and in a small tube, it could certainly be relied upon under a column of water several times longer, under a pressure of several atmospheres and in a much larger tube. The greater the pressure the smaller the bubbles of steam would be. Those formed under one atmosphere were about as large as kidney beans. Mr. Smith was anxious to have us exhibit the engine at the Fair of the American Institute in New York in the fall of 1870. This Institute was then at the height of its usefulness, and its annual fairs were crowded with exhibits and attracted wide attention. Mr. Allen and I consulted about it, and on account of the liability of getting more hot water than steam from the queer boilers that might be exhibited, we agreed that, as the engine would have to be tested for economy, it would not be safe to exhibit unless we could make a boiler according to Mr. Allen’s plan to supply the steam. With this boiler we could certainly get dry steam, and felt confident of getting it superheated. Our recommendation to that effect was adopted, and we prepared to exhibit two engines, one of them 16 inches diameter of cylinder by 30 inches stroke to make 150 revolutions per minute, and the other 6 inches in diameter by 12 inches stroke to make 300 revolutions per minute, and a boiler. We also made to drive our own shop, to take the place of the portable engine and boiler, an engine of the smaller size above named, except that the cylinder was, by thickening its walls, made 5 inches in diameter only. This was because this size would be ample for the power we required, and I would be able to show the effect of inertia of the heavy reciprocating parts in producing smooth and silent running, much better than with a 6-inch cylinder, which would have about 50 per cent. larger area with no greater weight in the reciprocating parts, except only in the piston. This exhibition, as we shall see, became of great importance. We made also an Allen boiler for ourselves, of four sections; really, as it proved, three or four times as large as we needed, but we could not well make it smaller. This exhibition at the American Institute was in every respect a great success, not a drawback of any kind about it. The little engine was used by Merrill & Sons to drive their exhibit of forging machinery, hammers and drops. The large engine gave motion to a miscellaneous exhibit of machinery in motion. The exhibition of machinery in motion closed each day for an hour from 12 to 1, and again from 6 to 7, but I ran these engines continuously from 9 A.M. to 10 P.M., to show that high speed asked no favors. There were five boilers, including our own, from the start. The other four were smaller than ours. Another boiler, the largest of all except ours, was started later, as will be told. Ours had a brick flue and chimney, but only 30 feet high. Those of the others were iron. There were a number of other engines and pumps and pulsometers, all steam eaters.