"Mr. President," he said, laying his hand on the arm of Mr. Samson's big chair, which was nearly on a level with his breast, and speaking with persuasive earnestness, "you are the executive head of a mighty nation--the nation that sets the pace for the world. It is in your power to do a vast, an incalculable, service to humanity. One official word from you would save millions upon millions of lives. I implore you, instead of interfering with my work, to give instant order for the construction of as many arks, based upon the plans I have perfected, as the navy yard can possibly turn out. Issue a proclamation to the people, warning them that this is their only chance of escape." By a curious operation of the human mind, this speech cost Cosmo nearly all the advantage that he had previously gained. His ominous suggestion of a great nebula rushing out of the heavens to overwhelm the earth had immensely impressed the imagination of his hearers, and his uncontradicted accusation that Professor Pludder was concealing the facts had almost convinced them that he was right. But when he mentioned "arks," the strain was relieved, and a smile broke out on the broad face of the President. He shook his head, and was about to speak, when Cosmo, perceiving that he had lost ground, changed his tactics. "Still you are incredulous!" he exclaimed. "But the proof is before you! Look at the blazing heavens! The annals of meteorology do not record another such summer as this. The vanguard of the fatal nebula is already upon us. The signs of disaster are in the sky. But, note what I say--this is only the _first_ sign. There is another following on its heels which may be here at any moment. To heat will succeed cold, and as we rush through the tenuous outer spirals the earth will alternately be whipped with tempests of snow and sleet, and scorched by fierce outbursts of solar fire. For three weeks the atmosphere has been heated by the inrush of invisible vapor--but look out, I warn you, for the change that is impending!" These extraordinary words, pronounced with the wild air of a prophet, completed the growing conviction of the listeners that they really had a madman to deal with, and Professor Pludder, having recovered his self--command, rose to his feet. "Mr. President," he began, "the evidence which we have just seen of an unbalanced mind--"