She was happy, too, in the prospect of making as much money the next summer. For the Wizard, Uncle John told her, had not the secret yet. He had succeeded in making a platinum wire, encased in a glass globe, give a light equal to that of twenty-five candles without melting. But he needed to exhaust all the air from the glass globe, and still one one-hundred-thousandth of the original volume remained. "But that's not sufficient," commented Uncle John. "I know enough about the matter to be sure that so much air as that would prevent the platinum from giving out the light it ought to give. Still, within a short time, Dora, I expect even the Portland papers will describe Mr. Edison's success with the electric light." Uncle John's prediction was fulfilled. By the first of October the vacuum was so nearly perfect that only one-millionth part of the original air was left in the glass bulb. By the last of that same month, moreover, the whole secret was practically in Edison's grasp. He had stopped experimenting with platinum for a burner and had gone back to carbon, on which he had pinned his faith at first. But this time he used the carbon only as a coating for a piece of cotton thread that he had bent into a loop and sealed up in the almost perfect vacuum of glass. When this lamp was connected with the battery, it flashed forth with the brightness that the inventor had so long waited to see. But how long would it burn? There was no sleep for Edison till that question was answered; and it was not answered for forty hours--nearly two days of growing delight and diminishing anxiety. Such a discovery meant the end of all fruitless experimenting. The secret of the incandescent light was revealed; and the newspapers all over the country--the _Daily Eastern Argus_ of Portland among them--spread the knowledge of the great event in science and prophesied the speedy conquest of kerosene and gas. Late in November Uncle John sent Dora a copy of the _Scientific American_ which gave the authoritative account of what had been accomplished. [Illustration: EDISON IN HIS LIBRARY.]