It was strenuous work, fighting waves in a heavy amphibian, and incomparably more tiring than driving her through the air. Moreover it took his whole power of will and concentration to keep her head from playing off and becoming the forerunner of sure disaster. His back and shoulders began to ache under the strain; and soon his leg muscles were an added source of torture because of the excessive pressure he was forced to use on the rudder pedals. He dared not shift his gaze aft, so when they had been travelling the monstrous treadmill grind for an hour by the clock, he hailed his father: “How are we making it?”