Regarding the rate of propulsión of the fnture flying machine, Professor J. Elfteth Watkins, the distinguished mechanical expert, declares that it simply dependa upon the size of the propeller used and the rate at which the fans are revolved. In his opinión the old theory that the atmosphere was too tenuons a medium for a propeller to act upon has been demonBtrated to be nonsense. Sufficient resistance is offered by it to render possible an enonnous speed, so that it would not be too much to snrmise that a properly constructed air ship might accomplish the distance between Chicago and New York within an hour's time. Necessarily, however, there woold be a limit to rapidity of flight, inasmuch as a propeller ceases to propel after a certain number of revolntions per second has been reached. It is open to any one's observation that a vessel's propeller, operating in the water, often revolves mach faster when the craft is moving slowly than when it is going fast. Attention was called by Mr. Hazen to the treniendous revolution which the introduction of practical air ships would work in the methods of ofïense and defense in war. Portitications, on which it is suggested that Uncle Sam shall expend PO, 000,000 as soon as possible, would be of little use against flying machines that could drop dynamite and other explosives from aloft. Likewise ships of war, however heavily armored, would be at the mercy of hostile aerial navigators. COSTLY GÜNS RENDERED USELESS. In such a case batteries of a description altogether new would have to be devised for shooting vertically, and the general defending a position on terra firma would be obliged to assail the winged foe with volleys of bombs directed upward, as one would shoot ducks on the wing. Should such a state of affairs come to pass-, it seems likely that the conflicts of the future between nations will have to be fought out in the air between squadrons of flying men-ofwar. About that time one would imagine, it would be considered that the period had arrived, so long looked for by military thinkers, when there could be no more fighting because it would be too vastly destructive. Having achieved the conqnest of the ■waters, it is natural that man should likewise desire the mastery of the air, and thus in a)l ages the human race has been ambitious to fly. The earliest attempt in this direction recorded by tradition is the mythical account of Djbdalus, who, having constructed the celebrated labyrinth for Minos, king of Orete, was so unfortunate as to offend that monarch, and being imprisoned, escaped with the aid of wings made of feathers cemented with wax, Another ancient story of Archytas, of Tarentum,' who constructed a wooden pigeon that had power to fly, so nicely was it balanced by weight and put to motion by inclosed air. If there is any truth in the account, it seems probable that Archytas was a fakir and worked his bird with a string, as is done in the stage. The ancients, generally speaking, made no attempts in the direction of aeronautics, b#lieving that the power of flight could only appertain to the most powerful gods. OLD SCHEMES FOR FLYXNG. Four centuries ago an ingenious gentleman named Lauretus Lauras published a statement to the effect that swan's eggs filled with quicksilver, when exposed to the sun, would ascend in the air, but it is not recorded that the experiment was ever subjected satisfactorily to scientific test. In 1670 a Jesuit, Francis Lana, proposed to make four copper balls, each twenty-five feet in diameter and only four one-thousandths of an inch in thickness, from which the air was to be exhausted. To these balls a basket was to be attached, with a mast and sail, and the calculation was that the contrivance would carry 1,200 pounds. Unfortunately it was discovered that the exeessive thinness of the copper spheres would cause them to be broken when a vacunm was created inside of them by the pressure of the attnosphere from without. Nevertheless, this suggestion approached more nearly to a practicable idea in aerostatics than an)r other offered up to the time of the invenüon of the balloon in 1783 by the brothers Montgolfier. So late as 1775 Joseph ü-alien, a Dominican friar and professor in philosophy, contended that it would be possible to collect the rarefled air of some lofty mountain top and inclose it in a huge vessel a mile in diameter, which would carry fifty-four times as much weight as did Noah's ark. Funnily enough, nearly all the early theorists on this subject imagined that the atmosphere merely covered the earth like a shallow ocean, on which the aerial vessels they had in mind were intended to float, like ships in the sea, with their upper portions in the diffuse ether that lay above. - Washington Star.