"Why should it be there and not all over?"
"Because it is much heavier than the air we[p. 157] breathe, and remains at the bottom, just like water. If you recall, this part is lower than the corridor through which we came, so that it could not run out. I have always observed that in all the other caves the floors within were higher than the entrance, and in such cases there is no liability of getting poisonous gases."
"But how are we to make the investigation, under the circumstances?"
"We must remove the gas."
"How can that be done?"
"Several ways are open; one would be to tap the floor and drain the gas out, which would be difficult to do with our resources. Another plan would be to force in a lot of air, so as to render the gas inert, or we might put in enough air to make it burn, and consume it."
"Why, will it burn?"
"Most assuredly; all it needs is enough air; but I am afraid this plan will not be a very safe one for us. If the floor of the cave is not at any place more than four feet below the entrance, we can go about safely, but in such case we must move about with the utmost caution, so as not to get too much of the gas in the system."
"I am afraid it will be a difficult thing to go in unless we know absolutely where the low places are, or unless we survey the bottom of the cave," said George, brightening up at the idea.
"What would happen if we threw a light into the bottom where the gas is?"