Engineers have, until recent years, fought shy of anything relating to aerial navigation. Those who ventured, in spite of the odium attached to that study, to look into it at all, became very soon satisfied that the great obstacle in the way was the lack of a motor sufficiently light to sustain its weight and that of an aeroplane, upon the air. Fifteen years ago the lightest steam motor was the marine engine weighing 60 pounds to the H.P., while the gas engine weighed very much more; the locomotive weighed 200 pounds per H.P. During the past fifteen years a great change has taken place. Steam motors have been produced weighing only 10 pounds per horse–power, and gas engines have been lightened down to 12½ to 15 pounds per horse–power, so that the status, so far as engineers are concerned, is very greatly changed, and there is some hope that, for some limited purposes at least, man will eventually be able to fly through the air.