“This doesn’t look much like an underground city,” objected Ned. “I think it’s an abandoned railway tunnel.”
At that instant Jerry shut off the power and applied the brakes with a jerk.
“What’s the matter?” asked the professor.
“There’s some sort of a wall or obstruction ahead,” was the answer, and Jerry pointed to where, in the glare of the lamp, could be seen a wall that closed up the passageway completely.
“I guess this is the end,” remarked Ned, ruefully.
The naturalist got out of the car and ran forward. He seemed to be examining the obstruction carefully. He struck it two or three blows.
“Hurrah!” he cried. “Come on, boys, this is only a big wooden door! We can open it!”
In an instant the three lads had joined him. They found that the passage was closed by a big portal of planks, bolted together and swinging on immense hinges. There was also a huge lock or fastening.
“Can we open the door?” inquired Bob. “It looks as if it was meant to stay shut.”
“We’ll soon see,” answered Jerry.