I had hoped that my old friend Daniel Kinnear Clark might turn up as the English member in our group of judges at the Centennial Exposition, but in this I was disappointed. The English judge in our group was Mr. Barlow, son of the celebrated author of “A Treatise on the Strength of Materials,” which, if I remember rightly, was the first authoritative treatise on that subject. Mr. Barlow, however, was not of much help to us; he came late and attended but one meeting. That, I remember very well, was the meeting at which I presented my classification. He left Philadelphia with his son to visit Niagara Falls, and we never saw him again. I remember his giving me a very cordial invitation to visit him when I should find myself in England. Two of my English engineering acquaintances appeared at this exhibition. One of them was a judge in the group which embraced sewing machines. I remember asking him what was the most interesting mechanical device he had seen at the exhibition; he told me it was the automatic tension in the Wilcox & Gibbs sewing machine. In a walk with him through Machinery Hall one day, I called his attention to a locomotive built by the Baldwin Locomotive Works. After looking it over cursorily he remarked that he did not see anything particular in it. I could not help replying, “That may not be the fault of the locomotive.” I had thought him a light weight in England, and that superficial remark confirmed my opinion. The other friend, as I am proud to call him, I have always considered mechanically the most interesting man I ever met. It was Mr. Smith, of Smith & Coventry, the machine-tool builders of Salford. Mr. Smith was the brains of the concern. He had come over to learn what America could teach him, and the only thing he took back, so far as I know, was the twist-drill, the manufacture of which was begun by that firm after his return. I shall have something to add later to what I have already said respecting his wonderful improvements in machine tools. In one of the pleasant walks we took together, our attention was arrested by the exhibit of Riehlé Brothers, the celebrated scale manufacturers of Philadelphia. Among other novel and interesting features of their exhibit this firm showed a ³⁄₄-inch bolt broken by a stress applied to it through a nut of only one half the standard thickness, or three eighths of an inch deep, and that run on loosely by hand. This astonishing revelation drew from Mr. Smith the ejaculation, “Why, old Whitworth lied.” Mr. Whitworth had stated that he had ascertained by experiment that a nut to be as strong as the bolt must have a depth equal to the diameter of the bolt, and this had been accepted as mechanical truth by the entire engineering world, no one ever thinking to make the simple measurement which would show that the force required to strip the threads of any bolt in a nut of this standard depth would be nearly three times the strength of the bolt. He