After the boys returned home it was decided that they and Mr. Britten would set out for Florida the next morning. In the meantime, the elderly diver telegraphed his caretaker to get the "Betsy B." in order and arrange to hire a tug-boat. [Illustration: They Planned to Start the Next Day] Late in the afternoon Tom called his chum on the phone. "Can you spare me a few minutes?" he asked. "Think I'm going to have something interesting to show you." "Be right over," replied Ned. "Where are you?" "In the lab." A few minutes later young Newton had joined his friend. "What's up?" he asked Tom as he entered. [Illustration: "What's up?" Asked Ned] Tom had discovered that his bendable glass mixture had cooled to a critical temperature, making it necessary to remove it from the furnace at once lest it be ruined. In a small secret chamber beneath his private laboratory he had set up a sort of miniature glass works which would have astonished any ordinary glass worker, for the young inventor had devised an entirely new method of procedure. As to its outcome, well, even to its inventor that feature remained in doubt. [Illustration: A Miniature Glass Works] "Do you think it'll work, Tom?" asked Ned Newton anxiously as he followed the youthful scientist down the stairs. "Your experiments have cost a mint of money already--" "Don't croak," chuckled Tom. "I've a few pennies left, haven't I?" "You won't have so very many after you finish with your new telescope idea," declared Ned grimly. "And THAT certainly won't bring in any dividends." [Illustration: Ned Followed Tom] "Nor is it intended to," said Tom a bit sharply. "There is, you know, such a thing as pursuing knowledge for its own sake." "I'm sorry. You ought to know, though, that I'm thinking only of your interests, not of mine," he said as they reached the room below. "Forgive me, old man!" Tom clapped Ned warmly on the back. "Don't feel for a minute that I don't appreciate everything you've done for me. To tell you the truth, I'm as worried about this new glass as you are. That's why I jumped on you. Let's forget it!" [Illustration: "Forgive Me, Old Man!"] "Right!" The two were standing now before the cylindrical furnace containing the mixture of silicates and other ingredients from which Tom Swift hoped would emerge a glass as flexible as rubber and as strong as steel. The thermometer on the front stood at twenty-one degrees Centigrade. [Illustration: They Looked at the Thermometer] "She's just right," muttered the inventor, consulting a complicated chart hanging on the wall. "Now we'll see!" The asbestos-coated door clanged open. Tom drew out a shallow tray, the contents of which were buried in a black powder. "Charcoal!" he explained, setting the pan on a table. "It prevents any rapid temperature change. Even common glass must be cooled slowly or it becomes as brittle as peanut candy." [Illustration: Tom Drew out a Shallow Tray]