Writing of these improvements, Mr. Eric Stuart Bruce, Vice-President of the Aerial League of the British Empire, remarks that their importance cannot be over-estimated: ‘We have only to look at nature for their _raison d’être_, and observe the flight of seagulls over the sea. How varied are the flexings of nature’s aeroplanes in their wonderful manœuvrings to maintain and recover equilibrium!’ A feature of these early experiments was the placing of the operator prone upon the gliding machine, instead of in an upright position, to secure greater safety in alighting and to diminish the resistance. This, however, was only a temporary expedient while the Wrights were feeling their way. In the motor-driven aeroplanes the navigator and his companion were comfortably seated. After the experiment of 1901, the Wrights carried on laboratory researches to determine the amount and direction of the pressure produced by wind upon planes and arched surfaces exposed at various angles of incidence. They discovered that the tables of the air pressures which had been in use were incorrect. As the result of these experiments the Wrights produced in 1902 a new and larger machine. This had 28·44 square metres of sustaining surfaces, about twice the area of previous experiments. At first the machine was flown in the manner of a kite, with the view of learning whether it would soar in a wind. Experiments showed that the machine soared whenever the wind was of sufficient force to keep the angle of incidence between four and eight degrees. Later, in 1903, screw propellers were applied and four flights made. Definite progress favoured the venture. Two hundred and sixty metres were covered at a height of two metres! In the following year, 1904, there was further marked progress, many successful flights, some ‘circular,’ being made. In the next year came an astonishing achievement: the Wrights flew no less than 24¼ miles in half an hour. This was rightly deemed at the time a great flight forward. But a period of silence and seeming inactivity followed. It was not until 1908 that further revelations were made. It was then seen that the Wrights had not been idle. Indeed, it is said (and with obvious justice) that ‘to the labours of the Wright brothers we owe the advent of the mobile and truly efficient military air scout.’ CHAPTER VI FURTHER DEVELOPMENTS AND CERTAIN ENEMY MACHINES