"I acknowledge it. But we must make sacrifices, if we would master the UNKNOWN. Newton lived on bread and water when he wrote his immortal Principia. He condemned himself to the coarse fare of a prison, in order that his intellect might soar untrammelled to the stars. I have improved on Newton--I eat nothing. As for sleep, I grudge a single hour of it which comes between me and the completion of my great work." "But how long can you stand this dreadful strain upon your powers?" "Till daylight to-morrow, with safety. By that time I shall have overcome the last obstacle. Of this I am confident. Then, ho! for unbounded wealth and undying fame. The toil has been severe, but the reward will be glorious." "I congratulate you," said Marcus, "on the near approach of your final triumph. And, in order that I may not delay you a single moment, I will bid you 'good-night.'" Marcus rose, but he hoped that the inventor would ask him to stay. The inventor did so. "Pray don't hurry, Mr. Wilkeson; I would like to have a brief conversation with you. A few minutes only." He drew a chair to the side of Marcus, and seated himself. "Mr. Wilkeson," he said, in a deliberate voice, as if he were repeating carefully-considered words, "it is unnecessary for me to say that I have the highest opinion of you. Providence seems to have sent you to me at a time when I was in the greatest need. You saved me from starving. The world will be as much indebted to you for my grand invention, as it was to the generous patronage of Queen Isabella for the discovery of America." "Pooh!" interrupted Marcus, blushing. "The praise is none too high," continued the inventor. "It is true, I have repaid your advances of money tenfold, by giving you an interest in my future but certain fortune. But that does not diminish my gratitude." Marcus knew that this flattering exordium meant something serious. It was a favorite theory of his, that danger, or any kind of anticipated, disagreeable thing, was best met halfway. So he said, with a feeble attempt at a smile: "I infer from this ominous opening that you have received another lying anonymous letter about me. If I am right, Mr. Minford, be good enough to let me see it at once, according to your promise." "You have guessed correctly, Mr. Wilkeson. I have received a second anonymous letter, which I intended showing to you after a further brief explanation. But I can readily appreciate your anxiety to read it without delay. Here it is." He drew forth a letter, and handed it to Marcus. Marcus immediately recognized the envelope and the address as similar to those of the first letter, which he still had in his possession. He pulled the letter nervously from its yellow sheath, and read as follows: MR. MINFORD: