The engine originally weighed about ten tons. The boiler was thirteen feet long and three feet six inches in diameter. The cylinders were nine inches by twenty inches. There were four driving wheels, four feet six inches in diameter, arranged with outside cranks for connecting parallel rods, but owing to the sharp curves on the road these rods were never used. The driving wheels were made with cast iron hubs and wooden (locust) spokes and felloes. The tires were of wrought iron, three quarters of an inch thick, the tread being five inches and the depth of flange one and a half inches. The gauge was originally five feet from center to center of rails. The boiler was composed of sixty-two flues seven feet six inches long, two inches in diameter; the furnace was three feet seven inches long and three feet two inches high, for burning wood. The steam ports were one and one-eighth inches by six and a half inches; the exhaust ports one and one-eighth by six and a half inches; grate surface, ten feet eight inches; fire box surface, thirty-six feet; flue surface, two hundred and thirteen feet; weight, without fuel or water, twenty-two thousand four hundred and twenty-five pounds. After the valves were in gear and the engine in motion, two levers on the engineman's side moved back and forth continuously. When it was necessary to put the locomotive on the turntable, enginemen who were skilled in the handling of the engines first put the valves out of gear by turning the handle down, and then worked the levers by hand, thus moving the valves to the proper position and stopping the engine at the exact point desired. The reversing gear was a very complicated affair. The two eccentrics were secured to a sleeve or barrel, which fitted loosely on the crank shaft, between the two cranks, so as to turn freely. A treadle was used to change the position of this loose eccentric sleeve on the shaft of the driving wheel (moving it to the right or left) when it was necessary to reverse. Two carriers were secured firmly to the body of this shaft (one on each side of the eccentrics); one carrier worked the engine ahead, the other back. The small handle on the right side of the boiler was used to lift the eccentric rod (which passed forward to the rock shaft on the forward part of the engine) off the pin, and thus put the valves out of gear before it was possible to shift the sleeve and reverse the engine. Great similarity will be noticed in the American locomotives built for many years after the arrival of the "John Bull," especially in the matter of making the keys, brasses, etc., on the connecting rods, and in the construction of valves, fire box and tubes. Even the old plan of setting the ends of the exhaust nozzle high up in the smoke box, which was discontinued when the petticoat pipe came in use, is now again resorted to in connection with the extended smoke box of modern locomotives. FIRST TRIAL OF THE LOCOMOTIVE.