Thud! What was that?
Efficiency had fainted dead away! The last blow had been too much for her. And the Principles gathered mournfully round, but with the aid of the Propeller Slip[1] and a friendly lift from the Surface she was at length revived and regained a more normal aspect.
Said the Stagger with a raffish air, "My dear young lady, I assure you that from the experiences of a varied career, I have learned that perfection is impossible, and I am sure the Designer will be quite satisfied if you become the Most Efficient Compromise."
"Well, that sounds so common sense," sighed Efficiency, "I suppose it must be true, and if the Designer is satisfied, that's all I really care about. Now do let's get on with the job."
So the Chalk drew a nice long slim body to hold the Engine and the tanks, etc., with room for the Pilot's and Passenger's seats, and placed it exactly in the middle of the Biplane. And he was careful to make its position such that the Centre of Gravity was a little in advance of the Centre of Lift, so that when the Engine was not running and there was consequently no Thrust, the Aeroplane should be "nose-heavy" just to the right degree, and so take up a natural glide to Earth—and this was to help the Pilot and relieve him of work and worry, should he find himself in a fog or a cloud. And so that this tendency to glide downwards should not be in evidence when the Engine was running and descent not desired, the Thrust was placed a little below the Centre of Drift or Resistance. In this way it would in a measure pull the nose of the Aeroplane up and counter-balance the "nose-heavy" tendency.
And the Engine was so mounted that when the Propeller-Thrust was horizontal, which is its most efficient position, the Angle of Incidence and the Area of the surfaces were just sufficient to give a Lift a little in excess of the Weight. And the Camber was such that, as far as it was concerned, the Lift-Drift Ratio should be the best possible for that Angle of Incidence. And a beautifully simple under-carriage was added, the outstanding features of which were simplicity, strength, light-weight, and minimum drift. And, last of all, there was the Elevator, of which you will hear more by-and-by. And this is what it looked like then:
