I will improve the time while we are waiting for this preparatory work to be finished by telling of two Allen engines already running and made in the United States. The first one had been made by my old friend Mr. Richards, the inventor of the indicator. He was at that time the engineer of the Colt Armory in Hartford. They built a new shop four stories in height and 500 feet long. Mr. Richards designed and arranged the power in this shop and its transmission. He adopted the Allen engine, with which he alone in this country was familiar. I have written to Professor Richards for a description of these engines and received the following reply: “227 Edwards St., New Haven, Ct. “October 9, 1903. “_Dear Mr. Porter_: “In a sort of way you rather stole a march on me, by writing me before I had written to you, for it had been my intention for a number of weeks to write, thanking you for the frequent mention of my name in your ‘Reminiscences’ and for the kindly way in which you have spoken of me. Your papers have interested me greatly and bring back recollections of times which were for me very happy, when I first made your acquaintance and afterwards enjoyed the intimacy which grew up. “My neglect to write came from my almost unsurmountable repugnance to letter writing, which, if anything, grows yearly. “I am as nervous as usual, but in excellent strength, and by putting sulphur in my boots (and wearing the boots) am apparently pretty much cured of rheumatism. My students and I get along together very well; there are, however, so many of them now that I feel quite overwhelmed at times. About fifty men come to my classes, and in my department there are in all about one hundred and forty. “Now for the Colt’s Armory engines. There are two pairs in line with each other, vertical engines, Porter-Allen type, in the second story and in the middle of the building, which is 500 feet long. The line shaft, stretching 250 feet each way from the engines, forms an extension of the engine crank-shaft. Between the engines are pulleys driving the first-story line shaft beneath them and the third-story line above. All 500 feet long. Cylinder bore, 12¹⁄₂ inches; stroke, 24 inches; speed, 130 revolutions per minute. “The dimensions and general form of the running gear were made from drawings sent to me by you. The valve-gear differs only in divorcing the exhaust valves from the steam valves by placing them on the opposite side of the cylinder and driving them from a separate eccentric on that side, and not from the link.