The Moon-spot had disappeared and gone to her eclipse behind the Earth, when an incident occurred to vary the monotony of our existence a little, and to suggest to me a diversion that had been hitherto forbidden. Our supply of water in the outer tank had long ago boiled away, and I had lighted the gas to heat water for the doctor's coffee. I had taken the cup up to him and remained chatting with him, when presently I smelled something burning from the compartment below. I descended quickly, and saw that my light bedclothes, which now weighed less than a feather, and often floated from their place, had been drawn into the flame by the draft of the burning gas. They were floating about the compartment now, all aflame and threatening to set fire to everything. We had not a drop of water to spare; but for once I thought of the right thing to do without hesitation. I pushed out the ventilating cylinder, hurried back to the doctor's compartment and thrust in the bulkhead. Within two minutes all the air had escaped from my room, and the fire had died for lack of oxygen. I waited a few minutes longer for the smoke to escape, and then we admitted condensed air, but only to the remarkably low pressure of eighteen. Within five minutes the compartment was ready again, and there was not a trace of smoke or smell of fire to be perceived. "I congratulate you on your quick perception and prompt action," said the doctor when it was over. "Quick rubbish!" I exclaimed. "I have been a dundering fool for four weeks by the Moon! I might just as well have been smoking ever since I contrived this self-ventilating arrangement. The compartment becomes a perfectly clean vacuum at each operation, yet I had to wait for this bed clothing to catch fire before I could think of so simple a thing!"