But a severer test awaited the Sea Eagle, namely, the trying out of her capacity actually to rise into the air. The craft was run partially ashore, and the great wings bolted in place and the stay wires adjusted. The stay wires were tightened by turn buckles till they were taut as fiddle strings, assuring stability of the wings. But in addition the wings were, of course, partially supported on the light but strong skeleton framework before noticed.
Much to the disappointment of the others, only Frank and Harry Chester and Dr. Perkins were to participate in the flying trials. But they took it all in good part, being promised rides later if the tests were successful. As before, the Sea Eagle, after she had been backed off and the propellers started, skimmed along the top of the water like a flying fish. But all at once the watchers on shore saw her rise bodily from the water and soar upward into the air. Higher and higher went the craft, gliding like a gull through the ether. It was an inspiring sight, and a perfect tornado of yells broke from Ben Stubbs, Billy and Pudge. But those on board the Sea Eagle could not hear the sounds of enthusiasm above the roaring of the motor.
Under Dr. Perkins’ skillful guidance the Sea Eagle climbed the aërial staircase till a height shown by the barograph to be almost 4,000 feet had been attained.
“Now to test the buoyancy apparatus,” cried the doctor suddenly. “Shut off power, Frank.”
Frank, who knew what was coming, obeyed the order and turned a valve admitting the pure hydrogen gas from one of the cylinders into the buoyancy devices. Instantly the upper wings swelled, till they resembled puffed-out mattresses more than anything else, and the “volplaning” downward movement was perceptibly checked. But, setting the descending device, Dr. Perkins headed the Sea Eagle for the water, and, skillfully manipulating the craft, landed it as lightly as a drifting feather on the water by the hull of the Betsy Jane.
Now came a further trial of the capabilities of the wonderful new craft which, so far, had proven such a success. Dr. Perkins set the planes in a rising position and allowed the Sea Eagle to hover above the Betsy Jane, like the bird for which the aërial craft had been named. Then suddenly he began a rapid descent, landing finally on the very summit of the inclined runway before mentioned. The sides of the Sea Eagle were equipped with large metal hooks, which were hastily thrown out by the boys and attached to four “eyes” arranged to receive them.
When this had been done the suction pump was set to work, and the inflated wings emptied of the gas, which was forced back into its receiver, and the valve closed. It was calculated that less than two per cent of the gas was lost during the process. The Sea Eagle was now once more a simple hydroplane, without any buoyancy device.
At a word from Dr. Perkins the hooks which had held the machine in place were disengaged, and instantly the craft began to glide down the runway. Half way down the engine was started, and when the graceful craft reached the abrupt end of the incline, the Sea Eagle went soaring off into space like a huge white-winged bird. This test was regarded by Dr. Perkins as the most important, for it proved the entire practicability of launching the Sea Eagle from a ship far out on the ocean.
After circling in the air a few times the tests were concluded by a rapid drop toward the earth right above the summit of the island. Just as it seemed as if the new craft must end her career by being dashed to bits against the construction shed, a skillful twist of the steering device sent her soaring upward once more. Two more swinging aërial loops were described, and then, with hardly a jar or vibration, the Sea Eagle was brought to rest by her inventor, almost in front of the shed where she had been assembled.
As the thrilling and wonderful trip was concluded, the boys came pressing about Dr. Perkins, showering congratulations and good wishes.