the money to carry forward the experiments. While the guns were being tested at Vincennes, an officer remarked, "If you cannot get stronger metal for your guns, such heavy projectiles will be of little use." And then Mr. Bessemer began to ask himself if he could not improve iron. But he had never studied metallurgy. This, however, did not deter him; for he immediately obtained the best books on the subject, and visited the iron-making districts. Then he bought an old factory at Baxter House, where Richard Baxter used to live, and began to experiment for himself. After a whole year of labor he succeeded in greatly improving cast-iron, making it almost as white as steel.