On May 6, 1896, after a long wait for propitious weather, the aerodrome was despatched on a trial trip. It rose in the face of the wind and travelled for over half a mile at the rate of twenty-five miles an hour. The water and fuel being then exhausted it settled lightly on the water and was again launched. Its flight on both occasions was steady, and limited only by the rapid consumption of its power-producing elements. The Professor believes that larger machines would remain in the air for a long period and travel at speeds hitherto unknown to us. In both the machines that we have considered the propulsive power was a screw. No counterpart of it is seen in Nature. This is not a valid argument against its employment, since no animal is furnished with driving-wheels, nor does any fish carry a revolving propeller in its tail. But some inventors are strongly in favour of copying Nature as regards the employment of wings. Mr. Sydney H. Hollands, an enthusiastic aeromobilist, has devised an ingenious cylinder-motor so arranged as to flap a pair of long wings, giving them a much stronger impulse on the down than on the up stroke. The pectoral muscles of a bird are reproduced by two strong springs which are extended by the upward motion of the wings and store up energy for the down-stroke. Close attention is also being paid to the actual shape of a bird’s wing, which is not flat but hollow on its under side, and at the front has a slightly downward dip. “Aerocurves” are therefore likely to supersede the “aeroplane,” for Nature would not have built bird’s wings as they are without an object. The theory of the aerocurve’s action is this: that the front of the wing, on striking the air, gives it a downwards motion, and if the wing were quite flat its rear portion would strike air already in motion, and therefore less buoyant. The curvature of a floating bird’s wings, which becomes more and more pronounced towards the rear, counteracts this yielding of the air by pressing harder upon it as it passes towards their hinder edge. [Illustration: _M. Santos Dumont’s Airship returning to Longchamps after doubling the Eiffel Tower, October 19, 1901._] The aerocurve has been used by a very interesting group of experimenters, those who, putting motors entirely aside, have floated on wings, and learnt some of the secrets of balancing in the air. For a man to propel himself by flapping wings moved by legs or arms is impossible. Sir Hiram Maxim, in addressing the Aeronautical Society, once said that for a man to successfully imitate a bird his lungs must weigh 40 lbs., to consume sufficient oxygen, his breast muscles 75 lbs., and his breast bone be extended in front 21 inches. And unless his total weight were increased his legs must dwindle to the size of broomsticks, his head to that of an apple! So that for the present we shall be content to remain as we are!