The Marmonier gyroscopic pendulum, devised to secure automatic stability of aeroplanes. The wheels are driven by the aeroplane motor at high speed. The pendulum rod is extended upward above the axis and carries a vane which is engaged by any gust of wind from either side of the aeroplane, tending to tilt the pendulum, and bringing its gyroscopic resistance into play to warp the wings, or operate ailerons.] The caution shown by these experienced aviators cannot be too closely followed by a novice. These men do not say that their assiduous practice on the ground was the fruit of timidity. On the contrary, although they are long past the preliminary stages, their advice to beginners is uniformly in the line of caution and thorough practice. [Illustration: When the aeroplane is steered to the left, the pendulum swings to the right and depresses the right side of the plane, as in (_c_). The reaction of the air raises the right side of the plane until both surfaces are perpendicular to the inclined pendulum, as in (_d_). Diagrams showing action of Marmonier gyroscopic pendulum.] Even after one has become an expert, the battle is not won, by any means. While flying in calm weather is extremely pleasurable, a protracted flight is very fatiguing; and when it is necessary to wrestle with gusts of high wind and fickle air currents, the strain upon the strongest nerve is a serious source of danger in that the aviator is liable to be suddenly overcome by weariness when he most needs to be on the alert. [Illustration: In that inclined position the aeroplane makes the turn, and when the course again becomes straight, both the gyroscopic and centrifugal forces cease, and the pendulum under the influence of gravity becomes vertical. In this position it is inclined to the left with respect to the planes, on which its effect is to depress the left wing and so right the aeroplane, as in (_e_). Diagram showing action of Marmonier gyroscopic pendulum.] Engine troubles are much fewer than they used to be, and a more dependable form of motor relieves the mind of the aviator from such mental disturbance. Some device in the line of a wind-shield would be a real boon, for even in the best weather there is the ceaseless rush of air into one’s face at 45 to 50 miles an hour. The endurance of this for hours is of itself a tax upon the most vigorous physique. With the passing of the present spectacular stage of the art of flying there will doubtless come a more reliable form of machine, with corresponding relief to the operator. Automatic mechanism will supplant the intense and continual mental attention now demanded; and as this demand decreases, the joys of flying will be considerably enhanced. [Illustration: