"Therefore there is no other entrance to the pit but the one which has fallen in?"
"No; and the eastern shaft is also in ruins. The flames came from there; you must have seen them."
"Yes; and I couldn't understand how it was that the second explosion followed the first after an interval of a few minutes."
"That is easily explained. The communicating wall was already so thin that the explosion in the north pit blew it into fragments; the gas in the east pit undoubtedly was not kindled by the flames, for they had already gone out, but by the strong pressure of the air, which was heated to fever-heat by the accumulation of coal, and which, therefore, exploded through the shaft. So it is when you put sand into the barrel of a gun; the powder bursts the barrel before it throws out the sand."
It was plain that the engineer took a very cold-blooded view of the whole affair, and that the design for the new stone gate was a matter of more interest to him than the hundred and fifty lives which were in jeopardy. Ivan saw there was little assistance to be got from him.
"Before we can attempt the rescue of the men who are buried in the pit," he said, "we must pump the gas out of the opening of the cavern. Where is your air-pump?"
"Up there," returned the engineer, pointing to the sky; "that is to say, if it hasn't fallen down."
"You have no portable ventilator?"
"We never contemplated the necessity of having one."
"I have brought mine, if we can adjust it."