As he grew older he became irritable and exceedingly dogmatic, possibly because of his long contests with slow-moving government officials. Charles T. Porter, in his autobiography, brings out this side of his nature and shows that the initiative of subordinates in his shop was practically killed. Perhaps this limited his service somewhat in his later years, but when all is taken into account, he was, without question, one of the greatest of mechanical engineers. He was a master experimenter. Tests which he made were thorough, conclusive, and always led somewhere. His experiments, whether in machine tools, screw threads, or ordnance, always resulted in a design or process which sooner or later became standard. Whitworth’s position as a tool builder is not weakened by the fact that most of the general tools had been invented by the time he began his independent work. He raised the whole art of tool building by getting at the fundamental conditions. He led the way in the change from the weak, architectural style of framing; introduced the box design or hollow frame for machinery, taking his suggestion from the human body, and very greatly increased the weight of metal used. In 1850 Whitworth was, without doubt, the foremost tool builder in the world. He had introduced a standard of accuracy in machine tools unknown before, and so improved their design and workmanship that he dominated English tool practice for several generations. In fact, the very ascendency of Whitworth’s methods seems to have been an element in the loss of England’s leadership in tool building. Most of the progressive work for the next fifty years was done in America. In the foregoing chapters we have traced briefly the work of the great English mechanics from 1800 to 1850. Their services to engineering, and, in fact, to mankind, cannot be measured. When they began, machine tools in any modern sense did not exist. Under their leadership nearly all of the great metal-working tools were given forms which have remained essentially unchanged. England had the unquestioned leadership in the field of machine tools. Machine-tool building in Germany and France was one or two generations behind that of England, and nearly all their machinery was imported from that country. With the exception of the early and incomplete work of the ingenious French mechanics, which we have referred to from time to time, practically all of the pioneer work was done by Englishmen.