MECHANICAL FLIGHT. Attempts to imitate the flight of birds by mechanical contrivances antedate the balloon by several hundred years. Several very early instances are on record of persons who, apparently by some paraehnte-like contrivance, descended obliquely from high towers to a considerable distance; thus in the thirteenth or fourteenth century. Elmerus, a monk, is said to have flown more than a furlong from the top of a tower in Spain, hut the distance is probably much exaggerated; and in the seventeenth cen tury, Besnier, a locksmith of Sable, in France, after experiments from windows one story high was able to leap safely from very elevated positions, and to pass over houses or over rivers of considerable breadth. The first properly authenticated account of an artificial wing was given by Borelli in 1670, and his investigations and experiments furnished the principal basis for experiments until 1S67. In this year Pro fessor J. B. Pettigrew, an English scientist, pub lished the results of an elaborate and careful series of studies made by him upon the flight of birds, which wrought a revolution in the con struction of flying machines. Elastic aeroplanes were advocated by Mr. Brown. elastic. aerial screws by Ali.. Armour, and elastic aeroplanes, wings, and screws by M. Pimand. The latter constructed models to fly by three dinyxm it meth ods—(1) by means of screws acting vertically upward; (2) by aeroplanes propelled horizon tally by screws; and (3) by Wing,: which are flapped in an upward and downward direction. These models were so far successful as to make a considerable •gree of progress and offer hints for future guidanee. Mr. Henson designed a flying machine in 1841, combining aerial screws with extensive supporting structures. Mr. Wen ham. in 1807, thinking to improve upon Mr. Henson, invented what he designated his aero planes. Mr. Stringfellow, who was originally associated with Ali. 'Henson, and constructed a successful flying model in 1847, built a second model in 1811S, in which Mr. Wenham's aero planes were combined with aerial screws. model was on view at the exhibition of the Aeronautical Society of Great Britain, held at the Crystal Palace, London, in 1808. It was remarkably compact and light, and obtained the $500 prize of the exhibition for its engine, which was the lightest and inns!, powerful ever con structed. The machine for which it was made was not successful. In 1874 Mr. Moy invented an aerial steamer, consisting of a light, powerful skeleton frame resting on three wheels: a very effective light engine constructed on a new prin ciple, which dispensed with the old-fashioned cumbrous holier, narrow horizontal aeroplanes, and two very large aerial screws. In its general
features Nr. Moy's machine resembled that of Mr. Stringfellow.
Summarizing the methods of flight so far attempted, we have, therefore, (1) dirigible bal loons: (2) those forms of apparatus which were intended to sustain or lift their weight by screw propellers revolving on vertical axes; (3) those machines which were intended to sustain their weight on flapping or beating wings: and ) the aeroplane or aeroeurve contrivances which have been experimented with in recent years, to the practical exclusion of all other classes except the dirigible balloon. To understand the reason for this tendency toward the aeroplane or gliding machine, a brief comparative dismission of the different classes of flying machines is necessary.
As already staled, the future utility of the dirigible balloon is still the subject of differences of opinion. Its chief drawbacks are great bulk and extreme frailty, which seem to affect its practical advantages in other respects. Vertieal screw machines have much to recommend them, but they present drawbacks which more Hum counterbalance the advantages. The ability to rise directly into the air from any given spot would be an exceedingly desirable quality, and lie»ce a great many attempts have been made to develop a successful vertical screw maehine. Perhaps the greatest stumbling block to success has been that when the surfaces which form the blades of the screws are revolved over one spot they do not give any considerable lifting effect in proportion to the power consumed. It is stated by high authority that where one might from theory expect a lift of possibly 100 pounds per horse-power, the best result the inventor can produce on a practical scale is almost sure to be less than one-seventh of that figure: in fact, the lift With the lightest engines we can build is likely to be but little if any more than the weight of the machine itself. With engines weighing much more than four or five pounds per horse-power it is asserted that practical success with this type of apparatus is not possible. The third doss, or the beating wing machines, are subject to the same disadvantages in regard to the enormous power required as those of the vertical screw type. In addition to this, the problem of maintaining a stable equilibrium in windy weather still further seriously complicates matters so much, that it is considered that there is but small hope of practical machines opera led 011 this principle being produced. In conelm-ion, it is hardly necessary to point out that any com bination in a single machine of the salient fea tures of two or more of the classes of machines described tends to complicate rather than to improve the situation.