While visiting the French engine builders in the summer of 1900 in the attempt to find one willing to undertake the construction of a suitable engine for the aerodrome, it was pointed out to them that the great amount of weight which they claimed to be necessary for the cylinders, and which they stated made it impossible for them to build an engine which would meet the requirements as to power and weight, could be very greatly reduced by making the cylinders in the form of thin steel shells having cast-iron linings. All, however, to whom this suggestion was made declared that it was impossible to build satisfactory cylinders in this way; some of them even stated that they had tried it and found it impossible to keep the thin liners tight in the steel shells. The difficulty which they had encountered is due to the difference in expansion of the steel and the iron when raised to a rather high temperature by the heat of the explosions, if the cylinders are not well jacketed with water; and if the steel [p235] shells are water jacketed they then do not expand as much as the cast-iron liners, and this causes the latter to become “out of round” because of the compression strains produced in them when trying to expand more than the steel shells. As past experience had shown, however, that it was possible to keep the liners tight in small cylinders, it was believed that by taking proper care in the construction there would be no difficulty in this respect with the cylinders of this larger engine.