The flight-commander thinks it advisable to remain hidden by keeping inside the clouds. He must therefore steer entirely by compass, without sun or landmark to guide him. As we leave the clear air a left movement of the rudder, without corresponding bank, swings the machine to the north, so that its nose points away from the desired course. The pilot puts on a fraction of right rudder to counteract the deviation. We veer eastward, but rather too much, if the swaying needle of the compass is to be believed. A little left rudder again puts the needle into an anti-clockwise motion. With his attention concentrated on our direction, the pilot, impatient at waiting for the needle to become steady, unconsciously kicks the rudder-controls, first to one side, then to the other. The needle begins to swing around, and the compass is thus rendered useless for the time being. For the next minute or two, until it is safe to leave the clouds, the pilot must now keep the machine straight by instinct, and trust to his sense of direction. A similar mishap often happens when flying through cloud. Pilots have been known to declare that all compasses are liable to swing of their own accord when in clouds, though the real explanation is probably that they themselves have disturbed the needle unduly by a continuous pressure on each side of the rudder-bar in turn, thus causing an oscillation of the rudder and a consequent zigzagged line of flight. The trouble is more serious than it would seem to the layman, as when the compass is out of action, and no other guides are available, one tends to drift round in a large circle, like a man lost in the jungle. Should the craft be driven by a rotary engine, the torque, or outward wash from the propeller, may make a machine edge more and more to the left, unless the pilot is careful to allow for this tendency. Such a drift to the left has taken us well to the north of a straight line between Toutprès and Passementerie, as we discover on leaving the clouds for a second or two, so as to correct the error with the aid of landmarks. But the compass has again settled down to good behaviour, and we are able to get a true course before we climb back to the sheltering whiteness. A flight inside the clouds is far from pleasant. We are hemmed in by a drifting formlessness that looks like thin steam, but, unlike steam, imparts a sensation of coldness and clamminess. The eye cannot penetrate farther than about a yard beyond the wing tips. Nothing is to be seen but the aeroplane, nothing is to be heard but the droning hum of the engine, which seems louder than ever amid the isolation.