The tendency towards the horizontal type of engine, in place of the beam-engine, began to be quite marked in England about that time. This was favorable to the use of the Allen engine. The only thing that seemed wanting to its success was a directly connected jet condenser. No one believed that an air-pump could be made to run successfully at the speed of 150 double strokes per minute. Yet this had to be done, or I could not look for any considerable adoption of the high-speed engine. This subject occupied my mind continually. When I returned from Oporto, I had thought out the plan of this condenser, and at once set about the drawings for it. No alteration was ever made from the first design of the condenser, which I intended to show with the engine at the coming Paris Exposition in 1867, and which I finally did succeed in showing there, but under very different and unexpected relations. The philosophy of this condenser is sufficiently shown in the accompanying vertical cross-section. A hollow ram, only equal in weight to the water which it displaced, ran through a stuffing-box at the front end of the chamber, and was connected with an extension of the piston-rod of the engine. So the center line of the engine extended through this single-acting ram, which had the full motion of the piston. It ran through the middle of a body of water, the surface of which fell as the ram was withdrawn, and rose as it returned. A quiet movement of the water was assured by three means: First, the motion of the ram was controlled by the crank of the engine, and so began and ceased insensibly. Second, the motion of the ram, of two feet, produced a rise or fall of the surface of the water of only about one inch. Third, the end of the ram was pointed, a construction which does not appear in this sectional view, permitting it to enter and leave the water at every point gradually. Both the condenser and the hot-well were located above the chamber in which the ram worked.