To this day the mechanical means by which his famous gold paint is produced remains a secret. The machinery is driven by a steam-engine in an adjoining room; and into the room where the automatic machinery is at work none but the inventor and his assistants have ever entered. When a sufficient quantity of work is done, a bell is rung to give notice to the engine-man to stop the engine; and in this way the machinery has been in constant use for over forty years without having been either patented or pirated. Its profit was as great as its success. At first he made 1,000 per cent profit; and though there are other products that now compete with this bronze, it still yields 300 per cent profit. "All this time," says the successful inventor thirty years afterward, "I have been afraid to improve the machinery, or to introduce other engineers into the works to improve them. Strange to say, we have thus among us a manufacture wholly unimproved for thirty years. I do not believe there is another instance of such a thing in the kingdom. I believe that if I had patented it, the fourteen years would not have run out without other people making improvements in the manufacture. Of the five machines I use, three are applicable to other processes, one to color-making especially; so much so that notwithstanding the very excellent income which I derive from the manufacture, I had once nearly made up my mind to throw it open and make it public, for the purpose of using part of my invention for the manufacture of colors. Three out of my five assistants have died; and if the other two were to die and myself too, no one would know what the invention is." Since this was said (in 1871), Sir Henry has rewarded the faithfulness of his two surviving assistants by handing over to them the business and the factory. BESSEMER STEEL. Sir Henry Bessemer was first led to turn his attention to the improvement of the manufacture of iron by a remark of Commander Minie, who was superintending certain trials of the results of Sir Henry's experiments in obtaining rotation of shot fired from a smooth-bore gun. "The shots," said Minie, "rotate properly; but if you cannot get stronger metal for your guns, such heavy projectiles will be of little use."