The two had gone to examine an old well, near the house, and were speculating upon the possibility of cleansing it from its trash and other impurities, so as to be fit for use, when Harold's knife slipped from his hand and fell down the well. It did not fall into the water, but was caught by a half decayed board that floated on its surface.
"I cannot afford to lose that knife," said Harold, looking around for something to aid his descent, "I must go down after it."
"You had better be careful how you do that," interposed Robert, "it may not be safe."
"What," asked Harold, "are you afraid of the well's caving?"
"Not so much of its caving," replied Robert, "as of the bad air that may have collected at the bottom."
Harold snuffed at the well's mouth to detect such ill odours as might be there, and said, "I perceive no smell."
"You mistake my meaning," remarked Robert. "In all old wells, vaults and places under ground, there is apt to collect a kind of air or gas, like that which comes from burning charcoal, that will quickly suffocate any one who breathes it. Many a person has lost his life by going into such a place without testing it beforehand."
"Can you tell whether there is any of it here?" asked Harold.
"Very easily, with a little fire," answered Robert. "AIR THAT WILL NOT SUPPORT FLAME, WILL NOT SUPPORT LIFE."
They stuck a splinter of rich pine in the cleft end of a pole, and, lighting it by a match, let it softly down the well. To Harold's astonishment the flame was extinguished as suddenly as if it had been dipped in water, before it had gone half way to the bottom.