mid-rib to the bowsprit at the front of the machine, and for the rear wings to the main frame. Each wing when completely assembled weighed approximately 29 pounds, and had a rectangular surface 22.5 by 11.5 feet (measured on the chord of the curve), or 260 square feet, making the weight per square foot equal about 50 grammes, rather less than 1.5 times as much per square foot as the wings for the steam-driven models. The total supporting surface of the aerodrome was 1040 square feet, and as the aerodrome when equipped for flight weighed, including the aviator, 850 pounds this gave 1.22 square feet to the pound, or 0.82 pound to the square foot. Although this was a somewhat larger proportion of weight to supporting surface than it had originally been expected to have, there is every reason to believe that it was sufficient, for the quarter-size model, when weighted so that it had 1.22 square feet to the pound, flew well, as will later appear. [p207] CHAPTER VII EQUILIBRIUM AND CONTROL In an aerodrome it is essential not only that its component parts shall be so disposed that the initial equilibrium is correct and highly stable, but also that some efficient means be provided for quickly and accurately restoring the equilibrium, if for any reason it is disturbed. If the aerodrome is of sufficient size and power to carry a human being it is, of course, possible merely to supply an efficient means of controlling the lateral and horizontal equilibrium of the machine and depend upon the intelligence and skill of the operator, as developed by practice and experience, to maintain the proper equilibrium of the machine while in the air. This method, however, is open to the objection that no matter how skilled the aviator may be there remains the probability of a serious if not fatal accident as the result of any momentary lapse or diversion of attention until the “sense of equilibrium” has been developed. One of the chief problems, therefore, which had impressed itself from the beginning of the work, was to devise some means by which the equilibrium of the aerodrome would be automatically maintained under the varying conditions of flight, so as to leave the aviator free, as far as possible, to control the direction of flight and to devote his attention to other important matters connected with the proper functioning of the various parts of the aerodrome. In the development of the models it had been absolutely necessary to develop some efficient automatic control, as they were far too small to carry an aviator, and the conditions of flight in the open air, even on the calmest day, were such that constant readjustments of the equilibrium were necessary. The success attained in the automatic control of the equilibrium of the models had been so great, and so much time would have been required for an aviator to acquire skill sufficient to control a machine without such automatic equilibrium,