He plumped himself down on the sand again and fixed his gaze upon the bobbing piece of bamboo and the inflated bladders. Tom had known, without his father’s declaration to that effect, that one of the chief problems he had to solve in the matter of building a better flying boat than anybody else was the problem of constructing his invention so that it could settle in a rough sea without being capsized. The puzzling thought was with him, day and night. It ran in his head like a tune that sometimes seems to fill one’s mind to the expulsion of everything else. Yet, when the young inventor was left alone again and tried to settle himself to his problem in statics, his thought weaved a pattern something like this: “A shell of some light metal—aluminum, we’ll say—buoyed on the outside by additional air chambers. Humph, it would look extremely awkward. But, as Mr. Nestor says very often, the look of a thing isn’t what counts. Poor Mr. Nestor! What will those two women do if he does not live? “How about double walls from stem to stern for air chambers? Humph! Bless my blown-up bladders! as Mr. Damon might say,” and he chuckled. “Mr. Damon catching a tarpon so big that he thought he should have spent a week landing it. Humph! “And he starts in a day or two for Iceland. Br-r-r! That’s one cold country, I bet! Cold! Iceland! Why, if Mr. Nestor went there for a few weeks—Great Scott!” exclaimed Tom Swift, suddenly rising and forgetting all about his bamboo stick and pigs’ bladders floating on the lake. “What have I been thinking of? Wakefield Damon is just the man for us!” He started away from the lake at top speed, forgetting for the time all about his plans for a flying boat that would astonish the world. CHAPTER VIII THE EXPEDITION SETS OFF Tom Swift was quite sure that Mr. Wakefield Damon had not been up from Waterfield since the specialist had diagnosed Mr. Nestor’s trouble, and probably had not heard of Dr. Raddiker’s advice. The last Tom had heard from his eccentric friend, he was making preparations to leave for New York very shortly. The young inventor did not even halt at the house to tell his father what he purposed doing; but he got out his electric runabout and made as good time as the town speed ordinance allowed to Mary Nestor’s house. Mary and her mother were in no more cheerful state of mind than they had been when Tom had last seen them. They had canvassed all the possible ways they could think of to bring about the desired trip for Mr. Nestor into the North, but had accomplished nothing. “Every way seems shut by a door that is barred and locked, Tom,” sighed Mary to her sympathetic friend. “We do not know what to do.” “Put on your hat and jacket and come for a ride,” proposed the young fellow. “But that won’t help father,” she complained. “And I ought not to take you from your work and let you drive me about the country. It isn’t right.”