Seeing that the Frenchman was unable or unwilling to respond, he concluded to help himself, by beginning first of all to prepare a little tea.

To do this, fire was necessary; so, to light his lamp, he struck a match.
But what was his surprise at seeing the sulphur tip of the match blazing with a light so bright and dazzling that his eyes could hardly bear it! Touching it to the gas burner, a stream of light flashed forth equal in its intensity to the flame of an electric lamp.

Then he understood it all in an instant.

The dazzling glare, his maddened brain, his gnawing stomach--all were now clear as the noon-day Sun.
"The oxygen!" he cried, and, suddenly stooping down and examining the tap of the air apparatus, he saw that it had been only half turned off.
Consequently the air was gradually getting more and more impregnated with this powerful gas, colorless, odorless, tasteless, infinitely precious, but, unless when strongly diluted with nitrogen, capable of producing fatal disorders in the human system.

Ardan, startled by M'Nicholl's question about the means of returning from the Moon, had turned the cock only half off.
The Captain instantly stopped the escape of the oxygen, but not one moment too soon.