The construction of water jackets for this engine proved an exceedingly formidable task, it being impossible to braze the jackets directly to the walls of the cylinders without risk of ruining them. It therefore became necessary to attach them by means of stuffing boxes, which, on account of their large size [p223] and the necessity for keeping the weight a minimum, was a most difficult piece of work. The work was rendered still more difficult by the fact that the water jackets had to be made in halves which were brazed together after they had been fitted over the head of the cylinder. Even when the work was done in the most careful way this method of construction gave a great deal of trouble from the leaking of the stuffing boxes or the jackets themselves. However, after much delay, the water jackets were finally completed, and upon test the engine was found to develop 21.5 horse-power at 825 R. P. M., the engine itself weighing 120 pounds. Further changes were made in this engine, especially in the pistons, a new set of which were constructed which weighed 15 pounds less than the original set. On account of the difficulty with the leakage of the water around the stuffing boxes of the water jackets, and also from imperfections in the brazed joints of the jackets themselves, it was found impossible to rely on the power that the engine would develop at any particular time, as the water leaking from the jackets and running down on the spark plugs of the lower cylinders caused these cylinders to work erratically, and this not only materially reduced the power but also caused jerky impulses in the absence of fly wheels. It seemed so desirable to obtain as soon as possible a first test in actual flight of the large machine that the writer offered to put this engine in the aerodrome frame and make a test with it if the machine were launched over the water, but with the launching track mounted directly on the river bank. However, Mr. Langley felt it so necessary to make the initial test from the top of the house-boat and at an elevation of 30 feet or more that he would not consent to this, and as the engine at its best did not develop quite 24 horse-power, which had been calculated as the minimum which should be provided, it was thought unwise to attempt to make the first test from the top of the house-boat until the aerodrome had been provided with engines that could be depended on to develop continuously not less than 24 horse-power. It then became necessary either to build a duplicate engine and use both of them in the aerodrome, the original plan as already explained having been to have two engines developing the 24 horse-power together; or, second, to construct an entirely new engine large enough to furnish a minimum of 24 horse-power and use this single engine.