Just as Mr. Henderson was about to open the door there came a fiercer blast of heat than any that had preceded.  At the same instant the conditions in the Mermaid became so fearful that each of the travelers felt himself fainting away.

“Go to—­ storeroom—­ get cylinder—­ get in——­” the professor murmured, and then he fell forward in a faint.

CHAPTER XVI

 The new land

“What is it?  Tell us!” exclaimed Jack, almost in his last breath, for, a few seconds later he too toppled over senseless.  Then Washington went down, while Andy, Bill and Tom succumbed to the terrible heat.

Mark felt his head swimming.  His eyes were almost bulging from their sockets.  He dimly remembered trying to force himself to go to the storeroom and see what was there.  He started toward it with that intention, but fell half way to it.

As he did so he saw something which impressed itself on his mind, half unconscious as he was.

The door of the storeroom suddenly opened, and from it came a giant shape, that seemed to expand until it filled the whole of the apartment where the stricken ones lay.  It was like the form of some monster, half human, half beast.  Mark shuddered, and then, closing his eyes, he felt himself sinking down into some terrible deep and black pit.  A second later the whole ship was jarred as though it had hit something.

How long he and the others remained unconscious Mark did not know.  He was the first to revive, and his first sensation was one as though he had slept hard and long, and did not want to get up.  He felt very comfortable, although he was lying flat on the floor, with his head jammed against the side of a locker.  It was so dark that he could not distinguish his hand held close to his face.

“I wonder if I’m dead, and if all the others are dead too,” he thought to himself.  “What has happened?  Let’s see, the last I remember was some horrible shape rushing from the storeroom.  I wonder what it could have been?  Surely that was not the secret the professor referred to.”

Mark shuddered as he recalled the monster that seemed to have grown more terrible as each second passed.  Then the boy raised himself up from his prostrate position.

“Well, at any rate, some one has turned off the heat,” he murmured.  “It’s very comfortable in here now.  I wish I could strike a light.”

He listened intently, to learn if any of the others were moving about.  He could hear them breathing, but so faintly as to indicate they were insensible.  Mark stretched out his hand and felt that some one was lying close to him, but who of the adventurers it was he could not determine.

“If only the dynamo was working we could have light,” he said.  “But it seems to have stopped,” and, indeed there was a lacking of the familiar purr and hum of the electrical machine.  In fact none of the apparatus in the ship was working.