His long strides soon brought him to the house.  The old building wore a gloomy look.  He did not speculate on the reason of this.  It was probably because there was no light visible in any of the front windows, and very little light in the street lamps.  The gas burned low and blue, and flickered in the wind.

Ringing the bell, Marcus was admitted by one of the numerous children belonging to somebody in the house (Marcus could never determine to whom), and walked up to the inventor’s room.  His heart beat with strange emotion as he rapped at the door.  For a moment he was sorry that he had come.

“Come in,” said the inventor, in a voice more sepulchral than usual.

Marcus entered the apartment.  The inventor received him with a feeble shake of the hand, bearing no resemblance to the hearty one which he used to bestow in the early days of their acquaintance.  Marcus noticed that Mr. Minford’s hand was hot.  He also observed that his eyes were preternaturally lustrous, and that the circles under them were deep and dark.  His cheeks were deathly pale, saving a little red spot in the centres.  He looked like a man in a state of fearful mental exaltation and nervous excitement.

Marcus was not in the habit of worrying people upon the subject of their ill health; but the inventor looked so palpably bad, that Marcus could not forbear to say, in a tone of anxiety, “You are unwell, sir.”

“Oh, no!  Quite well, I assure you,” said the inventor, with a weary smile.  “Though I should be sick, perhaps, but for the glorious hope that bears me up.  I have not eaten, or slept, for forty-eight hours.”

“But, my dear sir, this is trifling with your health.”

“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.”