My father’s proposed machine, of which he made a sketch, was of the Hélicoptère type, having two screws both on the same axis--the lower one to be right hand and mounted on a tubular shaft, and the top one to be left hand and mounted on a solid shaft running through the lower tubular shaft. These screws were to be rotated in reverse directions by means of a small pinion engaging a bevel gear attached to each of the shafts. His plan contemplated large screws with very fine pitch, and he proposed to obtain horizontal motion by inclining the axis forward. He admitted that there was no motor in existence light enough, but thought one might be invented, and that an engine might be worked by a series of explosions in the cylinder, that is, what is known to-day as internal combustion; but he was not clear how such an engine could be produced. He, however, said that a flying machine would be so valuable in time of war, that it mattered little how expensive the explosive might be, even if fulminate of mercury had to be used. It is interesting to note in this connection that the great Peter Cooper of New York thought out an identical machine about the same time, and actually commenced experiments. It seems that this gentleman regarded fulminate of mercury as altogether too feeble and inert, because we find that he selected chloride of nitrogen as his explosive agent. However, his work was soon brought to an end by the loss of the sight of one eye, after which time he had no further dealings with this lively explosive.